RESUMEN
Impaired neurogenesis in Down syndrome (DS) is characterized by reduced neurons, increased glial cells, and delayed cortical lamination. However, the underlying cause for impaired neurogenesis in DS is not clear. Using both human and mouse iPSCs, we demonstrate that DS impaired neurogenesis is due to biphasic cell cycle dysregulation during the generation of neural progenitors from iPSCs named the "neurogenic stage" of neurogenesis. Upon neural induction, DS cells showed reduced proliferation during the early phase followed by increased proliferation in the late phase of the neurogenic stage compared to control cells. While reduced proliferation in the early phase causes reduced neural progenitor pool, increased proliferation in the late phase leads to delayed post mitotic neuron generation in DS. RNAseq analysis of late-phase DS progenitor cells revealed upregulation of S phase-promoting regulators, Notch, Wnt, Interferon pathways, and REST, and downregulation of several genes of the BAF chromatin remodeling complex. NFIB and POU3F4, neurogenic genes activated by the interaction of PAX6 and the BAF complex, were downregulated in DS cells. ChIPseq analysis of late-phase neural progenitors revealed aberrant PAX6 binding with reduced promoter occupancy in DS cells. Together, these data indicate that impaired neurogenesis in DS is due to biphasic cell cycle dysregulation during the neurogenic stage of neurogenesis.
RESUMEN
Microglial cells are one of the interstitial elements of the pineal gland (PG). We recently reported the pattern of microglia colonization and activation, and microglia-Pax6+ cell interactions during normal pineal ontogeny. Here, we describe the dynamics of microglia-Pax6+ cell associations and interactions after surgical or pharmacological manipulation. In adult rats, the superior cervical ganglia (SCG) were exposed, and either bilaterally excised (SCGx) or decentralized (SCGd). In the SCGx PGs, the density of Iba1+ microglia increased after surgery and returned to sham baseline levels 13 days later. Pineal microglia also responded to SCGd, a more subtle denervation. The number of clustered Iba1+ /PCNA+ /ED1+ microglia was higher 4 days after both surgeries compared to the sham-operated group. However, the number of Pax6+ /PCNA- cells and the percentage of Pax6+ cells contacted by and/or phagocytosed by microglia increased significantly only after SCGx. Separate groups of rats were treated with either bacterial lipopolysaccharides (LPS) or doxycycline (DOX) to activate or inhibit pineal microglia, respectively. Peripheral LPS administration caused an increase in the number of clustered Iba1+ /PCNA+ /ED1+ microglial cells, and in the percentage of Pax6+ cells associated with and/or engulfed by microglia. In the LPS-treated PGs, we also noted an increase in the number of PCNA+ cells that were Iba1- within the microglial cell clusters. The density of Pax6+ cells did not change after LPS treatment. DOX administration did not influence the parameters analyzed. These data suggest that pineal microglia are highly receptive cells capable of rapidly responding in a differential manner to surgical and pharmacological stimuli.
Asunto(s)
Microglía/fisiología , Estimulación Física , Glándula Pineal/efectos de los fármacos , Glándula Pineal/cirugía , Animales , Antibacterianos/farmacología , Proteínas de Unión al Calcio/metabolismo , Doxiciclina/farmacología , Ganglios Espinales/cirugía , Lipopolisacáridos/farmacología , Masculino , Proteínas de Microfilamentos/metabolismo , Microglía/efectos de los fármacos , Neurocirugia , Factor de Transcripción PAX6 , Fagocitosis , Glándula Pineal/citología , Ratas , Ratas WistarRESUMEN
Our previous analysis of progenitor domains in the pretectum of Xenopus revealed three molecularly distinct anteroposterior subdivisions, identified as precommissural (PcP), juxtacommissural (JcP), and commissural (CoP) histogenetic domains (Morona et al. [2011] J Comp Neurol 519:1024-1050). Here we analyzed at later developmental stages the nuclei derived from these areas, attending to their gene expression patterns and histogenesis. Transcription-factor gene markers were used to selectively map derivatives of each domain: Pax7 and Pax6 (CoP); Foxp1 and Six3 (JcP); and Xiro1, VGlut2, Ebf1, and Ebf3 (PcP). Additional genoarchitectural information was provided by the expression of Gbx2, NPY, Lhx1, and Lhx9. This allowed both unambiguous characterization of the anuran pretectal nuclei with regard to their origin in the three early anteroposterior progenitor domains, and their comparison with counterparts in the chick and mouse pretectum. Our observations demonstrated a molecular conservation, during practically all the stages analyzed, for most of the main markers used to define genoarchitecturally the main derivatives of each pretectal domain. We found molecular evidence to propose homologous derivatives from the CoP (olivary pretectal, parvocellular, and magnocellular posterior commissure and lateral terminal nuclei), JcP (spiriformis lateral and lateral terminal nuclei), and PcP (anterior pretectal nucleus) to those described in avian studies. These results represent significant progress in the comprehension of the diencephalic region of Xenopus and show that the organization of the pretectum possesses many features shared with birds. J. Comp. Neurol. 525:715-752, 2017. © 2016 Wiley Periodicals, Inc.