Charcot-Marie-Tooth disease type 4B (CMT4B) is a demyelinating autosomal re
cessive motor and sensory neuropathy characterised by focally folded myelin
sheaths in the peripheral nerve. The CMT4B gene has been localised by homo
zygosity mapping and haplotype sharing in the 11q23 region. A cDNA encoding
for the beta 2 subunit of the human brain sodium channel, SCN2B, has been
recently assigned to the same chromosomal interval by FISH. The SCN2B gene
has been considered a good candidate for CMT4B on the basis of protein homo
logy, chromosomal localisation, and putative biological function of the cod
ed product. In this paper, we report the genomic structure of the SCN2B gen
e consisting of 4 exons and 3 introns spanning a region of approximately 12
Kb. In addition, a search for mutations in patients affected with CMT4B as
well as a refined physical localisation excludes SCN2B as the CMT4B gene.