The spinal cord contains neural networks that enable regionally distinct motor outputs along the body axis. Nevertheless, it remains unclear how segment-specific motor computations are processed because the cardinal interneuron classes that control motor neurons appear uniform at each level of the spinal cord. V2a interneurons are essential to both forelimb and hindlimb movements, and here we identify two major types that emerge during development: type I neurons marked by high Chx10 form recurrent networks with neighboring spinal neurons and type II neurons that downregulate Chx10 and project to supraspinal structures. Types I and II V2a interneurons are arrayed in counter-gradients, and this network activates different patterns of motor output at cervical and lumbar levels. Single-cell RNA sequencing (RNA-seq) revealed type I and II V2a neurons are each comprised of multiple subtypes. Our findings uncover a molecular and anatomical organization of V2a interneurons reminiscent of the orderly way motor neurons are divided into columns and pools.

中文翻译：

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脊髓和脊髓上 V2a 中间神经元亚型的分级阵列是前肢和后肢运动控制的基础。

脊髓包含神经网络，可以沿身体轴实现区域不同的运动输出。然而，由于控制运动神经元的主要中间神经元类在脊髓的每个水平上看起来是一致的，因此具体节段的运动计算是如何处理的仍然不清楚。V2a 中间神经元对前肢和后肢运动都是必不可少的，在这里我们确定了发育过程中出现的两种主要类型：以高 Chx10 为标志的 I 型神经元与邻近的脊髓神经元和 II 型神经元形成循环网络，后者下调 Chx10 并投射到脊髓上结构。I 型和 II 型 V2a 中间神经元排列成反梯度，该网络在颈椎和腰椎水平激活不同模式的运动输出。单细胞 RNA 测序 (RNA-seq) 显示 I 型和 II 型 V2a 神经元均由多个亚型组成。我们的发现揭示了 V2a 中间神经元的分子和解剖结构，让人联想到运动神经元被有序地分为列和池的方式。