8 POTASSIUM CHANNEL FAMILIES REVEALED BY THE C-ELEGANS GENOME PROJECT

The wealth of accumulating data from the Caenorhabditis elegans genome sequencing project has rapidly accelerated the discovery of novel pot assium channel genes and now places within reach the possibility of de scribing the total complement of potassium channels used by an individ ual species. Using annotated GenBank sequences, BLAST searches of unfi nished sequences and degenerate oligonucleotide polymerase chain react ion (PCR) screens, we have identified and compiled genes for 38 C. ele gans potassium channel and two cyclic nucleotide-gated cation channel subunits, representing eight conserved multigene families. Novel famil ies of potassium channel genes were revealed, as well as conserved hom ologues of all known vertebrate families. Two separate families repres ent C. elegans homologues for human potassium channels recently implic ated in hereditary long QT arrhythmias. Of particular note is an excep tionally large class of at least 23 genes with a novel subunit structu re having two tandem 'P' domains; these channels may form as dimers in contrast to all other potassium channel types which form as tetramers . The 40 potassium channel genes are evenly distributed on all six C. elegans chromosomes, with the exception of three instances of gene clu stering on the fifth and X chromosomes. Copyright (C) 1996 Elsevier Sc ience Ltd