Structure and expression of the variant melanin-concentrating hormone genes: Only PMCHL1 is transcribed in the developing human braid and encodes a putative protein

PMCHL1 and PMCNL2 are two copies of the so-called variant melanin-concentra ting hormone (MCH) gene that are located, respectively, on human chromosome 5p14 and 5q13 and that emerged recently during primate evolution. They cor respond to a 5'-end truncated version of the MCH gene mapped on chromosome 12q23 and encoding a neuropeptide precursor. The gene organization and regu lation of the expression of the variant MCH genes in the human brain are th e central issues we investigated. First, the structure and fine chromosomal mapping of the 5p and 5q variant MCH genes were established. These reveale d several point mutations and length variations of one CA/TA repeat which a llow discrimination between each copy. Using a combination of RACE-PCR, RT- PCR, and sequencing analysis, we provided strong evidence for the expressio n of the PMCHL1 gene but not the PMCHL2 gene in the human fetal, newborn, a nd adult brains. Sense, potentially coding, RNAs, as well as noncoding anti sense RNAs, were identified and displayed a region-specific expression in t he human brain. Strikingly, sense unspliced RNAs of the PMCHL1 gene carried a novel open reading frame and may produce an NLS-containing protein of 8 kDa named VMCH-p8. These transcripts were translated in vitro and in transf ected COS cells. Therefore, the PMCHL1 gene provides a unique example of th e generation of a gene in the Hominoidae lineage which is specifically tran scribed in the developing human brain and has the capacity to be translated into a putative novel protein.