Tbx2 is essential for patterning the atrioventricular canal and for morphogenesis of the outflow tract during heart development.
Tbx2 is a member of the T-box transcription factor gene family, and is expressed in a variety of tissues and organs during embryogenesis. In the developing heart, Tbx2 is expressed in the outflow tract, inner curvature, atrioventricular canal and inflow tract, corresponding to a myocardial zone that is excluded from chamber differentiation at 9.5 days post coitus (dpc). We have used targeted mutagenesis in mice to investigate Tbx2 function. Mice heterozygous for a Tbx2 null mutation appear normal but homozygous embryos reveal a crucial role for Tbx2 during cardiac development. Morphological defects are observed in development of the atrioventricular canal and septation of the outflow tract. Molecular analysis reveals that Tbx2 is required to repress chamber differentiation in the atrioventricular canal at 9.5 dpc. Analysis of homozygous mutants also highlights a role for Tbx2 during hindlimb digit development. Despite evidence that TBX2 negatively regulates the cell cycle control genes Cdkn2a, Cdkn2b and Cdkn1a in cultured cells, there is no evidence that loss of Tbx2 function during mouse development results in increased levels of p19(ARF), p16(INK4a), p15(INK4b) or p21 expression in vivo, nor is there evidence for a genetic interaction between Tbx2 and p53.
Harrelson
Zachary
Z
Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA.
Kelly
Robert G
RG
Goldin
Sarah N
SN
Gibson-Brown
Jeremy J
JJ
Bollag
Roni J
RJ
Silver
Lee M
LM
Papaioannou
Virginia E
VE
D000818:Animals; D019521:Body Patterning / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D018390:Gene Targeting; D006321:Heart / Q000196:embryology* / Q000502:physiology; D006325:Heart Atria / Q000196:embryology; D006352:Heart Ventricles / Q000201:enzymology; D017880:Limb Deformities, Congenital / Q000235:genetics; D051379:Mice; D009154:Mutation; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*
C097348:T-Box Domain Protein 2; D020825:T-Box Domain Proteins