Family conflicts are common, especially where one parent invests more heavily in offspring provision; Mike Ritchie and Constantino Macias Garcia will study how such conflict may influence gene expression variation in the placenta-like structures of species of Mexican fish
Family relationships are not always peacefully cooperative. Parents may differ in how much effort they wish to invest in parental care; a good evolutionary strategy may be to maximise the effort your sexual partner expends rather than your own, as this would leave you with more resources to spend in future reproduction. Parents and offspring also differ greatly in how much resource should ideally be devoted to current reproduction. It has been appreciated for some time that such conflict may influence patterns of gene expression in the placentae of live-bearing animals.
Genes which influence resource transfer between mothers and offspring are often expressed in the embryo or placenta and the optimal level of expression may differ between partners. Gene expression in placentae and embryos can be ‘fine tuned’ by epigenetic regulation such as methylation, where specific alleles can be regulated or programmed by the parents to show reduced expression in their offspring, so the amount of methylation in placentae can represent the outcome of intra-family genetic conflict and resolution.
Much of what we know about such systems comes from humans and standard laboratory mammals. However, vertebrate live-bearing originally evolved in fish, and fish vary greatly in the extent of live-bearing versus egg-laying and in the intensity of sexual selection and sexual conflict.
This project aims to measure the extent of methylation in the trophotaenia (placenta-like organ) of a group of live-bearing Mexican fish, the Goodeidae. Our team will sequence the genome of several species of the group and examine patterns of gene expression and genome methylation in the placentae and other tissues. Specifically, we wish to examine if there are greater genetic signatures of family conflict in species with more elaborate mating systems, which is an indication of greater levels of sexual selection, where conflict should be more intense. This will provide new insights into the evolutionary patterns of gene regulation during the evolution of live-bearing reproduction, and will widen our perspective of the epigenetic regulation of placental genes in vertebrates and on the evolutionary extent of genetic family conflicts.