Implication of the SH3TC2 gene in Charcot-Marie-Tooth disease associated with deafness and/or scoliosis: Illustration with four new pathogenic variants.
We screened SH3TC2 in 50 unrelated Greek patients with suspected demyelinating Charcot-Marie-Tooth disease and pedigree compatible with recessive inheritance.
We screened for SH3TC2 pathogenic variants in 84 AR or sporadic CMT probands, PMP2 pathogenic variants in 39 AD or sporadic CMT1 probands, and BSCL2 pathogenic variants in 50 AD or sporadic CMT2 probands, using polymerase chain reaction and Sanger sequencing.
Scoliosis and cranial nerve involvement are frequent features of this CMT4 subtype, and their presence should prompt the clinician to look for SH3TC2 gene mutations.
Among the 520 participants (274 males) aged 3 to 20 years, CMT type 1A (CMT1A) was the most prevalent type (252 [48.5%]), followed by CMT2A (31 [6.0%]), CMT1B (15 [2.9%]), CMT4C (13 [2.5%]), and CMTX1 (10 [1.9%]).
Four private mutations responsible for three forms demyelinating of Charcot-Marie-Tooth (CMT) or hereditary motor and sensory neuropathy (HMSN) have been associated with the Gypsy population: the NDRG1 p.R148X in CMT type 4D (CMT4D/HMSN-Lom); p.C737_P738delinsX and p.R1109X mutations in the SH3TC2 gene (CMT4C); and a G>C change in a novel alternative untranslated exon in the HK1 gene causative of CMT4G (CMT4G/HMSN-Russe).
In the context of inherited neuropathy, giant axons are typically associated with autosomal recessive giant axonal neuropathy caused by gigaxonin mutations but have also been reported in association with NEFL- and SH3TC2-associated Charcot-Marie-Tooth disease.
To describe the clinical and electrophysiological features evoking CMT4C, an autosomal recessive (AR) form of Charcot-Marie-Tooth disease (CMT) due to mutations in the SH3TC2 gene, we screened the coding sequence of SH3TC2 gene in 102 unrelated patients with a demyelinating or intermediate CMT and a family history compatible with an AR transmission.
We identified and validated compound, heterozygous, causative alleles in SH3TC2 (the SH3 domain and tetratricopeptide repeats 2 gene), involving two mutations, in the proband and in family members affected by Charcot-Marie-Tooth disease.
Five families with AR demyelinating CMT and SH3TC2 mutations were identified, four families were homozygous for the R954X mutation and the fifth family was compound heterozygous for the R954X and E657K mutations.
Mutations in SH3TC2 (KIAA1985) cause Charcot-Marie-Tooth disease (CMT) type 4C, a demyelinating inherited neuropathy characterized by early-onset and scoliosis.
The authors searched for SH3TC2 gene mutations in 10 consanguineous CMT families putatively linked to the CMT4C locus on the basis of haplotype segregation and linkage analysis.