Investigating the transition from head to trunk formation in vertebrate development

在发育过程中，脊椎动物的身体计划是如何形成的一直是发育生物学领域的一个有趣的问题。基本的脊椎动物身体计划包括三个领域；头，躯干和尾巴。原肠胚形成开始后，胚胎由前到后，由头到尾逐渐发育。换句话说，脊椎动物发育过程中形成的第一个结构是头，而躯干/尾巴则逐渐添加到胚胎的后端。人们一直认为躯干和尾巴是由头部组织的一部分后置而形成的。然而，最近的研究表明，头部和躯干的形成在空间和时间上是独立的，并且使用不同的模式机制。然而，对于如何控制这两种不同模式机制的转变知之甚少。在这一转变过程中形成的细胞产生了颈部结构，即头和躯干之间的解剖连接处。有趣的是，在脊椎动物的进化过程中，颈部区域的多样性相对较好（例如，羊膜动物出现枕骨，鸟类和哺乳动物分别出现颈部区域的数量变化/限制）。因此，了解头躯干转换的发育机制将为研究脊椎动物的形态发生和进化提供新的视角。

How the vertebrate body plan is established during development has been a main interesting question in the field of developmental biology. The basic vertebrate body plan consists of three domains; head, trunk and tail. After the beginning of gastrulation, the embryo develops progressively from anterior to posterior, from head to tail. In other words, the first structure forming in vertebrate development is the head and the trunk/tail are progressively added to the posterior end of the embryo. It has been thought that the trunk and tail are formed by posteriorizing a part of head tissues. However, recent studies show that head and trunk are formed in a spatially and temporally independent manner and use different patterning mechanisms. However, very little is known about how the transition of the two different patterning mechanisms is controlled. The cells forming during this transition give rise to the neck structures, the anatomical junction between head and trunk. Interestingly, the neck region is relatively well diversified in vertebrate evolution (e.g. emergence of occipital bones in amniotes and number variation/restriction in the cervical region in birds and mammals, respectively). Thus, understanding the developmental mechanisms of the head/trunk transition will provide new insight into vertebrate morphogenesis and evolution.