A neuropeptide molt-inhibiting hormone (MIH) negatively regulates crustacean molting glands (Y-organs). We report here the molecular cloning of a cDNA encoding putative MIH of the Dungeness crab, Cancer magister. A cDNA library was commercially prepared using poly (A+) RNA isolated from C. magister eyestalk neural ganglia. The library was screened using as probe a previously cloned portion of a cDNA encoding MIH of the blue crab, Callinectes sapidus. DNA sequence analysis of one positive clone revealed a 339 base pair open reading frame encoding a 78 amino acid putative MIH and a 35 amino acid signal peptide. The deduced amino acid sequence of C. magister MIH shows high sequence identity (80-98%) with MIH of three other brachyuran crabs, but lower identity (26-45%) with MIH and MIH-like peptides from astacurans and shrimp. Studies using reverse transcription-polymerase chain reaction (RT-PCR) indicate the MIH gene is expressed in eyestalk but not control (muscle, gill, gonad, hepatopancreas) tissue.
