The Structural Abnormalities Are Deeply Involved in the Cause of RPGRIP1-Related Retinal Dystrophy in Japanese Patients.

Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy. RPGRIP1-related LCA accounts for 5-6% of LCA. We performed whole-exome sequencing and whole-genome sequencing (WGS) on 29 patients with clinically suspected LCA and examined ophthalmic findings in patients with biallelic pathogenic variants of RPGRIP1. In addition to five previously reported cases, we identified five cases from four families with compound heterozygous RPGRIP1 variants using WGS. Five patients had null variants comprising frameshift variants, an Alu insertion, and microdeletions. A previously reported 1339 bp deletion involving exon 18 was found in four cases, and the deletion was relatively prevalent in the Japanese population (allele frequency: 0.002). Microdeletions involving exon 1 were detected in four cases. In patients with RPGRIP1 variants, visual acuity remained low, ranging from light perception to 0.2, and showed no correlation with age. In optical coherence tomography images, the ellipsoid zone (EZ) length decreased with age in all but one case of unimpaired EZ. The retinal structure was relatively preserved in all cases; however, there were cases with great differences in visual function compared to their siblings and a 56-year-old patient who still had a faint EZ line. Structural abnormalities may be important genetic causes of RPGRIP1-related retinal dystrophy in Japanese patients, and WGS was useful for detecting them.

A case of siblings with juvenile retinitis pigmentosa associated with NEK1 gene variants.

BACKGROUND: Axial spondylometaphyseal dysplasia(axial SMD) is associated with early-onset retinal dystrophy and various skeletal dysplasias of varying severity. NEK1 is the causative gene for short rib polydactyly syndrome and axial SMD. Here, we report a case of siblings with juvenile retinitis pigmentosa (RP) and NEK1 variants not associated with systemic disorders. MATERIALS AND METHODS: The patients were a 7-year-old-girl and a 9-year-old boy with RP, who were followed for 9 years. Whole exome sequencing (WES) was performed on the siblings and their parents, who were not consanguineous. RESULTS: The corrected visual acuity of the girl and the boy at first visit was binocular 20/63 and 20/100 OD and 20/63 OS, respectively. The siblings had narrowing of retinal blood vessels and retinal pigment epithelium atrophy in the fundus and showed an extinguished pattern in electroretinogram. On optical coherence tomography, there was a mottled ellipsoid band with progressive loss in the outer macular, the edges of which corresponded to the ring of hyperautofluorescence on fundus autofluorescence imaging. The siblings showed progressive visual field constriction. Radiological examination did not reveal any skeletal abnormalities. We identified two rare heterozygous NEK1 variants in the patients: c.240 G>A; p.(M80I) and c.634_639dup;p.(V212_L213dup). Heterozygous variants were recognized in the father and mother, respectively. According to the guidelines of the American College of Medical Genetics and Genomics, both variants were classified as likely pathogenic. CONCLUSION: This is the first report of RP patients with NEK1 variants not associated with skeletal abnormalities.

Maternal Uniparental Isodisomy of Chromosome 4 and 8 in Patients with Retinal Dystrophy: SRD5A3-Congenital Disorders of Glycosylation and RP1-Related Retinitis Pigmentosa.

PURPOSE: Uniparental disomy (UPD) is a rare chromosomal abnormality. We performed whole-exosome sequencing (WES) in cases of early-onset retinal dystrophy and identified two cases likely caused by UPD. Herein, we report these two cases and attempt to clarify the clinical picture of retinal dystrophies caused by UPD. METHODS: WES analysis was performed for two patients and their parents, who were not consanguineous. Functional analysis was performed in cases suspected of congenital disorders of glycosylation (CDG). We obtained clinical case data and reviewed the literature. RESULTS: In case 1, a novel c.57G>C, p.(Trp19Cys) variant in SRD5A3 was detected homozygously. Genetic analysis suggested a maternal UPD on chromosome 4, and functional analysis confirmed CDG. Clinical findings showed early-onset retinal dystrophy, intellectual disability, and epilepsy. In case 2, an Alu insertion (c.4052_4053ins328, p.[Tyr1352Alafs]) in RP1 was detected homozygously. Maternal UPD on chromosome 8 was suspected. The clinical picture was consistent with RP1-related retinitis pigmentosa. Although the clinical features of retinal dystrophy by UPD may vary, most cases present with childhood onset. CONCLUSIONS: There have been limited reports of retinal dystrophy caused by UPD, suggesting that it is rare. Genetic counseling may be encouraged in pediatric cases of retinal dystrophy.

