Birth of two chimeric genes in the Hominidae lineage

How genes with newly characterized functions originate remains a fundamenta l question. PMCHL1 and PMCHL2, two chimeric genes derived from the melanin- concentrating hormone (MCH) gene, offer an opportunity to examine such an i ssue in the human Lineage. Detailed structural, expression, and phylogeneti c analysis showed that the PMCHL1 gene was created near 25 million years ag o (Ma) by a complex mechanism of exon shuffling through retrotransposition of an antisense MCH messenger RNA coupled to de novo creation of splice sit es. PMCHL2 arose 5 to 10 Ma by an event of duplication involving a large ch romosomal region encompassing the PMCHL1 Locus. The RNA expression patterns of those chimeric genes suggest that they have been submitted to strong re gulatory constraints during primate evolution.