A G1103R mutation in CRB1 is co-inherited with high hyperopia and Leber congenital amaurosis

PURPOSE: To identify the genetic basis of recessive inheritance of high hyperopia and Leber congenital amaurosis (LCA) in a family of Middle Eastern origin. MATERIALS AND METHODS: The patients were examined using standard ophthalmic techniques. DNA samples were obtained and genetic linkage was carried out using polymorphic markers flanking the known genes and loci for LCA. Exons were amplified and sequenced. RESULTS: All four members of this family affected by LCA showed high to extreme hyperopia, with average spherical refractive errors ranging from +5.00 to +10.00. Linkage was obtained to 1q31.3 with a maximal LOD score of 5.20 and a mutation found in exon 9 of the CRB1 gene, causing a G1103R substitution at a highly conserved site in the protein. CRB1 is a vertebrate homolog of the Drosophila crumbs gene, which is required for photoreceptor morphogenesis, and has been associated with either retinitis pigmentosa (RP) or LCA. This sequence variant has previously been reported as a compound heterozygote in one sporadic LCA patient. CONCLUSION: Although hyperopia has been associated with LCA, it is typically moderate and variable between patients with the same mutation. In addition, some CRB1 mutations can be associated with either RP or LCA. We have shown that hyperopia and LCA are linked to the mutant CRB1 gene itself and are not dependent on unlinked modifiers.     

Mutation screening of Pakistani families with congenital eye disorders

To map the disease loci several Pakistani families suffering from autosomal recessive retinitis pigmentosa with preserved para-arteriolar retinal pigment epithelium and Leber congenital amaurosis (LCA) were analyzed. Analysis revealed close genetic linkage between the disease phenotype of some of the families (3330RP, 111RP and 010LCA) and the microsatellite markers on chromosome 1q31. Mutation screening of the candidate gene CRB1 revealed a G to A transversion in exon 7 in arRP family 330RP and a T to C substitution in another arRP family, 111RP. In exon 9 of the CRB1 gene a T to C transversion was found in the family suffering from LCA (010LCA).The LCA phenotype of another family (011LCA) in which the CRB1 locus was excluded, showed linkage with microsatellite markers D17S1294 and D17S796 on chromosome 17p13.1. The association of the candidate gene GUCY2D (17p13.1) with the disease phenotype was excluded as no disease-associated mutation was found in any of its exons. Mutation screening of another candidate gene, AIPL1 located in the same region, showed a novel homozygous C to A substitution in exon 2. These sequence changes are unique for the Pakistani families and some of these have not been reported previously.     

CRB1: One Gene,Many Phenotypes

Abstract

Mutations in the CRB1 gene cause severe retinal degenerations, which may present as Leber congenital amaurosis, early onset retinal dystrophy, retinitis pigmentosa, or cone-rod dystrophy. Some clinical features should alert the ophthalmologist to the possibility of CRB1 disease. These features are nummular pigmentation of the retina, atrophic macula, retinal degeneration associated with Coats disease, and a unique form of retinitis pigmentosa named para-arteriolar preservation of the retinal pigment epithelium (PPRPE). Retinal degenerations associated with nanophthalmos and hyperopia, or with keratoconus, can serve as further clinical cues to mutations in CRB1. Despite this, no clear genotype-phenotype relationship has been established in CRB1 disease. In CRB1-disease, as in other inherited retinal degenerations (IRDs), it is essential to diagnose the specific disease-causing gene for the disease as genetic therapy has progressed considerably in the last few years and might be applicable.     

A new novel nonsense mutation in AIPL1 in a LCA4 family

ABSTRACT

Purpose: To investigate the disease-causing gene in a Chinese family with Leber congenital amaurosis 4 (LCA4).

Materials and methods: Four members of an LCA family underwent ophthalmological examination and systemic assessment. DNA samples were obtained from their peripheral blood. Whole exome sequencing (WES) was performed in the two patients. After data filtering, Sanger sequencing was performed to verify the mutation within this family.

Results: The two patients were diagnosed as having LCA4 and with keratoconus (KCN). The older brother also has intellectual disability, epilepsy, Tourette syndrome and an abnormal gait, while the younger one has an abnormal bulge at the end of his sternum. A novel p.Gln81* mutation in the AIPL1 gene was determined as causing LCA4 in this family. Protein structure change prediction showed AIPL1 p.Gln81* mutation coded a very short AIPL1 peptide and could not form a normal structure as an normal AIPL1 protein.

