Vesicular sorting controls the polarity of expanding membranes in theC. elegansintestine

Abstract

Biological tubes consist of polarized epithelial cells with apical membranes building the central lumen and basolateral membranes contacting adjacent cells or the extracellular matrix. Cellular polarity requires distinct inputs from outside the cell, e.g., the matrix, inside the cell, e.g., vesicular trafficking and the plasma membrane and its junctions. 1Many highly conserved polarity cues have been identified, but their integration during the complex process of polarized tissue and organ morphogenesis is not well understood. It is assumed that plasmamembrane-associated polarity determinants, such as the partitioning-defective (PAR) complex, define plasma membrane domain identities, whereas vesicular trafficking delivers membrane components to these domains, but lacks the ability to define them. In vitro studies on lumenal membrane biogenesis in mammalian cell lines now indicate that trafficking could contribute to defining membrane domains by targeting the polarity determinants, e.g., the PARs, themselves. 2This possibility suggests a mechanism for PARs' asymmetric distribution on membranes and places vesicle-associated polarity cues upstream of membraneassociated polarity determinants. In such an upstream position, trafficking might even direct multiple membrane components, not only polarity determinants, an original concept of polarized plasma membrane biogenesis 3,4 that was largely abandoned due to the failure to identify a molecularly defined intrinsic vesicular sorting mechanism. Our two recent studies on C. elegans intestinal tubulogenesis reveal that glycosphingolipids (GSLs) and Vesicular sorting controls the polarity of expanding membranes in the C. elegans intestine Hongjie Zhang, Ahlee Kim, Nessy Abraham, Liakot A. Khan and Verena Göbel* Department of Pediatrics; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA the well-recognized vesicle components clathrin and its AP-1 adaptor are required for targeting multiple apical molecules, including polarity regulators, to the expanding apical/lumenal membrane. 5,6These findings support GSLs' long-proposed role in in vivo polarized epithelial membrane biogenesis and development and identify a novel function in apical polarity for classical post-Golgi vesicle components. They are also compatible with a vesicle-intrinsic sorting mechanism during membrane biogenesis and suggest a model for how vesicles could acquire apical directionality during the assembly of the functionally critical polarized lumenal surfaces of epithelial tubes.

High resolution dynamic mapping of the C. elegans intestinal brush border

“…The soil nematode C. elegans has been widely used as a in vivo model of intestinal luminogenesis, polarity, and host defence (Zhang et al, 2013, Zhang and Hou, 2013, Sato et al, 2014). Intestinal organogenesis in C. elegans encompasses cell division and intercalation steps from the E blastomere ancestor to form a primordium containing two rows of eight cells (E16 stage) which ends up, after a last round of division, with twenty cells arranged into nine rings (or ints) forming a ellipse-shaped tube that runs along the whole body of the worm (Leung et al, 1999, Asan et al, 2016).…”