ABSTRACT
The recent discovery of short neural precursors (SNPs) in the murine neocortical ventricular zone (VZ) challenges the widely held view that radial glial cells (RGCs) are the sole occupants of this germinal compartment and suggests that precursor variety is an important factor of brain development. Here, we use in utero electroporation and genetic fate mapping to show that SNPs and RGCs cohabit the VZ but display different cell cycle kinetics and generate phenotypically different progeny. In addition, we find that RGC progeny undergo additional rounds of cell division as intermediate progenitor cells (IPCs), whereas SNP progeny generally produce postmitotic neurons directly from the VZ. By clearly defining SNPs as bona fide VZ residents, separate from both RGCs and IPCs, and uncovering their unique proliferative and lineage properties, these results demonstrate how individual neural precursor groups in the embryonic rodent VZ create diversity in the overlying neocortex.
Subject(s)
Cell Cycle/physiology , Cerebral Ventricles/cytology , Gene Expression Regulation, Developmental/genetics , Neocortex/cytology , Neurons/physiology , Stem Cells/physiology , Amino Acid Transport System X-AG/genetics , Analysis of Variance , Animals , Animals, Newborn , Bromodeoxyuridine/metabolism , Cerebral Ventricles/embryology , Cerebral Ventricles/growth & development , Electroporation/methods , Eye Proteins/metabolism , Green Fluorescent Proteins/genetics , Homeodomain Proteins/metabolism , Ki-67 Antigen/metabolism , Luminescent Proteins/genetics , Mice , Mice, Inbred ICR , Mice, Transgenic , Nerve Tissue Proteins/metabolism , Neuroglia/metabolism , PAX6 Transcription Factor , POU Domain Factors/metabolism , Paired Box Transcription Factors/metabolism , Repressor Proteins/metabolism , T-Box Domain Proteins/metabolism , Tubulin/metabolism , Red Fluorescent ProteinABSTRACT
Brain-derived neurotrophic factor (BDNF) has emerged as a prominent mediator of neuronal development and synaptic plasticity. BDNF activates multiple signal transduction cascades that regulate cellular function through phosphorylation, transcription, and translation. Ethanol is known to inhibit neurotrophin signaling, but a thorough pharmacological analysis of the effect of ethanol on BDNF signaling in developing neurons has not been performed. These experiments were undertaken to determine the interactions between membrane depolarization, BDNF concentration, and ethanol concentration on extracellular signal-regulated protein kinase (ERK) activation in neurons. We examined cerebellar granule cells grown under physiological (5mM) or elevated (25mM) potassium culture conditions after 3 days in vitro. BDNF-stimulated ERK phosphorylation (pERK) within 10min and supported stimulation from 20 to 60min. Ethanol decreased basal pERK and reduced the magnitude of BDNF stimulation of ERK under both conditions. The NMDA receptor antagonist 2-amino-5-phosphonovalerate did not effect basal pERK or inhibit BDNF stimulation of ERK, suggesting that NMDA receptors do not modulate BDNF stimulation of ERK in short-term cultures. These data characterize the pharmacological effects of ethanol on growth factor signaling and provide the basis of a model for further characterization of the biochemical mechanisms of ERK inhibition by ethanol. Perturbation of BDNF signal transduction by ethanol may underlie some of the cognitive deficits and developmental abnormalities resulting from ethanol exposure.