Retinitis pigmentosa with optic neuropathy and COQ2 mutations: A case report.

PURPOSE: To report the clinical findings of a Japanese patient presenting with retinitis pigmentosa (RP) together with optic neuropathy and COQ2 mutations. OBSERVATIONS: The patient had experienced night blindness and photophobia since his 20s. At 27 years of age, he experienced sudden vision loss in his left eye. We performed comprehensive ophthalmic examinations. Trio-based whole-exome sequencing was performed to identify the candidate variants, which were confirmed by Sanger sequencing. Fundus examination revealed typical RP findings with an additional Leber hereditary optic neuropathy (LHON). The patient's visual acuity was severely affected, and the visual field showed central scotoma. Electroretinograms were non-recordable under scotopic condition and showed reduced response under photopic conditions. Genetic analysis revealed compound heterozygous COQ2 variants in the patient: c.469C > T [p.(P157S], and c.518G > A [p.(R173H)]. Co-segregation analysis in the unaffected parents confirmed that the two variants were in trans. During the 4-year follow-up period, his visual acuity and central scotoma gradually improved. CONCLUSION: This is the first description of a case of RP together with LHON harboring COQ2 mutations. Additional cases are necessary to more accurately determine the clinical course and mutation spectrum in this condition.

Genotype-Phenotype Correlations in RP1-Associated Retinal Dystrophies: A Multi-Center Cohort Study in JAPAN.

BACKGROUND: Little is known about genotype-phenotype correlations of RP1-associated retinal dystrophies in the Japanese population. We aimed to investigate the genetic spectrum of RP1 variants and provide a detailed description of the clinical findings in Japanese patients. METHODS: In total, 607 patients with inherited retinal diseases were examined using whole-exome/whole-genome sequencing (WES/WGS). PCR-based screening for an Alu element insertion (c.4052_4053ins328/p.Tyr1352AlafsTer9) was performed in 18 patients with autosomal-recessive (AR)-retinitis pigmentosa (RP) or AR-cone dystrophy (COD)/cone-rod dystrophy (CORD), including seven patients with heterozygous RP1 variants identified by WES/WGS analysis, and 11 early onset AR-RP patients, in whom no pathogenic variant was identified. We clinically examined 25 patients (23 families) with pathogenic RP1 variants, including five patients (five families) with autosomal-dominant (AD)-RP, 13 patients (11 families) with AR-RP, and seven patients (seven families) with AR-COD/CORD. RESULTS: We identified 18 pathogenic RP1 variants, including seven novel variants. Interestingly, the Alu element insertion was the most frequent variant (32.0%, 16/50 alleles). The clinical findings revealed that the age at onset and disease progression occurred significantly earlier and faster in AR-RP patients compared to AD-RP or AR-COD/CORD patients. CONCLUSIONS: Our results suggest a genotype-phenotype correlation between variant types/locations and phenotypes (AD-RP, AR-RP, and AR-COD/CORD), and the Alu element insertion was the most major variant in Japanese patients with RP1-associated retinal dystrophies.

Regional differences in genes and variants causing retinitis pigmentosa in Japan.

