Divergent evolution of the prolactin-inducible protein gene and related genes in the mouse genome

The prolactin-inducible protein (PIP/GCDFP15) family consists of small secretory polypeptides that are found in various body fluids. In order to study evolutionary events to this family, we cloned member genes and analyzed their sequences. A database search revealed the presence of a novel paralogous gene on mouse chromosome 6q34 and a nonprocessed pseudogene adjacent to PIP on human chromosome 7q34. The mouse PIP and four related genes displayed higher nonsynonymous and synonymous substitution ratios in comparison to other mammalian PIP orthologues; furthermore, these genes exhibited distinct distributions among tissues such as seminal vesicle, colon, and mammary gland. A pair of duplicated genes could have existed prior to radiation to the human and rodents. While only PIP is active in the human lineage, species-specific gene duplications have given rise to functional variants in rodents. Adaptive evolution potentially has occurred among the PIP and its related genes in the mouse genome. (C) 2003 Elsevier B.V. All rights reserved.