Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal disorders characterized by night blindness, constricted visual fields, abnormal color vision, and retinal degeneration. The prevalence of RP is approximately 1 per 4000 persons, with more than 1 million affected individuals existing worldwide [
Autosomal dominant RP (adRP) makes up 30 to 40% of the overall RP cases, while mutations in the rhodopsin (
Dominant (or heterozygous)
The frequency of the
To date, only a small number of
The protocol of this study was approved by the Institutional Research Board of The Jikei University School of Medicine and National Hospital Organization Tokyo Medical Center. The protocol adhered to the tenets of the Declaration of Helsinki, and informed consent was obtained from all participants.
Ten unrelated adRP patients from ten Japanese families were recruited for this study. RP diagnosis was based on the visual field, fundus examination, and electroretinogram (ERG) findings. Detailed ophthalmic examinations were conducted in the two families that exhibited the
Pedigrees of the two Japanese families with RP and amino acid sequence alignment of the rhodopsin in different vertebrate species. (a) and (b) The solid squares (male) and circles (female) represent the affected individuals. The proband of each family is indicated by the arrows. (c) The tryptophan residue at position 126 is highly conserved. The conserved amino acids between the different species are shown in the black boxes. The less and least conserved amino acids are highlighted in the gray or white boxes, respectively.
After obtaining venous blood samples from ten adRP patients, genomic DNA was extracted. Whole-exome sequencing was performed in all ten adRP patients using a previously described method [
Sanger sequencing for
The models for molecular dynamics (MD) simulation were generated using two bovine rhodopsin/opsin crystal structures as the templates: the dark-adapted rhodopsin (Protein Data Bank ID: 1U19, chain A) and the ligand-free form opsin (Protein Data Bank ID: 3CAP, chain A). To examine the impact of the p.W126L mutation on protein conformation, 11-
MD simulations were run by the Not (just) Another Molecular Dynamics program [
Patient II-2 (a proband) was a 58-year-old man, who was referred to our hospital because of suspicion of RP. BCVA at his first visit to our hospital was 1.5 (with +1.50 diopter (dpt), cylinder (cyl) −1.25 dpt axial (Ax) 20°) in his right eye and 0.7 (with +1.50 dpt., cyl. −0.50 dpt. Ax. 150°) in his left eye. No abnormalities were found except for slight senile cataracts in the anterior segments and media of both eyes. Intraocular pressures were within the normal range in both eyes. Fundus examination revealed retinal degeneration around the inferior vascular arcade in his right (Figure
Fundus photographs, optical coherence tomography (OCT) images, and visual fields with Goldmann kinetic perimetry (GP) for the two Japanese families with retinitis pigmentosa. (a) Fundus photograph, OCT, and GP in the right eye of patient II-2 in family 1. (b) Fundus photograph, OCT, and GP in the right eye of patient III-1 in family 1. (c) Fundus photograph, OCT, and GP in the right eye of patient II-1 in family 2. (d) Fundus photograph, OCT, and GP in the right eye of patient III-1 in family 2. (e) A fundus autofluorescence image in the right eye of patient III-1 in family 2. See the Results section for details.
Full-field electroretinograms (ERGs). (a) and (b) ERG of both patient II-2 (a) and patient III-1 (b) in family 1 shows diminished amplitudes of the rod, standard combined, cone, and 30-Hz flicker responses. (c) ERG of patient II-1 in family 2 is nonrecordable for the rod, standard combined and 30-Hz flicker responses.
