title: miR-786 regulation of a fatty-acid elongase contributes to rhythmic calcium-wave initiation in C. elegans.
abstract: BACKGROUND
  Rhythmic behaviors are ubiquitous phenomena in animals. In C. elegans, defecation is an ultradian rhythmic behavior: every ∼50 s a calcium wave initiating in the posterior intestinal cells triggers the defecation motor program that comprises three sequential muscle contractions. Oscillatory calcium signaling is central to the periodicity of defecation. The posteriormost intestinal cells function as the pacemaker for this rhythmic behavior, although it is unclear how the supremacy of these cells for calcium-wave initiation is controlled.
  
  
  RESULTS
  We describe how the loss of the mir-240/786 microRNA cluster, which results in arrhythmic defecation, causes ectopic intestinal calcium-wave initiation. mir-240/786 expression in the intestine is restricted to the posterior cells that function as the defecation pacemaker. Genetic data indicate that mir-240/786 functions upstream of the inositol 1,4,5-trisphosphate (IP(3)) receptor. Through rescue analysis, it was determined that miR-786 functions to regulate defecation. Furthermore, we identified elo-2, a fatty-acid elongase with a known role in defecation cycling, as a direct target for miR-786. We propose that the regulation of palmitate levels through repression of elo-2 activity is the likely mechanistic link to defecation.
  
  
  CONCLUSIONS
  Together, these data indicate that miR-786 confers pacemaker status on posterior intestinal cells for the control of calcium-wave initiation through the regulation of elo-2 and, subsequently, palmitate levels. We propose that a difference in fatty-acid composition in the posterior intestinal cells may alter the activities of membrane proteins, such as IP(3)-receptor or TRPM channels, that control pacemaker activity in the C. elegans intestine.
authors.affiliation: Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA.
authors.forename: Benedict J
authors.initials: BJ
authors.lastname: Kemp
authors.forename: Erik
authors.initials: E
authors.lastname: Allman
authors.forename: Lois
authors.initials: L
authors.lastname: Immerman
authors.forename: Megan
authors.initials: M
authors.lastname: Mohnen
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Peters
authors.forename: Keith
authors.initials: K
authors.lastname: Nehrke
authors.forename: Allison L
authors.initials: AL
authors.lastname: Abbott
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001683:Biological Clocks; D017173:Caenorhabditis elegans; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D003672:Defecation; D000081031:Fatty Acid Elongases; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism*; D010169:Palmitic Acids / Q000378:metabolism
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; C581524:MIRN786 microRNA, C elegans; D035683:MicroRNAs; D010169:Palmitic Acids; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases; D002118:Calcium