Cadherins in maternal–foetal interactions: red queen with a green beard?

Abstract

Cadherins are homophilic cell surface adhesion proteins, some of which mediate interactions between maternal and foetal tissues during mammalian pregnancy. David Haig suggested that these proteins may exhibit 'green-beard gene' effects, whereby the nature of binding between identical alleles in mother and foetus leads to differential levels of resource transfer. The selfish effects of such self-recognizing alleles should, however, be suppressed over evolutionary time by unlinked genes, which is expected to lead to antagonistic coevolution between placentally expressed cadherins and unlinked modifiers. Such molecular coevolution should leave a signature of positive selection, with high ratios of non-synonymous to synonymous amino acid substitution. We present evidence that three placentally expressed cadherin genes, E-cadherin, P-cadherin and VE-cadherin, have been subject to positive selection. By contrast, a 'control' cadherin that is not expressed in the placenta, H-cadherin, showed no evidence of selection. These results provide support for the hypothesis that the cadherin genes involved in maternal-foetal interactions have been subject to green-beard-effect mutations over the course of evolutionary history, leading to antagonistic coevolution with suppressing elements from the parliament of genes.

Stochastic spread ofWolbachia

“…More speculatively, evolutionary theorists have explored the dynamics of a dominant gene that it in some way harms individuals that do not carry it. For this to happen, these individuals must be recognizable, and it has become customary to call the identifying trait a 'green beard' (Dawkins 1982;Keller & Ross 1998;Axelrod et al 2004;Summers & Crespi 2005;Jansen & van Baalen 2006). Deterministic theory predicts that both types of gene will spread when initially rare if they have no costs, while if costs are present there will be a threshold frequency above which deterministic spread occurs, analogous to the case of Wolbachia.…”

Evolutionary biology of cancer

“…For example, cadherins, a class of homophilic self-recognition proteins involved in cell adhesion and tissue invasion in both placentation and carcinogenesis, might be prone to positively selected 'green-beard' mutations during placental development, which favor the specific allele involved but harm other alleles [52,53]. Similarly, Zhang and Rosenberg [44] suggested that the positive selection that they inferred on the ANG gene, which is instrumental in angiogenesis during placentation as well as cancer, was related to maternal-fetal conflict.…”

Self-recognition, color signals, and cycles of greenbeard mutualism and altruism

“…One reason we may not find many examples of greenbeards is that we typically look for simple ones with few genes (7)(8)(9)(10)(11)(12). Other examples with many shared genes are described as kin selection (29)(30)(31), even without a pedigree (32,33).…”

“…Dawkins (6) coined Hamilton's social supergene a greenbeard in a hypothetical example of altruists that sported a green beard distinct in color from other beards sported by nonaltruists. Despite studies consistent with greenbeard altruism (7)(8)(9)(10)(11)(12), few provide definitive evidence for greenbeard altruism.…”