Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute, Bron, France.
Institute of Neuroscience, Université Catholique de Louvain, Belgium.
Cereb Cortex. 2020 Mar 21;30(2):656-671. doi: 10.1093/cercor/bhz116.
Perturbation of the developmental refinement of the corticospinal (CS) pathway leads to motor disorders. While non-primate developmental refinement is well documented, in primates invasive investigations of the developing CS pathway have been confined to neonatal and postnatal stages when refinement is relatively modest. Here, we investigated the developmental changes in the distribution of CS projection neurons in cynomolgus monkey (Macaca fascicularis). Injections of retrograde tracer at cervical levels of the spinal cord at embryonic day (E) 95 and E105 show that: (i) areal distribution of back-labeled neurons is more extensive than in the neonate and dense labeling is found in prefrontal, limbic, temporal, and occipital cortex; (ii) distributions of contralateral and ipsilateral projecting CS neurons are comparable in terms of location and numbers of labeled neurons, in contrast to the adult where the contralateral projection is an order of magnitude higher than the ipsilateral projection. Findings from one largely restricted injection suggest a hitherto unsuspected early innervation of the gray matter. In the fetus there was in addition dense labeling in the central nucleus of the amygdala, the hypothalamus, the subthalamic nucleus, and the adjacent region of the zona incerta, subcortical structures with only minor projections in the adult control.
皮质脊髓（CS）通路发育精细化的干扰会导致运动障碍。虽然非灵长类动物的发育精细化过程有详细的记录，但在灵长类动物中，对发育中的 CS 通路的侵入性研究仅限于新生儿和产后阶段，此时精细化程度相对较低。在这里，我们研究了食蟹猴（Macaca fascicularis）CS 投射神经元分布的发育变化。在胚胎第 95 天和第 105 天，在脊髓颈段注射逆行示踪剂后显示：（i）回溯标记神经元的面积分布比新生儿更广泛，并且在额前叶、边缘叶、颞叶和枕叶发现了密集的标记；（ii）与成年动物相比，双侧和单侧投射 CS 神经元的分布在位置和标记神经元数量方面相当，而成年动物的对侧投射比同侧投射高一个数量级。来自一次主要限制注射的发现提示了一个迄今未被怀疑的早期灰质神经支配。在胎儿中，除了在杏仁核中央核、下丘脑、底丘脑核和与之相邻的未定带区域有密集的标记外，在成年对照中，这些皮质下结构只有少量投射。
