title: Regulation of the UNC-5 netrin receptor initiates the first reorientation of migrating distal tip cells in Caenorhabditis elegans.
abstract: Cell migrations play a critical role in animal development and organogenesis. Here, we describe a mechanism by which the migration behaviour of a particular cell type is regulated temporally and coordinated with over-all development of the organism. The hermaphrodite distal tip cells (DTCs) of Caenorhabditis elegans migrate along the body wall in three sequential phases distinguished by the orientation of their movements, which alternate between the anteroposterior and dorsoventral axes. The ventral-to-dorsal second migration phase requires the UNC-6 netrin guidance cue and its receptors UNC-5 and UNC-40, as well as additional, UNC-6-independent guidance systems. We provide evidence that the transcriptional upregulation of unc-5 in the DTCs is coincident with the initiation of the second migration phase, and that premature UNC-5 expression in these cells induces precocious turning in an UNC-6-dependent manner. The DAF-12 steroid hormone receptor, which regulates developmental stage transitions in C. elegans, is required for initiating the first DTC turn and for coincident unc-5 upregulation. We also present evidence for the existence of a mechanism that opposes or inhibits UNC-5 function during the longitudinal first migration phase and for a mechanism that facilitates UNC-5 function during turning. The facilitating mechanism presumably does not involve transcriptional regulation of unc-5 but may represent an inhibition of the phase 1 mechanism that opposes or inhibits UNC-5. These results, therefore, reveal the existence of two mechanisms that regulate the UNC-5 receptor that are critical for responsiveness to the UNC-6 netrin guidance cue and for linking the directional guidance of migrating distal tip cells to developmental stage advancements.
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada. M5S 1A8, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Su
authors.forename: D C
authors.initials: DC
authors.lastname: Merz
authors.forename: M T
authors.initials: MT
authors.lastname: Killeen
authors.forename: Y
authors.initials: Y
authors.lastname: Zhou
authors.forename: H
authors.initials: H
authors.lastname: Zheng
authors.forename: J M
authors.initials: JM
authors.lastname: Kramer
authors.forename: E M
authors.initials: EM
authors.lastname: Hedgecock
authors.forename: J G
authors.initials: JG
authors.lastname: Culotti
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D002465:Cell Movement; D012734:Disorders of Sex Development; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D015801:Helminth Proteins / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology; D009420:Nervous System / Q000254:growth & development*; D011956:Receptors, Cell Surface; D017978:Receptors, Growth Factor / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic
chemical_list: D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D017978:Receptors, Growth Factor; D011993:Recombinant Fusion Proteins; C077588:UNC-5 protein, C elegans