Transthyretin gene mutation and expression in patients with familial vitreous amyloidosis

Abstract

Objective To observe the transthyretin (TTR) gene mutation, protein and mRNA expression in patients with familial vitreous amyloidosis. Methods Subjects were divided into three groups: (1) illness group: seven patients with familial vitreous amyloidosis. (2) No-illness group: 9 unaffected family members. (3) Control group: 9 healthy individuals in same area. Subjects' peripheral venous blood were collected and DNA were extracted, 4 exons of TTR gene were amplified by reverse transcription polymerase chain reaction(RT-PCR), the gene fragments were sequencing by the fluorescence labelling method. Serum TTR protein expression was detected by Western blot, and TTR mRNA in leukocyte was assayed by RT-PCR. Results 4 exons of TTR gene of all samples were amplified, and DNA sequencing data showed that 7 patients and 3 subjects DNA from unaffected family members had mutated in the 3rd exon of 107th base, changing from G to C. Heterozygous mutation occurred in codon of the 83th amino acid in exon 3, namely, Gly83Arg, resulted in the change of GGC to CGC. The protein and mRNA expression of TTR was lower in illness group than no-illness group and control groups(P<0.05). Compared with control group, TTR mRNA expression in unaffected family members groups was significant decreased(P<0.05). Conclusion Heterozygous mutation occurred in codon of the 83th amino acid in exon 3, namely Gly83Arg, and suggested that Gly83Arg is connected with the change of TTR mRNA and protein expression. Key words: Amyloidosis, familial/genetics; Thyroid hormones; DNA mutational analysis