title: Collier transcription in a single Drosophila muscle lineage: the combinatorial control of muscle identity.
abstract: Specification of muscle identity in Drosophila is a multistep process: early positional information defines competence groups termed promuscular clusters, from which muscle progenitors are selected, followed by asymmetric division of progenitors into muscle founder cells (FCs). Each FC seeds the formation of an individual muscle with morphological and functional properties that have been proposed to reflect the combination of transcription factors expressed by its founder. However, it is still unclear how early patterning and muscle-specific differentiation are linked. We addressed this question, using Collier (Col; also known as Knot) expression as both a determinant and read-out of DA3 muscle identity. Characterization of the col upstream region driving DA3 muscle specific expression revealed the existence of three separate phases of cis-regulation, correlating with conserved binding sites for different mesodermal transcription factors. Examination of col transcription in col and nautilus (nau) loss-of-function and gain-of-function conditions showed that both factors are required for col activation in the ;naïve' myoblasts that fuse with the DA3 FC, thereby ensuring that all DA3 myofibre nuclei express the same identity programme. Together, these results indicate that separate sets of cis-regulatory elements control the expression of identity factors in muscle progenitors and myofibre nuclei and directly support the concept of combinatorial control of muscle identity.
authors.affiliation: Centre de Biologie du Développement, UMR 5547 CNRS/UPS, IFR 109, Institut d'Exploration Fonctionnelle des Génomes, 118 route de Narbonne, 31062 Toulouse cedex 9, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Dubois
authors.forename: Jonathan
authors.initials: J
authors.lastname: Enriquez
authors.forename: Virginie
authors.initials: V
authors.lastname: Daburon
authors.forename: Fabien
authors.initials: F
authors.lastname: Crozet
authors.forename: Gaelle
authors.initials: G
authors.lastname: Lebreton
authors.forename: Michèle
authors.initials: M
authors.lastname: Crozatier
authors.forename: Alain
authors.initials: A
authors.lastname: Vincent
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000502:physiology; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D008954:Models, Biological; D009124:Muscle Proteins / Q000235:genetics / Q000502:physiology; D009132:Muscles / Q000196:embryology*; D009154:Mutation; D032446:Myoblasts / Q000166:cytology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; D009124:Muscle Proteins; D014157:Transcription Factors; C104357:kn protein, Drosophila; C066817:nau protein, Drosophila