title: Reciprocal asymmetry of SYS-1/beta-catenin and POP-1/TCF controls asymmetric divisions in Caenorhabditis elegans.
abstract: beta-Catenins are conserved regulators of metazoan development that function with TCF DNA-binding proteins to activate transcription. In Caenorhabditis elegans, SYS-1/beta-catenin and POP-1/TCF regulate several asymmetric divisions, including that of the somatic gonadal precursor cell (SGP). In the distal but not the proximal SGP daughter, SYS-1/beta-catenin and POP-1/TCF transcriptionally activate ceh-22 to specify the distal fate. Here, we investigate the distribution of SYS-1/beta-catenin and its regulation. Using a rescuing transgene, VNS::SYS-1, which fuses VENUS fluorescent protein to SYS-1, we find more VNS::SYS-1 in distal than proximal SGP daughters, a phenomenon we call "SYS-1 asymmetry." In addition, SYS-1 asymmetry is seen in many other tissues, consistent with the idea that SYS-1 regulates asymmetric divisions broadly during C. elegans development. In particular, SYS-1 is more abundant in E than MS, and SYS-1 is critical for the endodermal fate. In all cases, SYS-1 is reciprocal to POP-1 asymmetry: cells with higher SYS-1 have lower POP-1, and vice versa. SYS-1 asymmetry is controlled posttranslationally and relies on frizzled and dishevelled homologs, which also control POP-1 asymmetry. Therefore, upstream regulators modulate the SYS-1 to POP-1 ratio by increasing SYS-1 and decreasing POP-1 within the same cell. By contrast, SYS-1 asymmetry does not rely on WRM-1, which appears specialized for POP-1 asymmetry. We suggest a two-pronged pathway for control of SYS-1:POP-1, which can robustly accomplish differential gene expression in daughters of an asymmetric cell division.
authors.affiliation: Department of Biochemistry and Zoology and Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Phillips
authors.forename: Ambrose R
authors.initials: AR
authors.lastname: Kidd
authors.forename: Ryan
authors.initials: R
authors.lastname: King
authors.forename: Jeff
authors.initials: J
authors.lastname: Hardin
authors.forename: Judith
authors.initials: J
authors.lastname: Kimble
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019521:Body Patterning / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006066:Gonads / Q000166:cytology; D006609:High Mobility Group Proteins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013234:Stem Cells / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C109217:CEH-22 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D008164:Luminescent Proteins; C502083:Sys-1 protein, C elegans; D014157:Transcription Factors; C096787:pop-1 protein, C elegans; C054562:yellow fluorescent protein, Bacteria