Developmental gene expression provides clues to relationships between sponge and eumetazoan body plans

Abstract

Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology. We address the sponge-eumetazoan transition by analyzing expression of a broad range of eumetazoan developmental regulatory genes in Sycon ciliatum (Calcispongiae). Here we show that many members of surprisingly numerous Wnt and Tgfb gene families are expressed higher or uniquely in the adult apical end and the larval posterior end. Genes involved in formation of the eumetazoan endomesoderm, such as b-catenin, Brachyury and Gata, as well as germline markers Vasa and Pl10, are expressed during formation and maintenance of choanoderm, the feeding epithelium of sponges. Similarity in developmental gene expression between sponges and eumetazoans, especially cnidarians, is consistent with Haeckel's view that body plans of sponges and cnidarians are homologous. These results provide a framework for further studies aimed at deciphering ancestral developmental regulatory networks and their modifications during animal body plans evolution.

TALEN and CRISPR/Cas9-mediated genome editing in the early-branching metazoan Nematostella vectensis

“…On a general note, a broad effort is underway to reconstruct the evolution of animal complexity through comparative studies of phylogenetically informative lineages, including cnidarians [23][24][25] , ctenophores 26,27 , placozoans 28,29 and sponges 30,31 . While sequencing projects have produced an abundance of information about the genomic foundations of animal evolution 32 , emerging genetic tools of the kind described herein now permit functional interrogation of the ancestral molecular toolkit employed in the diversification of early animal body plans.…”

Asymmetric Distribution of pl10 and bruno2, New Members of a Conserved Core of Early Germline Determinants in Cephalochordates

“…By the early neurula stages, the punctate distribution may be masked by the zygotic tailbud expression (discussed below). Another dead-box containing gene, pl10, has been implicated in germ cell specification, and in some cases regeneration, from sponges to annelids (Alié et al, 2011;Rebscher et al, 2012;Leininger et al, 2014;Kozin and Kostyuchenko, 2015). PL10 is closely related phylogenetically to the Vasa protein (Kerner et al, 2011), but expression of pl10 has so far not been described in any cephalochordate.…”

Phylogenetic evidence for the modular evolution of metazoan signalling pathways

“…Among cnidarians, cWNT signalling has been shown to facilitate the establishment of embryonic [65,77,78] and adult [29,72] organizing centres in both anthozoan and hydrozoan model systems. Although functional studies in sponges are lacking, studies of WNT gene expression in situ suggest that this pathway is also asymmetrically expressed along the larval swimming axis and during development of the adult axis (defined by the aquiferous system) [36,79,80]. Treatment with pharmacological activators of cWNT signalling (e.g.…”