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A Dlx5–Wnt5 regulation involved in the control of GABAergic differentiation
Poster Session 2 Abstracts 3 June 2008 / Int. J. Devl Neuroscience 26 (2008) 867–892
feedback and modulation of target development. In a previous study in rats, by others, 5-methoxytryptophan treated damns gave birth to pups with cytoarchitectonic derangement in presubicular cortex. To ascertain the effects of 5-HT in cortical neuronal migration experimental animals were fed a low tryptophan diet (LT). With this diet was intended to lower 5-HT levels through reduction in tryptophan availability, necessary for 5-HT synthesis. The dietary intake is men and rodents only source of tryptophan. Wistar pregnant rats and their litters were used. They were divided in three groups: one group was fed LT through gestation and lactation, other was fed with LT diet with added tryptophan into the formulation (LTT) and the last group was fed with the standard 18% protein diet. Every diet was continued to feed pups after weaning. Rats were sacrificed at postnatal days (P) 0, 20 and 30. Brains were processed for tryptophan hydroxylase immunohistochemistry (P0), Golgi (P30) and Nissl (P20) staining and photodocumented. Serotonin content in the brain was measured at P0, P20 and P30 by HPLC of brain extracts. In animals fed with LT cytoarchitectonic derangement was found in neocortex and hippocampus allocortex, visualized at P20 and P30. These results suggest that a 5-HT level set point at ontogeny is essential in events such as cortical neuronal migration.
877
monolayer, remain multipotent and capable of GABA differentiation. Examining differentiating NS, we observed that Dlx expression follows a temporal sequence that recapitulates basal neurogenesis: Dlx2 is expressed in proliferating cells while Dlx5 is upregulated during differentiation, followed by GAD1 and CR. These results provide a molecular validation for the use of NS. In the same assay Wnt5a expression is upregulated during differentiation. These data link the transcription functions of Dlx5 with the diffusible molecule Wnt5a in the control of interneuron differentiation in the OB. doi: 10.1016/j.ijdevneu.2008.09.156 [P2.32] Suppression of interneuron programs and maintenance of selected spinal motor neuron fates by the transcription factor AML1/Runx1 N. Stifani *, A.R.O. Freitas, A. Liakhovitskaia, A. Medvinsky, A. Kania, S. Stifani McGill University, Canada *Corresponding author. Keywords: Runx1; Motor neuron; Identity
doi: 10.1016/j.ijdevneu.2008.09.155 [P2.31] A Dlx5–Wnt5 regulation involved in the control of GABAergic differentiation G.R. Merlo 1,*, S. Paina 1, A. Moiana 2, E. Cattaneo 2, S. DeMarchis 1, G. Corte 3 1
University of Torino, Italy University of Milano, Italy 3 University of Genova, Italy *Corresponding author. 2
Keywords: Interneuron; GABA; Wnt; Olfactory
Fate determination of progenitor cells involves a cooperation of genetic and environmental factors. In the embryonic forebrain the interneuron precursors originate in the GE, migrate to the olfactory bulb (OB) and cortex, and differentiate into various interneuron subtypes. Genetic and local regulations of this process are still poorly understood. Dlx genes are essential for interneuron differentiation. Dlx5 marks migrating progenitors, committed to differentiate into GABA+ and CR+ interneurons, and has been directly linked to the expression of the GABA+ phenotype. In Dlx5 mutant OB lamination is altered and interneuron differentiation is impaired. When we grafted normal LGE progenitors on slices of Dlx5 mutant brains, a reduced number of CR+ and GABA+ neurons was obtained, indicating that the Dlx5-null environment is unfavourable for differentiation. By microarray profiling of Dlx5 null neurospheres, we identified Wnt5a as a putative Dlx5 target. Indeed, Wnt5a expression is reduced in the Dlx5 null OB. Wnt5a is a ‘‘non-canonical’’ Wnt that utilizes beta-cateninindependent pathways; we indeed fail to detect expression of the BATnlacZ Wnt-responsive transgene in the OB. Functionally Wnt5a applied on slice cultures of the OB, promotes interneuron differentiation. To confirm the role of Dlx–Wnt regulation in GABA differentiation, we adopted the model of neural stem (NS) cells, reported by Conti et al. (PloS Biol 3: e283). These cells proliferate as a
