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Wnts regulate the timing and efficiency of OPC generation in the telencephalon
Poster Abstracts / Int. J. Devl Neuroscience 28 (2010) 655–719
sion pathway genes (LRRTM2, PSD-95 and CASK) in order to begin to understand the function of gene networks underlying the emergence of early behaviours. We have generated morpholinos against NRXN-1a, NRXN1b and CNTNAP2 and injected them individually into one cell embryos and then assessed the touch and escape responses at 30 and 45 h, respectively. Knock down of either NRXN1a, NRXN1b or CNTAP2 significantly reduced the touch response at 30 hpf to a similar extent. The high penetrance of these phenotypes (71–84%) suggest that these genes are playing a major role in the development of the underlying neural circuitry responsible for this behaviour. In contrast, at 45 hpf knock down of NRXN-1a had no effect on the escape response, knock down of NRXN1b either extinguished or reduced the response, while knock down of CNTNAP2 produced an abnormal response. These very different phenotypes suggest very different roles of these synaptic adhesion network genes in the underlying neural circuitry. Our analyses are beginning to reveal the most critical genes involved in development of neural circuits underlying a simple behaviour. Keywords: Zebrafish; Synapse; Behavior; Adhesion doi:10.1016/j.ijdevneu.2010.07.134 [P2.05] The canonical Wnt pathway regulates Tbr2-positive intermediate progenitor maturation in the neocortex R.N. Munji ∗ , Y. Choe, S.J. Pleasure University of California-San Francisco, USA Keywords: Wnt; Cortex; Intermediate progenitors; Periventricular heterotopia In this study, we focus on the role of the canonical Wnt pathway in neocortical neurogenesis. At present, conclusions from previous studies have not converged on a parsimonious model for the role of the canonical Wnt pathway in neocortical neurogenesis, some suggesting a role in promoting neural progenitor differentiation while others in promoting primary progenitor (PP) self-renewal and, in consequence, inhibition of intermediate progenitor (IP) production. We hypothesized that the canonical Wnt pathway might function to regulate both differentiation and selfrenewal, possibly in different progenitor populations and/or at different developmental time-points. To address our hypothesis, we analyzed canonical Wnt function from E13.5, a time-point when horizontal expansion of the neocortical epithelium has slowed while neuronal production continues, and up to P2, when embryonic neurogenesis has primarily subsided, and utilized in utero electroporation (EP) of secreted effectors of the pathway, Wnt3a ligand and Dkk1 inhibitor, to perturb the pathway upstream of intracellular events. Overexpression of Wnt3a at E13.5 horizontally expanded the neocortical epithelium and induced premature differentiation of Tbr2-positive IPs into neurons. These prematurely born neurons predominantly fail to reach the cortical plate and accumulate deep in the cortical epithelium, leading to the formation of periventricular heterotopias. In contrast, overexpression of Dkk1 reduced neuronal production. Our results suggest that the canonical Wnt pathway has a dual role in neocortical neurogenesis, promoting self-renewal of PPs and differentiation of Tbr2-positive IPs. Moreover, these results contribute to our understanding of cortical organization and suggest a connection between the canonical Wnt pathway and periventricular heterotopia disorders. doi:10.1016/j.ijdevneu.2010.07.135
687
[P2.06] Wnts regulate the timing and efficiency of OPC generation in the telencephalon A.J. Langseth 1,∗ , R.N. Munji 1 , Y. 1,2 1 Pozniak , S.J. Pleasure
Choe 1 , T.
Huynh 1 , C.D.
