Activity-dependent development of the body's touch receptors. Activity-dependent development of the body's touch receptors

We report a role for activity in the development of the primary sensory neurons that detect touch. Genetic deletion of Piezo2, the principal mechanosensitive ion channel in somatosensory neurons, caused profound changes in the formation of mechanosensory end organ structures. Peripheral nervous system specific deletion of the voltage-gated sodium channel Nav1.6 (Scn8a), which resulted in altered electrophysiological responses to mechanical stimuli, also disrupted somatosensory neuron morphologies, supporting a role for neuronal activity in end organ formation. Single cell RNA sequencing of Piezo2 mutants revealed changes in gene expression in the sensory neurons activated by light mechanical forces, whereas other neuronal classes were minimally affected, and genetic deletion of Piezo2-dependent genes partially reproduced the defects in mechanosensory neuron structures observed in Piezo2 mutants. These findings indicate that mechanically evoked neuronal activity acts early in life to shape the maturation of mechanosensory end organs that underlie our sense of gentle touch. Overall design: Dorsal root ganglia from segmental levels C2 and below were dissected and dissociated to obtain neurons for single cell RNA sequencing analysis. In the first bioreplicate, DRG from two Cdx2-Cre/+; Piezo2flox/flox animals (age P24) were dissected and assigned as “Mutant sample 1” and DRG from three control littermates were dissected on the same day and assigned as “Control sample 1.” In the second bioreplicate, DRG from three Cdx2-Cre/+; Piezo2flox/flox animals (age P21) were dissected and assigned as “Mutant sample 2” and DRG from two control littermates were dissected and assigned as “Control sample 2.”

本研究揭示了感知触觉的初级感觉神经元的活动在其发育进程中的功能。躯体感觉神经元中主要的机械敏感性离子通道Piezo2（Piezo2）的基因敲除，可导致机械感受终末器官结构的形成发生显著改变。对电压门控钠通道Nav1.6（Scn8a）进行外周神经系统特异性敲除，该操作可改变躯体感觉神经元对机械刺激的电生理反应，同时破坏其形态结构，这一结果支持神经元活动在终末器官形成中的作用。对Piezo2敲除突变体的单细胞RNA测序分析显示，轻机械力激活的感觉神经元的基因表达发生了改变，而其他神经元类别受影响极小；此外，Piezo2依赖基因的敲除可部分重现Piezo2突变体中观察到的机械感觉神经元结构缺陷。上述研究结果表明，机械刺激诱发的神经元活动在生命早期即可发挥作用，塑造机械感受终末器官的成熟过程——而后者正是我们感知轻柔触觉的结构基础。

实验整体设计：解剖并解离节段水平C2及以下的背根神经节（Dorsal root ganglia，DRG）以获取神经元，用于单细胞RNA测序分析。在第一个生物学重复中，解剖了2只Cdx2-Cre/+; Piezo2flox/flox小鼠（日龄P24）的背根神经节，将其记为"Mutant sample 1"；同日解剖了3只同窝对照小鼠的背根神经节，记为"Control sample 1"。在第二个生物学重复中，解剖了3只Cdx2-Cre/+; Piezo2flox/flox小鼠（日龄P21）的背根神经节，将其记为"Mutant sample 2"；同日解剖了2只同窝对照小鼠的背根神经节，记为"Control sample 2"。