ISRN HematologyVolume 2011 (2011), Article ID 921706, 9 pagesdoi:10.5402/2011/921706

Review Article

Notch Signaling in T-Cell Development and T-ALL

Xiaoyu Li and Harald von Boehmer

Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA

Received 5 November 2010; Accepted 15 December 2010

Academic Editors: H. Strobl, A. M. Will, and T. Yokota

Copyright © 2011 Xiaoyu Li and Harald von Boehmer. Xiaoyu Li and . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The Notch signaling pathway is an evolutionarily conserved cell signaling system present in most multicellular organisms, as it controls cell fate specification by regulating cell proliferation, differentiation, apoptosis, and survival. Regulation of the Notch signaling pathway can be achieved at multiple levels. Notch proteins are involved in lineage fate decisions in a variety of tissues in various species. Notch is essential for T lineage cell differentiation including T versus B and αβ versus γδ lineage specification. In this paper, we discuss Notch signaling in normal T-cell maturation and differentiation as well as in T-cell acute lymphoblastic lymphoma/leukemia.

1. Notch Signaling Pathway

The Notch gene was initially described in a mutant strain of fruit fly Drosophila melanogaster with notched wing blades in 1917 by Morgan [1]. This notched wing phenotype resulted from a partial loss of function of the Drosophila Notch gene, which was cloned and characterized in the mid-1980s [2, 3]. The Notch signaling pathway is an evolutionarily conserved cell signaling system present in most multicellular organisms, as it controls cell fate specification by regulating cell proliferation, differentiation, apoptosis, and survival [4]. Mammals possess four transmembrane Notch receptors (Notch1, 2, 3, and 4), [5–10] which can interact with five Notch ligands (Delta-like 1 (DL1), Delta-like 3 (DL3), Delta-like 4 (DL4), Jagged1 and Jagged2) [11–16]. The Notch receptors are synthesized as single protein which are proteolytically cleaved in the Golgi by a furin-like protease at site S1 during transport to the cell surface, resulting in heterodimers consisting of the extracellular domain and the transmembrane domain followed by the intracellular domain of the Notch receptor [17]. The extracellular domain of Notch contains 29–36 epidermal growth factor- (EGF-) like repeats (36 in Notch1 and Notch2, 34 in Notch3, and 29 in Notch4) that are responsible for ligand binding interactions [18]. The EGF-like repeats are followed by three cysteine-rich LIN12-Notch repeats (LNRs) that prevent ligand-independent activation of Notch signaling pathway [19, 20] and the heterodimerization domain (HD). The intracellular domain of Notch contains an RAM23 domain followed by six ankyrin repeats (ANK) involved in binding to the CSL transcription factor [21, 22], a transactivation domain (TAD), and a PEST motif (polypeptide enriched in proline (P), glutamic acid (E), serine (S), and threonine (T)) that regulates protein stability [23, 24].

Ligand-receptor interaction between neighboring cells triggers two successive proteolytic cleavages of the receptor, which release the intracellular portion of the Notch receptor (ICN) from the plasma membrane. The first cleavage is mediated by ADAM (a disintegrin and metalloprotease) proteases at site S2, located on the extracellular side, about 12 amino acids away from the transmembranse domain, which is a key regulatory step in Notch activation [20]. The second proteolytic cleavage is mediated by the γ-secretase complex containing presenilin and nicastrin within the transmembrane domain at site S3. This releases intracellular domain of Notch which then translocates to the nucleus, where it binds to the DNA-binding transcriptional factor CSL [25, 26] (known as CBF1 in human, suppressor of hairless in Drosophila, LAG in Caenorhabditis elegans, and also called RBP-Jκ in mice). In the absence of ICN, CSL represses transcription by binding to the promoters of target genes and recruiting histone deacetylases and corepressors such as SMRT/NcoR and SHARP/MINT/SPEN [27, 28]. When ICN binds to CSL, it recruits the coactivators including Mastermind-like1 (MAML1) [29, 30] and histone acetyltransferase [31], which binds to ICN in the ICN-CSL-DNA complex, thereby converting the CSL complex into a transcriptional activator.

2. Modulation of Notch Signaling

Regulation of Notch signaling pathway can be achieved at multiple levels. First, Fringe proteins have been identified as Golgi-localized glycosyltransferases that inhibit Notch signaling by interfering with Notch receptor-ligand interactions through glycosylation [32–36]. Koch and co-workers showed that T cell specific ectopic expression of Lunatic Fringe decreases T-cells and induces lymphoid progenitor to adopt the B-cell fate in the thymus [37]. Second, the γ-secretase inhibitors (GSIs) effectively block activation of Notch receptor by preventing proteolytic cleavage at site S3, releasing the Notch intracellular domain (ICN) [38]. It has been shown that treatment of T-ALL cells with the GSI results in cell cycle arrest followed by apoptosis [39]. Third, MAMLs are important for Notch-dependent CSL transcriptional activation [29, 30]. Dominant negative mutants of MAML are capable of inhibiting Notch signaling since DNMAML1 contains only the N-terminal ICN-binding basic domain which allows them to bind to ICN but lacks the activation domain therefore, DNMAML1 antagonizes Notch1 signaling by inhibiting recruitment of transcription coactivators [40–42]. Studies from the Pear group show that expression of DNMAML1 leads to marked inhibition of early T-cell differentiation and to the appearance of intrathymic B cells, phenotypes consistent with inhibition of Notch1 [43]. Fourth, Fbw7 is the F-box component of an SCF-E3 ubiquitin ligase complex (SCFFBW7). Fbw7 targets Notch1 for ubiquitination and degradation [44–46]. The PEST domain in the C terminus of the Notch1 receptor is essential for phosphorylation-mediated and proteasome-dependent degradation of Notch1, because Fryer et al. reported that CycC:CDK8 phosphorylates the ICN1 within the TAD and PEST domains, and CycC:CDK8 expression strongly enhances ICN1 hyperphosphorylation and PEST-dependent degradation by the Fbw7 in vivo [47], suggesting that Notch1 protein stability could be a critical regulator of intracellular signaling thresholds.

3. Notch in T-Cell Development

3.1. T versus B Lineage

Notch proteins are involved in lineage fate decisions in a variety of tissues in various species [4]. Notch is essential for T lineage cell differentiation. Loss-of-function experiments have shown that Notch plays a crucial role in determining T lymphoid versus B lymphoid lineage decision [48–50]. Conditional deletion of Notch1 in hematopoietic progenitors induces a block of early T-cell development and accumulation of ectopic immature B-cells in the thymus [49, 50]. Similar phenotype was observed in the mice harboring Cre-mediated deletion of RBP-J created by Han et al. [48]. Moreover, interference with Notch receptor-ligand interactions or inhibition of Notch-mediated transcription results in failure of T cell development and promotion of B cell development [37, 43]. Conversely, gain-of-function analyses involving overexpression of constitutively active Notch1 in bone marrow lineage negative progenitors indicate that activated Notch1 results in thymic-independent T-cell development at the expense of B-cell development in the BM and does not influence granulocyte maturation [51]. Nevertheless, other studies suggest that constitutive Notch1 activity blocks or delays myeloid differentiation concomitant with ectopic T-cell development [52–55]. Thus, whether or not activated Notch1 affects myeloid differentiation remains controversial. Taken together, these findings demonstrate that Notch1 singaling is essential to induce T-cell lineage commitment from the multipotent hematopoietic progenitor cells (HPCs).

3.2. Early T-Cell Development

The earliest intrathymic T-cell precursors, ETPs, which are characterized by high expression of c-Kit receptor and low expression of the interleukin 7 receptor alpha chain (IL7R), are found in the double-negative DN1 thymocyte subset (CD4⁻CD8⁻CD25⁻CD44⁻) [56–59]. Notch signaling is required not only for generation of the ETP population but also for transitions of ETP-to-DN2 and ETP-to-DN3 suggesting that Notch1 activation is needed continuously to promote survival or proliferation throughout the early stages of intrathymic T-cell development [58, 59]. Consistent with these findings, a number of in vitro studies provide supportive evidences showing that Notch receptor-ligand interactions are necessary for induction and maintenance of T-cell lineage specification at both the DN1 and DN2 stages of T-cell development [60, 61] and that enforced expression of Notch inhibitor Nrarp (Notch-regulated ankyrin-repeat protein) in mouse HSCs results in a profound block during progression through early stages of thymocyte maturation (DN1–DN3) [62].

