Résumé
Background Congenital aniridia is a rare bilateral hereditary ophthalmopathy which impact panocular.Researches showed that congenital aniridia can be caused by different mutation locus of PAX6 genes,and the mutations are multifarious.Objective This study was to detect and anaiyze the mutations of a Chinese family with congenital aniridia by using targeted sequence capture sequencing and direct Sanger sequencing.Methods This study was approved by Ethic Committee of the First Affiliated Hospital of Zhengzhou University and followed Declaration of Helsinki.Written informed consent was obtained from subjects or their custodians before any related medical examination.A cross-sectional study was performed.A Chinese congenital aniridia family was included at the First Affiliated Hospital of Zhengzhou University in March,2016.All the family members received systemic medical examinations including nervous system and oral glucose tolerance test and then the ocular examinations were carried out.The periphery blood of 10 ml was collected from the members for genomic DNA extraction.Targeted sequence capture sequencing was performed on the DNA of proband to screen out the suspicious mutant locus.The mutation was verified by comparing the Sanger direct sequencing results from all family members.Results A total of 3 generations of 9 members were included in this congenital aniridia pedigree,and the Ⅰ 1 was dead without eye abnormality.Three patients (Ⅱ2 and her children Ⅲ1,Ⅲ2) and 5 normal family members were determined,showing an autosomal dominant inheritance pattern.No abnormal signs were found in nervous system and oral glucose tolerance test in the families.The reduce of visual acuity,ocular hypertension (21 mmHg),absence of biocular iris,opacification of corneal stroma,horizontal nystagmus,hapoplasia of fovea were found in all the sufferers.In addition,the ptosis of the left eye,congenital cataract of the right eye in Ⅱ 2 patient as well as biocular cataract and subluxation of lenses also were exhibited.The c.183C＞A mutation of the PAX6 gene was screened out to be a possible pathogenic mutation.The result of Sanger direct sequencing in the families verified a co-segregation of this mutation with mutant phenotypes.Conclusions PAX6 gene c.183C ＞A,a rare mutation in Chinese population,is a virulence mutation site in this aniridia family.
Résumé
Background Aniridia is a rare congenital hereditary eye disease.Studies determined that PAX6 gene mutation is closely associated with congenital aniridia,but the mutation locus are varied.Objective This study was to identify virulence mutation locus of PAX6 gene of a Chinese family pedigree with autosomal dominant aniridia.Methods A Chinese family affected with autosomal dominant aniridia was collected and examined in Affiliated First Hospital of Zhengzhou University in August 2014.Periphery blood of 10 ml was collected from all the families and 100 unrelated health controls.The genomic DNA was extracted by standardized phenol-chloroform method,and all exons and splicing junctions of PAX6 were amplified by PCR.Real-time fluorescence quantitative PCR was performed to examine the relative expression of PAX6 mRNA in patients and normal phenotype families and heahh controls.This study protocol was approved by Ethic Committee of Affiliated First Hospital of Zhengzhou University and complied with Helsinki Declaration.Written informed consent was obtained from subjects or custodian before any medical examination.Results This Chinese family inclued 3 generations and 9 members,with a classic autosomal dominant inheritance mode.Five patients were found,showing the absence of iris and cataract in 3 adult patients and only absence of the iris in 2 children,and other 4 members showed the normal phenotype.A novel heterozygous PAX6 deletion mutation c.796 del G (p.A266 fs) (GenBank ID:KP255960) in exon 10 was exclusively found in all affected individuals but not in any of the unaffected families or unrelated health controls.PAX6 mRNA level in lymphocytes was about 50％ lower in aniridia patients than in unaffected family members,indicating that this mutation caused nonsense-mediated mRNA decay.Conclusions A novel deletion mutation in PAX6 gene results in an abnormal PAX6 COOH-terminal extension in the Chinese aniridia family.This finding expands the mutation spectrum of PAX6 gene.