The rat melanin-concentrating hormone gene encodes an additional putative protein in a different reading frame.

The sequence of a novel melanin-concentrating hormone (MCH) transcript, composed of precisely joined exon I and exon III of the MCH gene, has been elucidated by RT-PCR analysis of hypothalamic RNA isolated from different rat strains. The deduced amino acid sequence predicted that it encodes in the exon I the same N-terminal moiety as MCH precursor part but diverges downstream, exon III being translated in a different reading frame than the MCH mRNA. This putative chimeric protein has been named MCH(M)-gene(G)-overprinted (O)-polypeptide(P). A peptide of 14 amino acids could be generated after cleavage at a basic site. Immunocytochemistry studies, using MGOP- and MCH-specific antisera, revealed overlapping expression in the dorsolateral hypothalamus. This suggests that MGOP or derived peptide(s) would participate in modulating the effect of pro-MCH generated peptides in the rat brain.