title: PAR-3 oligomerization may provide an actin-independent mechanism to maintain distinct par protein domains in the early Caenorhabditis elegans embryo.
abstract: Par proteins establish discrete intracellular spatial domains to polarize many different cell types. In the single-cell embryo of the nematode worm Caenorhabditis elegans, the segregation of Par proteins is crucial for proper division and cell fate specification. Actomyosin-based cortical flows drive the initial formation of anterior and posterior Par domains, but cortical actin is not required for the maintenance of these domains. Here we develop a model of interactions between the Par proteins that includes both mutual inhibition and PAR-3 oligomerization. We show that this model gives rise to a bistable switch mechanism, allowing the Par proteins to occupy distinct anterior and posterior domains seen in the early C. elegans embryo, independent of dynamics or asymmetries in the actin cortex. The model predicts a sharp loss of cortical Par protein asymmetries during gradual depletion of the Par protein PAR-6, and we confirm this prediction experimentally. Together, these results suggest both mutual inhibition and PAR-3 oligomerization are sufficient to maintain distinct Par protein domains in the early C. elegans embryo.
authors.affiliation: Department of Mathematical and Statistical Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada. atdawes@math.ualberta.ca
authors.forename: Adriana T
authors.initials: AT
authors.lastname: Dawes
authors.forename: Edwin M
authors.initials: EM
authors.lastname: Munro
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity; D003593:Cytoplasm / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D008958:Models, Molecular; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D034622:RNA Interference
chemical_list: D000199:Actins; D029742:Caenorhabditis elegans Proteins; D000205:Actomyosin; C097238:PAR-3 protein, C elegans; D017346:Protein Serine-Threonine Kinases