The vertebrate main-body axis is laid down during embryonic stages in an anterior-to-posterior (head-to-tail) direction, driven and supplied by posteriorly located progenitors. Whilst posterior expansion and segmentation appears broadly uniform along the axis, there is developmental and evolutionary support for at least two discrete modules controlling processes within different axial regions: a trunk and a tail module. Here, we identify Nuclear receptor subfamily 6 group A member 1 (Nr6a1) as a master regulator of trunk development in the mouse. Specifically, Nr6a1 was found to control vertebral number and segmentation of the trunk region, autonomously from other axial regions. Moreover, Nr6a1 was essential for the timely progression of Hox signatures, and neural versus mesodermal cell fate choice, within axial progenitors. Collectively, Nr6a1 has an axially-restricted role in all major cellular and tissue-level events required for vertebral column formation, supporting the view that changes in Nr6a1 levels may underlie evolutionary changes in axial formulae.

脊椎动物的主体轴在胚胎阶段以从前到后（头到尾）的方向铺设，由位于后部的祖细胞驱动和供应。虽然后部扩展和分割在轴上看起来大致一致，但在不同轴区域内至少有两个离散模块控制过程有发展和进化支持：躯干和尾部模块。在这里，我们将核受体亚家族 6 A 组成员 1 (Nr6a1) 鉴定为小鼠躯干发育的主要调节因子。具体而言，发现 Nr6a1 可以独立于其他中轴区域控制椎骨数量和躯干区域的分割。此外，Nr6a1 对于Hox的及时进展至关重要轴向祖细胞内的特征和神经与中胚层细胞命运选择。总的来说，Nr6a1 在脊柱形成所需的所有主要细胞和组织水平事件中具有轴向限制作用，支持 Nr6a1 水平变化可能是轴向公式进化变化基础的观点。