Structural and functional analysis of selected connexin32 mutations implicated in the pathogenesis of the X-linked form of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease is the most common genetic disorder of the peripheral nervous system. This devastating condition, for which there is no cure, affects about 1/3000 individuals, of which 10-12% carry the X-linked form, called CMT1X disease. Over 400 different genetic mutations associated with CMT1X disease have been identified in chromosome X, and in particular in the gene that encodes connexin32 protein (Cx32). This is a tetraspan membrane protein which forms reflexive junctional channels in the Schwann cell myelin sheath, providing a radial and fast pathway for ions and signalling molecules which are critical to maintain correct myelination. Despite the availability of a huge number of studies on normal and mutated Cx32 expression and function, a molecular interpretative framework of the observed CMT1X phenotype is still lacking. From a mechanistic point-of-view, the most pressing open question remains the elucidation of the molecular function of Cx32 in peripheral nerve myelin. Our laboratory has been active on connexin research for several years and has developed biophysical tools and methodologies in the van, in collaborations with our Italian and foreign partners, which are promising to provide crucial insight into the patho-biology of peripheral nerves and clues for the development of pharmacological treatments that in future could stop the disease progression or at least may alleviate the suffering of the numerous persons affected worldwide by Cx32 mutations. Specific aims of this project are the identification of cytoplasmic messenger molecules whose signalling is pathologically altered by mutations of Cx32 and the development of a novel culture preparation of Schwann cells to reproduce the in vivo expression pattern of Cx32 channels of human peripheral nerve myelin. This is not a merely academic exercise; it will contribute to the search for a cure once we understand what it is that goes wrong when connexins fail to perform.