3.3. β-Selection Checkpoint

There are two checkpoints during T-cell development, where cells are rescued from programmed cell death and progress in their development [63, 64]. Commitment to either the CD4⁺CD8⁺αβ or CD4⁻CD8⁻γδ lineage occurs at the first checkpoint [65]. DN3 cells that generate the productive TCR-β chain rearrangement which can be assembled into the pre-T-cell receptor (pre-TCR) complex consisting of a TCRβ chain, the invariant pTα chain [66], and CD3 molecules can survive the transition from DN3 to DN4, this process is termed β selection [67–69]. Loss of RAG-1 or RAG-2 in vivo results in total inability to initiate V(D)J rearrangement, leading to the arrest of developing αβ lineage thymocytes at the DN3 stage [70, 71]. At the second checkpoint in T-cell development, cells on the αβ lineage are rescued from cell death by binding of their αβ TCR to thymic MHC molecules, allowing CD4⁺CD8⁺ thymocytes to undergo positive and negative selection [63, 64]. Wolfer and colleagues reported that inactivation of Notch1 prior to the DN3 stage severely impairs αβ but not γδ T-cell development and partially blocks thymocyte development at the pre-TCR checkpoint due to a severe impairment of Vβ-DJβ rearrangement [72]. Conditional ablation of the gene encoding RBP-J at an earlier developmental stage results in enhanced generation and accelerated emigration of γδ T cells, whereas αβ T-cell development is arrested at the DN3 stage [73]. Inhibition of Notch signaling by DNMAML in DN3 stage leads to similar consequences [40]. Moreover, the OP9-DL1 in vitro T-cell differentiation system provides an ideal system to mimic in vivo T-cell development established by Zúñiga-Pflücker and colleagues [74, 75]. They made use of OP9-DL1 system to demonstrate that pre-TCR signaling concurrent with Notch receptor-ligand interactions are required for productive β selection outcomes including rescue from apoptosis, proliferation, and transition of DN thymocytes to the DP stage of T-cell development [76–78].

3.4. αβ versus γδ Lineage

In vitro experiments provided evidence that bifurcation of the αβ and γδ T-cell lineages is completed at the DN3 stage [77, 79–82]. Robey and colleagues examined the effect of Notch activity and the T-cell receptor in the αβ versus γδ T-cell lineage choice. They showed that cells with Notch+/− gene are less likely to become αβ T-cells than wild type cells with Notch+/+ gene that develop in the same mouse. In addition, they also provided evidence that γδ to αβ T cells are consistently higher in T cells derived from Notch+/− stem cells compared to wild-type cells, implying that reduced Notch activity favors the γδ lineage over the αβ lineage. We have shown that γδTCR-expressing cells can survive and expand in the absence Notch signals [83]. Mice deficient in Jagged2 exhibit altered thymic morphology and impaired differentiation of γδ lineage T cells [84], suggesting that Jagged2-mediated Notch signaling participates in γδ lineage differentiation. However, the role of Notch signals during αβ versus γδ T lineage decision remains controversial. Experiments by Wolfer and colleagues demonstrate that conditional deletion of Notch1 signaling at DN2-DN3 developmental stage leads to severe perturbation of αβ but not γδ lineage development [72]. In fact, Garbe et al. [83]as well as Ciofani et al. [77] demonstrated a stage-specific requirement for Notch signaling at the αβ and γδ T lineage bifurcation.

4. Notch Signaling in T-ALL

The involvement of Notch1 was first observed in the t(7;9)(q34;34.3) translocation, a rare recurrent chromosomal rearrangement present in <1% of human T-ALL patients. The t(7;9)(q34;34.3) translocation juxtaposes the C-terminal region of EGF repeat 34 of the human NOTCH1 gene next to the TCRβ promoter/enhancer, resulting in the activated expression of NOTCH1, which was named TAN1 for translocation-associated Notch homolog [5]. TAN1 was shown to function as a specific oncoprotein for T cells in the murine bone marrow transplantation model. The murine tumors induced by TAN1 in this model are phenotypically similar to the TAN1-associated human tumors [85]. Notch was originally thought to play a minor role in the molecular pathogenesis of human T-ALL due to the rare frequency of t(7;9)(q34;34.3) translocation involving Notch in human T-ALL cases. More recently, it was shown that more than 50% of human T-ALLs, including tumors from all major molecular oncogenic subtypes, have gain-of-function mutations that involve the extracellular heterodimerization domain and/or the C-terminal PEST domain of NOTCH1 [86]. Following this finding, activating mutations of Notch1 as well as mutants of genes that regulate turnover of intracellular Notch1 have been detected in mouse models of T-ALL [44, 45, 87–89]. Thus, these studies have sparked renewed interest in the pathogenesis of T-ALL and greatly expanded the role of NOTCH1 in the etiology and molecular tumorigenesis of this human disease with the hope of finding novel targeted therapies that interfere with NOTCH signaling.

4.1. E2A Inhibition

E-proteins are members of highly conserved basic helix-loop-helix (bHLH) family of transcription factors which plays a critical role in cellular differentiation. The E2A gene encodes two alternatively spliced transcripts which produce two proteins, E47 and E12 [90–92]. These proteins bind as homo- or heterodimers with other basic helix-loop-helix proteins as transcription factors to E-box consensus sequences and have an essential function in B-cell and T-cell development [93, 94]. E2A-deficient mice lack B cells and regularly develop T-ALL [95]. Notch inhibition of E47 was initially described by Ordentlich et al. [96] who demonstrated that Notch and Notch downstream target Deltex act on E2A-encoded E47 by inhibiting signaling through Ras. Two mechanisms of E2A inhibition by Notch have been reported: Notch-mediated upregulation of the pre-TCR signaling leads to ERK-MAPK-dependent upregulation of the E2A inhibitors Id1 or Id3 which prevent binding of E2A-encoded proteins to E-box motifs [93, 97]. Alternatively, overexpression of Notch induces E2A protein degradation through ubiquitination-proteasome-mediated pathway both in vitro and in vivo [98, 99]. Most T-ALLs induced by other oncoproteins such as TAL1, LMO1, or LMO2 are characterized by inhibition of the transcriptional activity of the E2A proteins [100–105], suggesting that E2A could be an essential pathway in the leukemogenesis of T-ALL. In order to evaluate the role of E2A-encoded E47 protein as a potential tumor suppressor in murine T-ALL, we have introduced nondegradable mutant E47 by retroviral vector into intracellular domain of Notch1- (ICN1-) overexpressing tumors, and we found that overexpression of E47 led to suppression of tumor cell growth [98]. Taken together, these findings suggest that E2A may function as tumor suppressor, and inhibition of E2A activity is a common and critical event in the pathogenesis of T-cell lymphoma.

