The transcription factor Zeb2 controls fate specification and subsequent differentiation and maturation of multiple cell types in various embryonic tissues. It binds many protein partners, including activated Smad proteins and the NuRD co-repressor complex. How Zeb2 subdomains support cell differentiation in various contexts has remained elusive. Here, we have studied the role of Zeb2 and its domains in neurogenesis and neural differentiation in the young postnatal ventricular-subventricular zone (V-SVZ), where neural stem cells generate olfactory bulb-destined interneurons. Conditional Zeb2 knockouts and separate acute loss- and gain-of-function approaches indicated that Zeb2 is essential to control apoptosis and neuronal differentiation of V-SVZ progenitors before and after birth, and identified Sox6 as Zeb2-dependent and potential downstream target gene. Zeb2 genetic inactivation impaired the differentiation potential of the V-SVZ niche in a cell-autonomous fashion. We also provide evidence that its normal function in the V-SVZ involves non-autonomous mechanisms as well. Additionally, we could demonstrate distinct roles for Zeb2 protein-binding domains, suggesting that Zeb2 partners co-determine neuronal output from the mouse V-SVZ in both quantitative and qualitative manners in early postnatal life.

Neural connectivity requires neuronal differentiation, axon growth, and precise target innervation. Midbrain dopaminergic neurons project via the nigrostriatal pathway to the striatum to regulate voluntary movement. While the specification and differentiation of these neurons have been extensively studied, the molecular mechanisms that regulate midbrain dopaminergic axon growth and target innervation are less clear. Here we show that the transcription factor Zeb2 cell-autonomously represses Smad signalling to limit midbrain dopaminergic axon growth and target innervation. Zeb2 levels are downregulated in the embryonic rodent midbrain during the period of dopaminergic axon growth, when BMP pathway components are upregulated. Experimental knockdown of Zeb2 leads to an increase in BMP-Smad-dependent axon growth. Consequently there is dopaminergic hyperinnervation of the striatum, without an increase in the numbers of midbrain dopaminergic neurons, in conditional Zeb2 (Nestin-Cre based) knockout mice. Therefore, these findings reveal a new mechanism for the regulation of midbrain dopaminergic axon growth during central nervous system development.

During neurogenesis, generation, migration and integration of the correct numbers of each neuron sub-type depends on complex molecular interactions in space and time. MicroRNAs represent a key control level allowing the flexibility and stability needed for this process. Insight into the role of this regulatory pathway in the brain is still limited. We performed a sequential experimental approach using postnatal olfactory bulb neurogenesis in mice, starting from global expression analyses to the investigation of functional interactions between defined microRNAs and their targets. Deep sequencing of small RNAs extracted from defined compartments of the postnatal neurogenic system demonstrated that the miR-200 family is specifically induced during late neuronal differentiation stages. Using in vivo strategies we interfered with the entire miR-200 family in loss- and gain-of-function settings, showing a role of miR-200 in neuronal maturation. This function is mediated by targeting the transcription factor Zeb2. Interestingly, so far functional interaction between miR-200 and Zeb2 has been exclusively reported in cancer or cultured stem cells. Our data demonstrate that this regulatory interaction is also active during normal neurogenesis.

