Project description:During adult neurogenesis, newly formed olfactory bulb (OB) interneurons migrate radially to integrate into specific layers of the OB. Despite the importance of this process, the intracellular mechanisms that regulate radial migration remain poorly understood. Here we find that microRNA (miRNA) let-7 regulates radial migration by modulating autophagy in new-born neurons. Using Argonaute2-immunoprecipitation, we performed global profiling of miRNAs in adult-born OB neurons and identified let-7 as a highly abundant miRNA family. Knockdown of let-7 in migrating neuroblasts prevented radial migration and led to an immature morphology of newly formed interneurons. This phenotype was accompanied by a decrease in autophagic activity. Overexpression of Beclin-1 or TFEB in new-born neurons lacking let-7 resulted in re-activation of autophagy and restored radial migration. Thus, these results reveal a miRNA-dependent link between autophagy and adult neurogenesis with implications for neurodegenerative diseases where these processes are impaired.
Project description:Completion of neuronal migration is critical for brain development. Kif21b is a plus-end directed kinesin motor protein that promotes intracellular transport and controls microtubule dynamics in neurons. Here we report a physiological function of Kif21b during radial migration of projection neurons in the mouse developing cortex. In vivo analysis in mouse and live imaging on cultured slices demonstrate that Kif21b regulates the radial glia-guided locomotion of new-born neurons independently of its motility on microtubules. Unexpectedly we show that Kif21b directly binds and regulates the actin cytoskeleton both in vitro and in vivo in migratory neurons. We establish that Kif21b-mediated regulation of actin cytoskeleton dynamics influences branching and nucleokinesis during neuronal locomotion. Altogether, our results reveal atypical roles of Kif21b on the actin cytoskeleton during migration of cortical projection neurons
Project description:Zebrafish display widespread and pronounced adult neurogenesis, which is fundamental for their regeneration capability after central nervous system injury. However, the cellular identity and the biological properties of adult newborn neurons are elusive for most brain areas. Here, we used short-term lineage tracing of radial glia progeny to prospectively isolate newborn neurons from the her4.1+ radial glia lineage in the homeostatic adult forebrain. Transcriptome analysis of radial glia, newborn neurons and mature neurons using single cell sequencing identified distinct transcriptional profiles including novel markers for each population. Specifically, we detected 2 separate newborn neuron types, which showed diversity of cell fate commitment and location. Further analyses showed homology of these cell types to neurogenic cells in the mammalian brain, identified neurogenic commitment in proliferating radial glia and indicated that glutamatergic projection neurons fate are generated in the adult zebrafish telecephalon. Thus, we prospectively isolated adult newborn neurons from the adult zebrafish forebrain, identified markers for newborn and mature neurons in the adult brain, revealed intrinsic heterogeneity among adult newborn neurons and their homology to mammalian adult neurogenic cell types.
Project description:During the developmental formation of 6-layered neocortical structure of mammalian cerebral cortex, newborn excitatory neurons depart the ventricular zone and migrate toward the pial surface. At a middle stage of cortical development, newly differentiated postmitotic neurons adopt a multipolar shape (MP), and exhibit a random non-directional migration in the intermediate zone (multipolar migration). When these neurons pass through the subplate layer (SP), they convert to a bipolar shape (BP), and then migrate radially toward the pial surface (locomotion). In order to elucidate the molecular mechanisms of such neuronal migration, we performed a gene expression profiling of newborn excitatory neurons during their migration processes. After in utero electroporation of GFP expressing plasmid into E14 mouse cortex, GFP-positive cells were collected using FACS sorting method after one, two, or three days of electroporation. RNAs of collected GFP-positive cells at each day were purified and applied to microarray analyses. gene-ontology and pathway analyses revealed that genes encoding synaptic proteins, receptors and ECM-related proteins were up-regulated as the migration proceeds. On the other hand, genes encoding cell cycle regulation and immune-related proteins were down-regulated. We will discuss the relationship between the migration mode and the transition of the gene expression.
Project description:WAC is a known positive regulator of (macro)autophagy. WAC also forms a complex with RNF20/RNF40 to promote H2B monoubiquitination and hence to affect transcriptional regulation. This study addresses whether the WAC/RNF20/RNF40 complex regulates autophagy through effects on gene expression.