4.2. c-Myc Activation

The c-Myc proto-oncogene is a basic helix-loop-helix leucine zipper (b/HLH/LZ) protein involved in cellular growth and differentiation. c-Myc has been identified as a critical direct downstream target gene of NOTCH1 in leukemogenesis [89, 106, 107]. Inhibitors of c-Myc prevent Notch1 from rescuing T-ALL cells treated with γ-secretase inhibitor (GSI), and overexpression of c-Myc is sufficient to rescue most human T-ALL cell lines from GSI-induced growth arrest [107]. Palomero and co-workers showed that Notch1 controls a feed-forward-loop transcriptional network that regulates cell growth and proliferation and that Notch1 directly activates multiple biosynthetic routes and targets c-Myc using integrating gene expression array and ChIP-on-ChIP analysis [106]. Sharma and colleagues developed doxycycline- (Dox-) regulated Notch1-IC mouse T-ALL cell lines and identified c-Myc as a direct Notch1 target gene in Notch1-induced T-ALL transformation using gene expression profiling and chromatin immunoprecipitation (ChIP) analysis in this cell line [89]. Moreover, Notch1 inhibition leads to cell cycle arrest and decreases c-Myc mRNA levels [89]. The results are consistent with those in human T-ALL studies [106, 107], implying that the direct activation of c-Myc mediated by Notch1 is required to maintain leukemic growth. To evaluate the mechanism by which Notch1 directly targets c-Myc, Satoh et al. [108] have demonstrated that activated forms of Notch1 and its downstream effector CSL can bind to the responsive element (TTCCCAA) located between −195 bp and −11 bp of the c-Myc promoter by luciferase reporter assay and electrophoretic mobility shift assay (EMSA). The recruitment of Notch1 to the CSL-binding sites in the c-Myc promoter has been confirmed by other investigators [89, 106, 107, 109] by luciferase reporter assay, EMSA, or chromatin immuno-precipitation (ChIP) analysis. We have previously systematically investigated oncogenesis of T-ALL initiated by ICN1 overexpression in a bone marrow transplantation (BMT) model; we found that c-Myc is upregulated in nonmalignant ICN1-overexpressing cells as well as malignant ICN1-overexpressing cells at both of mRNA and protein levels [98]. Furthermore, we have shown that deletion of c-Myc at the CD4⁺CD8⁺ stage of T cell development prevented tumor formation induced by Notch1 [98]. Girard and colleagues performed provirus insertional mutagenesis in c-Myc transgenic mice to identify c-Myc collaborators in leukemogenesis; they observed that Notch1 was mutated by provirus insertion upstream of the exon coding for the transmembrane domain of Notch1, resulting in high expression of truncated Notch1 RNAs and proteins [110]. Moreover, in collaboration with the Look lab, we have reported that dysregulated Myc expression is shared between ICN1-induced murine model and most human T-ALLs with Notch1 gene mutations [111]. These results suggest a collaboration of c-Myc and Notch1 in oncogenesis.

4.3. Cell Cycle Progression

Cell cycle progression is regulated at several checkpoints of cellular process. Notch signaling has been shown to be a potent regulator of cell cycle progression in T-ALL cells [86, 89, 112]. Sicinski and colleagues [113] have studied the function of cyclin D3 in T-cell development and T-cell leukemogenesis, and they found that cyclin D3−/−) mice show impaired expansion of immature T lymphocytes, characterized by a marked deficit of CD4⁺CD8⁺ T cells. Cyclin D3 deficiency inhibits T-ALL induced by Notch1, suggesting the requirement of cyclin D3 for the growth of T-ALL tumors derived from immature T cells. To evaluate the mechanism by which Notch1 regulates cell-cycle progression in T-ALL, experiments from Joshi group [114] show that cyclin D3 functions together with its catalytic partners CDK4 and CDK6 to facilitate cell cycle progression in Notch1-dependent T-cell lymphoma, because Notch1 binds directly to the region of −1764 bp to −1537 bp of cyclin D3 promoter and specifically regulates cyclin D3 promoter activity revealed by ChIP analysis and luciferase reporter assay. Inhibition of Notch activation with GSI treatment abrogates the occupancy of Ntoch1 to the cyclin D3 promoter, suggesting that cyclin D3 is a direct target of the Notch/CSL signaling pathway [114]. While cyclin D3 expression contributes to cell-cycle progression in Notch-mediated human T-ALL cell lines, overexprssion of CDK4 or CDK6 together with cyclin D3 partially rescues these cell lines from GSI-induced G1 arrest. Moreover, cyclin D3 and CDK4 are highly expressed in Notch-dependent leukemic mice [114], which is consistent with our previous report [98]. Cyclin-dependent kinases (CDKs) and cyclin-dependent kinase inhibitors (CKIs) play important roles in the regulation of G1/S phase transition [115]. Sarmento [116] and colleagues provided the first evidence that Notch signaling links to the F-box protein SKP2, which is the subunit of the E3-ubiquitin ligase SCFSKP2that degrades p27Kip1 and p21Cip1. Their data showed that Notch signaling pathway specifically degrades p27Kip1 and p21Cip1 by directly inducing CSL-dependent transcription of SKP2, which subsequently enhances CDK2 kinase activity and accelerates cell cycle entry into S phase. Depletion of SKP2 by siRNA in G1 phase stabilizes p27Kip1 and p21Cip1, abolishes Notch effect on G1-S progression, and results in a significant reduction of cells in S phase [116]. This is consistent with observations from other groups demonstrating that GSI inhibition of Notch signaling in human T-ALL cell lines results in G0/G1 cell cycle arrest by downregulation of SKP2, upregulation of p27Kip1, and derepression of RB [117, 118].

4.4. ARF-Mdm2-p53 Pathway

The ARF-Mdm2-p53 tumor surveillance pathway is important for Myc-mediated apoptosis in primary mouse embryofibroblasts (MEFs) [119], whereas this pathway is frequently inactivated in Myc-induced lymphoma in vivo [120]. To evaluate whether or not c-myc-ARF-Mdm2-p53 axis is intact in ICN1-dependent tumor cells, we have shown that p53 and p19arf were downregulated and Mdm2 was upregulated at both mRNA and protein levels in the tumor cells compared with nontumorigenic ICN1-overexpressing cells [98]. This study indicates that dysregulation of the c-Myc-p53 axis occurs in the face of genomic stability as revealed by spectral karyotype (SKY) and array-base comparative genomic hybridization (aCGH). Consistent with these observations, the Beverly group [121] reported that Notch suppresses p53 in lymphomagenesis in Notch1 transgenic mice, and p53 is activated upon inhibition of Notch signaling by GSI. They further proposed that Notch suppresses p53 in lymphomagenesis through repression of the ARF-Mdm2-p53 pathway.

4.5. PTEN/PI3K/Akt-mTOR Pathway

To identify novel pro-oncogenic pathways regulated by Notch, Chan et al. [122] used reverse phase protein (RPP) microarrays to profile the phosphorylation changes in a large number of signaling proteins in 13 T-ALL cell lines treated with GSI they found that the phosphorylation of multiple signaling proteins in the mTOR pathway was suppressed by inhibition of Notch signaling in a Notch-dependent manner, as this phenomenon can be rescued by expression of ICN1 and mimicked by dominant negative MAML1, suggesting that Notch signals positively regulate activity of the mTOR pathway in T-ALL. More importantly, the effect of GSI on the mTOR pathway can also be rescued by c-Myc because c-Myc is a direct transcriptional target of Notch. Inhibition of mTOR by rapamycin combined with GSI treatment synergistically inhibited T-ALL cell growth [122]. Consistently, the work from other group showed that Notch1 signaling confers chemoresistance in a wild-type p53-dependent manner. Notch inhibited p53 through the PI3K-Akt/protein kinase B- (PKB-) mammalian target of rapamycin (mTOR) pathway, and the inhibition of this pathway reversed the chemoresistance [123]. PTEN, a tumor suppressor which negatively regulates PI3-kinase-Akt signaling pathway, is consistently downregulated in GSI-resistant T-ALL cell lines [124]. The Palomero group found that transcriptional downregulation of PTEN mediates physiologic upregulation of the PI3K-AKT pathway; mutational loss of PTEN and aberrant Akt activation induce resistance to GSI in T-cell leukemia [124]. In contrast to these findings, Medyouf et al. [125] reported that T-ALLs remain dependent on Notch signaling and found no correlation between PTEN status and resistance to Notch inhibition in primary human T-ALL and mouse model of T-ALL.

