GONUTS has been updated to MW1.31 Most things seem to be working but be sure to report problems.

Have any questions? Please email us at ecoliwiki@gmail.com

PMID:19727199

From GONUTS
Jump to: navigation, search
Citation

Koshiba-Takeuchi, K, Mori, AD, Kaynak, BL, Cebra-Thomas, J, Sukonnik, T, Georges, RO, Latham, S, Beck, L, Beck, L, Henkelman, RM, Black, BL, Olson, EN, Wade, J, Takeuchi, JK, Nemer, M, Gilbert, SF and Bruneau, BG (2009) Reptilian heart development and the molecular basis of cardiac chamber evolution. Nature 461:95-8

Abstract

The emergence of terrestrial life witnessed the need for more sophisticated circulatory systems. This has evolved in birds, mammals and crocodilians into complete septation of the heart into left and right sides, allowing separate pulmonary and systemic circulatory systems, a key requirement for the evolution of endothermy. However, the evolution of the amniote heart is poorly understood. Reptilian hearts have been the subject of debate in the context of the evolution of cardiac septation: do they possess a single ventricular chamber or two incompletely septated ventricles? Here we examine heart development in the red-eared slider turtle, Trachemys scripta elegans (a chelonian), and the green anole, Anolis carolinensis (a squamate), focusing on gene expression in the developing ventricles. Both reptiles initially form a ventricular chamber that homogenously expresses the T-box transcription factor gene Tbx5. In contrast, in birds and mammals, Tbx5 is restricted to left ventricle precursors. In later stages, Tbx5 expression in the turtle (but not anole) heart is gradually restricted to a distinct left ventricle, forming a left-right gradient. This suggests that Tbx5 expression was refined during evolution to pattern the ventricles. In support of this hypothesis, we show that loss of Tbx5 in the mouse ventricle results in a single chamber lacking distinct identity, indicating a requirement for Tbx5 in septation. Importantly, misexpression of Tbx5 throughout the developing myocardium to mimic the reptilian expression pattern also results in a single mispatterned ventricular chamber lacking septation. Thus ventricular septation is established by a steep and correctly positioned Tbx5 gradient. Our findings provide a molecular mechanism for the evolution of the amniote ventricle, and support the concept that altered expression of developmental regulators is a key mechanism of vertebrate evolution.

Links

PubMed PMC2753965 Online version:10.1038/nature08324

Keywords

Animals; Chick Embryo; Evolution, Molecular; Gene Expression Regulation, Developmental; Heart/anatomy & histology; Heart/embryology; Lizards/anatomy & histology; Lizards/embryology; Lizards/genetics; Mice; Organogenesis; T-Box Domain Proteins/deficiency; T-Box Domain Proteins/genetics; T-Box Domain Proteins/metabolism; Turtles/anatomy & histology; Turtles/embryology; Turtles/genetics

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

MOUSE:TBX5

involved_in

GO:0003218: cardiac left ventricle formation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

MOUSE:TBX5

involved_in

GO:0003281: ventricular septum development

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

CHICK:TBX5

involved_in

GO:0003281: ventricular septum development

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete

CHICK:TBX5

involved_in

GO:0003218: cardiac left ventricle formation

ECO:0000270: expression pattern evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

See Help:References for how to manage references in GONUTS.