IDENTIFICATION OF 2 NOVEL GENES SPECIFICALLY EXPRESSED IN THE D-GROUPNEURONS OF THE TERRESTRIAL SNAIL CNS

A search for genes specifically expressed in the giant interneurons of parietal ganglia of the snail Helix lucorum yielded, among others, tw o genes named HDS1 and HDS2. According to data obtained by Northern hy bridization and whole-mount in situ hybridization, both genes are neur ospecific and expressed almost exclusively in the peptidergic D-group neurons (Sakharov, 1974) located in the right parietal ganglion. In si ne hybridization of the HDS1 and HDS2 probes with CNS of several relat ed species of the Helicoidea superfamily identified in all cases simil arly located homologous groups of neurons. Sequencing of the near full -length cDNA copies of the HDS1 and HDS2 genes revealed open reading f rames 107 and 102 amino acids long for HDS1 and HDS2, respectively. Bo th putative proteins contain a hydrophobic leader peptide and putative recognition sites for furin-like and PC-like endopeptidases. Predicte d amino acid sequences of the HDS1 and HDS2 proteins were found to be moderately homologous to each other, as well as to the LYCP preprohorm one expressed by the light yellow cells of the freshwater snail Lymnae a stagnalis. These results confirm an earlier hypothesis that the D-gr oup of the Helix family and the light yellow cells of Lymnaea stagnali s represent homologous neuronal groups. Our data suggest that the HDS1 and HDS2 genes encode precursors of secreted molecules, most likely n europeptides or neurohormones.