title: Six3 activation of Pax6 expression is essential for mammalian lens induction and specification.
abstract: The homeobox gene Six3 regulates forebrain development. Here we show that Six3 is also crucial for lens formation. Conditional deletion of mouse Six3 in the presumptive lens ectoderm (PLE) disrupted lens formation. In the most severe cases, lens induction and specification were defective, and the lens placode and lens were absent. In Six3-mutant embryos, Pax6 was downregulated, and Sox2 was absent in the lens preplacodal ectoderm. Using ChIP, electrophoretic mobility shift assay, and luciferase reporter assays, we determined that Six3 activates Pax6 and Sox2 expression. Misexpression of mouse Six3 into chick embryos promoted the ectopic expansion of the ectodermal Pax6 expression domain. Our results position Six3 at the top of the regulatory pathway leading to lens formation. We conclude that Six3 directly activates Pax6 and probably also Sox2 in the PLE and regulates cell autonomously the earliest stages of mammalian lens induction.
authors.affiliation: Department of Genetics and Tumor Cell Biology, St Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Lagutin
authors.forename: Michael
authors.initials: M
authors.lastname: Mende
authors.forename: Andrea
authors.initials: A
authors.lastname: Streit
authors.forename: Guillermo
authors.initials: G
authors.lastname: Oliver
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005136:Eye Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D007908:Lens, Crystalline / Q000002:abnormalities / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D055748:SOXB1 Transcription Factors; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D000097607:Homeobox Protein SIX3
chemical_list: D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D055748:SOXB1 Transcription Factors; D015534:Trans-Activators; D000097607:Homeobox Protein SIX3; C000605732:Pax6 protein, mouse; C527783:Sox2 protein, mouse