Conclusion: Although KCN has been associated with LCA4, this type of LCA is typically moderate in severity and variable between patients. The present cases also have some systemic abnormalities.     

Identification of novel mutations in patients with Leber congenital amaurosis and juvenile RP by genome-wide homozygosity mapping with SNP microarrays

PURPOSE: Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) cause severe visual impairment early in life. Thus far, mutations in 13 genes have been associated with autosomal recessive LCA and juvenile RP. The purpose of this study was to use homozygosity mapping to identify mutations in known LCA and juvenile RP genes. METHODS: The genomes of 93 consanguineous and nonconsanguineous patients with LCA and juvenile RP were analyzed for homozygous chromosomal regions by using SNP microarrays. This patient cohort was highly selected, as mutations in the known genes had been excluded with the LCA mutation chip, or a significant number of LCA genes had been excluded by comprehensive mutation analysis. Known LCA and juvenile RP genes residing in the identified homozygous regions were analyzed by sequencing. Detailed ophthalmic examinations were performed on the genotyped patients. RESULTS: Ten homozygous mutations, including seven novel mutations, were identified in the CRB1, LRAT, RPE65, and TULP1 genes in 12 patients. Ten patients were from consanguineous marriages, but in two patients no consanguinity was reported. In 10 of the 12 patients, the causative mutation was present in the largest or second largest homozygous segment of the patient's genome. CONCLUSIONS: Homozygosity mapping using SNP microarrays identified mutations in a significant proportion (30%) of consanguineous patients with LCA and juvenile RP and in a small number (3%) of nonconsanguineous patients. Significant homozygous regions which did not map to known LCA or juvenile RP genes and may be instrumental in identifying novel disease genes were detected in 33 patients.     

A novel mutation disrupting the cytoplasmic domain of CRB1 in a large consanguineous family of Palestinian origin affected with Leber congenital amaurosis

Leber congenital amaurosis (LCA) is a genetically heterogeneous autosomal recessive condition responsible for congenital blindness or greatly impaired vision since birth. Eight LCA loci have been mapped, but only six out of eight genes have been hitherto identified. A genome-wide screen for homozygosity was conducted in a large consanguineous family originating from Palestine, for which no mutation was found in any of the six known LCA genes and that excluded the LCA3 and LCA5 loci. Evidence for homozygosity, however, was found in all affected patients of the family on chromosome 1q31, a region in which the human homologue of the Drosophila melanogaster crumbs gene (CRB1) has been mapped. Consequently, we proposed a hypothesis that the disease-causing mutation in this family might lie in an unexplored region of this LCA gene. As a matter of fact, while no mutation was found in any of the 11 CRB1 exons originally reported, we identified a 10-bp (del 4121-4130) deletion segregating with the disease in a later reported 12th exon lying in the 3' end of the gene. Interestingly, this deletion disrupts an amino acid sequence that was shown to be crucial for the function of the protein in the Drosophila counterpart (CRB).     

Genotyping microarray (disease chip) for Leber congenital amaurosis: detection of modifier alleles

PURPOSE: Leber congenital amaurosis (LCA) is an early-onset inherited disorder of childhood blindness characterized by visual impairment noted soon after birth. Variants in at least six genes (AIPL1, CRB1, CRX, GUCY2D, RPE65, and RPGRIP1) have been associated with a diagnosis consistent with LCA or early-onset retinitis pigmentosa (RP). Genetically heterogeneous inheritance complicates the analyses of LCA cases, especially in patients without a family history of the disorder, and conventional methods are of limited value. METHODS: To overcome these limitations, arrayed primer extension (APEX) technology was used to design a genotyping microarray for early-onset, severe retinal degenerations that includes all of the >300 disease-associated variants currently described in eight genes (in addition to the six just listed, the early-onset RP genes LRAT and MERTK were added). The resultant LCA array allows simultaneous detection of all known disease-associated alleles in any patient with early-onset RP. The array was validated by screening 93 confirmed patients with LCA who had known mutations. Subsequently, 205 novel LCA cases were screened on the array, followed by segregation analyses in families, if applicable. RESULTS: The microarray was >99% effective in determining the existing genetic variation and yielded at least one disease-associated allele in approximately one third of the novel patients. More than two (expected) variants were discovered in a substantial fraction (22/300) of the patients, suggesting a modifier effect from more than one gene. In support of the latter hypothesis, the third allele segregated with a more severe disease phenotype in at least five families. CONCLUSIONS: The LCA genotyping microarray is a robust and cost-effective screening tool, representing the prototype of a disease chip for genotyping patients with a genetically heterogeneous condition. Simultaneous screening for all known LCA-associated variants in large LCA cohorts allows systematic detection and analysis of genetic variation, facilitating prospective diagnosis and ultimately predicting disease progression.     