1
University of California, San Francisco, USA Genentech, Inc., USA Keywords: Oligodendrocyte; Neural Precursor; Wnt; Cell Fate 2
Oligodendrocyte precursor cells (OPCs) are generated from multiple progenitor domains in the telencephalon in developmental succession from ventral to dorsal. Each domain also generates neurons at earlier developmental stages. Previous studies have demonstrated that Wnt signaling inhibits the differentiation of OPCs into mature oligodendrocytes, but we also wanted to explore the hypothesis that Wnt signaling limits the generation of OPCs from multipotential neural precursors during forebrain development. First, we manipulated both extracellular Wnt ligands and inhibitors and the transcriptional output of the Wnt pathway in neural progenitor cultures and found that Wnt signaling acts directly on progenitor cells to regulate the production of OPCs. Furthermore, we found that endogenous Wnt signaling in these cultures is a major limitation on the efficiency of generating OPCs from multipotent neural precursors. To examine similar events in vivo, we electroporated a soluble Wnt inhibitor or a dominant-negative transcriptional regulator into embryonic mouse neocortical ventricular zone several days before the usual onset of OPC production and showed that decreasing Wnt signaling in this progenitor domain results in enhanced early production of OPCs. Our studies indicate that Wnt signaling is a regulator of the timing and extent of OPC production in the developing mammalian telencephalon. It is hoped that understanding the mechanisms that regulate OPC specification will aid in the development of therapies for oligodendrocyte replacement in demyelinating diseases including perinatal hypoxic-ischemic brain injury, leukodystrophies, and multiple sclerosis. doi:10.1016/j.ijdevneu.2010.07.136 [P2.07] Doublecortin expression in the prefrontal cortex of developing human and in adults with schizophrenia S.J. Fung 1,2,∗ , S. Sivagnanasunduram 1 , M.J. Webster 3 , C. Shannon Weickert 1,2 1
Schizophrenia Research Institute, Australia University of New South Wales, Australia 3 Stanley Medical Research Institute, USA Keywords: Doublecortin; Schizophrenia; Prefrontal cortex 2
Postnatal neurogenesis occurs in the subventricular zone and hippocampus of the primate brain. There is also increasing evidence to suggest that new neurons may be present in other regions of the mature brain, including the prefrontal cortex, which is involved in higher executive functions and cognition and is impaired in schizophrenia. To determine if postnatal migration of new neurons may occur in the prefrontal cortex and to address whether migration of immature neurons might be altered in disease we measured the expression of doublecortin, a marker of immature migrating neurons, in human dorsolateral prefrontal cortex (DLPFC) during postnatal development and in schizophrenia. We used quantitative RT-PCR and western blot analysis to measure doublecortin expression in a developmental cohort with
sion pathway genes (LRRTM2, PSD-95 and CASK) in order to begin to understand the function of gene networks underlying the emergence of early behaviours. We have generated morpholinos against NRXN-1a, NRXN1b and CNTNAP2 and injected them individually into one cell embryos and then assessed the touch and escape responses at 30 and 45 h, respectively. Knock down of either NRXN1a, NRXN1b or CNTAP2 significantly reduced the touch response at 30 hpf to a similar extent. The high penetrance of these phenotypes (71–84%) suggest that these genes are playing a major role in the development of the underlying neural circuitry responsible for this behaviour. In contrast, at 45 hpf knock down of NRXN-1a had no effect on the escape response, knock down of NRXN1b either extinguished or reduced the response, while knock down of CNTNAP2 produced an abnormal response. These very different phenotypes suggest very different roles of these synaptic adhesion network genes in the underlying neural circuitry. Our analyses are beginning to reveal the most critical genes involved in development of neural circuits underlying a simple behaviour. Keywords: Zebrafish; Synapse; Behavior; Adhesion doi:10.1016/j.ijdevneu.2010.07.134 [P2.05] The canonical Wnt pathway regulates Tbr2-positive intermediate progenitor maturation in the neocortex R.N. Munji ∗ , Y. Choe, S.J. Pleasure University of California-San Francisco, USA Keywords: Wnt; Cortex; Intermediate progenitors; Periventricular heterotopia In this study, we focus on the role of the canonical Wnt pathway in neocortical neurogenesis. At present, conclusions from previous studies have not converged on a parsimonious model for the role of the canonical Wnt pathway in neocortical neurogenesis, some suggesting a role in promoting