PURPOSE: To investigate the regional differences in the genes and variants causing retinitis pigmentosa (RP) in Japan STUDY DESIGN: Retrospective multicenter study METHODS: In total, 1204 probands of each pedigree clinically diagnosed with nonsyndromic RP were enrolled from 5 Japanese facilities. The regions were divided into the Tohoku region, the Kanto and Chubu regions, and the Kyushu region according to the location of the hospitals where the participants were enrolled. We compared the proportions of the causative genes and the distributions of the pathogenic variants among these 3 regions. RESULTS: The proportions of genetically solved cases were 29.4% in the Tohoku region (n = 500), 29.6% in the Kanto and Chubu regions (n = 196), and 29.7% in the Kyushu region (n = 508), which did not differ statistically (P = .99). No significant regional differences in the proportions of each causative gene in genetically solved patients were observed after correction by multiple testing. Among the 29 pathogenic variants detected in all 3 regions, only p.(Pro347Leu) in RHO was an autosomal dominant variant; the remaining 28 variants were found in autosomal recessive genes. Conversely, 78.6% (275/350) of the pathogenic variants were detected only in a single region, and 6 pathogenic variants (p.[Asn3062fs] in EYS, p.[Ala315fs] in EYS, p.[Arg872fs] in RP1, p.[Ala126Val] in RDH12, p.[Arg41Trp] in CRX, and p.[Gly381fs] in PRPF31) were frequently found in ≥ 4 patients in the single region. CONCLUSION: We observed region-specific pathogenic variants in the Japanese population. Further investigations of causative genes in multiple regions in Japan will contribute to the expansion of the catalog of genetic variants causing RP.

Analysis of IKBKG/NEMO gene in five Japanese cases of incontinentia pigmenti with retinopathy: fine genomic assay of a rare male case with mosaicism.

Incontinentia pigmenti (IP) is an X-linked dominant genodermatosis that is usually lethal in utero in males, though exceptionally they survive very rarely either with Klinefelter syndrome or a somatic mosaicism. We performed genomic analysis of five Japanese IP patients including a rare boy case, all of whom were definite cases with retinopathy. Four patients including the boy revealed the recurrent exon 4-10 deletion in the sole known causative gene IKBKG/NEMO, which was confirmed by various specific PCR techniques. The boy's saliva DNA showed a mosaicism consisting of the deletion and intact alleles, but his blood DNA did not. Relative quantification analysis of the real-time PCR data by ∆∆CT method estimated the mosaicism ratio of the boy's saliva as 45:55 (deletion:intact). A genomic analysis for the recurrent deletion at the nucleotide sequence level has been performed directly using patient's DNA and it has been clarified that the breakpoints are within two MER67B repeats in the intron 3 and downstream of exon 10. This is the first report of the assay for the mosaicism ratio of a male IP case with a recurrent exon 4-10 deletion of IKBKG/NEMO and the sequencing analysis of the breakpoints of the recurrent deletion directly using patient's sample.

Usefulness of handheld electroretinogram system for diagnosing blue-cone monochromatism in children.

PURPOSE: To report the diagnosis of three childhood patients with blue-cone monochromatism (BCM) using S-cone electroretinograms (ERG) recorded with RETeval® Complete. STUDY DESIGN: Prospective clinical study. METHODS: We examined three boys initially suspected of having rod monochromatism. S-cone ERG was performed with red background and blue flashed light stimulation using two different intensities: 0.25 cd × s/m2 and 1 cd × s/m2. RESULTS: Case 1 was a 12-year-old boy with a visual acuity of 0.1 OU. Case 2 was an 8-year-old boy with a visual acuity of 0.3 OD and 0.2 OS. Both cases showed a myopic fundus and nystagmus without any other ocular abnormalities. Case 3 was a 6-year-old boy with a visual acuity of 0.3 OD and 0.4 OS. He also showed myopic fundus changes, but nystagmus was not observed. Rod and maximal responses recorded with RETeval® were likely to be within normal range; however, cone responses were absent in all cases. S-cone ERGs showed positive responses at 40 ms with 0.25 cd × s/m2 intensity in Case 2, and at approximately 30-40 ms with 1.0 cd × s/m2 intensity in all three cases. These ERG findings led to a diagnosis of BCM. CONCLUSIONS: S-cone ERG of RETeval® was helpful in diagnosing with minimal invasion BCM in childhood patients.

A case of childhood glaucoma with a combined partial monosomy 6p25 and partial trisomy 18p11 due to an unbalanced translocation.

