Assistant Professor, Baylor College of Medicine
Ph.D., University of Wisconsin, Madison, 2001
Postdoc, University of Wisconsin, Madison, 2001-03
Postdoc, Princeton University, 2003-09
Shaping cells, shaping embryos: Coordinated actin and membrane dynamics in flies and frogs
Cells take on specific shapes in order to perform specific jobs, and cells have the ability to rapidly change shape when normal physiology demands it. Cell shape relies on tight coupling between the plasma membrane and underlying actin cytoskeleton, and during cell shape change this coupling must be maintained even as membrane and actin are simultaneously remodeled.
The goal of my work is to understand how actin and membrane dynamics are coordinated during cell shape change: What molecular tethers link actin to membrane as each is remodeled? How do proteins and lipids of the plasma membrane influence actin dynamics? Conversely, how do actin dynamics influence membrane trafficking events as cells change shape?
We use early embryonic development as a model to study cell shape change. Specifically, we combine genetics, biochemistry and quantitative live imaging to ask how actin and membrane dynamics are coordinated during cycles of plasma membrane furrowing that accompany the first few hours of Drosophila development. Our recent results show that actin not only directs polarized exocytosis to support membrane growth, but also regulates endocytosis to achieve distinct cell shape changes (i.e. furrow ingression versus furrow regression). Ongoing projects are now aimed at 1) characterizing the activities of proteins poised to coordinate actin and endocytic dynamics at furrows, such as Dynamin, novel actin regulators Serendipity-α and Spitting Image, and BAR family proteins; 2) identifying proteins that coordinate actin remodeling and exocytosis at furrows, by RNAi and genetic screens; and 3) generating simulations from quantitative imaging and force measurements, to predict the underlying mechanics of furrow events. To compliment our fly work, we are also extending these studies to cytokinesis furrows in cleavage-stage Xenopus embryos. Ultimately, these combined fly and frog efforts will reveal the molecular mechanisms and biophysical parameters that govern coordinated actin and membrane dynamics over a range of phyla, cell shape changes and morphogenetic events.
Sokac AM, Bement WM (2000) Regulation and expression of metazoan unconventional myosins. International Review of Cytology 200:197-304.
Bement WM, Sokac AM, Mandato CA (2003) Four-dimensional imaging of cytoskeletal dynamics in Xenopus oocytes and eggs. Differentiation 71:518-527.
Sokac AM, Co C, Taunton J, Bement W (2003) Cdc42-dependent actin polymerization during compensatory endocytosis in Xenopus eggs. Nature Cell Biology 5:727-732.
Weber KL, Sokac AM, Berg JS, Cheney RE, Bement WM (2004) A microtubule-binding myosin required for nuclear anchoring and spindle assembly. Nature 431:325-329.
Sokac AM, Bement WM (2006) Kiss-and-coat and compartment mixing: coupling exocytosis to signal generation and local actin assembly. Molecular Biology of the Cell 17:1495-1502.
Sokac AM, Schietroma C, Gundersen CB, Bement WM (2006) Myosin-1c couples assembling actin to membranes to drive compensatory endocytosis. Developmental Cell 11:629-640.
Sokac AM, Wieschaus E (2008) Zygotically controlled F-actin establishes cortical compartments to stabilize furrows during Drosophila cellularization. Journal of Cell Science 121(Pt 11):1815-1824.
Sokac AM, Wieschaus E (2008) Local actin-dependent endocytosis is zygotically controlled to initiate Drosophila cellularization. Developmental Cell 14:775-786.
LeBlanc-Straceski JM, Sokac AM, Bement W, Sobrado P, Lemoine L (2009) Developmental expression of Xenopus myosin 1d and identification of a myo1d tail homology that overlaps TH1. Development, Growth & Differentiation 51:443-451.
Figard L, Sokac AM (2011) Imaging cell shape change in living Drosophila embryos. The Journal of Visualized Experiments 49:2503.
Anna Marie Sokac, Ph.D.
Department of Biochemistry and Molecular Biology
Baylor College of Medicine
One Baylor Plaza T303
Houston, Texas 77030, U.S.A.
Tel: (713) 798-3561
Fax: (713) 798-9438