title: Coupling between cytoplasmic concentration gradients through local control of protein mobility in the Caenorhabditis elegans zygote.
abstract: Cell polarity is characterized by the asymmetric distribution of factors at the cell cortex and in the cytoplasm. Although mechanisms that establish cortical asymmetries have been characterized, less is known about how persistent cytoplasmic asymmetries are generated. During the asymmetric division of the Caenorhabditis elegans zygote, the PAR proteins orchestrate the segregation of the cytoplasmic RNA-binding proteins MEX-5/6 to the anterior cytoplasm and PIE-1, POS-1, and MEX-1 to the posterior cytoplasm. In this study, we find that MEX-5/6 control the segregation of GFP::PIE-1, GFP::POS-1, and GFP::MEX-1 by locally increasing their mobility in the anterior cytoplasm. Remarkably, PIE-1, POS-1, and MEX-1 form gradients with distinct strengths, which correlates with differences in their responsiveness to MEX-5/6. We show that MEX-5/6 act downstream of the polarity regulators PAR-1 and PAR-3 and in a concentration-dependent manner to increase the mobility of GFP::PIE-1. These findings suggest that the MEX-5/6 concentration gradients are directly coupled to the establishment of posterior-rich PIE-1, POS-1, and MEX-1 concentration gradients via the formation of anterior-fast, posterior-slow mobility gradients.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755.
authors.forename: Youjun
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755.
authors.forename: Huaiying
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 erik.e.griffin@dartmouth.edu.
authors.forename: Erik E
authors.initials: EE
authors.lastname: Griffin
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000737:chemistry; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D015053:Zygote
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; C410587:MEX-5 protein, C elegans; C410589:MEX-6 protein, C elegans; D009687:Nuclear Proteins; C117258:POS-1 protein, C elegans; D016601:RNA-Binding Proteins; C104694:mex-1 protein, C elegans; C100950:pie-1 protein, C elegans; D049452:Green Fluorescent Proteins