Neuroscience Institute Cavalieri Ottolenghi (NICO), Orbassano, Italy.
Department of Veterinary Sciences, University of Turin, Torino, Italy.
Elife. 2020 Jul 21;9:e55456. doi: 10.7554/eLife.55456.
The adult mammalian brain is mainly composed of mature neurons. A limited amount of stem cell-driven neurogenesis persists in postnatal life and is reduced in large-brained species. Another source of immature neurons in adult brains is cortical layer II. These cortical immature neurons (cINs) retain developmentally undifferentiated states in adulthood, though they are generated before birth. Here, the occurrence, distribution and cellular features of cINs were systematically studied in 12 diverse mammalian species spanning from small-lissencephalic to large-gyrencephalic brains. In spite of well-preserved morphological and molecular features, the distribution of cINs was highly heterogeneous, particularly in neocortex. While virtually absent in rodents, they are present in the entire neocortex of many other species and their linear density in cortical layer II generally increased with brain size. These findings suggest an evolutionary developmental mechanism for plasticity that varies among mammalian species, granting a reservoir of young cells for the cerebral cortex.
成年哺乳动物大脑主要由成熟神经元组成。在出生后，大脑中仍存在有限数量的由干细胞驱动的神经发生，但在大脑较大的物种中这种神经发生会减少。成年大脑中不成熟神经元的另一个来源是皮质层 II。这些皮质不成熟神经元 (cINs) 在成年期保留了未分化的发育状态，尽管它们是在出生前产生的。在这里，我们在 12 种不同的哺乳动物物种中系统地研究了 cINs 的发生、分布和细胞特征，这些物种的大脑从小脑回到大脑回不等。尽管 cINs 保留了良好的形态和分子特征，但它们的分布具有高度的异质性，特别是在新皮质中。在啮齿动物中几乎不存在 cINs，但在许多其他物种的整个新皮质中都存在 cINs，并且它们在皮质层 II 中的线性密度通常随大脑大小而增加。这些发现表明了一种在哺乳动物物种中存在差异的进化发育可塑性机制，为大脑皮层提供了年轻细胞的储备。
