Mechanism of four-chambered heart formation in the vertebrates

在脊椎动物中，心脏的形态从鱼到哺乳动物都不同，与它们的生活方式有关。这一事实是众所周知的，但提供四室动物和非四室动物之间这种差异的分子机制尚不清楚。非鳄鱼类爬行动物在心脏的进化中占有独特的地位，因为它们的室腔明显是三腔心脏和四腔心脏之间的中间体。我们研究了Tbx5在爬行动物中的表达模式，发现陡峭和正确定位的Tbx5梯度对于室间隔的形成非常重要。这一发现普遍支持这一概念，即发育调节因子的表达变化是形态进化的一个重要方面。

In vertebrates the heart morphology is varied from fish to mammals relating their life style. This fact is well known, but the molecular mechanism that provides such differences between four-chambered animals and non-four-chambered animals is unclear. Non-crocodilian reptiles hold a unique place in the evolution of the heart, as their ventricular chambers are apparent intermediates between three-chambered heart and four-chambered heart. We studied Tbx5 expression pattern in the reptiles and found that a steep and correctly positioned Tbx5 gradient is important for ventricular septum formation. This findings generally support the concept that altered expression of developmental regulators is an important aspect of morphological evolution.