TGFBI and CHST6 gene analysis in Chinese stromal corneal dystrophies

Abstract

Aim: To investigate whether mutations in TGFBI gene or CHST6 gene correlated with stromal corneal dystrophies (CD) in 8 Chinese probands.

Methods: Eight unrelated patients with stromal corneal dystrophies were recruited in this study; all affected members were assessed by completely ophthalmologic examinations. Genomic DNA was extracted from peripheral leukocytes, 17 exons of TGFBI gene and the exon of CHST6 gene were amplified by polymerase chain reaction (PCR), sequenced directly and compared with the reference database.

Results: Three heterozygous mutations in TGFBI gene were identified in six patients: c. 370C>T (p.Arg124Cys) was found in exon 4 of TGFBI gene in three members, c. 371G>A (p.Arg124His) was found in one patient; c. 1663C>T (p.Arg555Trp) was found in exon 12 in other two members. In addition, four polymorphisms with the nucleotide changes rs1442, rs1054124, rs4669, and rs35151677 were found in TGFBI gene. Mutations were not identified in the rest of 2 affected individuals in TGFBI gene or CHST6 gene.

Conclusion: Within these patients, R124C, R124H and R555W mutations were co-segregated with the disease phenotypes and were specific mutations for lattice corneal dystrophy type I (LCD I), Avellino corneal dystrophy (ACD, GCD II), granular corneal dystrophy type I (GCD I), respectively. Our study highlights the prevalence of codon 124 and codon 555 mutations in the TGFBI gene among the Chinese stromal corneal dystrophies patients.

Keywords: Mutation screening; TGFBI gene; TGFBI protein; carbohydrate; corneal dystrophies; sulfotransferse CHST6.

Figure 1. The experimental maps of three loci mutations and four SNPs

A: The heterozygous c.370C>T(p.R124C) mutation in exon 4 in one of three CDLI families; B: The heterozygous c.371G>A (p.R124H) mutation in exon 4 in the GCDII family; C: The heterozygous c.1663C>T (p.R555W) mutation in exon 12 in two GCDI families; D: A heterozygous 1803A/G(L601L)SNP in exon 13; E: A homozygous 981G/G (V327V) SNP in exon 8; F: A heterozygous 651C/G(L217L) SNP in exon 6; G:A heterozygous 1620C/T(F540F)SNP in exon 12. Blank arrows highlight the position of nucleotide substitutions. Control electropherograms are shown for comparison purposes (A-G, bottom panel).