5. Conclusions and Perspectives

Large numbers of work over the last decade have demonstrated that Notch signaling is essential for T-cell lineage fate decision, and aberrant activation of Notch signaling plays a critical role in etiology and pathogenesis of T-cell acute lymphoblastic Lymphoma/Leukemia. Activated Notch signaling is required for the transformation and growth of T-cell lymphoma/leukemia; downstream pathways that transmit pro-oncogenic signaling are poorly understood. In the mouse model, Notch1-mediated T-ALL develops monoclonal tumor; thus, another unknown secondary genetic event needs to be elucidated. Altered expression of miRNAs has been involved in various types of cancers including hematopoietic malignancies; however, the role of miRNAs in T-cell development and T-ALL tumorigenesis is not well characterized, although few related studies have been reported [126–128]. In the future, combination of GSI and downstream pathway regulators such as mTOR inhibitor or CyclinD3 inhibitor will represent a novel approach for treating this aggressive human malignancy.

Acknowledgments

Work related to this paper is supported by the Claudia Adams Barr grant (X. Li) and by the National Institutes of Health Grant no. 5P01CA109901-040001 (H. von Boehmer).

References

T. H. Morgan, “The theory of the gene,” The American Naturalist, vol. 51, pp. 513–544, 1917.

K. A. Wharton, K. M. Johansen, T. Xu, and S. Artavanis-Tsakonas, “Nucleotide sequence from the neurogenic locus Notch implies a gene product that shares homology with proteins containing EGF-like repeats,” Cell, vol. 43, no. 3, part 2, pp. 567–581, 1985.

S. Kidd, M. R. Kelley, and M. W. Young, “Sequence of the notch locus of Drosophila melanogaster: relationship of the encoded protein to mammalian clotting and growth factors,” Molecular and Cellular Biology, vol. 6, no. 9, pp. 3094–3108, 1986.

S. Artavanis-Tsakonas, M. D. Rand, and R. J. Lake, “Notch signaling: cell fate control and signal integration in development,” Science, vol. 284, no. 5415, pp. 770–776, 1999.

L. W. Ellisen, J. Bird, D. C. West, A. L. Soreng, T. C. Reynolds, S. D. Smith, and J. Sklar, “TAN-1, the human homolog of the Drosophila Notch gene, is broken by chromosomal translocations in T lymphoblastic neoplasms,” Cell, vol. 66, no. 4, pp. 649–661, 1991.

F. F. Del Amo, D. E. Smith, P. J. Swiatek, M. Gendron-Maguire, R. J. Greenspan, A. P. McMahon, and T. Gridley, “Expression pattern of Motch, a mouse homolog of Drosophila Notch, suggests an important role in early postimplantation mouse development,” Development, vol. 115, no. 3, pp. 737–744, 1992.

G. Weinmaster, V. J. Roberts, and G. Lemke, “Notch2: a second mammalian Notch gene,” Development, vol. 116, no. 4, pp. 931–941, 1992.

M. Lardelli and U. Lendahl, “Motch A and Motch B—two mouse Notch homologues coexpressed in a wide variety of tissues,” Experimental Cell Research, vol. 204, no. 2, pp. 364–372, 1993.

M. Lardelli, J. Dahlstrand, and U. Lendahl, “The novel Notch homologue mouse Notch 3 lacks specific epidermal growth factor-repeats and is expressed in proliferating neuroepithelium,” Mechanisms of Development, vol. 46, no. 2, pp. 123–136, 1994.

H. Uyttendaele, G. Marazzi, G. Wu, Q. Yan, D. Sassoon, and J. Kitajewski, “Notch4/int-3, a mammary proto-oncogene, is an endothelial cell-specific mammalian Notch gene,” Development, vol. 122, no. 7, pp. 2251–2259, 1996.

B. Bettenhausen, M. Hrabe de Angelis, D. Simon, J. L. Guenet, and A. Gossler, “Transient and restricted expression during mouse embryogenesis of Dll1, a murine gene closely related to Drosophila Delta,” Development, vol. 121, no. 8, pp. 2407–2418, 1995.

S. L. Dunwoodie, D. Henrique, S. M. Harrison, and R. S. P. Beddington, “Mouse Dll3: a novel divergent Delta gene which may complement the function of other Delta homologues during early pattern formation in the mouse embryo,” Development, vol. 124, no. 16, pp. 3065–3076, 1997.

C. E. Lindsell, C. J. Shawber, J. Boulter, and G. Weinmaster, “Jagged: a mammalian ligand that activates Notch1,” Cell, vol. 80, no. 6, pp. 909–917, 1995.

C. Shawber, J. Boulter, C. E. Lindsell, and G. Weinmaster, “Jagged2: a Serrate-like gene expressed during rat embryogenesis,” Developmental Biology, vol. 180, no. 1, pp. 370–376, 1996.

J. R. Shutter, S. Scully, W. Fan, W. G. Richards, J. Kitajewski, G. A. Deblandre, C. R. Kintner, and K. L. Stark, “D114, a novel Notch ligand expressed in arterial endothelium,” Genes and Development, vol. 14, no. 11, pp. 1313–1318, 2000.

J. C. Aster, W. S. Pear, and S. C. Blacklow, “Notch signaling in leukemia,” Annual Review of Pathology, vol. 3, pp. 587–613, 2008.

C. M. Blaumueller, H. Qi, P. Zagouras, and S. Artavanis-Tsakonas, “Intracellular cleavage of Notch leads to a heterodimeric receptor on the plasma membrane,” Cell, vol. 90, no. 2, pp. 281–291, 1997.

I. Rebay, R. J. Fleming, R. G. Fehon, L. Cherbas, P. Cherbas, and S. Artavanis-Tsakonas, “Specific EGF repeats of Notch mediate interactions with Delta and Serrate: implications for Notch as a multifunctional receptor,” Cell, vol. 67, no. 4, pp. 687–699, 1991.

C. Sanchez-Irizarry, A. C. Carpenter, A. P. Weng, W. S. Pear, J. C. Aster, and S. C. Blacklow, “Notch subunit heterodimerization and prevention of ligand-independent proteolytic activation depend, respectively, on a novel domain and the LNR repeats,” Molecular and Cellular Biology, vol. 24, no. 21, pp. 9265–9273, 2004.

R. Kopan and M. X. G. Ilagan, “The canonical Notch signaling pathway: unfolding the activation mechanism,” Cell, vol. 137, no. 2, pp. 216–233, 2009.

M. E. Fortini and S. Artavanis-Tsakonas, “The suppressor of hairless protein participates in notch receptor signaling,” Cell, vol. 79, no. 2, pp. 273–282, 1994.

K. Tamura, Y. Taniguchi, S. Minoguchi, T. Sakai, T. Tun, T. Furukawa, and T. Honjo, “Physical interaction between a novel domain of the receptor Notch and the transcription factor RBP-Jkappa/Su(H),” Current Biology, vol. 5, no. 12, pp. 1416–1423, 1995.

N. Gupta-Rossi, O. Le Bail, H. Gonen, C. Brou, F. Logeat, E. Six, A. Ciechanover, and A. Israël, “Functional interaction between SEL-10, an F-box protein, and the nuclear form of activated Notch1 receptor,” Journal of Biological Chemistry, vol. 276, no. 37, pp. 34371–34378, 2001.

C. Öberg, J. Li, A. Pauley, E. Wolf, M. Gurney, and U. Lendahl, “The Notch intracellular domain is ubiquitinated and negatively regulated by the mammalian Sel-10 homolog,” Journal of Biological Chemistry, vol. 276, no. 38, pp. 35847–35853, 2001.

B. de Strooper, W. Annaert, P. Cupers, P. Saftig, K. Craessaerts, J. S. Mumm, E. H. Schroeter, V. Schrijvers, M. S. Wolfe, W. J. Ray, A. Goate, and R. Kopan, “A presenilin-1-dependent γ-secretase-like protease mediates release of notch intracellular domain,” Nature, vol. 398, no. 6727, pp. 518–522, 1999.