Background: Chromosomal deletion involving the 6p25 region results in a clinically recognizable syndrome characterized by anterior eye chamber anomalies with risk of glaucoma and non-ocular malformations (6p25 deletion syndrome). We report a newborn infant case of childhood glaucoma with a combination of partial monosomy 6p25 and partial trisomy 18p11 due to an unbalanced translocation.Materials and methods: The patient was a 0-year-old girl. Both eyes showed aniridia and left eye Peters anomaly with multiple malformations. To identify the chromosomal aberrations in the patient with clinically suspected 6p25 deletion syndrome, we performed cytogenetic analysis (G-banding and multicolor fluorescent in-situ hybridization) and array-based comparative genomic hybridization (array-CGH) analysis.Results: Cytogenetic analyses revealed a derivative chromosome 6 with its distal short arm replaced by an extra copy of the short arm of chromosome 18. Array-CGH analysis detected a 4.6-Mb deletion at 6pter to 6p25.1 and 8.9-Mb duplication at 18pter to 18p11.22. To determine the breakpoint of the unbalanced rearrangement at the single-base level, we performed a long-range PCR for amplifying the junctional fragment of the translocation breakpoint. By sequencing the junctional fragment, we defined the unbalanced translocation as g.chr6:pter_4594783delinschr18:pter_8911541.Conclusions: A phenotype corresponding to combined monosomy 6p25 and trisomy 18p11 presented as childhood glaucoma associated with non-acquired (congenital) ocular anomalies consist of aniridia and Peters anomaly and other systemic malformations. To the best of our knowledge, this is the first report which demonstrated the breakpoint sequence of an unbalanced translocation in a Japanese infant with childhood glaucoma.

Long-term observation of a Japanese mucolipidosis IV patient with a novel homozygous p.F313del variant of MCOLN1.

Mucolipidosis type IV (MLIV) is an autosomal recessively inherited lysosomal storage disorder characterized by progressive psychomotor delay and retinal degeneration that is associated with biallelic variants in the MCOLN1 gene. The gene, which is expressed in late endosomes and lysosomes of various tissue cells, encodes the transient receptor potential channel mucolipin 1 consisting of six transmembrane domains. Here, we described 14-year follow-up observation of a 4-year-old Japanese male MLIV patient with a novel homozygous in-frame deletion variant p.(F313del), which was identified by whole-exome sequencing analysis. Neurological examination revealed progressive psychomotor delay, and atrophy of the corpus callosum and cerebellum was observed on brain magnetic resonance images. Ophthalmologically, corneal clouding has remained unchanged during the follow-up period, whereas optic nerve pallor and retinal degenerative changes exhibited progressive disease courses. Light-adapted electroretinography was non-recordable. Transmission electron microscopy of granulocytes revealed characteristic concentric multiple lamellar structures and an electron-dense inclusion in lysosomes. The in-frame deletion variant was located within the second transmembrane domain, which is of putative functional importance for channel properties.

Novel biallelic splice-site BBS1 variants in Bardet-Biedle syndrome: a case report of the first Japanese patient.

PURPOSE: To report the clinical and genetic features of a 9-year-old female Japanese patient with Bardet-Biedl syndrome (BBS). METHODS: Genetic analysis using whole-exome sequencing (WES) was performed for the patient and her parents to identify disease-causing variants. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to investigate the impact of splice-site variants. Comprehensive ophthalmic and systemic examinations, including electroretinography (ERG), were performed. RESULTS: In the patient, WES identified novel compound heterozygous splice-site variants (c.124+2T>G and c.723+2T>G) in the BBS1 gene, and RT-PCR revealed skipping of exons 2 and 8 (p.N17AfsX56 and p.T198_K241del). Each parent had one of the variants. Ophthalmologically, the patient's decimal best-corrected visual acuity was 0.6 in the right eye and 0.4 in the left eye. Funduscopy revealed no apparent retinal degeneration or narrowed blood vessels in the periphery, but macular abnormalities were found on fundus autofluorescence imaging and optical coherence tomography images. Unexpectedly, non-recordable responses in rod ERG were found, with a non-recordable response of the right eye and an extremely reduced and delayed a-wave of the left eye in standard ERG, non-recordable responses in cone ERG, and extremely decreased responses in 30 Hz flicker ERG. Finally, the patient fulfilled four primary features of BBS diagnostic criteria: rod-cone dystrophy, polydactyly, central obesity, and learning disabilities, being diagnosed with BBS. CONCLUSIONS: This is the first report of a BBS patient with biallelic splice-site BBS1 variants in the Japanese population. Disparity between funduscopic and ERG findings may be a feature of BBS1-associated rod-cone dystrophy.

