A missense mutation in the γD crystallin gene (CRYGD)associated with autosomal dominant "coral-like" cataract linked tochromosome 2q

[摘要] Purpose: Hereditary cataract is a clinically and geneticallyheterogeneous lens disorder that usually presents as a sight-threateningtrait in childhood. The purpose of this study was to map and identifythe mutation underlying an autosomal dominant form of coral-shapedcataract segregating in a three generation Caucasian pedigree.Methods: Genomic DNA was prepared from blood leucocytes, genotypingwas performed using microsatellite markers, and LOD scores werecalculated using the LINKAGE programs. Mutation detection was performedusing direct sequencing and primer extension analysis. Followingsite-directed mutagenesis, mutant and wild type expression constructswere transfected into a human lens epithelial cell line (HLE B-3) andrecombinant protein was detected by immunoblotting, imunofluorescence,and immunogold microscopy. Cell death was monitored by fluorescenceactivated cell sorting.Results: Significant evidence of linkage was detected at markersD2S371 (LOD score [Z]=3.81, recombination fraction [θ]=0) andD2S369 (Z=3.64, θ=0). Haplotyping indicated that the disease genelay in the approximate 10 Mb physical interval between D2S1384 andD2S128, containing the γ-crystallin gene (CRYGA-CRYGD)cluster on chromosome 2q33.3-q34. Sequencing of the CRYGA-CRYGDcluster identified a C->A transversion in exon 2 of CRYGD thatwas predicted to result in the non-conservative substitution ofthreonine for proline at amino-acid residue 23 (P23T) in the processedCRYGD protein. Transfection studies suggested that the P23T mutant wasless soluble than its wild type counterpart when expressed in HLE B-3cells.Conclusions: This study has identified an eighth type of cataractmorphology associated with CRYGD and suggests that a CRYGDmutation may underlie the historically important "coralliform" cataractfirst reported in 1895.

[学科分类] 生物化学/生物物理