G. Struhl and A. Adachi, “Nuclear access and action of Notch in vivo,” Cell, vol. 93, no. 4, pp. 649–660, 1998.

H. Y. Kao, P. Ordentlich, N. Koyano-Nakagawa, Z. Tang, M. Downes, C. R. Kintner, R. M. Evans, and T. Kadesch, “A histone deacetylase corepressor complex regulates the Notch signal transduction pathway,” Genes and Development, vol. 12, no. 15, pp. 2269–2277, 1998.

F. Oswald, M. Winkler, Y. Cao, K. Astrahantseff, S. Bourteele, W. Knöchel, and T. Borggrefe, “RBP-Jκ/SHARP recruits CtIP/CtBP corepressors to silence notch target genes,” Molecular and Cellular Biology, vol. 25, no. 23, pp. 10379–10390, 2005.

L. Wu, J. C. Aster, S. C. Blacklow, R. Lake, S. Artavanis-Tsakonas, and J. D. Griffin, “MAML1, a human homologue of Drosophila mastermind, is a transcriptional co-activator for NOTCH receptors,” Nature Genetics, vol. 26, no. 4, pp. 484–489, 2000.

L. Wu, T. Sun, K. Kobayashi, P. Gao, and J. D. Griffin, “Identification of a family of mastermind-like transcriptional coactivators for mammalian Notch receptors,” Molecular and Cellular Biology, vol. 22, no. 21, pp. 7688–7700, 2002.

H. Kurooka and T. Honjo, “Functional interaction between the mouse Notch1 intracellular region and histone acetyltransferases PCAF and GCN5,” Journal of Biological Chemistry, vol. 275, no. 22, pp. 17211–17220, 2000.

K. Brückner, L. Perez, H. Clausen, and S. Cohen, “Glycosyltransferase activity of Fringe modulates Notch-Delta interactions,” Nature, vol. 406, no. 6794, pp. 411–415, 2000.

D. J. Moloney, V. M. Panin, S. H. Johnston, J. Chen, LI. Shao, R. Wilson, Y. Wang, P. Stanley, K. D. Irvine, R. S. Haltiwanger, and T. F. Vogt, “Fringe is a glycosyltransferase that modifies Notch,” Nature, vol. 406, no. 6794, pp. 369–375, 2000.

S. Munro and M. Freeman, “The Notch signalling regulator Fringe acts in the Golgi apparatus and requires the glycosyltransferase signature motif DxD,” Current Biology, vol. 10, no. 14, pp. 813–820, 2000.

N. Haines and K. D. Irvine, “Glycosylation regulates Notch signalling,” Nature Reviews Molecular Cell Biology, vol. 4, no. 10, pp. 786–797, 2003.

U. Koch, J. S. Yuan, J. A. Harper, and C. J. Guidos, “Fine-tuning Notch1 activation by endocytosis and glycosylation,” Seminars in Immunology, vol. 15, no. 2, pp. 99–106, 2003.

U. Koch, T. A. Lacombe, D. Holland, J. L. Bowman, B. L. Cohen, S. E. Egan, and C. J. Guidos, “Subversion of the T/B lineage decision in the thymus by Lunatic Fringe-mediated inhibition of Notch-1,” Immunity, vol. 15, no. 2, pp. 225–236, 2001.

R. Kopan and M. X. G. Ilagan, “γ-secretase: proteasome of the membrane?” Nature Reviews Molecular Cell Biology, vol. 5, no. 6, pp. 499–504, 2004.

H. D. Lewis, M. Leveridge, P. R. Strack, C. D. Haldon, J. O'Neil, H. Kim, A. Madin, J. C. Hannam, A. T. Look, N. Kohl, G. Draetta, T. Harrison, J. Kerby, M. S. Shearman, and D. Beher, “Apoptosis in T cell acute lymphoblastic leukemia cells after cell cycle arrest induced by pharmacological inhibition of notch signaling,” Chemistry and Biology, vol. 14, no. 2, pp. 209–219, 2007.

I. Maillard, L. Tu, A. Sambandam, Y. Yashiro-Ohtani, J. Millholland, K. Keeshan, O. Shestova, L. Xu, A. Bhandoola, and W. S. Pear, “The requirement for Notch signaling at the β-selection checkpoint in vivo is absolute and independent of the pre-T cell receptor,” Journal of Experimental Medicine, vol. 203, no. 10, pp. 2239–2245, 2006.

Y. Nam, A. P. Weng, J. C. Aster, and S. C. Blacklow, “Structural requirements for assembly of the CSL·intracellular Notch1·Mastermind-like 1 transcriptional activation complex,” Journal of Biological Chemistry, vol. 278, no. 23, pp. 21232–21239, 2003.

L. Tu, T. C. Fang, D. Artis, O. Shestova, S. E. Pross, I. Maillard, and W. S. Pear, “Notch signaling is an important regulator of type 2 immunity,” Journal of Experimental Medicine, vol. 202, no. 8, pp. 1037–1042, 2005.

I. Maillard, A. P. Weng, A. C. Carpenter, C. G. Rodriguez, H. Sai, L. Xu, D. Allman, J. C. Aster, and W. S. Pear, “Mastermind critically regulates Notch-mediated lymphoid cell fate decisions,” Blood, vol. 104, no. 6, pp. 1696–1702, 2004.

J. O'Neil, J. Grim, P. Strack, S. Rao, D. Tibbitts, C. Winter, J. Hardwick, M. Welcker, J. P. Meijerink, R. Pieters, G. Draetta, R. Sears, B. E. Clurman, and A. T. Look, “FBW7 mutations in leukemic cells mediate NOTCH pathway activation and resistance to γ-secretase inhibitors,” Journal of Experimental Medicine, vol. 204, no. 8, pp. 1813–1824, 2007.

B. J. Thompson, S. Buonamici, M. L. Sulis, T. Palomero, T. Vilimas, G. Basso, A. Ferrando, and I. Aifantis, “The SCF ubiquitin ligase complex as a tumor suppressor in T cell leukemia,” Journal of Experimental Medicine, vol. 204, no. 8, pp. 1825–1835, 2007.

B. J. Thompson, V. Jankovic, J. Gao, S. Buonamici, A. Vest, J. M. Lee, J. Zavadil, S. D. Nimer, and I. Aifantis, “Control of hematopoietic stem cell quiescence by the E3 ubiquitin ligase Fbw7,” Journal of Experimental Medicine, vol. 205, no. 6, pp. 1395–1408, 2008.

C. J. Fryer, J. B. White, and K. A. Jones, “Mastermind recruits CycC:CDK8 to phosphorylate the Notch ICD and coordinate activation with turnover,” Molecular Cell, vol. 16, no. 4, pp. 509–520, 2004.

H. Han, K. Tanigaki, N. Yamamoto, K. Kuroda, M. Yoshimoto, T. Nakahata, K. Ikuta, and T. Honjo, “Inducible gene knockout of transcription factor recombination signal binding protein-J reveals its essential role in T versus B lineage decision,” International Immunology, vol. 14, no. 6, pp. 637–645, 2002.

F. Radtke, A. Wilson, G. Stark, M. Bauer, J. van Meerwijk, H. R. MacDonald, and M. Aguet, “Deficient T cell fate specification in mice with an induced inactivation of Notch1,” Immunity, vol. 10, no. 5, pp. 547–558, 1999.

A. Wilson, H. R. MacDonald, and F. Radtke, “Notch 1-deficient common lymphoid precursors adopt a B cell fate in the thymus,” Journal of Experimental Medicine, vol. 194, no. 7, pp. 1003–1012, 2001.

J. C. Pui, D. Allman, L. Xu, S. DeRocco, F. G. Karnell, S. Bakkour, J. Y. Lee, T. Kadesch, R. R. Hardy, J. C. Aster, and W. S. Pear, “Notch1 expression in early lymphopoiesis influences B versus T lineage determination,” Immunity, vol. 11, no. 3, pp. 299–308, 1999.

