title: A muscle-specific promoter directs Pitx3 gene expression in skeletal muscle cells.
abstract: The Pitx homeobox transcription factor genes have been implicated in different developmental processes, including determination of hind limb identity for Pitx1, left-right asymmetry for Pitx2, and eye development and survival of midbrain dopaminergic neurons for Pitx3. Pitx1 and Pitx2 have partly redundant activities in craniofacial development, including in pituitary organogenesis, as indicated by their names. These genes also exhibit redundant activities in the control of hind limb bud growth. Recent studies have shown expression of the three Pitx genes in muscle, with Pitx3 being the most widely expressed in all skeletal muscles. We now report the identification of a muscle-specific promoter within the Pitx3 gene that is situated between the first exon for eye and brain expression and exon 2 that contains the initiator ATG codon. Sequences proximal to this muscle-specific exon 1 are essential and sufficient to confer muscle-specific expression in transgenic mice, they are responsive to myogenic basic helix-loop-helix regulatory factors, and they recruit these factors in vivo. In agreement with exclusive use of the muscle-specific promoter in aphakia mice that are deleted of the brain promoter, the trimethyl-lysine 4 histone H3 promoter signature shifts to this promoter in embryonic day 13 ak limb bud muscle cells. Myogenic basic helix-loop-helix regulatory factor activation of Pitx3 transcription may be part of a positive feedback loop contributing to establishment of the myogenic program.
authors.affiliation: Laboratoire de Génétique Moléculaire, Institut de Recherches Cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, Quebec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Coulon
authors.forename: Aurore
authors.initials: A
authors.lastname: L'Honoré
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Ouimette
authors.forename: Emilie
authors.initials: E
authors.lastname: Dumontier
authors.forename: Pepijn
authors.initials: P
authors.lastname: van den Munckhof
authors.forename: Jacques
authors.initials: J
authors.lastname: Drouin
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D005091:Exons / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism*; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D009928:Organ Specificity; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018398:Homeodomain Proteins; D017570:MyoD Protein; D014157:Transcription Factors; C433629:homeobox protein PITX3