Tbx2 and Tbx3 regulate the dynamics of cell proliferation during heart remodeling.
BACKGROUND
The heart forms from a linear tube that is subject to complex remodeling during embryonic development. Hallmarks of this remodeling are the looping of the heart tube and the regionalization into chamber and non-chamber myocardium. Cardiomyocytes in the future chamber myocardium acquire different cellular and physiological characteristics through activation of a chamber-specific genetic program, which is in part mediated by T-box genes.


RESULTS
We characterize two new zebrafish T-box transcription factors, tbx3b and tbx2a, and analyze their role during the development of the atrioventricular canal. Loss- and gain-of-function analyses demonstrate that tbx3b and tbx2a are necessary to repress the chamber-genetic program in the non-chamber myocardium. We also show that tbx3b and tbx2a are required to control cell proliferation in the atrioventricular canal and that misregulation of cell proliferation in the heart tube influences looping. Furthermore, we characterize the heart phenotype of a novel Tbx3 mutation in mice and show that both the control of cell proliferation and the repression of chamber-specific genetic program in the non-chamber myocardium are conserved roles of Tbx3 in this species.


CONCLUSIONS
Taken together, our results uncover an evolutionarily conserved role of Tbx2/3 transcription factors during remodeling of the heart myocardium and highlight the importance of controlling cell proliferation as a driving force of morphogenesis.
Ribeiro
Inês
I
Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America.
Kawakami
Yasuhiko
Y
Büscher
Dirk
D
Raya
Angel
A
Rodríguez-León
Joaquín
J
Morita
Masanobu
M
Rodríguez Esteban
Concepción
C
Izpisúa Belmonte
Juan Carlos
JC
D000818:Animals; D049109:Cell Proliferation; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015027:Zebrafish
D014157:Transcription Factors