Neuropeptides play critical roles in neurotransmission in vertebrates and invertebrates. We are interested in identifying the neuropeptides used by the ASH sensory neurons. Genetic and molecular evidence suggests that ASH neuropeptides may play critical roles in differential synaptic signaling of sensory information. Previous analysis in C. elegans (CGC#3193) has focused on the FMRFamide related peptide ( flp ) neuropeptide genes. The ASH neurons do not contain FMRFamide immunoreactivity. We have identified and are characterizing 21 putative neuropeptide like protein ( nlp ) genes of C. elegans. nlp genes were identified using a structure-based (not homology-based) C. elegans database searching strategy. Neuropeptides are encoded as preproproteins that contain a signal sequence and mono- or dibasic endopeptidase sites which flank the active neuropeptides. Multiple repeats of virtually identical, active neuropeptides are frequently found within the same gene. Standard database searching programs were used to identify C. elegans nlp genes: those which encode proteins with a signal peptide and 2 or more repeats of related putative neuropeptides flanked by di- or monobasic amino acids. This strategy eliminates the need for significant sequence identity with previously identified neuropeptides. Six of the predicted genes correspond to ESTs. The neuropeptides encoded by the nlp genes vary in their relationship to neuropeptides identified in other species. For example,
nlp-1 and
nlp-2 (C01C4.1 and T24D8.5-3) predicted peptides have approximately 40% identity with buccalin and myomodulin neuropeptides from other invertebrates, respectively. In contrast, predicted peptides encoded by
nlp-10 (F37A8.4) are not homologous to any known neuropeptide. To address if nlp genes are expressed in neurons, we are generating 21 nlp::GFP reporter constructs. So far, all 19 reporter constructs tested express GFP exclusively or predominantly in neurons. Two nlp genes are expressed in ASH sensory neurons, 5 in the pharynx, 5 in the ventral nerve cord and 2 in the HSN neurons. We will address nlp gene function using immunohistochemical, genetic and molecular techniques.