Molecular and pathological studies in Charcot-Marie-Tooth disease 1A

Molecular and clinical features of inherited neuropathies due to PMP22 duplication

PMP22 is a transmembrane glycoprotein component of myelin, important for myelin functioning. Mutation of PMP22 gene which encodes for the production of PMP22 glycoprotein is associated with a variety of inherited neuropathies. This literature review sought to review the molecular mechanism and clinical features of inherited neuropathies caused by PMP22 duplication. PMP22 duplication causes CMT1A which accounts for more than half of all CMT cases and about 70% of CMT1 cases. It manifests with muscle weakness, depressed reflexes, impaired distal sensation, hand and foot deformities, slowing of NCV and onion bulbs. With no specific treatment available, it is managed conservatively. Future treatment may be based on the molecular genetics of the disease.

Expression of peripheral myelin protein zero in sural nerve of patients with Charcot-Marie-Tooth disease 1B

A Charcot-Marie-Tooth disease 1B (CMT1B) family with a mutation of the Po gene is presented. A to G substitution of nucleotide 389 in exon 3 resulted in Lys 131 Arg substitution. Immunostaining for Po in biopsied sural nerve from one family member with CMT1B was expressed in a small number of myelinated fibers. Immunoblot analysis for Po revealed that it was of normal molecular weight (29 kDa) although significantly reduced in amount. This heterozygous mutation could lead to a reduction in the total amount of normal protein in peripheral nerves through a mechanism of loss of function.

Charcot-Marie-Tooth disease type 1A duplication by PCR analysis

By generating new junctional fragments from the recombinant Charcot-Marie-Tooth (CMT) 1A-REPs in CMT1A patients, a 3.2-kb recombination hot spot is observed in three quarters of CMT1A patients. By a polymerase chain reaction (PCR) method the authors analyzed eight patients CMT1A duplication, confirmed by Southern blot, to detect a recombination hot spot. Four patients had a novel 3.2-kb junctional fragment by PCR analysis. These four patients with a novel 3.2-kb junctional fragment had an abnormal 1789-bp fragment in addition to 1986-bp fragment after NsiI digestion (type 1). One patient who demonstrated no novel 3.2-kb junctional fragment had an abnormal 336-bp fragment in addition to 265 bp (type 2). Three patients with CMT1A duplication were not diagnosed as having CMT1A on the basis of PCR analysis. The PCR-based DNA test is valuable for screening to detect CMT1A duplication.