Genetic Studies Of A Family With Atypical Corneal Dystrophy And A Family With Primary Open-angle Glaucoma

Purpose To examine the clinical characteristics and analyze the genetic mutations of two families: one with atypical corneal dystrophy(CD),and the other with primary open-angle glaucoma(POAG).Methods 1.Total of thirteen members from three generations of a CD family was enrolled.Thorough ophthalmologic examinations,family trees mapping,and clinical characteristics analysis were conducted.After informed consent of all members of this family was obtained,Average interval of about 10 c M(Marshfield genetic linkage map),a total of 366 STR loci were analyzed by linkage analysis and haplotype inference in six DNA samples(four samples came from patients)in order to identify the regions containing possible pathological genes of the disease.Then,DNA samples of two patients were used for whole exome sequencing,candidate genes were further identified in the regions selected by linkage analysis and haplotype inference.The candidate genes were verified by Sanger sequencing in the CD family with 200 healthy people as controls.ANNOVAR and GERP were used to predict protein functions.2.Total of twenty-three members from five generations of a POAG family was enrolled.Thorough ophthalmologic examinations,family trees mapping,and clinical characteristics analysis were conducted.After informed consent of all members of POAG family was obtained,Peripheral blood DNAs of two patients and one unaffected member in the POAG family were extracted for exome sequencing.After sequencing data analysis and variance filtering,candidate genes were obtained.We selected the candidate genes which locate in linkage regions of common associated genes of POAG,and verified those variants in the rest members of families and 200 controls by Sanger sequencing in target genes.If no mutations were found in linkage intervals,we next searched variants across whole genome.SIFT and Polyphen were used to predict the functional impacts caused by mutations.Result 1.Six members were diagnosed as CD.The mean age of disease onset was16.5 years old.The clinical characteristics of this disease include: ivory-white nubecula appear in corneal endothelium and Descemet’s membrane,which expands along corneal edge at its onset and extends to central corneal during disease progression.Nubecula usually appear symmetrically in both eyes of each patient.Nubecula affect deep stromal layer at the age about 40,and continuously extend to shallow stromal layer with age.We first reported this special kind of CD,and revealed a novel heterozygous mutation c.1331G>A in KIAA1522 gene in all six patients.The newly identified variant was absent in other family members as well as control subjects.2.Six members were diagnosed as POAG,with severe clinical manifestations,and history of high intraocular pressures.The mean age of disease onset was 26.3 years old and 67% of affected patients required filtering surgery.However,other family members were asymptomatic.In six affected and three asymptomatic members,sequencing revealed a mutation c.C1456 T in exon 3 of myocilin gene(MYOC).Furthermore,we also identified a novel mutation c.G322 A in beta-1,4-galactosyltransferase 3 gene(B4GALT3)in these subjects,which was not reported previously in POAG patients.These two newly identified variants were absent in other family members as well as control subjects.Conclusion 1.We were the first group to report CD with special clinical characteristics that ivory-white nubecula appear in corneal endothelium and Descemet’s membrane,which expand along the corneal edge and extend to central cornea as the disease progresses.The mutations(c.1331G>A)in KIAA1522 gene may be associated with the pathogenesis of CD in this family.2.The mutations c.1456C<T(p.L486F)in MYOC and c.322G<A(p.V108I)in B4GALT3 are likely responsible for the pathogenesis of POAG in this family.