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Heparan sulfate endosulfatases are required for normal brain development
832
Symposium and Short Talk Abstracts 2 June 2008 / Int. J. Devl Neuroscience 26 (2008) 829–833
[SY3.1] Self-avoidance mediated by DSCAM in the developing mammalian retina P.G. Fuerst 1, A. Koizumi 2, R.H. Masland 2, R.W. Burgess 1,* 1
The Jackson Laboratory, USA Massachusetts General Hospital, USA *Corresponding author.
2
Keywords: Dendrites; Morphology; Self-recognition; Tiling
During the development of the vertebrate retina, neurons establish both a vertical and lateral organization, which provides the anatomical basis for functional circuitry. Retinal neurons establish their spatial domains by arborizing their processes, which requires the self-avoidance of neurites from an individual cell, and by spacing their cell bodies, which requires positioning the soma and establishing a zone within which other cells of the same type are excluded. The lateral mosaics of distinct cell types form independently and can overlap. The molecular cues that direct these processes in the vertebrate retina are not known. We have shown that some types of retinal amacrine cells from mice with a spontaneous mutation in Dscam, a gene encoding an Igsuperfamily member adhesion molecule, have defects in the arborization of processes and the spacing of cell bodies. In the mutant retina, cells that would normally express Dscam have hyperfasciculated processes, preventing them from creating an orderly arbor. The cell bodies of these neurons are randomly distributed or pulled into clumps rather than being spaced in regular mosaics. Our results indicate that mouse DSCAM mediates isoneuronal self-avoidance for arborization, and heteroneuronal self-avoidance within specific cell types to prevent fasciculation and to preserve mosaic spacing. These functions are highly analogous to those of Drosophila Dscam and Dscam2, and are necessary for establishing orderly retinal circuitry. DSCAM may serve a similar role in other regions of the mammalian central nervous system, and this function may be shared by other members of the Dscam gene family. doi: 10.1016/j.ijdevneu.2008.09.024
whereas the double knockout (DKO) mice are neonatally lethal, suggesting SulfFP1 and SulfFP2 are functionally redundant. Disaccharide profile analysis revealed that the percentages of the trisulfated disaccharide unit in HS are selectively increased in knockout mice, indicating that SulfFPs remodel HS sulfation patterns in vivo. DKO mice had smaller brains but did not show gross defects, which were seen in HS-deficient mice created by brain-specific disruption of an HS-synthesizing enzyme Ext1. However, after careful examination of the neonatal brains, we found that DKO mice had a unique axon guidance defect in a particular nerve tract. Introduction of exogenous SulfFPs by in utero electroporation along the nerve tract region, but not into the axonextending neurons, could rescue the phenotype in the DKO mice, suggesting that SulfFPs alter the extracellular environment along the nerve tract. Our findings indicate that the appropriate sulfation patterns generated by SulfFPs are required for establishing normal neural network. doi: 10.1016/j.ijdevneu.2008.09.025 Symposium session 4: The dopaminergic neuron—from specification to treatment of Parkinson‘s disease Session Chair: Theo Palmer The Chapel, 15.00-17.00 [SY4.0] T. Palmer Stanford University, USA
[Abstract not available at time of print] doi: 10.1016/j.ijdevneu.2008.09.026 [SY4.1] E. Huang University of California, San Francisco, USA
[SY3.2] Heparan sulfate endosulfatases are required for normal brain development M. Masu *, T. Okada, S. Nagamine, K. Keino-Masu University of Tsukuba, Japan *Corresponding author. Keywords: Heparan sulfate; Sulfatase; Axon guidance
Heparan sulfate (HS) regulates cell proliferation, migration, axon guidance, and synaptogenesis. HS is an unbranched polysaccharide chain covalently attached to proteoglycan core proteins and consists of repeating disaccharides of uronic acid and Nacetylglucosamine. The disaccharide units can be sulfated at the 2O position of uronic acid and the 6-O and N positions of Nacetylglucosamine. Previous biochemical studies have demonstrated that the structures with specific sulfation patterns in highly sulfated domains of HS interact with signaling molecules and receptors. Recently, evolutionarily conserved sulfatases, Sulfatase FP1 (SulfFP1) and Sulfatase FP2 (SulfFP2), have been identified as a novel class of sulfatases that desulfate 6-O sulfate in HS extracellularly and thus modulate HS-dependent signaling. In order to investigate the physiological roles of SulfFPs during neural development, we generated knockout mice. Single knockouts of SulfFP1 and SulfFP2 appeared to be normal, healthy, and fertile,
[Abstract not available at time of print] doi: 10.1016/j.ijdevneu.2008.09.027 [ST2] The floor plate gene, foxa2, is required for the generation and maintenance of midbrain dopamine neurons R. Kittappa 1,*, W.W. Chang 1, R.B. Awatramani 2, R.D.G. McKay 1 1
National Institute of Neurological Disorders and Stroke, USA Northwestern University School of Medicine, USA *Corresponding author. 2
The production of midbrain dopamine neurons in the laboratory is a leading example of the potential of stem cell-based therapies in medicine. To optimize methods for the differentiation of dopamine neurons from stem cells, we need a more precise understanding of their embryonic development. Previous studies suggested that dopamine neuron fate is induced by the floor plate and the morphogen, shh. Using a genetic labeling method, we demonstrate that, contrary to previous studies, dopamine neurons are derived from the shh-expressing cells of the floor plate, itself. The forkhead transcription factor, foxa2 (formerly HNF-3beta), is
Symposium and Short Talk Abstracts 2 June 2008 / Int. J. Devl Neuroscience 26 (2008) 829–833
[SY3.1] Self-avoidance mediated by DSCAM in the developing mammalian retina P.G. Fuerst 1, A. Koizumi 2, R.H. Masland 2, R.W. Burgess 1,* 1
The Jackson Laboratory, USA Massachusetts General Hospital, USA *Corresponding author.
