RNA sequencing of cervical spinal cord neurons targeted by CFA or RFA of mouse motor cortex. Mus musculus

Corticospinal neurons (CSNs) synapse directly on spinal neurons, a diverse group of neurons with unique structural and functional properties necessary for body movements. CSNs modulating forelimb behavior fractionate into caudal forelimb area (CFA) and rostral forelimb area (RFA) motor cortical populations. Despite their prominence, the full diversity of spinal neurons targeted by CFA and RFA CSNs is uncharted. Here we use anatomical and RNA-sequencing methods to show that CSNs synapse onto a remarkably selective group of spinal cell types, favoring inhibitory populations that regulate motoneuron activity and gate sensory feedback. CFA and RFA CSNs target similar spinal cell types, with notable exceptions that suggest these populations differ in how they influence behavior.

皮质脊髓神经元（Corticospinal neurons, CSNs）可直接与脊髓神经元形成突触连接——后者是一类结构与功能特性独特、对躯体运动不可或缺的多样化神经元群体。调控前肢运动行为的CSNs，可进一步划分为尾侧前肢区（Caudal forelimb area, CFA）与嘴侧前肢区（Rostral forelimb area, RFA）的运动皮层神经元集群。尽管该类神经元的研究价值已得到广泛认可，但CFA与RFA的CSNs所靶向的脊髓神经元的完整多样性仍未被全面阐明。本研究通过解剖学与RNA测序（RNA-sequencing）技术证实：CSNs可与一类高度选择性的脊髓细胞类型形成突触连接，且更倾向于靶向那些调控运动神经元活动并门控感觉反馈的抑制性神经元群体。CFA与RFA的CSNs所靶向的脊髓细胞类型整体相似，但存在显著差异，提示二者对躯体运动行为的调控机制存在区别。