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Gene Review:

tbx5a - T-box 5a

Danio rerio

Synonyms: SO:0000704, T-box protein 5, T-box transcription factor TBX5-A, heartstrings, hst, ...

Fischer, S. et al., Szeto, D.P. et al., Begemann, G. et al., Ahn, D.G. et al., Mercader, N. et al., et al.

Ahn, Kourakis, Rohde, Silver, Ho,

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High impact information on tbx5

The function of the tbx5 gene in the development of zebrafish forelimbs seems to involve the directed migration of individual lateral-plate mesodermal cells into the future limb-bud-producing region [1].
T-box gene tbx5 is essential for formation of the pectoral limb bud [1].
While it is known that Fgf, Wnt and retinoic acid (RA) signals are involved in this cascade, their precise regulatory hierarchy has not been determined in any species. tbx5 is the earliest gene expressed in the limb bud mesenchyme [2].
We show that the zebrafish fgf24 gene, which belongs to the Fgf8/17/18 subfamily of Fgf ligands, acts downstream of tbx5 to activate fgf10 expression in the lateral plate mesoderm [3].
Fgf8, which is expressed in the intermediate mesoderm, is thought to initiate forelimb formation by activating wnt2b, which then induces the expression of tbx5 in the adjacent lateral plate mesoderm [3].

Biological context of tbx5

In particular, we found that the loss of hrT function led to a dramatic upregulation of tbx5, a gene required for normal heart morphogenesis [4].
Conversely, we show that overexpression of hrT causes a significant downregulation of tbx5, indicating that one key role of hrT is to regulate the levels of tbx5 [4].
Here, we report the cloning of the zebrafish tbx5.1 gene and characterise its expression during zebrafish embryogenesis and early larval development of wild type and mutant embryos that affect pectoral fin patterning. tbx5.1 is expressed during development of the heart, the pectoral fins and the eye [5].

Anatomical context of tbx5

The development of vertebrate limb buds is triggered in the lateral plate mesoderm by a cascade of genes, including members of the Fgf and Wnt families, as well as the transcription factor tbx5 [3].

Other interactions of tbx5

Whole mount in situ hybridization revealed specific expression of these genes in the eye and Fin buds. zf-tbx5 expression is restricted to the pectoral Fin bud, whilst zf-tbx4 transcripts are confined in the pelvic Fin bud [6].

References

T-box gene tbx5 is essential for formation of the pectoral limb bud. Ahn, D.G., Kourakis, M.J., Rohde, L.A., Silver, L.M., Ho, R.K. Nature (2002) [Pubmed]
Prdm1 acts downstream of a sequential RA, Wnt and Fgf signaling cascade during zebrafish forelimb induction. Mercader, N., Fischer, S., Neumann, C.J. Development (2006) [Pubmed]
The zebrafish fgf24 mutant identifies an additional level of Fgf signaling involved in vertebrate forelimb initiation. Fischer, S., Draper, B.W., Neumann, C.J. Development (2003) [Pubmed]
HrT is required for cardiovascular development in zebrafish. Szeto, D.P., Griffin, K.J., Kimelman, D. Development (2002) [Pubmed]
Developmental regulation of Tbx5 in zebrafish embryogenesis. Begemann, G., Ingham, P.W. Mech. Dev. (2000) [Pubmed]
Differential expression of Tbx4 and Tbx5 in Zebrafish fin buds. Tamura, K., Yonei-Tamura, S., Belmonte, J.C. Mech. Dev. (1999) [Pubmed]

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