Hardege, Iris et al. (2017) International Worm Meeting "Luqin-like peptide ligands of NPR-22 are involved in pharyngeal pumping and feeding behaviours in C. elegans."

Beets, Isabel, Zels, Sven, Schafer, William, Schoofs, Liliane, Chew, Yee Lian, Hardege, Iris

[International Worm Meeting, 2017]

The C. elegans NPR-22 receptor has been recently linked to a number of RFamide neuropeptide ligands involved in behavioural modulation, including the regulation of quiescence via FLP-11 and intestinal serotonin induced fat loss via FLP-7. However, the broader expression pattern of NPR-22, including expression in pharyngeal muscles, suggests a complex role for this receptor and potential modulation by additional peptide ligands. Here we described the function of a luqin-like RF-amide neuropeptides, that are potent activators of NPR-22 activation in cell-based GPCR activation assays. In hermaphrodites, the luqin-like precursor gene is expressed in a single pharyngeal motorneuron, M1, but in males, expression can be seen in several male-specific neurons. Due to expression of the luqin-like peptide gene in M1 and evidence of npr-22 expression in pharyngeal muscle we sought to observe the pumping rate of animals overexpressing the Luqin-like precursor gene as well as mutant animals containing deletions in either the peptide gene or npr-22. Overexpression resulted in a reduced pharyngeal pumping rate, whereas peptide null mutants showed a slight but significant increase in pumping rate. There was no significant change in the pumping rate of npr-22 mutants compared to N2. This suggests a potential inhibitory role for luqin-like peptides in regulation of pharyngeal pumping and feeding behaviour. Concurrent with changes in pharyngeal pumping rate, single worm tracking data revealed that peptide-overexpressing animals are statistically shorter in length, had a reduced tracking distance and lower foraging rates than wild type worms. These data suggest a novel role for luqin-like peptide ligands in control of pharyngeal pumping and feeding behaviours, which potentially require the NPR-22 receptor. In addition, given the expression of these peptides in male-specific neurons, including some cells in the male tail, we are currently investigating if luqin-like peptides are involved in male mating behaviour in C. elegans.

Rothman JH (1991) International C. elegans Meeting "ZYGOTIC EMBRYONIC LETHAL MUTANTS IDENTIFIED IN A GENOME-WIDE SCREEN."

Rothman JH

[International C. elegans Meeting, 1991]

A straightforward screening procedure has allowed identification of zygotic embryonic lethal (ZEL) mutants representative of the entire C. elegans genome. From 15,800 Fl clones, an archive of 572 potential ZELs (frozen directly on plates) was assembled. The frozen cultures, containing ~40% heterozygotes, can be sampled repeatedly, providing sufficient numbers of homozygous mutant embryos for phenotypic screening. The terminal phenotypes of ~450 mutants were examined by Nomarski microscopy. 16 mutations were found to be distributed over all six linkage groups and multiple alleles of particular genes have been identified based on the similar phenotypes of the corresponding mutants. Selected mutants have been examined by immunofluorescence with a panel of monoclonal antibodies and by time-lapse video microscopy. Owing to the central role of the hypodermis in embryogenesis, mutants defective in hypodermal development are of particular interest and three general classes of such mutants have been identified. In mutants of the first class, which have been examined in the most detail, the hypodermis consistently fails to enclose the embryo prior to elongation; the resulting embryos are largely 'naked' with only a localized patch of hypodermis. So far, mutations in at least three zen (= zygotic enclosure defective) genes in this class have been identified. zen-2 Il mutants express all cell fate markers examined apparently normally and may be specifically defective in the ventrally directed hypodermal migration. zen-3 V mutants fail to express a seam cell-specific antigen and appear to make too few hypodermal cells; non-hypodermal cell types are apparently normal. (For a description of zen1, see other abstract by J. Rothman). A number of mutants defective in pharynx development were identified in the screen. Unlike pha-l mutants, described by H. and R. Schnabel (Science 250: 686, 1990), all of these are defective in elongation. The most severe of three alleles of pel-l I (pel = pharynx and elongation defective) results in the absence of a discernible pharynx and a reduced number of cells expressing pharynx-specific antigens. Mutations in pel-2 IV and pel-4 111 appear to block late stages of pharynx differentiation and morphogenesis, as is seen in pha- l mutants. pel-3 11 mutants undergo nearly complete elongation but are variably blocked in pharynx morphogenesis. Two allelic ZEL mutations ( e2501 11 and e2510 11) lead to accumulation of cell death corpses, similar to the phenotype of viable engulfment-defective ced mutants described by E. Hedgecock and by R. Ellis and B. Horvitz. The appearance of cell corpses, but not the embryonic lethality, is suppressed by a ced-3 mutation. These mutants may be defective in a cell surface recognition system common both to cell corpse engulfment and to a process essential for embryonic viability.