A novel human CRYGD mutation in a juvenile autosomal dominant cataract

[摘要] Purpose: Identification of causalmutation in the crystallin, connexin, and paired box 6 (PAX6)genes associated with childhood cataract in patients from India. Methods: In this study, forty eightmembers from seventeen families and 148 sporadic cases of childhoodcataract were evaluated. Clinical and ophthalmologic examinations wereperformed on available affected and unaffected family members. Samplesof genomic DNA were PCR amplified to screen for mutations in thecandidate genes viz., alpha-A crystallin (CRYAA), beta- B2crystallin (CRYBB2), gamma-A crystallin (CRYGA), gamma-Bcrystallin (CRYGB), gamma-C crystallin (CRYGC), gamma-Dcrystallin (CRYGD), gap junction alpha-3 (GJA3), gapjunction alpha-8 (GJA8), and PAX6 based on polymerasechain reaction and single strand conformation polymorphism (PCR-SSCP)analysis. Samples showing any band mobility shift were subjected tobidirectional sequencing to confirm the variation. Co-segregation ofthe observed change with the disease phenotype was further tested byrestriction fragment length polymorphism (RFLP) for the appropriaterestriction site. Results: DNA sequencing analysis of CRYAA,CRYBB2, CRYGA-D, GJA3, GJA8, and PAX6 ofthe affected members of a family (C-35) showed a novel heterozygousmissense mutation C>A at position 229 in CRYGD in threeaffected members of family C-35 with anterior polar coronary cataract.This variation C229A substitution created a novel restriction site forAluI and resulted in a substitution of highly conserved arginine atposition 77 by serine (R77S). AluI restriction site analysis confirmedthe transversion mutation. Analysis of the available unaffected membersof the family (C-35) and 100 unrelated control subjects (200chromosomes) of the same ethnic background did not show R77S variation.Data generated using ProtScale and PyMOL programs revealed that themutation altered the stability and solvent-accessibility of the CRYGDprotein. Conclusions: We describe here a familyhaving anterior polar coronary cataract that co-segregates with thenovel allele R77S of CRYGD in all the affected members. Thesame was found to be absent in the ethnically matched controls (n=100)studied. Interestingly the residue Arg has been frequently implicatedin four missense (R15C, R15S, R37S, and R59H) and in one truncationmutation (R140X) of CRYGD. In two of the reported mutations Argresidues have been replaced with Serine. This finding further expandsthe mutation spectrum of CRYGD in association with childhoodcataract and demonstrates a possible mechanism of cataractogenesis.Screening of other familial (n=48) and sporadic (n=148) cases ofchildhood cataract, did not reveal any previously reported or novelmutation in the candidate genes screened.

[学科分类] 生物化学/生物物理