Patient III-1 was a 31-year-old woman, who reported night blindness. The clinical findings of patient III-1 were essentially similar to those found for patient II-2. BCVA at her first visit to our hospital was 1.5 (with cyl. −0.50 dpt. Ax. 160°) in her right eye and 1.2 (with cyl. −1.00 dpt. Ax. 35°) in her left eye. There were no abnormalities found in the anterior segments and media of either eye. Intraocular pressures were within the normal range in both eyes. Fundus examination revealed retinal degeneration in the nasal area of her right (Figure
Patient II-1 (a proband) was a 35-year-old woman referred to our hospital for assessment of a causative gene for her RP. BCVA was 0.7 (with no correction) in her right eye and 0.6 (with cyl. −1.75 dpt. Ax. 30°) in her left eye. There were no abnormalities found in the anterior segments and media of either eye. Intraocular pressures were within the normal range in both eyes. Fundus examination revealed diffuse retinal degeneration and intraretinal pigment deposits with a bone-spicule configuration around the vascular arcade to the periphery of her right (Figure
Patient III-1 was a 14-year-old boy, who was first found to have night blindness at 6 years of age. At the age of 11, a dark-adapted single flash ERG performed at another hospital showed that there were reduced responses in both eyes (data not shown). BCVA was 1.2 (with +6.50 dpt., cyl. −2.00 dpt. Ax. 180°) in his right eye and 1.0 (with +7.00 dpt., cyl. −1.50 dpt. Ax. 10°) in his left eye. Fundus examination revealed retinal degeneration of the inferotemporal areas in his right (Figure
The obtained sequence data were analyzed in accordance with the filtering steps discussed in the Material and Methods section. Table
The rare variants found in the two Japanese families with
JU0678-062JIKEI | Gene | Gene Bank ID | Exon | Nucleotide change | AA change | State | SNP ID | |
---|---|---|---|---|---|---|---|---|
Chrom | Position | |||||||
2 | 202498104 |
|
NM_001044385 | 5 | c.325C>T | p.R109X | Hetero | |
3 | 129249734 |
|
NM_000539 | 2 | c.377G>T | p.W126L | Hetero | |
4 | 6290790 |
|
NM_006005 | 4 | c.392T>G | p.V131G | Hetero | |
4 | 6302786 |
|
NM_006005 | 8 | c.1264G>T | p.A422S | Hetero | |
7 | 33427676 |
|
NM_198428 | 19 | c.2035C>T | p.R679W | Hetero | |
8 | 10480476 |
|
NM_178857 | 2 | c.236G>A | p.R79H | Hetero | |
14 | 21792816 |
|
NM_020366 | 14 | c.1802C>T | p.S601L | Hetero | rs3748360 |
16 | 49670817 |
|
NM_015069 | 4 | c.2243_2245del | p.748_749del | Hetero | |
|
||||||||
JU0575-037JIKEI | Gene | Gene Bank ID | Exon | Nucleotide change | AA change | State | SNP ID | |
Chrom | Position | |||||||
|
||||||||
1 | 94476477 |
|
NM_000350 | 40 | c.5593C>T | p.H1865Y | Hetero | rs201707267 |
2 | 112751865 |
|
NM_006343 | 9 | c.1334G>A | p.R445Q | Hetero | rs202242962 |
3 | 129252550 |
|
NM_000539 | 5 | c.1036G>C | p.A346P | Hetero | |
11 | 17531103 |
|
NM_153676 | 18 | c.1813A>C | p.I605L | Hetero | |
16 | 16291933 |
|
NM_001171 | 10 | c.1283A>G | p.N428S | Hetero | rs201880691 |
Chrom = choromosome, AA = amino acid, Homo = homozygous, and Hetero = heterozygous.
For the cosegregation analysis, we investigated whether six of the family 1 members and four of the family 2 members had either the p.W126L or the p.A346P mutation. Our results revealed there was complete cosegregation of each mutation with the RP phenotype in each family (Figures
By using energy minimization and MD simulations, we investigated the possible effects of the p.W126L mutation on the structure of the human opsin moiety that was represented by either the dark-adapted like (high affinity for 11-
Projected view from the cytoplasmic side of the backbone before and after the 1 ns molecular dynamics (MD) simulations. The side chain of the position 126 in each model is shown by the bold sticks in the corresponding colors. (a) Dark-adapted like models. Blue: wild-type after 1 ns MD; green: wild-type before MD. (b) Dark-adapted like models. Red: W126L after 1 ns MD; green: W126L before MD. (c) Light-adapted like models. Blue: wild-type after 1 ns MD; green: wild-type before MD. (d) Light-adapted like models. Red: W126L after 1 ns MD; green: W126L before MD.