neural progenitor differentiation while others in promoting primary progenitor (PP) self-renewal and, in consequence, inhibition of intermediate progenitor (IP) production. We hypothesized that the canonical Wnt pathway might function to regulate both differentiation and selfrenewal, possibly in different progenitor populations and/or at different developmental time-points. To address our hypothesis, we analyzed canonical Wnt function from E13.5, a time-point when horizontal expansion of the neocortical epithelium has slowed while neuronal production continues, and up to P2, when embryonic neurogenesis has primarily subsided, and utilized in utero electroporation (EP) of secreted effectors of the pathway, Wnt3a ligand and Dkk1 inhibitor, to perturb the pathway upstream of intracellular events. Overexpression of Wnt3a at E13.5 horizontally expanded the neocortical epithelium and induced premature differentiation of Tbr2-positive IPs into neurons. These prematurely born neurons predominantly fail to reach the cortical plate and accumulate deep in the cortical epithelium, leading to the formation of periventricular heterotopias. In contrast, overexpression of Dkk1 reduced neuronal production. Our results suggest that the canonical Wnt pathway has a dual role in neocortical neurogenesis, promoting self-renewal of PPs and differentiation of Tbr2-positive IPs. Moreover, these results contribute to our understanding of cortical organization and suggest a connection between the canonical Wnt pathway and periventricular heterotopia disorders. doi:10.1016/j.ijdevneu.2010.07.135
687
[P2.06] Wnts regulate the timing and efficiency of OPC generation in the telencephalon A.J. Langseth 1,∗ , R.N. Munji 1 , Y. 1,2 1 Pozniak , S.J. Pleasure
Choe 1 , T.
Huynh 1 , C.D.
1
University of California, San Francisco, USA Genentech, Inc., USA Keywords: Oligodendrocyte; Neural Precursor; Wnt; Cell Fate 2
Oligodendrocyte precursor cells (OPCs) are generated from multiple progenitor domains in the telencephalon in developmental succession from ventral to dorsal. Each domain also generates neurons at earlier developmental stages. Previous studies have demonstrated that Wnt signaling inhibits the differentiation of OPCs into mature oligodendrocytes, but we also wanted to explore the hypothesis that Wnt signaling limits the generation of OPCs from multipotential neural precursors during forebrain development. First, we manipulated both extracellular Wnt ligands and inhibitors and the transcriptional output of the Wnt pathway in neural progenitor cultures and found that Wnt signaling acts directly on progenitor cells to regulate the production of OPCs. Furthermore, we found that endogenous Wnt signaling in these cultures is a major limitation on the efficiency of generating OPCs from multipotent neural precursors. To examine similar events in vivo, we electroporated a soluble Wnt inhibitor or a dominant-negative transcriptional regulator into embryonic mouse neocortical ventricular zone several days before the usual onset of OPC production and showed that decreasing Wnt signaling in this progenitor domain results in enhanced early production of OPCs. Our studies indicate that Wnt signaling is a regulator of the timing and extent of OPC production in the developing mammalian telencephalon. It is hoped that understanding the mechanisms that regulate OPC specification will aid in the development of therapies for oligodendrocyte replacement in demyelinating diseases including perinatal hypoxic-ischemic brain injury, leukodystrophies, and multiple sclerosis. doi:10.1016/j.ijdevneu.2010.07.136 [P2.07] Doublecortin expression in the prefrontal cortex of developing human and in adults with schizophrenia S.J. Fung 1,2,∗ , S. Sivagnanasunduram 1 , M.J. Webster 3 , C. Shannon Weickert 1,2 1
Schizophrenia Research Institute, Australia University of New South Wales, Australia 3 Stanley Medical Research Institute, USA Keywords: Doublecortin; Schizophrenia; Prefrontal cortex 2
Postnatal neurogenesis occurs in the subventricular zone and hippocampus of the primate brain. There is also increasing evidence to suggest that new neurons may be present in other regions of the mature brain, including the prefrontal cortex, which is involved in higher executive functions and cognition and is impaired in schizophrenia. To determine if postnatal migration of new neurons may occur in the prefrontal cortex and to address whether migration of immature neurons might be altered in disease we measured the expression of doublecortin, a marker of immature migrating neurons, in human dorsolateral prefrontal cortex (DLPFC) during postnatal development and in schizophrenia. We used quantitative RT-PCR and western blot analysis to measure doublecortin expression in a developmental cohort with