Identification of a Novel LCA6 Mutation in an Emirati Family

ABSTRACT

Purpose: To determine the cause of Leber congenital amaurosis (LCA) in a consanguineous Emirati family.

Methods: The clinical diagnosis was made on the basis of medical history, ophthalmoscopy and standard ERG. The diagnosis was confirmed by molecular genetic analysis of known LCA genes by Next-Generation Sequencing (NGS). The latter was performed by Bioscientia Institut, Germany (as a clinical service for Latifa Hospital, Dubai).

Results: The next generation sequencing of known LCA genes revealed a homozygous 1bp-insertion c.2608_2609insA in exon 16 of the RPGRIP1 gene. This mutation, which was confirmed by conventional Sanger sequencing, leads to a frameshift, resulting in a premature stop codon (p.Leu870TyrfsX7) and subsequently in a degradation of the m-RNA or in a truncation of the RPGRIP1 protein. The segregation analysis of the identified mutation was performed for the parental samples. Both parents carry the frameshift mutation in a heterozygous state.

Conclusion: We report a novel RPGRIP1 mutation causing LCA in a consanguineous Emirati family. To the best of our knowledge, this alteration has not been described in the literature so far.     

Microarray-based mutation detection and phenotypic characterization of patients with Leber congenital amaurosis

PURPOSE: To test the efficiency of a microarray chip as a diagnostic tool in a cohort of northwestern European patients with Leber congenital amaurosis (LCA) and to perform a genotype-phenotype analysis in patients in whom pathologic mutations were identified. METHODS: DNAs from 58 patients with LCA were analyzed using a microarray chip containing previously identified disease-associated sequence variants in six LCA genes. Mutations identified by chip analysis were confirmed by sequence analysis. On identification of one mutation, all protein coding exons of the relevant genes were sequenced. In addition, sequence analysis of the RDH12 gene was performed in 22 patients. Patients with mutations were phenotyped. RESULTS: Pathogenic mutations were identified in 19 of the 58 patients with LCA (32.8%). Four novel sequence variants were identified. Mutations were most frequently found in CRB1 (15.5%), followed by GUCY2D (10.3%). The p.R768W mutation was found in 8 of 10 GUCY2D alleles, suggesting that it is a founder mutation in the northwest of Europe. In early childhood, patients with AIPL1 or GUCY2D mutations show normal fundi. Those with AIPL1-associated LCA progress to an RP-like fundus before the age of 8, whereas patients with GUCY2D-associated LCA still have relatively normal fundi in their mid-20s. Patients with CRB1 mutations present with distinct fundus abnormalities at birth and consistently show characteristics of RP12. Pathogenic GUCY2D mutations result in the most severe form of LCA. CONCLUSIONS: Microarray-based mutation detection allowed the identification of 32% of LCA sequence variants and represents an efficient first-pass screening tool. Mutations in CRB1, and to a lesser extent, in GUCY2D, underlie most LCA cases in this cohort. The present study establishes a genotype-phenotype correlation for AIPL1, CRB1, and GUCY2D.     

CRB1 heterozygotes with regional retinal dysfunction: implications for genetic testing of leber congenital amaurosis

