Meeting Abstract

66.6  Friday, Jan. 6  The Early Embryo: Genomic analysis of gene expression in an early diverging lineage of metazoans, the Ctenophora BROWNE, W.E.*; SCHNITZLER, C.E.; GILDEA, D.; NGUYEN, A.-D.; MAXWELL, E.; RYAN, J.F.; BAXEVANIS, A.D.; University of Miami; NHGRI/NIH; NHGRI/NIH; NHGRI/NIH; NHGRI/NIH; NHGRI/NIH; NHGRI/NIH wbrowne@bio.miami.edu

The defining characteristic of metazoans is the possession of distinct tissues, typically composed of multiple terminally differentiated cell types. However, biologists still grapple with understanding the molecular genetic underpinnings of how differential cell fates are established and maintained. The ctenophore Mnemiopsis leidyi has an early cleavage program particularly well suited for investigation by developmental and genetic studies, providing a unique window for the broader examination of early cell fate restriction in metazoans as the undifferentiated single-cell embryo becomes a collection of constrained and differentiated cell types. Mnemiopsis leidyi has become a powerful model system for understanding ctenophore development with the completion of the genome. Here, we present a comprehensive analysis of mRNA and miRNA expression data from the fertilized zygote. Our experimental approach takes advantage of next-gen RNAseq approaches to examine temporal and spatial changes in gene expression. Preliminary analysis highlights the presence of a complex transcriptome with a diverse developmental gene complement suggesting that maternal transcripts are playing an important role in early cell fate decisions. Our data reveal the presence of novel miRNAs and an absence of clear Drosha/Pasha homologs implicating a novel miRNA biogenesis pathway. Our genomics approach provides us with quantitative data that will shed light on transcriptional changes accompanying the transition from totipotency to restricted pluripotent states during early Mnemiopsis embryogenesis. Further, an improved understanding of embryonic gene expression dynamics in ctenophores is fundamentally important to identifying key developmental and molecular genetic events associated with early metazoan evolution.