Unravelling the origins of animal cell type differentiation

NAJLE, SEBASTIÁN R.

San Diego

Encuentro; ASCB-EMBO 2018; 2018

American Society for Cell Biology - European Molecular Biology Organization

Cell differentiation is a fundamental attribute of complex multicellular organisms, underpinning the functional specialization of cells and tissues during embryonic development. It has been proposed that animal multicellularity originated by a transition from temporal to spatial cell differentiation. However, it is not clear whether spatial cell-type differentiation is a consecuence of multicellularity or if it was already presente in the last common ancestor of animals. To elucidate this, we have setup inDrops single-cell RNAseq in unicellular holozoans, the closest relatives to animals. Unicellular holozoans display different types of simple multicellularity during their life cycles: clonal colonies in choanoflagellates, aggregative behavior in the filasterean amoeba Capsaspora owczarzaki, and the multinucleated coenocytic development of ichthyosporeans. Those colonies and aggregates are assumed to be without cell differentiation. However, there is no molecular data proving that all cells within those colonies or aggregates or coenocytes are identical. The possibility of analyzing differential gene expression at the single-cell level in C. owczarzaki aggregates allowed us to found an unexpected heterogeneoity of gene expression in the individual cells. The characterization of these putative cell-types, as well as the molecular mechanisms underlying programs of cell differentiation will allow us to better understand the origin of cell-type differentiation during the evolution of animal multicellularity.