PURPOSE: To test human CRB1 heterozygotes for possible clinical or functional retinal changes and to evaluate whether a patient with Leber congenital amaurosis (LCA) with CRB1 mutations not consistent with previously described CRB1 phenotypes carried a modifier allele in another LCA gene. METHODS: Seven unrelated heterozygous carriers of CRB1 mutations underwent phenotyping by full eye examinations (indirect ophthalmoscopy and slit lamp biomicroscopy) and functional testing (standard full-field electroretinography [ERG] and multifocal ERG). For genotyping of the LCA patients and their parents, denaturing high-performance liquid chromatography (dHPLC) analyses were performed, followed by sequence analysis of CRB1, followed by sequence analysis of the AIPL1 and CRX genes to identify a putative modifier effect in a patient with an atypical CRB1 phenotype. RESULTS: Reduced full-field ERG b-wave amplitudes were observed with scotopic -2 dB flash (140 microV; P < 0.05), normal full-field cone ERGs, and significant regional retinal dysfunction on mfERG in five of seven carriers of CRB1 mutations. A known AIPL1 mutation (p. R302L) was identified as a potential modifier allele in a patient with LCA carrying two CRB1 mutations and with a prominent maculopathy. CONCLUSIONS: In human heterozygotes of CRB1 mutations (parents of offspring with LCA), distinctive regional retinal dysfunctions were found by multifocal ERG measurements that were consistent with the focal histologic abnormalities reported for the two CRB1 knockout mice models. This phenotypic finding may identify CRB1 carriers and point to the causal gene defect in affected LCA offspring, significantly facilitating the molecular diagnostic process. Evidence suggests a modifier allele in AIPL1 in a patient with LCA with prominent atrophic macular lesions and homozygous defects in CRB1.     

Duke University honors Gordon Klintworth

Leber congenital amaurosis (LCA; estimated prevalence 1?:?50,000–100,000) is an early-onset inherited cause of childhood blindness characterized by a severe retinal dystrophy immediately after birth. Variants in at least six genes, AIPL1, CRB1, CRX, GUCY2D, RPE65, and RPGRIP1, have been associated with a diagnosis consistent with LCA or early-onset retinitis pigmentosa and together account for less than 50% of all LCA cases. Genetically heterogeneous inheritance has complicated the molecular analysis of LCA cases, especially sporadic ones where conventional methods are of limited value. Until recently, the management of patients with LCA relied mainly on clinical examination, electrophysiology, and other ancillary tests. Genotyping, i.e., determining the exact genetic defect causing LCA in each specific case, was not routinely performed since the comprehensive screening of six genes by SSCP and/or direct sequencing is relatively inefficient and cost-prohibitive. Patients, therefore, were often left with no specific information on their disease status. Recent advances in genotyping technologies have allowed the introduction of comprehensive and affordable screening procedures to determine causal genetic variation, resulting in precise molecular diagnosis, more accurate visual prognosis, and suggestions towards treatment options.     

LCA5, a Rare Genetic Cause of Leber Congenital Amaurosis in Koreans

Purpose: Leber congenital amaurosis (LCA), the most severe form of inherited retinal dystrophy, is a genetically heterogenous disorder and more than nine genes only account for about half of LCA cases. Recently, LCA5 was identified as a rare genetic cause of LCA. Here, we analyzed the LCA5 gene in 14 LCA patients with no mutation identified in any other known LCA genes and 3 patients with one unclassified missense variant in RPGRIP1. Methods: We analyzed all exons and flanking regions of the LCA5 gene using direct sequencing. We included 170 control subjects in this study to screen novel sequence variant and analyzed the functional effect of a missense variant using in-silico prediction. Results: No pathogenic mutation in LCA5 was found in our seventeen patients including 3 patients with one unclassified missense variant in RPGRIP1. We identified one novel missense variant, c.1642C>T (p.Pro548Ser), in exon 9. We considered it benign because it was found in control subjects and predicted not to be harmful to protein function on in-silico prediction. We identified another intronic variant, which has been confirmed to be benign through mRNA analysis. Conclusions: This result shows that mutation in LCA5 is likely to be a rare genetic cause in Koreans and suggests that further investigation to identify other causative genes is necessary in Koreans.     

Exclusion of LCA5 locus in a consanguineous Turkish family with macular coloboma-type LCA

