A novel transgenic mouse model of Chinese Charcot-Marie-Tooth disease type 2L

We previously found that the K141N mutation in heat shock protein B8 (HSPB8) was responsible for Charcot-Marie-Tooth disease type 2L in a large Chinese family. The objective of the present study was to generate a transgenic mouse model bearing the K141N mutation in the human HSPB8 gene, and to determine whether this (K141N)HSPB8 transgenic mouse model would manifest the clinical phenotype of Charcot-Marie-Tooth disease type 2L, and consequently be suitable for use in studies of disease pathogenesis. Transgenic mice overexpressing (K141N)HSPB8 were generated using K141N mutant HSPB8 cDNA cloned into a pCAGGS plasmid driven by a human cytomegalovirus expression system. PCR and western blot analysis confirmed integration of the (K141N)HSPB8 gene and widespread expression in tissues of the transgenic mice. The (K141N)HSPB8 transgenic mice exhibited decreased muscle strength in the hind limbs and impaired motor coordination, but no obvious sensory disturbance at 6 months of age by behavioral assessment. Electrophysiological analysis showed that the compound motor action potential amplitude in the sciatic nerve was significantly decreased, but motor nerve conduction velocity remained normal at 6 months of age. Pathological analysis of the sciatic nerve showed reduced myelinated fiber density, notable axonal edema and vacuolar degeneration in (K141N)HSPB8 transgenic mice, suggesting axonal involvement in the peripheral nerve damage in these animals. These findings indicate that the (K141N)HSPB8 transgenic mouse successfully models Charcot-Marie-Tooth disease type 2L and can be used to study the pathogenesis of the disease.