Project description:WAC is a known positive regulator of (macro)autophagy. WAC also forms a complex with RNF20/RNF40 to promote H2B monoubiquitination and hence to affect transcriptional regulation. This study addresses whether the WAC/RNF20/RNF40 complex regulates autophagy through effects on gene expression. WAC, RNF20 and RNF40 were knocked-down using pools of siRNAs in HEK293A cells. Each knockdown was in triplicate and the control was RISCfree siRNA. mRNA expression profiles were investigated using an Illumina HT12v4 Bead Array.
Project description:During neocortical development, neurons undergo polarization, oriented migration, and layer type-specific differentiation. The transcriptional programs underlying these processes are not completely understood. Here we show that the transcription factor Bcl11a regulates polarity and migration of upper layer neurons. Bcl11a-deficient late-born neurons fail to correctly switch from multipolar to bipolar morphology resulting in impaired radial migration. We show that the expression of Sema3c is increased in migrating Bcl11a-deficient neurons and that Bcl11a is a direct negative regulator of Sema3c transcription. In vivo gain-of-function and rescue experiments demonstrate that Sema3c is a major downstream effector of Bcl11a required for the cell polarity switch and for the migration of upper layer neurons. Our data uncover a novel Bcl11a/Sema3c-dependent regulatory pathway used by migrating cortical neurons.
Project description:Since the discovery of radial glia as the source of neurons, their heterogeneity in regard to neurogenesis has been described by clonal and time-lapse analysis in vitro. However, the molecular determinants specifying neurogenic radial glia differently from radial glia that mostly self-renew remain ill-defined. Here, we isolated two radial glial subsets that co-exist at mid-neurogenesis in the developing cerebral cortex and their immediate progeny. While one subset generates neurons directly, the other is largely non-neurogenic but also gives rise to Tbr2-positive basal precursors, thereby contributing indirectly to neurogenesis. Isolation of ; these distinct radial glia subtypes allowed determining interesting differences in their transcriptome. These transcriptomes were also strikingly different from the transcriptome of radial glia isolated at the end of neurogenesis. This analysis therefore identifies, for the first time, the lineage origin of basal progenitors and the molecular differences of this lineage in comparison to directly neurogenic and gliogenic radial glia. Experiment Overall Design: Comparison of radial glial subtypes
Project description:During neocortical development, neurons undergo polarization, oriented migration, and layer type-specific differentiation. The transcriptional programs underlying these processes are not completely understood. Here we show that the transcription factor Bcl11a regulates polarity and migration of upper layer neurons. Bcl11a-deficient late-born neurons fail to correctly switch from multipolar to bipolar morphology resulting in impaired radial migration. We show that the expression of Sema3c is increased in migrating Bcl11a-deficient neurons and that Bcl11a is a direct negative regulator of Sema3c transcription. In vivo gain-of-function and rescue experiments demonstrate that Sema3c is a major downstream effector of Bcl11a required for the cell polarity switch and for the migration of upper layer neurons. Our data uncover a novel Bcl11a/Sema3c-dependent regulatory pathway used by migrating cortical neurons. Neocortex tissue from three control (Bcl11a+/+) and three Bcl11a mutants (Bcl11aΔflox/Δflox) embryos was collected at E14.5. Total RNA was isolated from each sample separately using the RNeasy kit (Qiagen). The isolated ENA was inspected for integrity and purity using an Agilent Bioanalyzer and a NanoDrop spectrophotometer, respectively. Microarray analyses were performed using 200 ng total RNA as starting material and 5.5 µg ssDNA per hybridization in a GeneChip Fluidics Station 450 (Affymetrix). The total RNAs were amplified and labeled following the Whole Transcript (WT) Sense Target Labeling Assay (Affymetrix). Labeled ssDNA was hybridized to Mouse Gene 1.0 ST Affymetrix GeneChip arrays (Affymetrix). The chips were scanned with a GeneChip Scanner 3000 (Affymetrix) and subsequent images analyzed using Affymetrix Expression Console Software (Affymetrix). A transcriptome analysis was performed using BRB-ArrayTools developed by Dr. Richard Simon and BRB-ArrayTools Development Team (http://linus.nci.nih.gov/BRB-ArrayTools.html).