Article

Thymosin beta 4 is dispensable for murine cardiac development and function.

Department of Medicine, University of California-San Diego, La Jolla, 92093, USA.
Circulation Research (Impact Factor: 11.09). 12/2011; 110(3):456-64. DOI: 10.1161/CIRCRESAHA.111.258616
Source: PubMed

ABSTRACT Thymosin beta 4 (Tβ4) is a 43-amino acid factor encoded by an X-linked gene. Recent studies have suggested that Tβ4 is a key factor in cardiac development, growth, disease, epicardial integrity, and blood vessel formation. Cardiac-specific short hairpin (sh)RNA knockdown of tβ4 has been reported to result in embryonic lethality at E14.5-16.5, with severe cardiac and angiogenic defects. However, this shRNA tβ4-knockdown model did not completely abrogate Tβ4 expression. To completely ablate Tβ4 and to rule out the possibility of off-target effects associated with shRNA gene silencing, further studies of global or cardiac-specific knockouts are critical.
We examined the role of Tβ4 in developing and adult heart through global and cardiac specific tβ4-knockout mouse models.
Global tβ4-knockout mice were born at mendelian ratios and exhibited normal heart and blood vessel formation. Furthermore, in adult global tβ4-knockout mice, cardiac function, capillary density, expression of key cardiac fetal and angiogenic genes, epicardial marker expression, and extracellular matrix deposition were indistinguishable from that of controls. Tissue-specific tβ4-deficient mice, generated by crossing tβ4-floxed mice to Nkx2.5-Cre and αMHC-Cre, were also found to have no phenotype.
We conclude that Tβ4 is dispensable for embryonic viability, heart development, coronary vessel development, and adult myocardial function.

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