Neuronal networks are formed with the cooperation of various cell types in the nervous system. The spinal cord offers a good and simple model for studying (i) the generation of cell diversity, (ii) the formation of specific connections, (iii) axonal targeting, and (iv) establishment of neuronal circuits. Individual spinal motor neuron identities are specified in large part by the intrinsic repertoire of transcription factors expressed by undifferentiated progenitors and maturing neurons. We have shown that the transcription factor AML1/Runx1 (Runx1) is expressed in selected spinal motor neuron subtypes after the onset of differentiation. Combinations of loss- and gain-of-function analyses demonstrated that Runx1 is both necessary and sufficient to suppress interneuron-specific developmental programs and promote maintenance of motor neuron characteristics. These findings show an important role for Runx1 during the consolidation of selected spinal motor neuron identities. Moreover, they suggest a requirement for a persistent suppression of interneuron genes within maturing motor neurons. doi: 10.1016/j.ijdevneu.2008.09.157 [P2.33] Simultaneous inactivation of Erk1 and Erk2 leads to perturbations in the control of the cell cycle during neurogenesis J. Pucilowska *, I.S. Samuels, C. Karlo, G.E. Landreth Case Western Reserve University, USA *Corresponding author. Keywords: Erk1/2; Neurogenesis; Cell cycle; Cortical development
The prototypical MAP kinases Erk1and Erk2 regulate cell proliferation and post-mitotic differentiation by transducing complex extracellular signals into changes in cell fate. Additionally, the Erk1/2 pathway is required for long lasting forms of synaptic plasticity facilitating learning and memory. However, their precise role in the developing nervous system remains elusive. It is our goal to understand the role that Erk1/2 plays in development of the CNS.
feedback and modulation of target development. In a previous study in rats, by others, 5-methoxytryptophan treated damns gave birth to pups with cytoarchitectonic derangement in presubicular cortex. To ascertain the effects of 5-HT in cortical neuronal migration experimental animals were fed a low tryptophan diet (LT). With this diet was intended to lower 5-HT levels through reduction in tryptophan availability, necessary for 5-HT synthesis. The dietary intake is men and rodents only source of tryptophan. Wistar pregnant rats and their litters were used. They were divided in three groups: one group was fed LT through gestation and lactation, other was fed with LT diet with added tryptophan into the formulation (LTT) and the last group was fed with the standard 18% protein diet. Every diet was continued to feed pups after weaning. Rats were sacrificed at postnatal days (P) 0, 20 and 30. Brains were processed for tryptophan hydroxylase immunohistochemistry (P0), Golgi (P30) and Nissl (P20) staining and photodocumented. Serotonin content in the brain was measured at P0, P20 and P30 by HPLC of brain extracts. In animals fed with LT cytoarchitectonic derangement was found in neocortex and hippocampus allocortex, visualized at P20 and P30. These results suggest that a 5-HT level set point at ontogeny is essential in events such as cortical neuronal migration.
