Imprinted genes influencing the quality of maternal care.

In mammals successful rearing imposes a cost on later reproductive fitness specifically on the mother creating the potential for parental conflict. Loss of function of three imprinted genes in the dam result in deficits in maternal care suggesting that, like maternal nutrients, maternal care is a resource over which the parental genomes are in conflict. However, the induction of maternal care is a complex and highly regulated process. Unsurprisingly many gene disruptions, as well as adverse environmental exposures in pregnancy, result in maternal care deficits. Recent compelling evidence for a more purposeful imprinting phenomenon comes from studying the impact of two imprinted genes, Phlda2 and Peg3, expressed in the placenta on the mother's behaviour. The explicit demonstration that imprinted genes expressed in the offspring influence maternal behaviour lends significant weight to the hypothesis that maternal care is a resource that has been manipulated by the paternal genome.