Roles of motor proteins in cerebellar Purkinje neuron biology

肌球蛋白10在小脑浦肯野神经元中的作用 浦肯野神经元(PN)是小脑的主神经元，因为它接受小脑皮质的所有输入，是皮质唯一的输出，对协调、平衡和学习精确的运动任务至关重要。我们先前表明，肌球蛋白Va将ER的小管运输到PN脊椎中，以促进突触可塑性和运动学习(Wagner等人，NAT。细胞生物。而肌球蛋白18A的靶点是鸟嘌呤核苷酸交换因子--PIx到Pn脊柱，以促进脊柱成熟(Alexander等人，FASEB J 2021)。在这里，我们描述了正在进行的努力，用来定义三叉神经节中肌球蛋白10(Myo10)的功能，这在中枢神经系统神经元中是独一无二的，拥有非常高水平的这种丝状肌球蛋白，并在没有事先神经支配的情况下进行丝足到脊椎的转换。在整个器官水平上，6周龄的Myo10基因敲除(KO)小鼠(Heimsath等，Sci.2017年)显示小脑发育不良、畸形和/或小脑叶缺失。此外，这些小鼠的小脑切片的Calbindin染色显示，在分子层内的PN胞体排列和PN树突枝的方向上存在缺陷。重要的是，对6个月大的成熟Myo10 KO小鼠的小脑切片进行Calbindin染色，发现PN形态上的主要缺陷，包括树突分枝减少和脊椎密度大幅降低。与这些观察结果一致的是，Myo10 KO小鼠在小脑功能(如维持平衡)方面表现出显著的缺陷。最后，在培养的三叉神经节中表达的GFP标记的Myo10显著定位于形成轴突前沿的丝状突起的顶端，而miRNA介导的Myo10在这些细胞中的敲除导致脊髓成熟和细胞极性的缺陷(树突分枝减少，轴突数量增加)。综上所述，这些结果表明Myo10是正常小脑发育、小脑功能以及PN结构和功能所必需的，并为未来旨在确定MyTH4/FERM肌球蛋白促进这些过程的分子机制的努力铺平了道路。

Myosin 10 function in cerebellar Purkinje neurons The Purkinje neuron (PN) is the master neuron of the cerebellum, as it receives all inputs into the cerebellar cortex, is the sole output from the cortex, and is essential for coordination, balance and learning precise motor tasks. We showed previously that myosin Va transports tubules of ER into PN spines to promote synaptic plasticity and motor learning (Wagner et al, Nat. Cell Biol. 2011), and that myosin 18A targets the guanine nucleotide exchange factor -Pix to PN spines to promote spine maturation (Alexander et al, FASEB J 2021). Here we describe ongoing efforts using to define the function of myosin 10 (Myo10) in PNs, which are unique among CNS neurons in possessing very high levels of this filopodial myosin, and in undergoing filopodia-to-spine conversion without prior innervation. At the whole organ level, six week-old Myo10 knockout (KO) mice (Heimsath et al, Sci. Rep. 2017) exhibit cerebellar hypoplasia and misshapen and/or missing cerebellar lobes. Additionally, Calbindin staining of cerebellar slices from these mice reveals defects in the alignment of PN soma and in the orientation of PN dendritic arbors within the molecule layer. Importantly, Calbindin staining of cerebellar slices from mature, six month-old Myo10 KO mice reveals major defects in PN morphology, including reduced dendritic arborization and greatly reduced spine density. Consistent with these observations, Myo10 KO mice exhibit significant defects in cerebellar function (e.g. maintaining balance). Finally, GFP-tagged Myo10 expressed in cultured PNs localizes dramatically at the tips of filopodia-like extensions at the leading edge of forming neurites, and the miRNA-mediated knockdown of Myo10 in these cells results in defects in spine maturation and cell polarity (reduced dendritic arborization, increased number of axons). Together, these results argue that Myo10 is required for normal cerebellar development, cerebellar function, and PN structure and function, and they pave the way for future efforts designed to identify the molecular mechanisms by which this MyTH4/FERM myosin promotes these processes.