[Mutation of the myelin Po gene in hereditary motor and sensory neuropathy]

Charcot-Marie-Tooth neuropathy type 1 (CMT1) or hereditary motor and sensory neuropathy (HMSN1) is the most common inherited peripheral neuropathy. Most cases show dominant inheritance. CMT1 loci map to chromosome 17 (CMT1A), chromosome 1 (CMT1B), another unknown autosome (CMT1C) and the X chromosome (CMTX). CMT1A has been demonstrated to be associated with a large DNA duplication of 17 p11.2 including the peripheral myelin protein-22 gene (PMP22) or a point mutation of PMP22. Myelin protein zero (Po), the major structural protein of peripheral myelin, is another integral myelin membrane protein like PMP22. We have mapped the locus of the Po gene to chromosome 1q22-q23 in the region of the CMT1B locus, investigated Po as a candidate gene in three families with CMT1B and identified that Po is a gene responsible for CMT1B. Dejerine-Sottas disease (HMSN3) has been considered as another demyelinating disease. However, we have demonstrated that a de novo mutation of Po gene is responsible for some sporadic cases with HMSN3. The term "Dejerine-Sottas disease" may have represented the severely affected and sporadic cases with CMT. Identification of the primary defect in the diseases enables us to classify the peripheral neuropathies based on their etiologies.