期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：36
页码：E5058-E5067
DOI：10.1073/pnas.1506377112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceUnderstanding development and evolution of the neocortex has important implications. We describe here a major difference between avian and mammalian dorsal pallial progenitors regarding their fate restrictions. In mouse cortex we identified an early population of radial glial cells that are delayed in the generation of neurons. After self-renewal and transit-amplifying mitoses, these murine progenitors become committed to the genesis of upper-layer callosal pyramidal neurons and glia. In the chick embryonic pallium we identified a homologous population of progenitors; however, these have no delayed neurogenesis and their lineage is therefore not segregated from that of the other pallial progenitors. We hypothesize on the relation between the early neurogenic delay of progenitors and the origin of the corpus callosum. The classical view of mammalian cortical development suggests that pyramidal neurons are generated in a temporal sequence, with all radial glial cells (RGCs) contributing to both lower and upper neocortical layers. A recent opposing proposal suggests there is a subgroup of fate-restricted RGCs in the early neocortex, which generates only upper-layer neurons. Little is known about the existence of fate restriction of homologous progenitors in other vertebrate species. We investigated the lineage of selected Emx2+ [vertebrate homeobox gene related to Drosophila empty spiracles (ems)] RGCs in mouse neocortex and chick forebrain and found evidence for both sequential and fate-restricted programs only in mouse, indicating that these complementary populations coexist in the developing mammalian but not avian brain. Among a large population of sequentially programmed RGCs in the mouse brain, a subset of self-renewing progenitors lack neurogenic potential during the earliest phase of corticogenesis. After a considerable delay, these progenitors generate callosal upper-layer neurons and glia. On the other hand, we found no homologous delayed population in any sectors of the chick forebrain. This finding suggests that neurogenic delay of selected RGCs may be unique to mammals and possibly associated with the evolution of the corpus callosum.
关键词：neocortex ; Emx2 ; cortical development ; neurogenesis ; chick
