The ever-expanding neuropeptide gene families in the nematode Caenorhabditis elegans

Abstract

Neuropeptides act as chemical signals in the nervous system to modulate behaviour. With the ongoing EST projects and DNA sequence determination of different genomes, the identification of neuropeptide genes has been made easier. Despite the relatively 'simple' repertoire of behaviours in the nematode Caenorhabditis elegans, this worm contains a surprisingly large and diverse set of neuropeptide genes. At least 109 genes encoding over 250 potential neuropeptides have been identified in C. elegans; all genes are likely to be expressed and many, if not all, of the predicted peptides are produced. The predicted peptides include: 38 insulin-like peptides, several of which are involved in development and reproductive growth, and over 70 FMRFamide-related peptides, some of which are involved in locomotion, reproduction, and social behaviour. Many of the C. elegans peptides are identical or highly similar to those isolated or predicted in parasitic nematodes, such as Ascaris suum, Haemonchus contortus, Ancylostoma caninum, Heterodera glycines and Meloidogyne arenaria, suggesting that the function of these peptides is similar across species. The challenge for the future is to determine the function of all the genes and individual peptides and to identify the receptors through which the peptides signal.

FMRFamide‐like peptides encoded on the flp‐18 precursor gene activate two isoforms of the orphan Caenorhabditis elegans G‐protein‐coupled receptor Y58G8A.4 heterologously expressed in mammalian cells

“…25 Since then, most of the FLP-18 peptides listed in Table I have been isolated and sequenced. 3,[26][27][28] Recently, SYFDEKKSVPGVLRF-NH 2 was isolated 3,27 and EMPGVLRF-NH 2 was both predicted and isolated 3,27 ; neither was included in the current study. When we tested KSVPGVLRF-NH 2 (a predicted sequence 25 ) and SVPGVLRF-NH 2 (the isolated peptide [26][27][28] ), both peptides were equally potent to activate FLP-18R1b but SVPGVLRF-NH 2 was two fold more potent at the FLP-18R1a receptor (Table I).…”

“…[1][2][3] Caenorhabditis elegans contains a very large and diverse family of neuropeptide genes. From at least 109 genes encoding over 250 potential neuropeptides identified in this nematode, more than 70 FLPs have been predicted and/or identified.…”

“…Many have been found to play roles in vital functions such as locomotion, reproduction, and social behavior (for review see Ref. 3 and references within). Many of the C. elegans peptides are identical or highly homologous to those isolated or predicted in parasitic nematodes, including Ascaris suum, Haemonchus contortus, Ancylostoma caninum, Heterodera glycines, and Meloidogyne arenaria, suggesting that the function of these peptides is similar across species.…”

Generation and modulation of chemosensory behaviors in C. elegans

“…1a,b), suggesting the possibility of cross-talk and feedback regulation of chemosensory function (discussed further below). Both electrical and chemical synapses are present, and individual chemosensory neurons also contain dense core vesicles and express neuropeptide genes [53, [59][60][61][62]. The major postsynaptic outputs of the chemosensory neurons are a few interneuron types, with each interneuron type receiving inputs from partly overlapping groups of chemosensory neurons [53] (Fig.…”

The secreted Alzheimer-related amyloid precursor protein fragment has an essential role inC. elegans

“…The conserved putative growth domain has striking similarities to insulin-like peptides 12 and could predict a biological function in metabolic processes. C. elegans encodes 40 insulin-like peptides, 13 but has only one functional insulin/ IGF-1 receptor, DAF-2. 14 The apl-1(yn5) mutation, which results in the production of only an extracellular fragment of APL-1 (APL-1EXT) that is slightly larger than sAPL-1, disrupts several metabolic processes, including developmental progression, reproductive fitness, and body size, similar to insulin/IGF-1 receptor mutants.…”