Coexistence of GNAT1 and ABCA4 variants associated with Nougaret-type congenital stationary night blindness and childhood-onset cone-rod dystrophy.

PURPOSE: A single variant (p.G38D) in the GNAT1 gene, encoding the rod-specific transducin α-subunit in phototransduction, has been reported only in one French family with Nougaret-type autosomal dominant congenital stationary night blindness (CSNB). We identified a Japanese family with Nougaret-type CSNB and cone-rod dystrophy (CORD). METHODS: Five patients with CSNB and two patients with childhood-onset CORD were recruited. We performed a comprehensive ophthalmic examination including electroretinography (ERG). Disease-causing variants were identified by whole exome sequencing, with candidates confirmed by Sanger sequencing in nine family members. RESULTS: The GNAT1 variant (p.G38D) was identified in all four CSNB patients, whereas the two CORD patients carried biallelic truncated known ABCA4 variants as well as the GNAT1 variant. Clinically, no remarkable findings were observed in fuduscopy, fundus autofluorescence, or optical coherence tomography images from the CSNB patients. No response was detectable by rod ERG. The a-waves of standard and bright flash ERG were delayed and broadened rather than biphasic, and b/a-wave amplitude ratio was negative. Cone and 30-Hz flicker responses were normal, and overall, the ERG findings were compatible with previous descriptions of Nougaret-type CSNB. ERG of the CORD patients with macular atrophy showed non-recordable rod response and severely decreased standard flash, cone and 30-Hz flicker responses. CONCLUSIONS: This is the second report of a Nougaret-type CSNB family with the GNAT1 variant. Our novel findings suggest that coexistence of the GNAT1 and biallelic ABCA4 variants is associated with an overlapping phenotype with both Nougaret-type CSNB and CORD.

Retinal structure in Leber's congenital amaurosis caused by RPGRIP1 mutations.

This study aimed to evaluate retinal structure in the early stage of Leber's congenital amaurosis (LCA) caused by RPGRIP1 mutations. Four patients from two families were included. Case 1 was a 13-year-old girl, cases 2 and 3 were 7-year-old monozygotic twin brothers of case 1, and case 4 was a 17-year-old boy. Comprehensive ophthalmic examinations were performed, including visual acuity measurements, perimetry, electroretinography (ERG), and optical coherence tomography (OCT). To identify potential pathogenic mutations, 74 genes known to cause retinitis pigmentosa or LCA were assessed using targeted next-generation sequencing. OCT showed photoreceptor outer nuclear layer (ONL) thinning in all patients. The lamellar structure was retained in all patients, whereas the ellipsoid zone was extinguished in cases 1, 2, and 3. In case 4, the ellipsoid zone was maintained at 9 years of age but became blurred at 17 years of age. In case 1, OCT indicated slight photoreceptor ONL thinning during the period between 7 and 11 years of age. Mutation analysis revealed RPGRIP1 mutations as the cause for autosomal recessive LCA in all patients. Photoreceptor ONL on OCT is relatively well preserved in the early stage of LCA caused by RPGRIP1 mutations.

Phenotypic Features of Oguchi Disease and Retinitis Pigmentosa in Patients with S-Antigen Mutations: A Long-Term Follow-up Study.

