Assessment of a mutation in the H5 domain of Girk2 as a candidate for the weaver mutation

A mutation in the GIRK2 inwardly rectifying K⁺ channel was mapped recently to the region of mouse chromosome 16 containing the wv gene and shown to occur in mutant but not in wild-type mice. We demonstrate tight linkage of the Girk2 mutation to the wv phenotype and refine the localization of the weaver (wv) gene on recombinational and physical maps. This linkage between Girk2 and wv has existed since at least 1988 in descendants of the original mutation maintained in C57BL/6 animals. Girk2 is shown to be transcribed in brain before the first recognized manifestation of the wv phenotype and in cultures of granule cells (GCs) isolated from cerebellum at postnatal day 8. Wild-type GCs grown in this culture system display an important developmental property-the ability to extend neurites. However, no inwardly rectifying K⁺ current is detected in GCs cultured from either wv/wv or +/+ cerebellum under a variety of conditions that activate related channels in other tissues. This suggests that if the Girk2 mutation is responsible for the wv phenotype, it does not act by altering these electrical properties of developing GCs.