2
Keywords: Dendrites; Morphology; Self-recognition; Tiling
During the development of the vertebrate retina, neurons establish both a vertical and lateral organization, which provides the anatomical basis for functional circuitry. Retinal neurons establish their spatial domains by arborizing their processes, which requires the self-avoidance of neurites from an individual cell, and by spacing their cell bodies, which requires positioning the soma and establishing a zone within which other cells of the same type are excluded. The lateral mosaics of distinct cell types form independently and can overlap. The molecular cues that direct these processes in the vertebrate retina are not known. We have shown that some types of retinal amacrine cells from mice with a spontaneous mutation in Dscam, a gene encoding an Igsuperfamily member adhesion molecule, have defects in the arborization of processes and the spacing of cell bodies. In the mutant retina, cells that would normally express Dscam have hyperfasciculated processes, preventing them from creating an orderly arbor. The cell bodies of these neurons are randomly distributed or pulled into clumps rather than being spaced in regular mosaics. Our results indicate that mouse DSCAM mediates isoneuronal self-avoidance for arborization, and heteroneuronal self-avoidance within specific cell types to prevent fasciculation and to preserve mosaic spacing. These functions are highly analogous to those of Drosophila Dscam and Dscam2, and are necessary for establishing orderly retinal circuitry. DSCAM may serve a similar role in other regions of the mammalian central nervous system, and this function may be shared by other members of the Dscam gene family. doi: 10.1016/j.ijdevneu.2008.09.024
whereas the double knockout (DKO) mice are neonatally lethal, suggesting SulfFP1 and SulfFP2 are functionally redundant. Disaccharide profile analysis revealed that the percentages of the trisulfated disaccharide unit in HS are selectively increased in knockout mice, indicating that SulfFPs remodel HS sulfation patterns in vivo. DKO mice had smaller brains but did not show gross defects, which were seen in HS-deficient mice created by brain-specific disruption of an HS-synthesizing enzyme Ext1. However, after careful examination of the neonatal brains, we found that DKO mice had a unique axon guidance defect in a particular nerve tract. Introduction of exogenous SulfFPs by in utero electroporation along the nerve tract region, but not into the axonextending neurons, could rescue the phenotype in the DKO mice, suggesting that SulfFPs alter the extracellular environment along the nerve tract. Our findings indicate that the appropriate sulfation patterns generated by SulfFPs are required for establishing normal neural network. doi: 10.1016/j.ijdevneu.2008.09.025 Symposium session 4: The dopaminergic neuron—from specification to treatment of Parkinson‘s disease Session Chair: Theo Palmer The Chapel, 15.00-17.00 [SY4.0] T. Palmer Stanford University, USA
[Abstract not available at time of print] doi: 10.1016/j.ijdevneu.2008.09.026 [SY4.1] E. Huang University of California, San Francisco, USA
[SY3.2] Heparan sulfate endosulfatases are required for normal brain development M. Masu *, T. Okada, S. Nagamine, K. Keino-Masu University of Tsukuba, Japan *Corresponding author. Keywords: Heparan sulfate; Sulfatase; Axon guidance
Heparan sulfate (HS) regulates cell proliferation, migration, axon guidance, and synaptogenesis. HS is an unbranched polysaccharide chain covalently attached to proteoglycan core proteins and consists of repeating disaccharides of uronic acid and Nacetylglucosamine. The disaccharide units can be sulfated at the 2O position of uronic acid and the 6-O and N positions of Nacetylglucosamine. Previous biochemical studies have demonstrated that the structures with specific sulfation patterns in highly sulfated domains of HS interact with signaling molecules and receptors. Recently, evolutionarily conserved sulfatases, Sulfatase FP1 (SulfFP1) and Sulfatase FP2 (SulfFP2), have been identified as a novel class of sulfatases that desulfate 6-O sulfate in HS extracellularly and thus modulate HS-dependent signaling. In order to investigate the physiological roles of SulfFPs during neural development, we generated knockout mice. Single knockouts of SulfFP1 and SulfFP2 appeared to be normal, healthy, and fertile,
[Abstract not available at time of print] doi: 10.1016/j.ijdevneu.2008.09.027 [ST2] The floor plate gene, foxa2, is required for the generation and maintenance of midbrain dopamine neurons R. Kittappa 1,*, W.W. Chang 1, R.B. Awatramani 2, R.D.G. McKay 1 1
National Institute of Neurological Disorders and Stroke, USA Northwestern University School of Medicine, USA *Corresponding author. 2
The production of midbrain dopamine neurons in the laboratory is a leading example of the potential of stem cell-based therapies in medicine. To optimize methods for the differentiation of dopamine neurons from stem cells, we need a more precise understanding of their embryonic development. Previous studies suggested that dopamine neuron fate is induced by the floor plate and the morphogen, shh. Using a genetic labeling method, we demonstrate that, contrary to previous studies, dopamine neurons are derived from the shh-expressing cells of the floor plate, itself. The forkhead transcription factor, foxa2 (formerly HNF-3beta), is