TY - JOUR TI - A unicellular relative of animals generates a layer of polarized cells by actomyosin-dependent cellularization AU - Dudin, Omaya AU - Ondracka, Andrej AU - Grau-Bové, Xavier AU - Haraldsen, Arthur AB AU - Toyoda, Atsushi AU - Suga, Hiroshi AU - Bråte, Jon AU - Ruiz-Trillo, Iñaki A2 - Thattai, Mukund A2 - VijayRaghavan, K A2 - Thattai, Mukund VL - 8 PY - 2019 DA - 2019/10/24 SP - e49801 C1 - eLife 2019;8:e49801 DO - 10.7554/eLife.49801 UR - https://doi.org/10.7554/eLife.49801 AB - In animals, cellularization of a coenocyte is a specialized form of cytokinesis that results in the formation of a polarized epithelium during early embryonic development. It is characterized by coordinated assembly of an actomyosin network, which drives inward membrane invaginations. However, whether coordinated cellularization driven by membrane invagination exists outside animals is not known. To that end, we investigate cellularization in the ichthyosporean Sphaeroforma arctica, a close unicellular relative of animals. We show that the process of cellularization involves coordinated inward plasma membrane invaginations dependent on an actomyosin network and reveal the temporal order of its assembly. This leads to the formation of a polarized layer of cells resembling an epithelium. We show that this stage is associated with tightly regulated transcriptional activation of genes involved in cell adhesion. Hereby we demonstrate the presence of a self-organized, clonally-generated, polarized layer of cells in a unicellular relative of animals. KW - cellularization KW - coenocyte KW - evolution KW - epithelium KW - actin KW - multicellularity JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -