Trichoplax, the simplest known animal, contains an estrogen-related receptor but no estrogen receptor: Implications for estrogen receptor evolution

Origin and diversification of steroids: Co-evolution of enzymes and nuclear receptors

“…A second explanation, which we favor, is that the similarities between invertebrate ERs and vertebrate ERs are an example of convergent evolution from an ancestral ERR [2,21]. As noted previously, convergent evolution is common in steroid binding proteins [13].…”

“…[3,7,[25][26]. The close sequence and structural similarity of the invertebrate ERs and ERR [46] and the presence of ERRs in primitive metazoans [2,21] suggests that the ancestral invertebrate ER evolved from an ERR and the ER ancestors was likely to have been constitutively active.…”

Phylogenetic evidence for the modular evolution of metazoan signalling pathways

“…Like the TGF-b and cWNT pathways, NRs evolved in the stem metazoan. These receptors have been described from cnidarians [87], placozoans [15,88], sponges [89,90] and ctenophores [91], but are missing from choanoflagellates [24], filastereans [26,35], fungi [92] and amoebozoans (table 3). Over 17 NRs have been identified among cnidarians, many of which lack clear orthology with bilaterian NRs but have clear orthologues in other cnidarians, suggesting that this gene family expanded through several rounds of cnidarianspecific duplication events [87,91].…”

“…Srivastava et al [15] identified four NRs from placozoans, orthologues of: hepatocyte nuclear factor 4 (HNF4), retinoid X receptor (RXR), an NR2 family member, and one that appears to lack orthology with other available sequences. Baker [88] also described an oestrogen-related receptor (family NR3) from T. adhaerens but indicated that it contained a hormone binding pocket that was too small to accommodate a hormone, suggesting it may not function the way NR3 family receptors do in bilaterians. Among sponges, two NRs have been identified from Amphimedon queenslandica, Suberites domuncula and Oscarella carmela-one, NR2, appears to be an orthologue of HNF4 and is found only in A. queenslandica and O. carmela; the second, apparently sponge-specific, is found in A. queenslandica, S. domuncula and O. carmela [85,91].…”

Estrogen Physiology from an Evolutionary Perspective

“…Nuclear receptors are found in basal animals, but not in plants or yeast or bacteria (Bertrand et al, 2004;Baker, 2005Baker, , 2008Bridgham et al, 2010;Sladek, 2011). Receptors for adrenal and sex steroids evolved in deuterostomes (Baker, 1997;Escriva et al, 2000;Thornton, 2001;Bertrand et al, 2004Bertrand et al, , 2011Baker, 2005;Bertrand et al, 2011;Sladek, 2011).…”