An αA-crystallin gene mutation, Arg12Cys, causing inherited cataract-microcornea exhibits an altered heat-shock response

[摘要] Purpose: To investigate the clinicalfeatures and molecular basis of inherited cataract-microcornea causedby an αA-crystallin gene (CRYAA) mutation in a Chinese family. Methods: A three-generation Chinesefamily with members having autosomal dominant cataract and microcorneawas recruited. Genomic DNA from peripheral blood or buccal swab samplesof five affected and five unaffected members were obtained. Based on 15genes known to cause autosomal dominant cataract, single nucleotidepolymorphisms (SNPs) or microsatellite markers were selected andgenotyped for two-point linkage analysis. Direct sequencing wasperformed to identify the disease-causing mutation. The expressionconstruct coding for recombinant COOH-terminal myc-His-tagged wild typeor R12C αA-crystallin protein (CRYAA) was expressed in COS-7 cells.Detergent solubility and subcellular distribution of wild type and R12CCRYAA were examined by western blotting and immunofluorescence,respectively. Heat-shock response was monitored by quantitativepolymerase chain reaction (qPCR) of heat-shock proteins 70 and 90α(HSP70 and HSP90α). Results: The five affected familymembers showed variable lens opacities and microcornea. Clinicalfeatures of cataract were asymmetric in two eyes of some affectedsubjects. A heterozygous missense substitution, c.34C>T, in CRYAA,which is responsible for the R12C amino acid change, segregated withautosomal dominant cataract (ADCC) in this family. This substitutionwas absent in 103 unrelated controls. When expressed in COS-7 cells,the R12C mutant CRYAA resembled the wild type protein in its solubilitywhen extracted with 0.5% Triton X-100 and with its cytoplasmiclocalization. However, mutant cells exhibited an altered heat-shockresponse, evidenced by the delayed expression of HSP70, when comparedto cells expressing wild type CRYAA. Conclusions: The R12C mutation in CRYAAwas responsible for a variable type of inherited cataract associatedwith microcornea in this Chinese family. The altered heat-shockresponse of mutant cells suggested a change of chaperoning capacity andnetworking, which could be associated with the pathogenesis ofhereditary cataract-microcornea syndrome.

[学科分类] 生物化学/生物物理