title: The HMX homeodomain protein MLS-2 regulates cleavage orientation, cell proliferation and cell fate specification in the C. elegans postembryonic mesoderm.
abstract: The proper formation of a complex multicellular organism requires the precise coordination of many cellular events, including cell proliferation, cell fate specification and differentiation. The C. elegans postembryonic mesodermal lineage, the M lineage, allows us to study mechanisms coordinating these events at single cell resolution. We have identified an HMX homeodomain protein MLS-2 in a screen for factors required for M lineage patterning. The MLS-2 protein is present in nuclei of undifferentiated cells in the early M lineage and in a subset of head neurons. In the M lineage, MLS-2 activity appears to be tightly regulated at the fourth round of cell division, coincident with the transition from proliferation to differentiation. A predicted null allele of mls-2, cc615, causes reduced cell proliferation in the M lineage, whereas a semi-dominant, gain-of-function allele, tm252, results in increased cell proliferation. Loss or overexpression of mls-2 also affects cleavage orientation and cell fate specification in the M lineage. We show that the increased cell proliferation in mls-2(tm252) mutants requires CYE-1, a G1 cell cycle regulator. Furthermore, the C. elegans Myod homolog HLH-1 acts downstream of mls-2 to specify M-derived coelomocyte cell fates. Thus MLS-2 functions in a cell type-specific manner to regulate both cell proliferation and cell fate specification.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Jiang
authors.forename: Vanessa
authors.initials: V
authors.lastname: Horner
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000254:growth & development*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D019070:Cell Lineage / Q000235:genetics / Q000502:physiology; D016000:Cluster Analysis; D004252:DNA Mutational Analysis; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology*; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D034622:RNA Interference; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D029742:Caenorhabditis elegans Proteins; D018398:Homeodomain Proteins; C508613:MLS-2 protein, C elegans