How do Cx32 and Cx47 mutants cause CNS demyelination?

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DESCRIPTION (provided by applicant): CNS myelination depends on the proper function of connexin32 (Cx32) and Cx47, which are gap junction proteins expressed by oligodendrocytes. Defects in the genes that encode these connexins, GJB1/Cx32 and GJA12/Cx47, cause CNS white matter tract disorders, including X-linked Charcot-Marie-Tooth Disease and Pelizaeus-Merzbacher-like Disease, respectively. Deletion of both GJB1/Cx32 and GJA12/Cx47 genes in mice results in a severe dysmyelinating phenotype and death by six weeks of age that does not occur with deletion of either gene alone, suggesting that these proteins serve overlapping functions. Anatomical and functional studies demonstrate that gap junctions couple astrocytes and oligodendrocytes, and Cx32 and Cx47 likely comprise the oligodendrocyte portion of these gap junction channels. We propose that mutations in the genes that encode Cx32 and Cx47 disrupt coupling between astrocytes and oligodendrocytes. The goal of this grant is to investigate the properties of mutant Cx32 and mutant Cx47 in the context of interactions with connexins expressed by the same cells and by apposing cells. This work should elucidate the molecular composition of gap junction channels that couple astrocytes and oligodendrocytes.