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Link to gametic imprinting?

Posted by AnimeshRay on 11 Jul 2013 at 20:50 GMT

Very interesting results. If true, it implies the existence of a mechanism of selection for certain imprinted genes in gametes or in early embryo that links sex-ratio bias to reproductive success (and likely gametic selection again) in subsequent generations. The data suggest that imprinted paternal contribution might be the driver. It was proposed some 22 years ago by Westoby and Haig (see http://www.sciencedirect.... for a review) that the paternal genomic contribution, when it dominates over the maternal contribution, tends to produce larger (more vigorous) embryos. Maternal imprinting usually suppresses these genes on the paternal genome, so as to reduce the embryo size (otherwise it competes against the maternal resources). Recent work links some of these imprinted loci to insulin-like-receptors and related processes, suggesting a metabolic link. Perhaps in those families with high male-to-female ratios the paternal contribution escapes the maternal suppression, and thus produce larger embryos and therefore more vigorous children, whose metabolic advantage in early life might translate to a higher reproductive success in later life. This makes me wonder whether human pedigrees with large sex-bias might show correlation (negative or positive) with diseases such as diabetes, and if true, whether a correction factor could be devised for better accuracy in GWAS studies for metabolic disorders where information on family pedigree for sex exists. There are other implications: which genes are involved in gametic selection in F1 in pedigrees with consistently high sex-ratio distortions, etc.

No competing interests declared.

RE: Link to gametic imprinting?

jpgarner replied to AnimeshRay on 16 Jul 2013 at 17:10 GMT

This is an interesting idea. It is certainly a plausible arms race - in a polygynous species male parents don't care about the future reproductive potential of a mother, and so might try to program a male embryo to extract extra resources at the expense of the mother's future reproduction. Thus the female is worried about her lifelong fitness, while the male parent may only be worried about the fitness contribution of this one offspring. However I'm not sure it makes long-term evolutionary sense. Generally speaking (all other things being equal) in arms races, the individuals with the most to lose will be under a stronger selection pressure (Dawkins' life-dinner principle). Females have so much more invested in reproduction, that when male and female parents' interests collide then the female parent should generally win out. So as described above, if the male is trying to overrule the female via some form of epigenetic imprinting, females will evolve countermeasures far faster. This is particularly true as the cellular machinery is contributed by the female so she has ample opportunity to nip such intercessions in the bud.

There's other non-adaptive scenarios through which diabetes might be linked to sex ratio - see the work of VJ Grant.

No competing interests declared.