Neurobiology of the Caenorhabditis elegans genome

Neurotransmitter receptors, neurotransmitter synthesis and release pathways , and heterotrimeric GTP-binding protein (G protein)-coupled second messeng er pathways are highly conserved between Caenorhabditis elegans and mammals , but gap junctions and chemosensory receptors have independent origins in vertebrates and nematodes. Most ion channels are similar to vertebrate chan nels but there are no predicted voltage-activated sodium channels. The C. e legans genome encodes at least 80 potassium channels, 90 neurotransmitter-g ated ion channels, 50 peptide receptors, and up to 1000 orphan receptors th at may be chemoreceptors, For many gene families, C. elegans has both conve ntional members and divergent outliers with weak homology to known genes; t hese outliers may provide insights into previously unknown functions of con served protein families.