Identification of novel sequence variants in the neurofilament‐light gene in a Japanese population: analysis of Charcot‐Marie‐Tooth disease patients and normal individuals

Abstract

Mutations of the neurofilament-light (NEFL/NF-L) gene were examined in 124 unrelated Japanese patients with Charcot-Marie-Tooth disease (CMT) without known gene mutations, and 248 normal Japanese individuals. A new method, which can detect basepair mismatches with RNase cleavage on agarose gel electrophoresis, coupled with DNA sequencing, identified 8 novel sequence variations in the NF-L gene. In these sequence variants, 5 variants were polymorphisms, including 3 single nucleotide polymorphisms (SNPs), and 3 other missense mutations (Pro22Thr, Asn97Ser and Ala148Val) were found in the patients with CMT phenotype. The variant alleles in the NF-L gene could influence the developing process of CMT phenotype and also might cause CMT phenotype.

NEFL Pro22Arg mutation in Charcot-Marie-Tooth disease type 1

“…We believed that this mutation was the underlying cause of the CMT1 phenotype in the FC99 family for the following reasons: cosegregation of the mutation with affected members of the pedigree, no similar mutation in controls (n = 210), well-conserved Pro22 among different species, and the findings of previous reports on the effect of different mutations at the Pro22 site. It seems that codon 22 is one of the mutational hot spots in the NEFL gene because three different Pro22 mutations, including the one found in this study, have been reported (Fabrizi et al 2004;Georgiou et al 2002;Yoshihara et al 2002). Three different families have been reported to have Pro22 mutations: Pro22Ser in a Slovenian family (Georgiou et al 2002) and an Italian family (Fabrizi et al 2004), and Pro22Thr in a Japanese family (Yoshihara et al 2002).…”

“…Histopathological features were only described in a Pro22Ser patient in an Italian family and featured giant axons with neurofilament accumulation (Fabrizi et al 2004). However, the Japanese family with the Pro22Thr mutation was reported to have the CMT1 phenotype based on clinical and electrophysiological features (Yoshihara et al 2002). Moreover, the FC99 family with Pro22Arg mutation also showed a CMT1 neuropathy with onion bulb formations in this study.…”

“…It seems that codon 22 is one of the mutational hot spots in the NEFL gene because three different Pro22 mutations, including the one found in this study, have been reported (Fabrizi et al 2004;Georgiou et al 2002;Yoshihara et al 2002). Three different families have been reported to have Pro22 mutations: Pro22Ser in a Slovenian family (Georgiou et al 2002) and an Italian family (Fabrizi et al 2004), and Pro22Thr in a Japanese family (Yoshihara et al 2002). Histopathological features were only described in a Pro22Ser patient in an Italian family and featured giant axons with neurofilament accumulation (Fabrizi et al 2004).…”

“…1b). This mutation was found in the (Yoshihara et al 2002) and c.64C [ T resulting in Pro22Ser (Fabrizi et al 2004;Georgiou et al 2002), but this Pro22Arg mutation was not reported in the inherited peripheral neuropathies mutation database. Amino acids at the mutated site are highly conserved in different species (Fig.…”

“…Particularly, two Pro22 mutations have been reported: Pro22Ser was found in CMT2E with giant axons in the sural nerve (Fabrizi et al 2004;Georgiou et al 2002), and Pro22Thr was found to be associated with CMT1F (Yoshihara et al 2002). It has been suggested that Pro22 mutations abolish the Thr-Pro phosphorylation sequence of the head domain of NEFL by proline-directed protein kinases (PDPKs) (Sasaki et al 2006).…”