Abstract
Twist1 encodes a transcription factor that plays a vital role in limb development. We have used a tamoxifen-inducible Cre transgene, Ubc-CreERT2, to generate time-specific deletions of Twist1 by inducing Cre activity in mouse embryos at different ages from embryonic (E) day 9.5 onwards. A novel forelimb phenotype of supernumerary pre-axial digits and enlargement or partial duplication of the distal radius was observed when Cre activity was induced at E9.5. Gene expression analysis revealed significant upregulation of Hoxd10, Hoxd11 and Grem1 in the anterior half of the forelimb bud at E11.5. There is also localized upregulation of Ptch1, Hand2 and Hoxd13 at the site of ectopic digit formation, indicating a posterior molecular identity for the supernumerary digits. The specific skeletal phenotypes, which include duplication of digits and distal zeugopods but no overt posteriorization, differ from those of other Twist1 conditional knockout mutants. This outcome may be attributed to the deferment of Twist1 ablation to a later time frame of limb morphogenesis, which leads to the ectopic activation of posterior genes in the anterior tissues after the establishment of anterior-posterior anatomical identities in the forelimb bud.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Basic Helix-Loop-Helix Transcription Factors / genetics
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Basic Helix-Loop-Helix Transcription Factors / metabolism
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Body Patterning
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Embryo, Mammalian / metabolism
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Embryonic Development
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Female
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Forelimb / growth & development
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Forelimb / metabolism
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Gene Expression Regulation, Developmental
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Intercellular Signaling Peptides and Proteins / genetics
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Intercellular Signaling Peptides and Proteins / metabolism
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Limb Buds / metabolism*
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Mice
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Mice, Knockout
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Nuclear Proteins / deficiency
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Patched Receptors
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Patched-1 Receptor
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Phenotype
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Twist-Related Protein 1 / deficiency
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Twist-Related Protein 1 / genetics
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Twist-Related Protein 1 / metabolism*
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Up-Regulation
Substances
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Basic Helix-Loop-Helix Transcription Factors
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Grem1 protein, mouse
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Hand2 protein, mouse
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Homeodomain Proteins
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Hoxd1 protein, mouse
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Hoxd10 protein, mouse
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Hoxd13 protein, mouse
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Intercellular Signaling Peptides and Proteins
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Nuclear Proteins
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Patched Receptors
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Patched-1 Receptor
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Ptch1 protein, mouse
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Receptors, Cell Surface
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Transcription Factors
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Twist-Related Protein 1
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Twist1 protein, mouse
Grants and funding
This research was funded by a Discovery Project Grant from the Australian Research Council (
www.arc.gov.au), grant number DP1094008 and a Bridging Grant from The University of Sydney ID 2013-00050. David Loebel was CMRI Kimberly Clark-Research Fellow, Heidi Bildsoe is a postgraduate scholar of the National Health and Medical Reserch Council (
www.nhmrc.gov.au), and Patrick Tam is a NHMRC Senior Principal Research Fellow. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.