PURPOSE: To present phenotypic features of 22 patients with S-antigen (SAG) mutations. DESIGN: Retrospective cohort study. PARTICIPANTS: Twenty-one Japanese patients from 16 families with a homozygous c.924delA mutation and 1 patient with a homozygous c.636delT mutation in the SAG gene. METHODS: Clinical records on symptoms; best-corrected visual acuity; and Goldmann perimetry, fundus photography, fundus autofluorescence (FAF), OCT, and electroretinography results were reviewed. MAIN OUTCOME MEASURES: Best-corrected visual acuity, Goldmann perimetry results, imaging findings, and electroretinography results. RESULTS: Ten patients had Oguchi disease and 12 had retinitis pigmentosa (RP) with mean follow-up periods of 13.8 and 10.2 years, respectively. Retinitis pigmentosa patients were older (mean age, 56.0 years) than those with Oguchi disease (mean age, 22.1 years; P < 0.001) at the initial visit. Night blindness noted in childhood was the most common initial symptom for both Oguchi disease (80.0%) and RP (91.7%) patients. Best-corrected visual acuity in the logarithm of the minimum angle of resolution (logMAR) was well preserved in Oguchi disease patients (mean, 0.02 logMAR in both eyes) but reduced in most RP patients (mean, 1.32 logMAR [right eye] and 1.35 logMAR [left eye]). Similarly, the visual field in the retinal area was preserved in Oguchi disease patients (mean, 677 mm2 right eye and 667 mm2 left eye) and reduced in RP patients (mean, 369 mm2 right eye and 294 mm2 left eye). Fundus images revealed a characteristic golden sheen with no retinal degeneration in Oguchi disease patients, excluding 2 with macular degeneration detected by FAF, OCT, or both and 1 with mild retinal degeneration confirmed by OCT and fluorescein angiography. Pigmentary retinal degeneration most evident posteriorly was observed in RP patients, accompanied by a characteristic golden sheen in 12 of 14 patients undergoing ultra-widefield fundus imaging. OCT showed disrupted macular structure, and FAF revealed variable hypofluorescence. Electroretinography identified absent rod responses in both diseases, along with relative preservation of cone responses in Oguchi disease patients. Three patients showed progressive loss of the golden sheen based on fundus images, including 1 who demonstrated RP 26 years after the initial diagnosis of Oguchi disease. CONCLUSIONS: Retinitis pigmentosa with SAG mutations often shows a characteristic golden sheen surrounding posterior pigmentary retinal degeneration. Oguchi disease can show progressive degeneration in adulthood, rarely resulting in RP.

Genetic characteristics of retinitis pigmentosa in 1204 Japanese patients.

BACKGROUND: The genetic profile of retinitis pigmentosa (RP) in East Asian populations has not been well characterised. Therefore, we conducted a large-scale sequencing study to investigate the genes and variants causing RP in a Japanese population. METHODS: A total of 1209 Japanese patients diagnosed with typical RP were enrolled. We performed deep resequencing of 83 known causative genes of RP using next-generation sequencing. We defined pathogenic variants as those that were putatively deleterious or registered as pathogenic in the Human Gene Mutation Database or ClinVar database and had a minor allele frequency in any ethnic population of ≤0.5% for recessive genes or ≤0.01% for dominant genes as determined using population-based databases. RESULTS: We successfully sequenced 1204 patients with RP and determined 200 pathogenic variants in 38 genes as the cause of RP in 356 patients (29.6%). Variants in six genes (EYS, USH2A, RP1L1, RHO, RP1 and RPGR) caused RP in 65.4% (233/356) of those patients. Among autosomal recessive genes, two known founder variants in EYS [p.(Ser1653fs) and p.(Tyr2935*)] and four East Asian-specific variants [p.(Gly2752Arg) in USH2A, p.(Arg658*) in RP1L1, p.(Gly2186Glu) in EYS and p.(Ile535Asn) in PDE6B] and p.(Cys934Trp) in USH2A were found in ≥10 patients. Among autosomal dominant genes, four pathogenic variants [p.(Pro347Leu) in RHO, p.(Arg872fs) in RP1, p.(Arg41Trp) in CRX and p.(Gly381fs) in PRPF31] were found in ≥4 patients, while these variants were unreported or extremely rare in both East Asian and non-East Asian population-based databases. CONCLUSIONS: East Asian-specific variants in causative genes were the major causes of RP in the Japanese population.

A Japanese family with cone-rod dystrophy of delayed onset caused by a compound heterozygous combination of novel CDHR1 frameshift and known missense variants.

We analyzed two siblings in a Japanese family with delayed onset cone-rod dystrophy (CRD) using whole-exome sequencing. A novel frameshift c.1106dup (p.H370Afs*17) variant and a known missense c.2027 T > A (p.I676N) variant in CDHR1 were identified. Both patients shared the same variants, although they displayed a significant difference in disease severity. A meta-analysis of the relationship between the severity and the variant type was performed using the reported cases in the literature and did not reveal a definitive correlation.

