Elsevier

Developmental Biology

Volume 211, Issue 1, 1 July 1999, Pages 100-108
Developmental Biology

Regular Article
Chamber-Specific Cardiac Expression of Tbx5 and Heart Defects in Holt–Oram Syndrome

https://doi.org/10.1006/dbio.1999.9298Get rights and content
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Abstract

To further define the role of a T-box transcription factor, Tbx5, in cardiac development, we have examined its expression in the developing mouse and chick heart and correlated this pattern with cardiac defects caused by human TBX5 mutations in Holt–Oram syndrome. Early in the developing heart, Tbx5 is uniformly expressed throughout the entire cardiac crescent. Upon formation of the linear heart tube, Tbx5 is expressed in a graded fashion, stronger near the posterior end and weaker at the anterior end. As the heart tube loops, asymmetric Tbx5 expression continues; Tbx5 is expressed in the presumptive left ventricle, but not the right ventricle or outflow tract. This pattern of expression is maintained in more mature hearts. Expression in the ventricular septum is restricted to the left side and is contiguous with left ventricular free wall expression. Trabeculae, vena cavae (inferior and superior), and the atrial aspect of the atrioventricular valves also express high levels of Tbx5. These patterns of Tbx5 expression provide an embryologic basis for the prevalence of atrial septal defects (ostium primum and secundum), ventricular muscular septal defects, and left-sided malformations (endocardial cushion defects, hypoplastic left heart, and aberrant trabeculation) observed in patients with Holt–Oram syndrome.

Keywords

heart development
transcription factor
gene expression
embryo

Cited by (0)

Mouse Tbx5 has been deposited in GenBank under Accession No. AF140427. The full-length cTbx5 sequence has been deposited in GenBank under Accession No. AF069396.

1

These authors contributed equally to the work presented here.