877
monolayer, remain multipotent and capable of GABA differentiation. Examining differentiating NS, we observed that Dlx expression follows a temporal sequence that recapitulates basal neurogenesis: Dlx2 is expressed in proliferating cells while Dlx5 is upregulated during differentiation, followed by GAD1 and CR. These results provide a molecular validation for the use of NS. In the same assay Wnt5a expression is upregulated during differentiation. These data link the transcription functions of Dlx5 with the diffusible molecule Wnt5a in the control of interneuron differentiation in the OB. doi: 10.1016/j.ijdevneu.2008.09.156 [P2.32] Suppression of interneuron programs and maintenance of selected spinal motor neuron fates by the transcription factor AML1/Runx1 N. Stifani *, A.R.O. Freitas, A. Liakhovitskaia, A. Medvinsky, A. Kania, S. Stifani McGill University, Canada *Corresponding author. Keywords: Runx1; Motor neuron; Identity
doi: 10.1016/j.ijdevneu.2008.09.155 [P2.31] A Dlx5–Wnt5 regulation involved in the control of GABAergic differentiation G.R. Merlo 1,*, S. Paina 1, A. Moiana 2, E. Cattaneo 2, S. DeMarchis 1, G. Corte 3 1
University of Torino, Italy University of Milano, Italy 3 University of Genova, Italy *Corresponding author. 2
Keywords: Interneuron; GABA; Wnt; Olfactory
Fate determination of progenitor cells involves a cooperation of genetic and environmental factors. In the embryonic forebrain the interneuron precursors originate in the GE, migrate to the olfactory bulb (OB) and cortex, and differentiate into various interneuron subtypes. Genetic and local regulations of this process are still poorly understood. Dlx genes are essential for interneuron differentiation. Dlx5 marks migrating progenitors, committed to differentiate into GABA+ and CR+ interneurons, and has been directly linked to the expression of the GABA+ phenotype. In Dlx5 mutant OB lamination is altered and interneuron differentiation is impaired. When we grafted normal LGE progenitors on slices of Dlx5 mutant brains, a reduced number of CR+ and GABA+ neurons was obtained, indicating that the Dlx5-null environment is unfavourable for differentiation. By microarray profiling of Dlx5 null neurospheres, we identified Wnt5a as a putative Dlx5 target. Indeed, Wnt5a expression is reduced in the Dlx5 null OB. Wnt5a is a ‘‘non-canonical’’ Wnt that utilizes beta-cateninindependent pathways; we indeed fail to detect expression of the BATnlacZ Wnt-responsive transgene in the OB. Functionally Wnt5a applied on slice cultures of the OB, promotes interneuron differentiation. To confirm the role of Dlx–Wnt regulation in GABA differentiation, we adopted the model of neural stem (NS) cells, reported by Conti et al. (PloS Biol 3: e283). These cells proliferate as a
Neuronal networks are formed with the cooperation of various cell types in the nervous system. The spinal cord offers a good and simple model for studying (i) the generation of cell diversity, (ii) the formation of specific connections, (iii) axonal targeting, and (iv) establishment of neuronal circuits. Individual spinal motor neuron identities are specified in large part by the intrinsic repertoire of transcription factors expressed by undifferentiated progenitors and maturing neurons. We have shown that the transcription factor AML1/Runx1 (Runx1) is expressed in selected spinal motor neuron subtypes after the onset of differentiation. Combinations of loss- and gain-of-function analyses demonstrated that Runx1 is both necessary and sufficient to suppress interneuron-specific developmental programs and promote maintenance of motor neuron characteristics. These findings show an important role for Runx1 during the consolidation of selected spinal motor neuron identities. Moreover, they suggest a requirement for a persistent suppression of interneuron genes within maturing motor neurons. doi: 10.1016/j.ijdevneu.2008.09.157 [P2.33] Simultaneous inactivation of Erk1 and Erk2 leads to perturbations in the control of the cell cycle during neurogenesis J. Pucilowska *, I.S. Samuels, C. Karlo, G.E. Landreth Case Western Reserve University, USA *Corresponding author. Keywords: Erk1/2; Neurogenesis; Cell cycle; Cortical development
The prototypical MAP kinases Erk1and Erk2 regulate cell proliferation and post-mitotic differentiation by transducing complex extracellular signals into changes in cell fate. Additionally, the Erk1/2 pathway is required for long lasting forms of synaptic plasticity facilitating learning and memory. However, their precise role in the developing nervous system remains elusive. It is our goal to understand the role that Erk1/2 plays in development of the CNS.