N. Carlesso, J. C. Aster, J. Sklar, and D. T. Scadden, “Notch1-induced delay of human hematopoietic progenitor cell differentiation is associated with altered cell cycle kinetics,” Blood, vol. 93, no. 3, pp. 838–848, 1999.

L. Li, L. A. Milner, Y. Deng, M. Iwata, A. Banta, L. Graf, S. Marcovina, C. Friedman, B. J. Trask, L. Hood, and B. Torok-Storb, “The human homolog of rat Jagged1 expressed by marrow stroma inhibits differentiation of 32D cells through interaction with Notch1,” Immunity, vol. 8, no. 1, pp. 43–55, 1998.

L. A. Milner, A. Bigas, R. Kopan, C. Brashem-Stein, I. D. Bernstein, and D. I. K. Martin, “Inhibition of granulocytic differentiation by mNotch1,” Proceedings of the National Academy of Sciences of the United States of America, vol. 93, no. 23, pp. 13014–13019, 1996.

S. Stier, T. Cheng, D. Dombkowski, N. Carlesso, and D. T. Scadden, “Notch1 activation increases hematopoietic stem cell self-renewal in vivo and favors lymphoid over myeloid lineage outcome,” Blood, vol. 99, no. 7, pp. 2369–2378, 2002.

D. Allman, A. Sambandam, S. Kim, J. P. Miller, A. Pagan, D. Well, A. Meraz, and A. Bhandoola, “Thymopoiesis independent of common lymphoid progenitors,” Nature Immunology, vol. 4, no. 2, pp. 168–174, 2003.

A. Bhandoola, A. Sambandam, D. Allman, A. Meraz, and B. Schwarz, “Early T lineage progenitors: new insights, but old questions remain,” Journal of Immunology, vol. 171, no. 11, pp. 5653–5658, 2003.

A. Sambandam, I. Maillard, V. P. Zediak, L. Xu, R. M. Gerstein, J. C. Aster, W. S. Pear, and A. Bhandoola, “Notch signaling controls the generation and differentiation of early T lineage progenitors,” Nature Immunology, vol. 6, no. 7, pp. 663–670, 2005.

J. B. Tan, I. Visan, J. S. Yuan, and C. J. Guidos, “Requirement for Notch1 signals at sequential early stages of intrathymic T cell development,” Nature Immunology, vol. 6, no. 7, pp. 671–679, 2005.

T. M. Schmitt, M. Ciofani, H. T. Petrie, and J. C. Zúñiga-Pflücker, “Maintenance of T cell specification and differentiation requires recurrent Notch receptor-ligand interactions,” Journal of Experimental Medicine, vol. 200, no. 4, pp. 469–479, 2004.

T. N. Taghon, E. S. David, J. C. Zúñiga-Pflücker, and E. V. Rothenberg, “Delayed, asynchronous, and reversible T-lineage specification induced by Notch/Delta signaling,” Genes and Development, vol. 19, no. 8, pp. 965–978, 2005.

T. J. Yun and M. J. Bevan, “Notch-regulated ankyrin-repeat protein inhibits Notch1 signaling: multiple Notch1 signaling pathways involved in T cell development,” Journal of Immunology, vol. 170, no. 12, pp. 5834–5841, 2003.

A. M. Michie and J. C. Zúñiga-Pflücker, “Regulation of thymocyte differentiation: pre-TCR signals and β-selection,” Seminars in Immunology, vol. 14, no. 5, pp. 311–323, 2002.

H. von Boehmer, I. Aifantis, J. Feinberg, O. Lechner, C. Saint-Ruf, U. Walter, J. Buer, and O. Azogui, “Pleiotropic changes controlled by the pre-T-cell receptor,” Current Opinion in Immunology, vol. 11, no. 2, pp. 135–142, 1999.

A. I. Garbe and H. von Boehmer, “TCR and Notch synergize in αβ versus γδ lineage choice,” Trends in Immunology, vol. 28, no. 3, pp. 124–131, 2007.

C. Saint-Ruf, K. Ungewiss, M. Groettrup, L. Bruno, H. J. Fehling, and H. von Boehmer, “Analysis and expression of a cloned pre-T cell receptor gene,” Science, vol. 266, no. 5188, pp. 1208–1212, 1994.

E. C. Dudley, H. T. Petrie, L. M. Shah, M. J. Owen, and A. C. Hayday, “T cell receptor β chain gene rearrangement and selection during thymocyte development in adult mice,” Immunity, vol. 1, no. 2, pp. 63–93, 1994.

H. J. Fehling, A. Krotkova, C. Saint-Ruf, and H. von Boehmer, “Crucial role of the pre-T-cell receptor gene in development of but not T cells,” Nature, vol. 375, no. 6534, pp. 795–798, 1995.

H. J. Fehling and H. V. Boehmer, “Early αβ T cell development in the thymus of normal and genetically altered mice,” Current Opinion in Immunology, vol. 9, no. 2, pp. 263–275, 1997.

P. Mombaerts, J. Iacomini, R. S. Johnson, K. Herrup, S. Tonegawa, and V. E. Papaioannou, “RAG-1-deficient mice have no mature B and T lymphocytes,” Cell, vol. 68, no. 5, pp. 869–877, 1992.

Y. Shinkai, G. Rathbun, K. P. Lam, E. M. Oltz, V. Stewart, M. Mendelsohn, J. Charron, M. Datta, F. Young, A. M. Stall, and F. W. Alt, “RAG-2-deficient mice lack mature lymphocytes owing to inability to initiate V(D)J rearrangement,” Cell, vol. 68, no. 5, pp. 855–867, 1992.

A. Wolfer, A. Wilson, M. Nemir, H. R. MacDonald, and F. Radtke, “Inactivation of Notch1 impairs VDJβ rearrangement and allows pre-TCR-independent survival of early αβ lineage thymocytes,” Immunity, vol. 16, no. 6, pp. 869–879, 2002.

K. Tanigaki, M. Tsuji, N. Yamamoto, H. Han, J. Tsukada, H. Inoue, M. Kubo, and T. Honjo, “Regulation of αβ/γδ T cell lineage commitment and peripheral T cell responses by Notch/RBP-J signaling,” Immunity, vol. 20, no. 5, pp. 611–622, 2004.

T. M. Schmitt and J. C. Zúñiga-Pflücker, “Induction of T cell development from hematopoietic progenitor cells by delta-like-1 in vitro,” Immunity, vol. 17, no. 6, pp. 749–756, 2002.

J. C. Zúñiga-Pflücker, “T-cell development made simple,” Nature Reviews Immunology, vol. 4, no. 1, pp. 67–72, 2004.

M. Ciofani, T. M. Schmitt, A. Ciofani, A. M. Michie, N. Çuburu, A. Aublin, J. L. Maryanski, and J. C. Zúñiga-Pflücker, “Obligatory role for cooperative signaling by pre-TCR and Notch during thymocyte differentiation,” Journal of Immunology, vol. 172, no. 9, pp. 5230–5239, 2004.

M. Ciofani, G. C. Knowles, D. L. Wiest, H. von Boehmer, and J. C. Zúñiga-Pflücker, “Stage-specific and differential notch dependency at the αβ and γδ T lineage bifurcation,” Immunity, vol. 25, no. 1, pp. 105–116, 2006.

M. Ciofani and J. C. Zúñiga-Pflücker, “Notch promotes survival of pre-T cells at the β-selection checkpoint by regulating cellular metabolism,” Nature Immunology, vol. 6, no. 9, pp. 881–888, 2005.

M. Ciofani and J. C. Zúñiga-Pflücker, “Determining versus T cell development,” Nature Reviews Immunology, vol. 10, no. 9, pp. 657–663, 2010.

T. Kreslavsky, A. I. Garbe, A. Krueger, and H. von Boehmer, “T cell receptor-instructed -αβ versus γδ lineage commitment revealed by single-cell analysis,” Journal of Experimental Medicine, vol. 205, no. 5, pp. 1173–1186, 2008.