BACKGROUND: Leber's congenital amaurosis (LCA) is an inherited retinal dystrophy, which causes severe visual impairment in early childhood. Recent molecular genetic studies have linked 11 loci (AIPL1, CRB1, CRX, GUCY2D, RPE65, RDH12, RPGRIP1, TULP1, LCA3, LCA5, and LCA9) to LCA. LCA5 is a new locus, which maps to the 6q11-q16 chromosomal region and was found to be associated with macular coloboma-type LCA in a Pakistani family. Herein, we describe the molecular genetic features of a consanguineous Turkish family in which four children have macular coloboma-type LCA. METHODS: Haplotype analysis was performed on the DNA of the family members using microsatellite markers against GUCY2D, RPE65, and LCA5. Genomic DNA was screened for mutations by means of single-strand conformational polymorphism (SSCP) analysis in exons of the RPE65 and CRX genes. RESULTS: In haplotype analysis, no linkage to LCA5 or GUCY2D loci was detected. None of the tested markers showed homozygosity or segregation between affected siblings. PCR-SSCP mutation analysis revealed no mutations in the screened RPE65 and CRX genes. CONCLUSION: We excluded LCA5 as the genetic cause of macular coloboma-type LCA in this Turkish family. Macular coloboma-type LCA shows genetic heterogeneity and it is not possible to establish a phenotype-genotype correlation with LCA5 and macular coloboma.     

CRB1 mutations may result in retinitis pigmentosa without para-arteriolar RPE preservation

Purpose: To report a new phenotype in retinitis pigmenotosa (RP) patients with CRB1 mutations at the RP12 locus. Patients: Thirty-seven patients from two Pakistani families with severe retinitis pigmentosa. Methods: Samples were screened with single-strand conformation polymorphism analysis followed by DNA sequencing of the coding sequence of the CRB1 gene. Results: Two novel CRB1 mutations were discovered. No patients had evidence of preservation of the para-arteriolar retinal pigment epithelium (PPRPE) that has been previously reported in all cases of RP associated with CRB1 mutations. Conclusions: Patients with severe autosomal recessive (or simplex) RP who lack the finding of PPRPE should not be excluded from molecular analysis of CRB1 purely because they lack the clinical feature of PPRPE. This report illustrates that RP at the RP12 locus is not clinically uniform. The absence of PPRPE cannot be used to exclude CRB1 as a potential molecular explanation for RP.     

Progression of phenotype in Leber's congenital amaurosis with a mutation at the LCA5 locus

BACKGROUND: Leber's congenital amaurosis (LCA) accounts for 5% of inherited retinal disease and is usually inherited as an autosomal recessive trait. Genetic and clinical heterogeneity exist. Mutations have been described in the RPE65, CRB1, RPGRIP1, AIPL1, GUCY2D, and CRX genes and other pedigrees show linkage to the LCA3 and LCA5 loci. The latter is a new locus which maps to 6q11-q16. The ocular findings and the evolution of the macula staphyloma are described in five members of a Pakistani family with consanguinity and a mutation in the LCA5 gene. METHODS: 13 family members including five affected individuals consented to DNA analysis and ocular examination including fundal photography. RESULTS: Ocular abnormalities are described. The most striking feature was the progression of macula abnormalities in three brothers resulting in a colobomatous appearance in the eldest compared to only mild atrophy in the youngest. The phenotypic pattern of this mutation in this Pakistani family contrasts with the "Old Order River Brethren" who were of Swiss descent, in whom the mutation was first described. CONCLUSION: The evolution of a new phenotypic picture is presented to a mutation in LCA5.     

CRB1 maculopathy presenting as fenestrated sheen macular dystrophy with 15-year follow-up

Introduction

We present two patients, the proband and the affected sibling, with biallelic CRB1 mutations leading to a macular dystrophy.

Case presentation

We present two patients, the proband and the affected sibling, with biallelic CRB1 mutations leading to a macular dystrophy. With 15 years of follow-up for the proband, we illustrate the natural history of CRB1 maculopathy based on clinical examination, multimodal imaging, and electrophysiology. In addition, we demonstrate the wide phenotypic spectrum of the condition with the affected sister harboring the same variants but with much milder phenotypic manifestations.

Conclusion

In addition to a previously described pathogenic variant, Ile167_Gly169del, one pathogenic missense variant in CRB1, Lys801Ter, not previously associated with macular dystrophy, is reported here. While CRB1 mutations have been more commonly described in retinitis pigmentosa (RP) and Leber congenital amaurosis (LCA), we demonstrate that mutations in CRB1 can cause a maculopathy with initial features similar to fenestrated sheen macular dystrophy (FSMD) that later evolves into severe macular atrophy.

     

Overlapping retinal phenotypes in a consanguineous family harboring mutations in CRB1 and RS1

Purpose: To describe and distinguish overlapping retinal phenotypes in a consanguineous family harboring mutations in CRB1 and RS1, two different genes that are associated with splitting of the central neurosensory retina.

