Tbx5 is essential for initiation of the forelimb, and its deletion in mice results in the failure of forelimb formation. Misexpression of dominant-negative forms of Tbx5 results in limb truncations, suggesting Tbx5 is also required for forelimb outgrowth. Here we show that Tbx5 is expressed throughout the limb mesenchyme in progenitors of cartilage, tendon and muscle. Using a tamoxifeninducible...

Despite the critical importance of TBX5 in normal development and disease, relatively little is known about the mechanisms by which TBX5 functions in the embryonic heart. Our present studies demonstrate that TBX5 is necessary to control the length of the embryonic cardiac cell cycle, with depletion of TBX5 leading to cardiac cell cycle arrest in late G(1)- or early S-phase. Blocking cell cycle ...

Heterozygous Tbx5(del/+) mice were generated to study the mechanisms by which TBX5 haploinsufficiency causes cardiac and forelimb abnormalities seen in Holt-Oram syndrome. Tbx5 deficiency in homozygous mice (Tbx5(del/del)) decreased expression of multiple genes and caused severe hypoplasia of posterior domains in the developing heart. Surprisingly, Tbx5 haploinsufficiency also markedly decrease...

Holt-Oram syndrome (HOS) is a disorder characterized by skeletal abnormalities in the upper limbs accompanied by cardiovascular defects. The diagnosis of HOS is based on these abnormalities and defects, both in the individual or in the parents, and is indicative of congenital transmission. All those affected by this syndrome have upper limb skeletal abnormalities, which preferentially affect th...

Transcriptional regulatory cascades during epicardial and coronary vascular development from proepicardial progenitor cells remain to be defined. We have used immunohistochemistry of human embryonic tissues to demonstrate that the TBX5 transcription factor is expressed not only in the myocardium, but also throughout the embryonic epicardium and coronary vasculature. TBX5 is not expressed in oth...

The recently identified zebrafish T-box gene hrT is expressed in the developing heart and in the endothelial cells forming the dorsal aorta. Orthologs of hrT are expressed in cardiovascular cells from Drosophila to mouse, suggesting that the function of hrT is evolutionarily conserved. The role of hrT in cardiovascular development, however, has not thus far been determined in any animal model. ...

RMRP, the RNA component of mitochondrial RNA processing endoribonuclease, is a non-coding RNA (ncRNA) part of the RNase MRP complex functioning in mitochondrial and ribosomal RNA processing. Even though various mutations in the RMRP gene are linked to developmental defects and pathogenesis, its relevance to cancer etiology has not been well established. Here we examined the expression of RMRP a...

Members of the T-box family of proteins play a fundamental role in patterning the developing vertebrate heart; however, the precise cellular requirements for any one family member and the mechanism by which individual T-box genes function remains largely unknown. In this study, we have investigated the cellular and molecular relationship between two T-box genes, Tbx5 and Tbx20. We demonstrate t...

BACKGROUND/AIMS Congenital heart defects (CHD) can occur with upper limbs deformities. Holt-Oram syndrome is the main type of heart-hand syndromes, characterized by upper limb radial ray malformations, CHD and/or conduction abnormalities. Mutations of the TBX5 gene, most of which are found within the T-box domain, are one cause of the disease. We aimed to find the cause of the disease in a fami...

Haploinsufficiency of T-box transcription factor 5 (TBX5) causes human Holt-Oram syndrome (HOS), a developmental disorder characterized by skeletal and heart malformations. Mice carrying a Tbx5 null allele (Tbx5(+/Delta)) have malformations in digits, wrists, and sternum joints, regions where Tbx5 is expressed. We demonstrate that mice deficient in connexin 40 (Cx40), a Tbx5-regulated gap junct...