T. Kreslavsky, M. Gleimer, and H. von Boehmer, “αβ versus γδ lineage choice at the first TCR-controlled checkpoint,” Current Opinion in Immunology, vol. 22, no. 2, pp. 185–192, 2010.

T. Kreslavsky and H. von Boehmer, “ TCR ligands and lineage commitment,” Seminars in Immunology, vol. 22, no. 4, pp. 214–221, 2010.

A. I. Garbe, A. Krueger, F. Gounari, J. C. Zúñiga-Pflücker, and H. von Boehmer, “Differential synergy of Notch and T cell receptor signaling determines αβ versus γδ lineage fate,” Journal of Experimental Medicine, vol. 203, no. 6, pp. 1579–1590, 2006.

R. Jiang, Y. Lan, H. D. Chapman, C. Shawber, C. R. Norton, D. V. Serreze, G. Weinmaster, and T. Gridley, “Defects in limb, craniofacial, and thymic development in Jagged2 mutant mice,” Genes and Development, vol. 12, no. 7, pp. 1046–1057, 1998.

W. S. Pear, J. C. Aster, M. L. Scott, R. P. Hasserjian, B. Soffer, J. Sklar, and D. Baltimore, “Exclusive development of T cell neoplasms in mice transplanted with bone marrow expressing activated Notch alleles,” Journal of Experimental Medicine, vol. 183, no. 5, pp. 2283–2291, 1996.

A. P. Weng, A. A. Ferrando, W. Lee, J. P. Morris, L. B. Silverman, C. Sanchez-Irizarry, S. C. Blacklow, A. T. Look, and J. C. Aster, “Activating mutations of NOTCH1 in human T cell acute lymphoblastic leukemia,” Science, vol. 306, no. 5694, pp. 269–271, 2004.

Y. W. Lin, R. A. Nichols, J. J. Letterio, and P. D. Aplan, “Notch1 mutations are important for leukemic transformation in murine models of precursor-T leukemia/lymphoma,” Blood, vol. 107, no. 6, pp. 2540–2543, 2006.

J. O'Neil, J. Calvo, K. McKenna, V. Krishnamoorthy, J. C. Aster, C. H. Bassing, F. W. Alt, M. Kelliher, and A. T. Look, “Activating Notch1 mutations in mouse models of T-ALL,” Blood, vol. 107, no. 2, pp. 781–785, 2006.

V. M. Sharma, J. A. Calvo, K. M. Draheim, L. A. Cunningham, N. Hermance, L. Beverly, V. Krishnamoorthy, M. Bhasin, A. J. Capobianco, and M. A. Kelliher, “Notch1 contributes to mouse T-cell leukemia by directly inducing the expression of c-myc,” Molecular and Cellular Biology, vol. 26, no. 21, pp. 8022–8031, 2006.

C. Murre, P. Schonleber McCaw, and D. Baltimore, “A new DNA binding and dimerization motif in immunoglobulin enhancer binding, daughterless, MyoD, and myc proteins,” Cell, vol. 56, no. 5, pp. 777–783, 1989.

X. H. Sun, “Multitasking of helix-loop-helix proteins in lymphopoiesis,” Advances in Immunology, vol. 84, pp. 43–77, 2004.

X. H. Sun and D. Baltimore, “An inhibitory domain of E12 transcription factor prevents DNA binding in E12 homodimers but not in E12 heterodimers,” Cell, vol. 64, no. 2, pp. 459–470, 1991.

I. Engel and C. Murre, “E2A proteins enforce a proliferation checkpoint in developing thymocytes,” The EMBO Journal, vol. 23, no. 1, pp. 202–211, 2004.

P. Matthias and A. G. Rolink, “Transcriptional networks in developing and mature B cells,” Nature Reviews Immunology, vol. 5, no. 6, pp. 497–508, 2005.

G. Bain, I. Engel, E. C. R. Maandag, H. P. J. Te Riele, J. R. Voland, L. L. Sharp, J. Chun, B. Huey, D. Pinkel, and C. Murre, “E2A deficiency leads to abnormalities in αβ T-cell development and to rapid development of T-cell lymphomas,” Molecular and Cellular Biology, vol. 17, no. 8, pp. 4782–4791, 1997.

P. Ordentlich, A. Lin, C. P. Shen, C. Blaumueller, K. Matsuno, S. Artavanis-Tsakonas, and T. Kadesch, “Notch inhibition of E47 supports the existence of a novel signaling pathway,” Molecular and Cellular Biology, vol. 18, no. 4, pp. 2230–2239, 1998.

C. Talora, A. F. Campese, D. Bellavia, M. Pascucci, S. Checquolo, M. Groppioni, L. Frati, H. von Boehmer, A. Gulino, and I. Screpanti, “Pre-TCR-triggered ERK signalling-dependent downregulation of E2A activity in Notch3-induced T-cell lymphoma,” EMBO Reports, vol. 4, no. 11, pp. 1067–1072, 2003.

X. Li, F. Gounari, A. Protopopov, K. Khazaie, and H. von Boehmer, “Oncogenesis of T-ALL and nonmalignant consequences of overexpressing intracellular NOTCH1,” Journal of Experimental Medicine, vol. 205, no. 12, pp. 2851–2861, 2008.

L. Nie, M. Xu, A. Vladimirova, and X. H. Sun, “Notch-induced E2A ubiquitination and degradation are controlled by MAP kinase activities,” The EMBO Journal, vol. 22, no. 21, pp. 5780–5792, 2003.

D. S. Chervinsky, X. F. Zhao, D. H. Lam, M. Ellsworth, K. W. Gross, and P. D. Aplan, “Disordered T-cell development and T-cell malignancies in SCL LMO1 double-transgenic mice: parallels with E2A-deficient mice,” Molecular and Cellular Biology, vol. 19, no. 7, pp. 5025–5035, 1999.

H. L. Hsu, I. Wadman, and R. Baer, “Formation of in vivo complexes between the TAL1 and E2A polypeptides of leukemic T cells,” Proceedings of the National Academy of Sciences of the United States of America, vol. 91, no. 8, pp. 3181–3185, 1994.

S. Herblot, A. M. Steff, P. Hugo, P. D. Aplan, and T. Hoang, “SCL and LMOI alter thymocyte differentiation: inhibition of E2A-HEB function and pre-T α chain expression,” Nature Immunology, vol. 1, no. 2, pp. 138–144, 2000.

J. O'Neil, J. Shank, N. Cusson, C. Murre, and M. Kelliher, “TAL1/SCL induces leukemia by inhibiting the transcriptional activity of E47/HEB,” Cancer Cell, vol. 5, no. 6, pp. 587–596, 2004.

T. H. Rabbitts, “LMO T-cell translocation oncogenes typify genes activated by chromosomal translocations that alter transcription and developmental processes,” Genes and Development, vol. 12, no. 17, pp. 2651–2657, 1998.

C. Grabher, H. von Boehmer, and A. T. Look, “Notch 1 activation in the molecular pathogenesis of T-cell acute lymphoblastic leukaemia,” Nature Reviews Cancer, vol. 6, no. 5, pp. 347–359, 2006.

T. Palomero, K. L. Wei, D. T. Odom, M. L. Sulis, P. J. Real, A. Margolin, K. C. Barnes, J. O'Neil, D. Neuberg, A. P. Weng, J. C. Aster, F. Sigaux, J. Soulier, A. T. Look, R. A. Young, A. Califano, and A. A. Ferrando, “NOTCH1 directly regulates c-MYC and activates a feed-forward-loop transcriptional network promoting leukemic cell growth,” Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 48, pp. 18261–18266, 2006.

A. P. Weng, J. M. Millholland, Y. Yashiro-Ohtani, M. L. Arcangeli, A. Lau, C. Wai, C. Del Bianco, C. G. Rodriguez, H. Sai, J. Tobias, Y. Li, M. S. Wolfe, C. Shachaf, D. Felsher, S. C. Blacklow, W. S. Pear, and J. C. Aster, “c-Myc is an important direct target of Notch1 in T-cell acute lymphoblastic leukemia/lymphoma,” Genes and Development, vol. 20, no. 15, pp. 2096–2109, 2006.

