Molecular cloning of myomodulin cDNA, a neuropeptide precursor gene expressed in neuron L10 of Aplysia californica.

Screening of an abdominal ganglion cDNA library of Aplysia californica with a synthetic oligonucleotide based on the myomodulin peptide sequence has been used to identify and characterize a cDNA clone expressed in interneuron L10. The complete sequence of 1,534 nucleotides in length shows an open reading frame of 370 amino acids that encodes a 42-kD pre-propeptide. Proteolytic cleavage of the precursor potentially gives rise to 10 copies of myomodulin A, single copies of 6 myomodulin-related peptides, and other unrelated sequences. Southern blot analysis of sperm DNA shows that the haploid Aplysia genome contains only one copy of the gene. RNA blot analyses of central nervous system (CNS) mRNA show that the myomodulin gene is expressed in all major ganglia and that a single transcript of around 1,600 nucleotides can be detected in pooled CNS mRNA, suggesting that the same sequence is transcribed in each ganglia. Nucleotide sequences of partial cDNA clones isolated from a cerebral ganglion and a CNS cDNA library are identical to the abdominal ganglion sequence, further suggesting that the same myomodulin gene is expressed in other ganglia.