Expression of the molt-inhibiting hormone-like gene in the eyestalk and brain of the white shrimp Penaeus vannamei.

Neuropeptides from the X-organ-sinus gland complex in the eyestalk have important roles in the regulation of growth and maturation in crustaceans. A complementary DNA encoding a molt-inhibiting hormone-like (MIH-like) neuropeptide from the eyestalk of Penaeus vannamei has been isolated and cloned in this laboratory. Using the reverse transcription-polymerase chain reaction (RT-PCR) method, the gene encoding the MIH-like neuropeptide was shown to be expressed in the brain as well as in the eyestalk. Subsequent cloning and sequencing of the PCR products showed that the MIH-like gene transcript of the brain shares 98% sequence identity with that of the eyestalk. In situ hybridization experiments showed that the MIH-like messenger RNA is exclusively localized in the X-organ complex in the medulla terminalis of the eyestalk, whereas in the brain the MIH-like gene transcript was detected in three regions including the neurosecretory cells, giant cells, and lateral cell bodies. These data suggest that the MIH-like peptide could have a specific function in nervous system activity other than its classic molt-inhibiting function.