Identification of Thymosin β4 as an effector of Hand1-mediated vascular development.
The bHLH transcription factor Hand1 (Heart and neural crest-derived transcript-1) has a fundamental role in cardiovascular development; however, the molecular mechanisms have not been elucidated. In this paper we identify Thymosin β4 (Tβ4/Tmsb4x), which encodes an actin monomer-binding protein implicated in cell migration and angiogenesis, as a direct target of Hand1. We demonstrate that Hand1 binds an upstream regulatory region proximal to the promoter of Tβ4 at consensus Thing1 and E-Box sites and identify both activation and repression of Tβ4 by Hand1, through direct binding within either non-canonical or canonical E-boxes, providing new insight into gene regulation by bHLH transcription factors. Hand1-mediated activation of Tβ4 is essential for yolk sac vasculogenesis and embryonic survival, and administration of synthetic TB4 partially rescues yolk sac capillary plexus formation in Hand1-null embryos. Thus, we identify an in vivo downstream target of Hand1 and reveal impaired yolk sac vasculogenesis as a primary cause of early embryonic lethality following loss of this critical bHLH factor.
Smart
Nicola
N
Molecular Medicine Unit, UCL-Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK.
Dubé
Karina N
KN
Riley
Paul R
PR
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D019295:Computational Biology; D024202:Electrophoretic Mobility Shift Assay; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013947:Thymosin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D015017:Yolk Sac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000099201:Thymosin beta(4)
D051792:Basic Helix-Loop-Helix Proteins; D013947:Thymosin; D000099201:Thymosin beta(4); C095572:Hand1 protein, mouse