Gene isolation with cDNA probes from identified Aplysia neurons: neuropeptide modulators of cardiovascular physiology.

The Aplysia abdominal ganglion neurons, R3-R14, modulate cardiovascular activity. In vitro translations of poly(A)+ RNA from these cells suggest that they contain a prevalent mRNA encoding a 14 kd protein. Utilizing differential screening techniques with 32P-labeled cDNA synthesized from the poly(A)+ RNA of identified neurons, we isolated the corresponding gene. The Aplysia haploid genome contains a single copy of this sequence, which is interrupted by two large introns and spans approximately 7 kb of genomic DNA. The R3-R14 neurons specifically express this gene, resulting in the synthesis of a 1.25 kb mRNA not found in other abdominal ganglion cells or in the head ganglia. The gene was shown to encode a 13.5 kd precursor, which is proteolytically cleaved into at least three peptides with molecular weights of 5.0, 3.3, and 1.3 kd. These peptides and glycine are thought to act as chemical messengers in the central nervous system and peripherally.