X-linked Retinitis Pigmentosa in Japan: Clinical and Genetic Findings in Male Patients and Female Carriers.

X-linked retinitis pigmentosa (XLRP) is a type of severe retinal dystrophy, and female carriers of XLRP demonstrate markedly variable clinical severity. In this study, we aimed to elucidate the clinical findings of male patients with and female carriers of XLRP in a Japanese cohort and demonstrate the genetic contribution. Twelve unrelated families (13 male patients, 15 female carriers) harboring pathogenic mutations in RPGR or RP2 were included, and comprehensive ophthalmic examinations were performed. To identify potential pathogenic mutations, targeted next-generation sequencing was employed. Consequently, we identified 11 pathogenic mutations, of which five were novel. Six and five mutations were detected in RPGR and RP2, respectively. Only one mutation was detected in ORF15. Affected male patients with RP2 mutations tended to have lower visual function than those with RPGR mutations. Female carriers demonstrated varying visual acuities and visual fields. Among the female carriers, 92% had electroretinographical abnormalities and 63% had a radial autofluorescent pattern, and the carriers who had higher myopia showed worse visual acuity and more severe retinal degeneration. Our results expand the knowledge of the clinical phenotypes of male patients with and female carriers of XLRP and suggest the possibility that RP2 mutations are relatively highly prevalent in Japan.

Clinical and genetic findings of a Japanese patient with RP1-related autosomal recessive retinitis pigmentosa.

PURPOSE: This study reports the ophthalmic and genetic findings of a Japanese patient with autosomal recessive retinitis pigmentosa (arRP) caused by retinitis pigmentosa 1 (RP1) mutations. PATIENT AND METHODS: The 34-year-old female patient and her unaffected parents underwent comprehensive ophthalmic examinations, including visual acuity measurements, perimetry, electroretinography (ERG), and optical coherence tomography. Fundus autofluorescence was also evaluated in the patient. To identify potential pathogenic variants, 111 inherited eye disease genes were examined by targeted next-generation sequencing. RESULTS: The patient had night blindness from the first decade of her life. Fundus examination revealed typical RP findings with additional macular degeneration. Her visual field and acuity were severely affected, and ERG scans showed undetectable responses. Bioinformatics analysis revealed two heterozygous potentially pathogenic variants in RP1 in the patient, one of which is novel. Co-segregation analysis in the unaffected parents confirmed that the two variants were in trans. The parents were both carriers of one RP1 variant but did not show any visual symptoms. Therefore, the identified compound heterozygous variants were proposed as the probable arRP-causing mutations in the family. CONCLUSION: This is the first description of a Japanese patient with arRP caused by RP1 mutations. Additional data are necessary to more accurately determine the clinical course and mutation spectrum in patients with RP1-related arRP.

Molecular Diagnosis of 34 Japanese Families with Leber Congenital Amaurosis Using Targeted Next Generation Sequencing.

Leber congenital amaurosis (LCA) is a genetically and clinically heterogeneous disease, and represents the most severe form of inherited retinal dystrophy (IRD). The present study reports the mutation spectra and frequency of known LCA and IRD-associated genes in 34 Japanese families with LCA (including three families that were previously reported). A total of 74 LCA- and IRD-associated genes were analysed via targeted-next generation sequencing (TS), while recently discovered LCA-associated genes, as well as known variants not able to be screened using this approach, were evaluated via additional Sanger sequencing, long-range polymerase chain reaction, and/or copy number variation analyses. The results of these analyses revealed 30 potential pathogenic variants in 12 (nine LCA-associated and three other IRD-associated) genes among 19 of the 34 analysed families. The most frequently mutated genes were CRB1, NMNAT1, and RPGRIP1. The results also showed the mutation spectra and frequencies identified in the analysed Japanese population to be distinctly different from those previously identified for other ethnic backgrounds. Finally, the present study, which is the first to conduct a NGS-based molecular diagnosis of a large Japanese LCA cohort, achieved a detection rate of approximately 56%, indicating that TS is a valuable method for molecular diagnosis of LCA cases in the Japanese population.