Expression of the L11 neuropeptide gene in the Aplysia central nervous system.

Neuron L11 in the abdominal ganglion of Aplysia californica is thought to be both cholinergic and peptidergic. In previous studies, we isolated a cDNA clone encoding the precursor for an L11 secreted protein(s) by differentially screening an abdominal ganglion cDNA library. We now report the isolation of genomic clones encoding the L11 cDNA sequences. Analysis of these clones reveals that the gene is present in a single copy per haploid genome. RNA blotting and cDNA cloning demonstrate that the L11 gene is expressed not only in the abdominal ganglion but in the head ganglia as well. To define the positions of cells expressing this gene and to follow their processes, we raised antibodies to synthetic peptides defined by the cDNA sequence. Histochemistry revealed about 100 neurons containing immunoreactive material. These cells arborize in the neuropil and are distributed throughout the central nervous system, representing about 0.5% of the Aplysia central neurons. In addition, cells in the abdominal ganglion send processes to the mantle floor at the base of the gill via the genital and branchial nerves. Our data suggest that this network of cells expresses the single L11 peptide gene.