LOCALIZATION SHAW-RELATED K-CHROMOSOMES( CHANNEL GENES ON MOUSE AND HUMAN)

Four related genes, Shaker, Shab, Shaw, and Shal, encode voltage-gated K+ channels in Drosophila. Multigene subfamilies corresponding to eac h of these Drosophila genes have been identified in rodents and primat es; this suggests that the four genes are older than the common ancest or of present-day insects and mammals and that the expansion of each i nto a family occurred before the divergence of rodents and primates. I n order to define these evolutionary relationships more precisely and to facilitate the search for mammalian candidate K+ channel gene mutat ions, we have mapped members of the Shaw-homologous gene family in hum ans and mice. Fluorescence in situ hybridization analysis of human met aphase chromosomes mapped KCNC2 (KShIIIA, KV3.2) and KCNC3 (KShIIID, K V3.3) to Chromosome (Chr) 19q13.3-q13.4. Inheritance patterns of DNA r estriction fragment length variants in recombinant inbred strains of m ice placed the homologous mouse genes on distal Chr 10 near Ms15-8 and Mdm-1. The mouse Kcnc1 (KShIIIB, NGK2-KV4, KV3.1) gene mapped to Chr 7 near Tam-1. These results are consistent with the hypothesis that th e generation of the mammalian KCNC gene family included both duplicati on events to generate family members in tandem arrays (KCNC2, KCNC3) a nd dispersion of family members to unlinked chromosomal sites (KCNC1). The KNCN2 and KCNC3 genes define a new synteny group between humans a nd mice