Genetic Sequencing And Analysis Of The Mutation In A Chinese Family With Congenital Aniridia

Backgrounds and AimsAniridia is a rare congenital and bilateral ocular disorder which invade panocular,usually autosomal dominant,the incidence in global population is about 1 in 40000 to 1 in 100000,about two-thirds of cases are familial,the rest one-third cases are sporadic.The classic congenital aniridia always has the main characteristics as bilateral absence of the iris(complete or partial),it might be associated with other ocular anomalies such as hypoplasia or dysfunction of cornea,anterior chamber,crystalline lens,retina and optic nerve.At the same time,about 13% cases with manifestation of iris absence may be companied with WAGR syndrome while about 2% cases can be companied with a extremely rare disease,Gillespie syndrome as autosomal recessive.Current studies have shown that,in addition to PAX6 gene,the mutations of ABCB6,FOXC1,PITX2,and some other genes can result in congenital aniridia or iris absence performance in common or individually.This study was designed to screen the pathogenic mutations of a family with congenital aniridia in Chinese Han population and to verify its association with the disease.Material and MethodsA three-generation family diagnosed with congenital aniridia which has 9 members in total was collected,excpet the patient I-1 has passed away(excluding aniridia),there are 3 patients and 5 normal phenotypes in it.All family members received examination of the nervous system and oral glucose tolerance test before the binoculus ophthalmologic examination.We extracted the DNAs in blood samples by using the Tiangen DNA extraction kit.According to the pathogenic genes reports of aniridia,we customized a Aniridia-related genes sequencing panel.The genome DNA of the proband was sequenced by the next-generation sequencing combined with target-capturing technique.The candidate genes were detected by analysis of the sequencing reslut.The primers were designed according to the upstream and downstream sequences.The pathogenicity was verified via Sanger sequencing in the family.ResultsAniridia in this family is autosomal dominant inheritance,in which the patients with complete iris absence in both eyes.The common manifestations in eyes are: low vision(no improvement with optical correction),high intraocular pressure,iris absence,corneal opacification,nystagmus,foveal hypoplasia.The specificity manifestations in this family are: patient?-2 with ptosis in left eye and congenital cataract in right eye,patient ?-2 with binocular congenital cataract and lens dislocation.According to the analysis of the results of fixed-point capture sequencing,13 suspicious mutant locus were screened out,the base replacement c.183C> A on exon 6 of PAX6 gene is the only one highly associated with disease,Sanger sequencing to this family confirmed that all patients in this family contained this mutation while the normal persons did not,the mutation is a nonsense mutation which leading to premature termination of DNA transcription and translations.Consulting NCBI snp,dbsnp,1000 genomes database we found that the incidence of this base replacement is very low in population,it does not belong to snp.This mutation was reported as a sporadic mutation by a western passage.Conclusions1.The pathogenic mutation of this aniridia family(PAX6 gene c.183C> A,p.Y61X)was screened and verified by he the next generation sequencing of the target gene of the proband which resulted in nonsense mutation causing premature termination codon(PTC),this allelic variation leaded to PAX6 haploinsufficiency.This mutation proved to be the nosogenesis of this family through Sanger sequencing combining with phenotypic analysis of the family members and healthy controls.2.The gene mutation site reported in this study is the second case found in the world and is the first case in the yellow population.It appears that the mutations of the locus may exist in different racial groups,and the mutations correspond to phenotypes Species and yellow people are congenital iris.3.While the patients have parent-child relationship in this family,the phenotypes are not totally same.In our study,we have not found a genetic variation that could explain these ocular specific phenotypes,the raw data and information will be resource and reference for the future epigenetics research of the disease.