In this study, we identified two
For the cosegregation analysis, further validation by Sanger sequencing in other family members demonstrated there was complete cosegregation of each mutation with the RP phenotype (Figures
With regard to the phenotypes of our patients, the p.W126L (family 1) and p.A346P (family 2) mutations are likely to be associated with sector RP and classic RP, respectively. However, it should be noted that patient III-1 (family 2) was not diagnosed with either classic or sector RP, as patient III-1 exhibited an early stage of RP. The phenotypes of patient II-1 (family 2) were similar to those previously reported for a patient of European descent who carried the p.A346P mutation and exhibited classic RP [
When trying to diagnose classic or sector RP, it is highly important that one understands the severity and prognosis of
Clinical summary of Japanese patients with autosomal dominant retinitis pigmentosa with heterozygous
Patient, gender | Type of adRP | Age at examination | Mutation | BCVA | Electroretinograms (ERGs) | Reference | Notes | ||
---|---|---|---|---|---|---|---|---|---|
R | L | Flash (rod plus cone) ERG | Full-field ERG | ||||||
Case |
Classic | 44 | p.P347L | 0.5 | 0.66 | NR | NR in 30-Hz flicker | [ |
Cataract |
Case |
Classic | 20 | p.P347L | 1.0 | 1.0 | NR | NR in 30-Hz flicker | [ |
|
Case |
ND | 11 | p.P347L | 1.0 | 1.0 | Reduced | Reduced in 30-Hz flicker | [ |
|
Case |
Classic | 75 | p.P347L | LP | LP | NR | NR in 30-Hz flicker | [ |
Severe cataract |
III-6, M | Sector | 49 | p.T17M | 0.2 | 0.2 | ND | Reduced in both rods and cones | [ |
B-CME, L-CNV |
Proband, F | Classic | 39 | p.E181K | 0.1 | 0.1 | ND | NR in rods, reduced in cones | [ |
B-CME |
III-5, F | Sector | 52 | p.N15S | ND | ND | ND | ND | [ |
|
II-2, M | Sector | 66 | p.G106R | 0.04 | 0.5 | ND | Reduced in both rods and cones | [ |
R-CME |
III-1, F | Sector | 44 | p.G106R | 1.2 | 1.2 | ND | Reduced in rods, normal in cones | [ |
|
III-2, F | Sector | 40 | p.G106R | 1.2 | 1.2 | ND | Reduced in rods, normal in cones | [ |
|
II-2 (FN.1), M | Sector | 58 | p.W126L | 1.5 | 0.7 | ND | Reduced in both rods and cones | Current study | |
III-1 (FN.1), F | Sector | 31 | p.W126L | 1.5 | 1.2 | ND | Reduced in both rods and cones | Current study | |
II-1 (FN.2), F | Classic | 35 | p.A346P | 0.7 | 0.6 | ND | NR in both rods and cones | Current study | |
III-1 (FN.2), M | ND | 14 | p.A346P | 1.2 | 1.5 | Reduced | ND | Current study |
BCVA = decimal best-corrected visual acuity; R = right eye; L = left eye; B = both eyes; M = male; F = female; FN = family number; ND = not described or not done; NR = nonrecordable; LP = light perception; CNV = choroidal neovascularization; and CME = cystoid macular edema.
In conclusion, we identified two
The authors declare there are no conflict of interests.
This study was supported by the Grants to Takeshi Iwata from the Ministry of Health, Labor and Welfare of Japan (13803661), to Masakazu Akahori and Takaaki Hayashi from the Ministry of Education, Culture, Sports, Science and Technology of Japan (Grant-in-Aid for Scientific Research C, 25462744 and 25462738), to Takaaki Hayashi from the Vehicle Racing Commemorative Foundation, and to Masaaki Furuno from the research Grant for RIKEN Omics Science Center MEXT. The authors wish to acknowledge RIKEN GeNAS for the sequencing of the exome enriched libraries using the Illumina HiSeq2000.