The evolution of reproduction-related NLRP genes.

NLRP proteins are important components of inflammasomes with a major role in innate immunity. A subset of NLRP genes, with unknown functions, are expressed in oocytes and early embryos. Mutations of Nlrp5 in mice are associated with maternal-effect embryonic lethality and mutations of NLRP7 in women are associated with conception of biparental complete hydatidiform moles (biCHMs), suggesting perturbed processes of genomic imprinting. Recessive mutations on NLRP2/7 in humans are associated with reproductive disorders and appear to be induced by a demethylation of the maternal pronucleus. In this study, we find that radiation of NLRP genes occurred before the common ancestor of Afrotheria and Boreoeutheria, with the clade of oocyte-expressed genes originating before the divergence of marsupial and eutherian mammals. There have been multiple independent duplications of NLRP2 genes one of which produced the NLRP7 gene associated with biCHMs.