Methods: Retrospective case series.

Results: Three siblings and their father had decreased vision from early childhood, but the father was unavailable for clinical examination. The proband, an 11-year old boy, had clinical features classic for CRB1-retinopathy (nummular pigmentary degeneration, relatively plump vessels, thickened retinal by optical coherence tomography with cystoid splitting in the central macula). The younger brother had right eye cataract with retinal detachment (presumed traumatic) and neurosensory retinal splitting in the central and peripheral retina with nummular pigmentary changes. It was assumed both brothers had the same disease until examination of the older sister, who had bilateral central and peripheral neurosensory retinal splitting in a pattern classic for X-linked retinoschisis and without any evidence for CRB1-retinopathy. The mother had an unremarkable clinical examination. ERG testing and directed genetic testing of CRB1 and RS1 for the family members confirmed CRB1-retinopathy in the proband, X-linked retinoschisis in the younger brother (hemizygous RS1 mutation), and X-linked retinoschisis in the older sister (homozygous RS1 mutation). The mother was confirmed as a carrier for both mutations.

Discussion: A consanguineous family affected by retinal degenerative disease may have homozygous mutations in more than one gene, and this includes the possibility of homozygosity for X-linked disease. Electroretinography can be useful in distinguishing CRB1-retinopathy from X-linked retinoschisis.     

Novel homozygous loss-of-function mutations in RP1 and RP1L1 genes in retinitis pigmentosa patients

ABSTRACT

Background: Retinitis pigmentosa (RP) is a heterogeneous group of ocular dystrophy. It is challenging to identify the underlying genetic defect in individuals with RP due to huge genetic heterogeneity. This study was designed to delineate the genetic defect(s) underlying RP in extended Saudi families and to describe the possible disease mechanism.

Materials and Methods: Fundus photography and a high definition optical coherence tomography (HD-OCT) were performed in order to detect the earlier stages of macular degeneration. Genomic DNA was extracted followed by genome-wide SNP genotyping and whole exome sequencing (WES). Exome data was filtered to identify the genetic variant(s) of interest.

Results: Clinical examination showed that affected individuals manifest key features of RP. The fundus exam shows pale optic disc and bone spicules at the periphery. OCT shows macular degeneration as early as at the age of 4 years. Whole genome scan by SNPs identified multiple homozygous regions. WES identified a 10 bps novel insertion mutation (c.3544_3545insAGAAAAGCTG; p.Ala1182fs) in the RP1 gene in both affected individuals of family A. Affected individual from family B showed a large insertion of 48 nucleotides in the coding part of the RP1L1 gene (c.3955_3956insGGACTAAAGTAATAGAAGGGCTGCAAGAAGAGAGGGTGCAGTTAGAGG; p.Ala1319fs). Sanger sequencing validates the autosomal recessive inheritance of the mutations.

Conclusion: The results strongly suggest that the insertion mutations in the RP1 and RP1L1 genes are responsible for the retinal phenotype in affected individuals from two families. Heterozygous individuals are asymptomatic carriers. We propose that the protective allele in other homozygous regions in heterozygous carriers contribute to the phenotypic variability in asymptomatic individuals.     

Targeted next-generation sequencing reveals that a compound heterozygous mutation in phosphodiesterase 6a gene leads to retinitis pigmentosa in a Chinese family

Purpose: Retinitis pigmentosa (RP) is a genetically heterogeneous disease with over 70 causative genes identified to date. However, approximately 40% of RP cases remain genetically unsolved, suggesting that many novel disease-causing mutations are yet to be identified. The purpose of this study is to identify the causative mutations of a Chinese RP family.

Methods: Targeted next-generation sequencing (NGS) for a total of 163 genes which involved in inherited retinal disorders were used to screen the possible causative mutations. Sanger sequencing was used to verify the mutations.

Results: As results, we identified two heterozygous mutations: a splicing site mutation c.1407 + 1G>C and a nonsense mutation c. 1957C>T (p.R653X) in phosphodiesterase 6A (PDE6A) gene in the RP patient. These two mutations are inherited from his father and mother, respectively. Furthermore, these mutations are unique in our in-house database and are rare in human genome databases, implicating that these two mutations are pathological.

Conclusion: By using targeted NGS method, we identified a compound heterozygous mutation in PDE6A gene that is associated with RP in a Chinese family.