Dominant Molecular Genetics With Clinical Characteristics Of Leber Congenital Amaurosis In The Population Of Western China

Leber congenital amaurosis(LCA)is one of the earliest inherited retinal dystrophies(IRD)that leads to blindness.LCA is characterized by severe visual impairment before 1 year old and extinction of electroretinogram waveform;it is mainly inherited by autosomal recessive pattern.To date,there have been 28 LCA-associated genes reported in China as well as other countries,including CRB1,RDH12,RIPGRIP1 and CEP290.The genetic mutations and clinical phenotypes of LCA are complicated for its molecular heterogeneity and phenotype heterogeneity.Purpose: The current study aimed to present the dominant molecular genetics and clinical features of Leber congenital amaurosis(LCA)in the Han population of western China.To screen LCA-associated genes,analyze the relationship between clinical features and genetic molecular characteristics,thus lay a theoretical foundation for diagnosis and therapy.Methods:1.There were 37 patients(74 eyes)with strictly defined Leber congenital amaurosis in the cohort of IRD(2009 to 2019).The collection of genetic information was performed among these patients and family members,such as written informed consent,basic information questionnaire and pedigree drawing and then analyzed mobidity statistics and geographic distribution of patients.2.Targeted region capture and targeted next-generation sequencing(NGS): In order to capture the coded regions of the 195 IRD genes,we designed a sequence gene capture array.Directional Sanger sequencing and segregation analysis were carried out among family members and normal control group of 200 people.In silico analysis was performed to predict the pathogenicity of novel mutations.3.The patients underwent comprehensive clinical examinations,including Best Corrected Visual Acuity(BCVA),Visual Field(VF),(Flash Visual Evoked Potential(FVEP),Flash Electroretinogram(FERG),Multi-focal Electroretinogram(mf ERG),Colored Fundus Photography,Fundus Fluorescein Angiography(FFA)and Optical Coherence Tomograpy(OCT).We summarized clinical features and then analyze correlations between phenotypes and genotypes.Results:1.In this study,a capture chip targeted by 195 IRD-related pathogenic genes was improved and designed.Among the 37 cases that were screened by NGS,34 harbored known LCA genes;the detection rate of mutations was 91.9%.2.There were 47 different alleles that incorporated 21 novel ones,including CRB1,RDH12,RPGRIP1 and CEP290.Eight were known LCA-associated genes,including CRB1,RDH12,RPGRIP1,CEP290,GUCY2 D,RPE65,LCA5 and AIPL1.Novel mutations are predicted to be pathogenic.There were not new pathogenic mutations in 200 controls.The three most frequently mutated genes included CRB1(27.0%),RDH12(24.3%),and RPGRIP1(18.9%).3.CRB1 and RPGRIP1 genes occupied a dominant proportion in the western Chinese population.The proportion of these two genes was similar in other regions of China as well.The difference existed in a larger proportion of RDH12-associated LCA in the western Chinese population.4.The 37 LCA patients in this study had poor vision;21 patients had low visual acuity and15 patients were defined as blind.And clinical examinations manifested round,bone spicule or fishnet latticed pigmentation in the fundus,with or without macular atrophy.Moreover,electrophysiological examinations showed severe visual impairment.5.The CRB1-associated LCA showed a pigmented fundus;the RDH12-associated LCA featured macular atrophy.However,the fundus change of the RPGRIP1-associated LCA was not consistent with the visual function defect.The CEP290-associated or RPE65-associated LCA manifested nearly normal fundus or white molting pigmentation.Conclusions:1.Strict clinical diagnostic criteria combined with NGS technology can help increase the detection rate of LCA.2.In this study,47 mutant alleles were detected,and 21 new mutations were discovered for the first time,which expanded the mutation spectrum of LCA in the Chinese population.3.The proportion of RDH12-associated LCA in the western Chinese population were larger than that in other regions.The new findings in our study group polished the spectrum of the novel mutations and the phenotypes of LCA with regional and ethnic variations.4.We analyzed the relationship between genotypes and phenotypes of LCA patients from western Chinese population for the first time.Novel mutations were found,but no new clinical phenotypes were found.This comprehensive database provided essential information for gene augmentation or retinoid supplementation therapies.