The Clinic And Basic Research On Leber Eye Disease And Congenital Cataract

Leber Inherited eye diseases include Leber congenital amaurosis(LCA) and Leber's hereditary optic neuropathy(LHON),and congenital cataract,both of them two important autosomal dominant,autosomal recessive and X-linked blinded eye disease in ophthalmology.In the present study,we have employed the molecular genetic technology, including clinical characterization of large families,linkage mapping of the chromosomal location of the disease causing genes,and mutational analysis,to study the two types of diseases.First part focus on the LCA,research on the clinic feature and screening the RPE65 mutation on 9 cases we had collected,the age from 4～28.Ocular examination included the:corrected visual acluity,optometry degree,ocular fundus image,fluorescein fundus angiography(FFA),and ERG Of 5 blood DNA samples had been isolated and used Denatuing High Performance Liquid Chromatography(DHPLC) to screen the mutation of all 14 exons of RPE65.If found some positive sign in DHPLC,direct sequencing would be performed for mutation analysis.The results showed the there is no visual stimuli and appear the visual impairment within 12 months after birth in all 9 patients,and the earliest symptom appeared in 3-month-old baby.The best corrected less than 20/100,and companied the nystagmus,ocular fundus images showed abnormal,and FFA also showed the abnormal.Of 2 families had the autosomal recessive inherited history,and of 3 the loop families history.Three patients were form consanguineous mating family.ERG cone and rod responses were markedly reduced or non-recordable in all cases.Mutation in the all fourteen exons of the RPE65 gene was not detected in the collected five patients.But the same single nucleotide polymorphisms(SNP) were found in the collected five patients. Second part analyzed a four generation family with LHON,and screened the NADH gene mutation,we clinically characterized a Chinese family with complete panetrance of LHON symptom.The patients in the family present with variable clinical features.By direct DNA sequence analysis,we identified both T14484C mutation and nearby T to C variant at nucleotide 14502 of mitochondria DNA.The T14502C variant altered I58 to V of the protein ND6,which was present in all patients of the family,but not in four unaffected family members and 200 normal controls.The co-existence of both T14484C mutation and T14502C substitution in all patients from the same LHON family suggests that T14502C may play a synergistic role with the primary mutation,and account for complete penetrance and absence of marked gender bias and visual recovery in the Chinese LHON family.The third part we had analyzed a family with autosomal dominant congenital cataract, and maped a gene responsible for infantile cataract in a large four-generation, non-consanguineous Chinese family.Congenital cataract is a clinically diverse and genetically heterogeneous disorder of the crystalline lens,and a leading cause of visual impairment.Twenty two family members including 17 cataract patients in the Chinese family were analyzed clinically.All of family members were genotyped with 382 microsatellite markers that provide genome-wide coverage by every 10 cM.Linkage analysis was carried out to identify the chromosomal location of the infantile cataract gene in the family.Candidate genes were studied by direct DNA sequence analysis.The results showed:Genome-wide linkage analysis provided evidence for a genetic locus for infantile cataract on chromosome 20p12.2-p11.23.The maximum LOD score was 5.15 for marker D20S471 at a recombination fraction of 0.Fine mapping defined the cataract gene within a 7.4 Mb interval between markers D20S915 and D20S912.No mutation was detected in potential candidate genes BFSP1 and CHMP4B.Our results suggest that there is a new gene for infantile cataract on chromosome 20p12.2-p11.23.Our results provide a frame to identify a new gene for infantile cataract by future studies of candidate genes at the 20q locus,which should provide insights into the pathogenic mechanisms of cataracts.