The Genetic Analysis For Inherited Cataract In Two Family

Purpose:To identify the genetic defect in a family with dust- nuclear cataract combined with high myopia and a family with autosomal dominant congenital membranous cataract.Demonstrate the functional analysis of a candidate gene in the family.Methods:The families with congenital cataract were recruited from the Tianjin Medical University Eye Centre.Family history datas were recorded.Clinical and ophthalmologic examinations were performed on affected and unaffected family members.Blood samples were collected from all the subjects for genomic DNA preparation.All the members were genotyped with microsatellite markers at loci considered to be associated with cataracts.Multiplex polymerase chain reaction(PCR) was carried out with microsatellite markers near to candidate loci related to congenital cataracts.PCR products from each DNA sample were separated on a 6% polyarcylamide gel and analyzed.Exclusion analysis was performed by allele sharing analysis and gene sequencing.Results:The clinical phenotype in the first family was inherited dust-nuclear cataract combined with high myopia.Congenital cataract and high myopia are the autosomal dominant modes of inheritance in this family.The complete coding region and splice site of HSF₄,MAF and BFSP₂ were screened by direct sequencing.Affected members of the second family had membranous cataracts.The disease locus of this family was mapped at 22q11.2-q12.1 about 2.4Mbp.we obtained multiple-sequence alignments of the complete coding region and splice site of CRYBB 1,CRYBB2,CRYBB3,CRYBA4 and did not find a mutation. CRYBB1,CRYBB2,CRYBB3,CRYBA4 were screened by direct sequencing.Conclusion The pathogenic gene in the first family should beidentified throughextensive scanning of genes,and a new disease-causing gene maybe exist in this family.The associations of HSF₄,MAF and BFSP₂ in this family were excluded.All known ADCC loci have been excluded from the second family,which further indicates the clinical and genetical heterogeneity of congenital cataract,and an important clue is provided for finding more cataract responsible genes.Further study should be carried out to screen other relevant genes or loci in patients with ADCC. The disease gene should be identified through genome-wide scan.