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Predicting the pathogenicity of RPE65 mutations.

ABSTRACT: To assist in distinguishing disease-causing mutations from nonpathogenic polymorphisms, we developed an objective algorithm to calculate an "estimate of pathogenic probability" (EPP) based on the prevalence of a specific variation, its segregation within families, and its predicted effects on protein structure. Eleven missense variations in the RPE65 gene were evaluated in patients with Leber congenital amaurosis (LCA) using the EPP algorithm. The accuracy of the EPP algorithm was evaluated using a cell-culture assay of RPE65-isomerase activity The variations were engineered into plasmids containing a human RPE65 cDNA and the retinoid isomerase activity of each variant was determined in cultured cells. The EPP algorithm predicted eight substitution mutations to be disease-causing variants. The isomerase catalytic activities of these RPE65 variants were all less than 6% of wild-type. In contrast, the EPP algorithm predicted the other three substitutions to be non-disease-causing, with isomerase activities of 68%, 127%, and 110% of wild-type, respectively. We observed complete concordance between the predicted pathogenicities of missense variations in the RPE65 gene and retinoid isomerase activities measured in a functional assay. These results suggest that the EPP algorithm may be useful to evaluate the pathogenicity of missense variations in other disease genes where functional assays are not available.

SUBMITTER: Philp AR

PROVIDER: S-EPMC2717180 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Predicting the pathogenicity of RPE65 mutations.

Philp A R AR Jin M M Li S S Schindler E I EI Iannaccone A A Lam B L BL Weleber R G RG Fishman G A GA Jacobson S G SG Mullins R F RF Travis Gabriel H GH Stone Edwin M EM

Human mutation 20090801 8

To assist in distinguishing disease-causing mutations from nonpathogenic polymorphisms, we developed an objective algorithm to calculate an "estimate of pathogenic probability" (EPP) based on the prevalence of a specific variation, its segregation within families, and its predicted effects on protein structure. Eleven missense variations in the RPE65 gene were evaluated in patients with Leber congenital amaurosis (LCA) using the EPP algorithm. The accuracy of the EPP algorithm was evaluated usin ...[more]

PMID: 19431183

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Project description:ImportanceNext-generation sequencing can detect variants of uncertain significance (VUSs), for some of which gene therapy would not be advantageous. Therefore, the pathogenicity of compound heterozygous or homozygous variants should be confirmed before bilateral vitrectomy and administration of voretigene neparvovec-rzyl.ObjectiveTo describe an in vitro mutagenesis assay for assessing the pathogenicity of variants in the RPE65 gene.Design, setting, and participantsThis case series was conducted at 2 tertiary referral centers. Clinical history, imaging, and electrophysiologic testing results were reviewed from September 5, 2008, to December 31, 2019. Participants were 4 pediatric patients with Leber congenital amaurosis who were evaluated for or met the inclusion criteria for phase 1 to 3 clinical trials or were referred for voretigene neparvovec-rzyl treatment.Main outcomes and measuresA functional assay was used to confirm the pathogenicity of novel RPE65 VUSs in 4 patients with Leber congenital amaurosis.ResultsFour patients with Leber congenital amaurosis had VUSs in RPE65. Patients 1 and 2 were siblings with the homozygous VUS c.311G>T p.(G104V). Patient 3 was a compound heterozygote with 1 known pathogenic allele, c.1202_1203insCTGG p.(Glu404AlafsTer4), and 1 VUS, c.311G>T p.(G104V), which segregated to separate alleles. Patient 4 was also a compound heterozygote with 1 pathogenic variant, c.11 + 5G>A, and 1 variant in trans, c.1399C>T p.(P467S). In vitro mutagenesis revealed that the G104V and P467S RPE65 proteins were catalytically inactive (0% isomerase activity). Patients 1 and 2 were excluded from participation in a phase 1 trial owing to high Adeno-associated virus 2 capsid-neutralizing antibodies. Patients 3 (G104V) and 4 (P467S) underwent successful surgical gene therapy with voretigene neparvovec-rzyl, and their response to lower white light intensity and visual field increased in fewer than 30 days after gene therapy intervention.Conclusions and relevanceFindings from this study suggest that, in patients with missense mutations in RPE65, functional assays of protein function can be performed to assess the pathogenicity of variants in both compound heterozygous and homozygous cases. Given the potential risks of gene therapy operations, in vitro RPE65 activity testing should be considered to avoid the possibility of treating a false genotype.

Dataset Information

Predicting the pathogenicity of RPE65 mutations.

Publications

Predicting the pathogenicity of RPE65 mutations.

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