title: Distinct Caenorhabditis elegans HLH-8/twist-containing dimers function in the mesoderm.
abstract: BACKGROUND
  The Caenorhabditis elegans basic helix-loop-helix (bHLH) factor HLH-8, the single Twist ortholog in the nematode genome, plays important roles in mesoderm development, including M lineage patterning and differentiation of vulval and enteric muscles. HLH-8 cooperates with HLH-2, the bHLH E/Daughterless ortholog, to regulate downstream target genes, but it is not known whether HLH-2 is an obligate partner for all HLH-8 functions.
  
  
  RESULTS
  Using hlh-2 loss-of-function alleles and RNAi, we discovered that HLH-2 is required in the vulval muscles but not in M patterning or enteric muscle development. Additionally, we found that expressing tethered HLH-8/HLH-8 dimers in hlh-8 null animals rescued M patterning and enteric but not vulval muscle development.
  
  
  CONCLUSIONS
  These results support a model whereby HLH-8/HLH-8 homodimers function in M lineage patterning and enteric muscles and HLH-8/HLH-2 heterodimers function in the M-derived vulval muscles. Interestingly, the different dimers function in the same M lineage cells and the switch in dimer function coincides with vulval muscle differentiation. The use of distinct Twist dimers is evolutionarily conserved, and C. elegans provides a paradigm for future dissection of differential promoter regulation by these dimers at a single cell resolution.
authors.affiliation: Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Philogene
authors.forename: Stephany G Meyers
authors.initials: SG
authors.lastname: Small
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Ann K
authors.initials: AK
authors.lastname: Corsi
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D019521:Body Patterning; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism*; D009130:Muscle, Smooth / Q000196:embryology* / Q000378:metabolism*; D009928:Organ Specificity; D055503:Protein Multimerization; D051879:Twist-Related Protein 1 / Q000235:genetics / Q000378:metabolism*; D014844:Vulva / Q000196:embryology / Q000502:physiology
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D029742:Caenorhabditis elegans Proteins; D051879:Twist-Related Protein 1; C106514:HLH-2 protein, C elegans; C497752:HLH-8 protein, C elegans