Molecular defects in the dysmyelinating mutant quaking.

The quaking [or quakingviable (qk[v])] mutant mouse, which exhibits severe dysmyelination of the central nervous system (CNS), has been studied extensively over the last 30 years. The genetic defect responsible for the dysmyelinating phenotype had remained elusive, however, until the recent cloning of a candidate gene, qkI (Ebersole et al.: Nature Genet 12:260-265, 1996). qkI encodes three proteins, QKI-5, QKI-6, and QKI-7, which are abundant in myelin-forming cells in wild-type mice but whose levels are severely reduced in myelin-forming cells of qk(v) mice, consistent with the notion that abnormalities of qkI expression underlie the qk(v) phenotype. This review discusses some of the known molecular defects in qk(v) in the context of this new information and the potential role of QKI proteins in myelinogenesis.