Assignment of the human pro-melanin-concentrating hormone gene (PMCH) to chromosome 12q23-q24 and two variant genes (PMCH1 and PMCHL2) to chromosome 5p14 and 5q12-q13.

Melanin-concentrating hormone (MCH) is a peptide that has been isolated from salmon pituitary and rat hypothalamus. In mammals, pro-MCH (PMCH) encodes two putative peptides, named NEI and NGE, in addition to MCH. Those peptides are expressed predominantly in hypothalamus and display a broad array of functions in rat brain. We have previously mapped the PMCH locus on human chromosome 12q and rat chromosome 7. Genomic cloning has revealed the existence of two distinct MCH genes in human: one authentic and one variant. In this report, we describe Southern blotting analysis with DNA from a panel of somatic cell hybrids and demonstrate that the authentic human MCH (hMCH) gene is located as expected on chromosome 12, while the variant form of hMCH gene is located on chromosome 5. Direct chromosomal assignment of the authentic and variant hMCH genes was obtained by using fluorescence in situ hybridization on metaphase chromosomes. A strong signal was observed in 12q23-q24 with the authentic hMCH genomic DNA probe. Surprisingly, two signals were conspicuously found in 5p14 and 5q12-q13 with different variant hMCH genomic DNA probes. These loci were designated PMCHL1 and PMCHL2. Evidence of physiological and pathological data in rodents together with locus linkage analyses in human suggests that hMCH authentic and variant genes may be involved in human brain disorders.