Caviness V S, Takahashi T, Miyama S, Nowakowski R S, Delalle I
Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, 02114, USA.
Exp Neurol. 1996 Feb;137(2):357-66. doi: 10.1006/exnr.1996.0037.
We review here a computational model of neocortical histogenesis based upon experiments in the developing cerebral wall of the mouse. Though based upon experiments in mouse, commonalities of developmental history and structure of neocortex across mammalian species suggest that the principles which support this model will be generally applicable to neocortical evolution and development across species. In its scope the model spans the successive histogenetic events: cell proliferation, cell migration, and the positioning of cell somata in neocortical layers following migration. Neurons are produced in a pseudostratified epithelium (PVE) which lines the ventricular cavaties of the embryonic cerebrum. The parameters which determine the rate and total number of neurons produced in the PVE are (1) the size of the founder population, (2) the number of integer cell cycles executed by the founder population and its progeny in the course of the neuronogenetic interval, (3) the growth fraction, and (4) the fraction of cells which exits the cycle (Q fraction) with each integer cycle. There is a systematic relationship between the integer cycle of origin and the sequence of cell migration, position in the cortex, and the extent to which a set of postmigratory neurons will be diluted in the cortex by the combined effects of tissue growth and cell death. Variation across species in the number of integer cell cycles as a function of the rate of progression of Q may be expected to modulate profoundly the total numbers of neurons that are produced but not the relative proportions of neurons assigned to the major neocortical layers.
在此，我们回顾一个基于对小鼠发育中的脑壁进行的实验所建立的新皮质组织发生的计算模型。尽管该模型基于对小鼠的实验，但跨哺乳动物物种的新皮质发育历史和结构的共性表明，支持此模型的原理通常将适用于跨物种的新皮质进化和发育。在其范围内，该模型涵盖了连续的组织发生事件：细胞增殖、细胞迁移以及迁移后细胞体在新皮质层中的定位。神经元在衬于胚胎大脑脑室腔的假复层上皮（PVE）中产生。决定PVE中产生的神经元速率和总数的参数有：（1）奠基群体的大小；（2）奠基群体及其后代在神经发生间隔期间执行的整数细胞周期数；（3）生长分数；（4）每个整数周期退出细胞周期的细胞分数（Q分数）。起源的整数周期与细胞迁移序列、在皮质中的位置以及一组迁移后神经元在皮质中因组织生长和细胞死亡的综合作用而被稀释的程度之间存在系统关系。作为Q进展速率的函数，跨物种在整数细胞周期数上的变化可能会深刻调节所产生的神经元总数，但不会调节分配到主要新皮质层的神经元的相对比例。
