Meeting Abstract
Precise control of temporal and spatial developmental gene expression is critical to animal multicellularity. Early diverging animals possess most known families of animal transcription factors. However, little is known about the preservation of developmental gene regulatory networks (GRNs) that emerged along with metazoan multicellularity. Sponges share a similar gene composition with other animals, including genes crucial to the identity of tissues sponges lack such as neurons and muscles. The emergence of such genes and their regulators soon after or concomitantly with metazoan multicellularity suggest that metazoan (animal) morphological diversity and complexity are primarily driven by gene regulatory innovations. We have characterized the evolution of regulatory elements and the transcriptional repertoire in the marine sponge Amphimedon queenslandica, revealing a highly gene dense genome with short introns, UTRs and alternative splicing patterns resembling those of unicellular eukaryotes. Amphimedon also possesses almost 3,000 lncRNAs and evidence of bidirectional transcription at gene promoters, both of which might be carrying out similar regulatory functions as those found in bilaterians. Gene co-expression analysis across Amphimedon development reveals 23 co-expressed gene modules enriched in specific biological functions, with tightly regulated expression patterns that precisely coincide with ontogenetic transitions. The preservation of co-expressed gene modules, transcription factors and epigenetic control elements in Amphimedon and other animals allows for the identification of conserved features of the first metazoan GRNs.
