Pundir Arvind Singh, Singh Utkarsha A, Ahuja Nikhil, Makhija Sonal, Dikshit P C, Radotra Bishan, Kumar Praveen, Shankar S K, Mahadevan Anita, Roy T S, Iyengar Soumya
Division of Systems Neuroscience, National Brain Research Centre (Deemed University), NH-8, Manesar, Gurgaon, Haryana, 122051, India.
Department of Forensic Medicine, Maulana Azad Medical College, Bahadur Shah Zafar Marg, New Delhi, 110002, India.
Brain Struct Funct. 2016 Sep;221(7):3641-74. doi: 10.1007/s00429-015-1124-6. Epub 2015 Oct 5.
We had earlier demonstrated a neurofilament-rich plexus of axons in the presumptive human auditory cortex during fetal development which became adult-like during infancy. To elucidate the origin of these axons, we studied the expression of the vesicular glutamate transporters (VGLUT) 1 and 2 in the human auditory cortex at different stages of development. While VGLUT-1 expression predominates in intrinsic and cortico-cortical synapses, VGLUT-2 expression predominates in thalamocortical synapses. Levels of VGLUT-2 mRNA were higher in the auditory cortex before birth compared to postnatal development. In contrast, levels of VGLUT-1 mRNA were low before birth and increased during postnatal development to peak during childhood and then began to decrease in adolescence. Both VGLUT-1 and VGLUT-2 proteins were present in the human auditory cortex as early as 15GW. Further, immunohistochemistry revealed that the supra- and infragranular layers were more immunoreactive for VGLUT-1 compared to that in Layer IV at 34GW and this pattern was maintained until adulthood. As for VGLUT-1 mRNA, VGLUT-1 synapses increased in density between prenatal development and childhood in the human auditory cortex after which they appeared to undergo attrition or pruning. The adult pattern of VGLUT-2 immunoreactivity (a dense band of VGLUT-2-positive terminals in Layer IV) also began to appear in the presumptive Heschl's gyrus at 34GW. The density of VGLUT-2-positive puncta in Layer IV increased between prenatal development and adolescence, followed by a decrease in adulthood, suggesting that thalamic axons which innervate the human auditory cortex undergo pruning comparatively late in development.
我们之前已经证明，在胎儿发育期间，人类推测的听觉皮层中存在一个富含神经丝的轴突丛，该轴突丛在婴儿期变得类似成人。为了阐明这些轴突的起源，我们研究了在不同发育阶段人类听觉皮层中囊泡谷氨酸转运体（VGLUT）1和2的表达。虽然VGLUT - 1的表达在内在和皮质 - 皮质突触中占主导地位，但VGLUT - 2的表达在丘脑 - 皮质突触中占主导地位。与出生后发育相比，出生前听觉皮层中VGLUT - 2 mRNA的水平更高。相比之下，VGLUT - 1 mRNA的水平在出生前较低，在出生后发育期间增加，在儿童期达到峰值，然后在青春期开始下降。早在孕15周时，人类听觉皮层中就同时存在VGLUT - 1和VGLUT - 2蛋白。此外，免疫组织化学显示，在孕34周时，与第IV层相比，颗粒上层和颗粒下层对VGLUT - 1的免疫反应性更强，并且这种模式一直维持到成年。至于VGLUT - 1 mRNA，在人类听觉皮层中，从产前发育到儿童期，VGLUT - 1突触的密度增加，此后它们似乎经历了磨损或修剪。VGLUT - 2免疫反应性的成人模式（第IV层中VGLUT - 2阳性终末的密集带）在孕34周时也开始出现在推测的颞横回中。第IV层中VGLUT - 2阳性斑点的密度在产前发育到青春期之间增加，随后在成年期下降，这表明支配人类听觉皮层的丘脑轴突在发育过程中相对较晚才进行修剪。