Y. Satoh, I. Matsumura, H. Tanaka, S. Ezoe, H. Sugahara, M. Mizuki, H. Shibayama, E. Ishiko, J. Ishiko, K. Nakajima, and Y. Kanakura, “Roles for c-Myc in self-renewal of hematopoietic stem cells,” Journal of Biological Chemistry, vol. 279, no. 24, pp. 24986–24993, 2004.

A. Klinakis, M. Szaboks, K. Politi, H. Kiaris, S. Artavanis-Tsakonas, and A. Efstratiadis, “Myc is a Notch1 transcriptional target and a requisite for Notch1-induced mammary tumorigenesis in mice,” Proceedings of the National Academy of Sciences of the United States of America, vol. 103, no. 24, pp. 9262–9267, 2006.

L. Girard, Z. Hanna, N. Beaulieu, C. D. Hoemann, C. Simard, C. A. Kozak, and P. Jolicoeur, “Frequent provirus insertional mutagenesis of Notch1 in thymomas of MMTV(D)/myc transgenic mice suggests a collaboration of c-myc and Notch1 for oncogenesis,” Genes and Development, vol. 10, no. 15, pp. 1930–1944, 1996.

T. Sanda, X. Li, A. Gutierrez, Y. Ahn, D. S. Neuberg, J. O'Neil, P. R. Strack, C. G. Winter, S. S. Winter, R. S. Larson, H. von Boehmer, and A. T. Look, “Interconnecting molecular pathways in the pathogenesis and drug sensitivity of T-cell acute lymphoblastic leukemia,” Blood, vol. 115, no. 9, pp. 1735–1745, 2010.

A. P. Weng, Y. Nam, M. S. Wolfe, W. S. Pear, J. D. Griffin, S. C. Blacklow, and J. C. Aster, “Growth suppression of pre-T acute lymphoblastic leukemia cells by inhibition of NOTCH signaling,” Molecular and Cellular Biology, vol. 23, no. 2, pp. 655–664, 2003.

E. Sicinska, I. Aifantis, L. Le Cam, W. Swat, C. Borowski, Q. Yu, A. A. Ferrando, S. D. Levin, Y. Geng, H. von Boehmer, and P. Sicinski, “Requirement for cyclin D3 in lymphocyte development and T cell leukemias,” Cancer Cell, vol. 4, no. 6, pp. 451–461, 2003.

I. Joshi, L. M. Minter, J. Telfer, R. M. Demarest, A. J. Capobianco, J. C. Aster, P. Sicinski, A. Fauq, T. E. Golde, and B. A. Osborne, “Notch signaling mediates G/S cell-cycle progression in T cells via cyclin D3 and its dependent kinases,” Blood, vol. 113, no. 8, pp. 1689–1698, 2009.

C. J. Sherr and J. M. Roberts, “CDK inhibitors: positive and negative regulators of G-phase progression,” Genes and Development, vol. 13, no. 12, pp. 1501–1512, 1999.

L. M. Sarmento, H. Huang, A. Limon, W. Gordon, J. Fernandes, M. J. Tavares, L. Miele, A. A. Cardoso, M. Classon, and N. Carlesso, “Notch1 modulates timing of G-S progression by inducing SKP2 transcription and p27 degradation,” Journal of Experimental Medicine, vol. 202, no. 1, pp. 157–168, 2005.

T. Dohda, A. Maljukova, L. Liu, M. Heyman, D. Grandér, D. Brodin, O. Sangfelt, and U. Lendahl, “Notch signaling induces SKP2 expression and promotes reduction of p27Kip1 in T-cell acute lymphoblastic leukemia cell lines,” Experimental Cell Research, vol. 313, no. 14, pp. 3141–3152, 2007.

S. S. Rao, J. O'Neil, C. D. Liberator, J. S. Hardwick, D. Xudong, T. Zhang, E. Tyminski, J. Yuan, N. E. Kohl, V. M. Richon, L. H. T. van der Ploeg, P. M. Carroll, G. F. Draetta, A. T. Look, P. R. Strack, and C. G. Winter, “Inhibition of NOTCH signaling by gamma secretase inhibitor engages the RB pathway and elicits cell cycle exit in T-cell acute lymphoblastic leukemia cells,” Cancer Research, vol. 69, no. 7, pp. 3060–3068, 2009.

C. J. Sherr, “Tumor surveillance via the ARF-p53 pathway,” Genes and Development, vol. 12, no. 19, pp. 2984–2991, 1998.

C. M. Eischen, J. D. Weber, M. F. Roussel, C. J. Sherr, and J. L. Cleveland, “Disruption of the ARF-Mdm2-p53 tumor suppressor pathway in Myc-induced lymphomagenesis,” Genes and Development, vol. 13, no. 20, pp. 2658–2669, 1999.

L. J. Beverly, D. W. Felsher, and A. J. Capobianco, “Suppression of p53 by Notch in lymphomagenesis: implications for initiation and regression,” Cancer Research, vol. 65, no. 16, pp. 7159–7168, 2005.

S. M. Chan, A. P. Weng, R. Tibshirani, J. C. Aster, and P. J. Utz, “Notch signals positively regulate activity of the mTOR pathway in T-cell acute lymphoblastic leukemia,” Blood, vol. 110, no. 1, pp. 278–286, 2007.

S. K. Mungamuri, X. Yang, A. D. Thor, and K. Somasundaram, “Survival signaling by Notch1: mammalian target of rapamycin (mTOR)-dependent inhibition of p53,” Cancer Research, vol. 66, no. 9, pp. 4715–4724, 2006.

T. Palomero, M. L. Sulis, M. Cortina, P. J. Real, K. Barnes, M. Ciofani, E. Caparros, J. Buteau, K. Brown, S. L. Perkins, G. Bhagat, A. M. Agarwal, G. Basso, M. Castillo, S. Nagase, C. Cordon-Cardo, R. Parsons, J. C. Zúñiga-Pflücker, M. Dominguez, and A. A. Ferrando, “Mutational loss of PTEN induces resistance to NOTCH1 inhibition in T-cell leukemia,” Nature Medicine, vol. 13, no. 10, pp. 1203–1210, 2007.

H. Medyouf, X. Gao, F. Armstrong, S. Gusscott, Q. Liu, A. L. Gedman, L. H. Matherly, K. R. Schultz, F. Pflumio, M. J. You, and A. P. Weng, “Acute T-cell leukemias remain dependent on Notch signaling despite PTEN and INK4A/ARF loss,” Blood, vol. 115, no. 6, pp. 1175–1184, 2010.

E. Coskun, E. K. von der Heide, C. Schlee, A. Kühnl, N. Gökbuget, D. Hoelzer, W.-K. Hofmann, E. Thiel, and C. D. Baldus, “The role of microRNA-196a and microRNA-196b as ERG regulators in acute myeloid leukemia and acute T-lymphoblastic leukemia,” Leukemia Research. In press.

T. Kaddar, W. W. Chien, Y. Bertrand, M. P. Pages, J. P. Rouault, G. Salles, M. Ffrench, and J. P. Magaud, “Prognostic value of miR-16 expression in childhood acute lymphoblastic leukemia relationships to normal and malignant lymphocyte proliferation,” Leukemia Research, vol. 33, no. 9, pp. 1217–1223, 2009.

K. J. Mavrakis, A. L. Wolfe, E. Oricchio, T. Palomero, K. de Keersmaecker, K. McJunkin, J. Zuber, T. James, K. Chang, A. A. Khan, C. S. Leslie, J. S. Parker, P. J. Paddison, W. Tam, A. Ferrando, and H. G. Wendel, “Genome-wide RNA-mediated interference screen identifies miR-19 targets in Notch-induced T-cell acute lymphoblastic leukaemia,” Nature Cell Biology, vol. 12, no. 4, pp. 372–379, 2010.