[DNA tests for mutant genes coding for transthyretins Gly42, Arg50 and Cys114 in Japanese cases of familial amyloid polyneuropathy].

Four different genes encoding variant transthyretins (TTR) have been known in Japanese cases with familial amyloidotic polyneuropathy (FAP); TTR Met30, Gly42, Arg50 and Cys114. First three mutant genes can be detected by restriction fragment length polymorphism using NsiI, Cfr13I and MvaI, respectively. Since a single base change responsible for TTR Cys114 produces no new restriction site, RFLP is not directly applicable for the detection of this gene. In this study, TTR Cys114 gene was amplified by polymerase chain reaction using mismatch primer to produce a new restriction site for HgiAI. The enzyme digestion of the product resulted in the appearance of extra fragments in the presence of the normal fragment. The accurate detections of all the four mutant genes are hereafter possible by these procedures.