Event Abstract Back to Event Smad-interacting-protein 1 (Sip1) contributes to the establishment of the postnatal neurogenic niche Elke Stappers1, Veronique Van Den Berghe2, Ruben Dries1, Elise Peyre3, Agata Stryjewska1, Andrea Conidi4, Annick Francis1, Wilfred Van IJcken4, Nicoletta Kessaris5, Magdalena Götz6, Laurent Nguyen3, Danny Huylebroeck1, 4 and Eve Seuntjens1, 3* 1 KU Leuven, Department of Development and Regeneration, Belgium 2 King's College, United Kingdom 3 University of Liège, GIGA-Neurosciences, Belgium 4 Erasmus MC, Netherlands 5 UCL, United Kingdom 6 Helmholtz Institute, Germany In the adult mouse brain, neuronal cells are continuously produced in the subventricular zone (SVZ) of the lateral ventricles. These immature neuroblasts migrate tangentially along the rostral migratory stream (RMS) to the olfactory bulb (OB), where they integrate as interneurons in the existing cellular network. Little is known however about the molecular mechanisms that steer the establishment of the postnatal SVZ neurogenic niche. The bulk of the SVZ niche develops from the lateral ganglionic eminence (LGE). Immature neural progenitors that give rise to the olfactory interneurons typically express Pax6. Here, we present Sip1 (Zfhx1b/Zeb2) as a novel factor important for the establishment of the postnatal neurogenic niche. Recent work in our lab showed that the zinc finger transcription factor Sip1 regulates cortical interneuron specification and migration during embryonic development. We also found that Sip1 is present in the LGE, as well as in the postnatal SVZ niche. These findings suggested that Sip1 might be involved in establishing the postnatal neurogenic niche. We used the Gsh2-Cre mouse line to conditionally delete Sip1 from the LGE during embryonic life. In the mutant, we found a significant raise in Pax6+ cells, but the number of doublecortin+ neurons arriving in the OB through the RMS was reduced. The excessive Pax6+ cells in the mutant migrated through the lateral cortical stream to the ventral forebrain, suggesting they either acquired a different fate or were misrouted. Intriguingly, a portion of these cells were not targeted by Cre, suggesting that Sip1 depletion affects their production in a non-cell-autonomous manner. As a result, the mutant OBs appeared smaller and more rounded at postnatal day 5 (P5), and the different layers were severely disorganized. The Sip1-depleted cells that still managed to reach the OB were disoriented and failed to populate the glomerular layer. Taken together, our data suggest that Sip1 is necessary to provide the young postnatal SVZ niche with the capacity to generate sufficient numbers of interneuron destined for the OB. Keywords: Neurogenesis, Stem Cells, differentiation, knockout mouse, subventricular zone (SVZ) Conference: 11th National Congress of the Belgian Society for Neuroscience, Mons, Belgium, 22 May - 22 May, 2015. Presentation Type: Poster presentation Topic: Neuroscience Citation: Stappers E, Van Den Berghe V, Dries R, Peyre E, Stryjewska A, Conidi A, Francis A, Van IJcken W, Kessaris N, Götz M, Nguyen L, Huylebroeck D and Seuntjens E (2015). Smad-interacting-protein 1 (Sip1) contributes to the establishment of the postnatal neurogenic niche. Front. Neurosci. Conference Abstract: 11th National Congress of the Belgian Society for Neuroscience. doi: 10.3389/conf.fnins.2015.89.00008 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 May 2015; Published Online: 05 May 2015. * Correspondence: Dr. Eve Seuntjens, KU Leuven, Department of Development and Regeneration, Leuven, Belgium, eve.seuntjens@kuleuven.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Elke Stappers Veronique Van Den Berghe Ruben Dries Elise Peyre Agata Stryjewska Andrea Conidi Annick Francis Wilfred Van IJcken Nicoletta Kessaris Magdalena Götz Laurent Nguyen Danny Huylebroeck Eve Seuntjens Google Elke Stappers Veronique Van Den Berghe Ruben Dries Elise Peyre Agata Stryjewska Andrea Conidi Annick Francis Wilfred Van IJcken Nicoletta Kessaris Magdalena Götz Laurent Nguyen Danny Huylebroeck Eve Seuntjens Google Scholar Elke Stappers Veronique Van Den Berghe Ruben Dries Elise Peyre Agata Stryjewska Andrea Conidi Annick Francis Wilfred Van IJcken Nicoletta Kessaris Magdalena Götz Laurent Nguyen Danny Huylebroeck Eve Seuntjens PubMed Elke Stappers Veronique Van Den Berghe Ruben Dries Elise Peyre Agata Stryjewska Andrea Conidi Annick Francis Wilfred Van IJcken Nicoletta Kessaris Magdalena Götz Laurent Nguyen Danny Huylebroeck Eve Seuntjens Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. 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In the adult brain, different cell types communicate with each other through cell-cell contacts and brain activity is regulated at the cell membrane. But long before the brain is fully functional, different excitatory and inhibitory cell types generated at distinct places migrate through the developing brain to their final position. The elements guiding these migrating neurons, either structural axonal scaffolds or chemical guidance factors, are relatively well described. However, the molecules involved in the individual short-timed membrane contacts migrating cells make with other cells during their migration process are less well understood. This update focuses on recent novel insights into the molecular nature of these cell-cell contacts and the cross-talk taking place at the cell membrane.

GABAergic interneurons mainly originate in the medial ganglionic eminence (MGE) of the embryonic ventral telencephalon (VT) and migrate tangentially to the cortex, guided by membrane-bound and secreted factors. We found that Sip1 (Zfhx1b, Zeb2), a transcription factor enriched in migrating cortical interneurons, is required for their proper differentiation and correct guidance. The majority of Sip1 knockout interneurons fail to migrate to the neocortex and stall in the VT. RNA sequencing reveals that Sip1 knockout interneurons do not acquire a fully mature cortical interneuron identity and contain increased levels of the repulsive receptor Unc5b. Focal electroporation of Unc5b-encoding vectors in the MGE of wild-type brain slices disturbs migration to the neocortex, whereas reducing Unc5b levels in Sip1 knockout slices and brains rescues the migration defect. Our results reveal that Sip1, through tuning of Unc5b levels, is essential for cortical interneuron guidance.

Bone morphogenetic proteins (BMPs) are considered important regulators of neural development. However, results mainly from a wide set of in vitro gain-of-function experiments are conflicting since these show that BMPs can act either as inhibitors or promoters of neurogenesis. Here, we report a specific and non-redundant role for BMP7 in cortical neurogenesis in vivo using knockout mice. Bmp7 is produced in regions adjacent to the developing cortex; the hem, meninges, and choroid plexus, and can be detected in the cerebrospinal fluid. Bmp7 deletion results in reduced cortical thickening, impaired neurogenesis, and loss of radial glia attachment to the meninges. Subsequent in vitro analyses of E14.5 cortical cells revealed that lack of Bmp7 affects neural progenitor cells, evidenced by their reduced proliferation, survival and self-renewal capacity. Addition of BMP7 was able to rescue these proliferation and survival defects. In addition, at the developmental stage E14.5 Bmp7 was also required to maintain Ngn2 expression in the subventricular zone. These data demonstrate a novel role for Bmp7 in the embryonic mouse cortex: Bmp7 nurtures radial glia cells and regulates fundamental properties of neural progenitor cells that subsequently affect Ngn2-dependent neurogenesis.

Signaling by the many ligands of the TGFβ family strongly converges towards only five receptor-activated, intracellular Smad proteins, which fall into two classes i.e. Smad2/3 and Smad1/5/8, respectively. These Smads bind to a surprisingly high number of Smad-interacting proteins (SIPs), many of which are transcription factors (TFs) that co-operate in Smad-controlled target gene transcription in a cell type and context specific manner. A combination of functional analyses in vivo as well as in cell cultures and biochemical studies has revealed the enormous versatility of the Smad proteins. Smads and their SIPs regulate diverse molecular and cellular processes and are also directly relevant to development and disease. In this survey, we selected appropriate examples on the BMP-Smads, with emphasis on Smad1 and Smad5, and on a number of SIPs, i.e. the CPSF subunit Smicl, Ttrap (Tdp2) and Sip1 (Zeb2, Zfhx1b) from our own research carried out in three different vertebrate models.