- Email: [email protected]
36 The lamines gene family in neural development and repair
33
34
DELTA-NOTCH SIGNALLING IN CENTRAL AND PLACODAL NEURUGENESSS
THE ROLE OF SIGNALLING THROUGH EPH RECEPTORS IN PATTERNING THE ZEBRAFISH NEURAL PLATE.
D. Henrique, J. Adam. A. Myat, C. Haddon, L. Smithers, S. Schneider-Maunoury, T. Ccche. D. Ish-Horowitz, Julian Lewis KFZF Developmental Biology Unit, Dept. of Zoology, University of Oxford, Oxford OX 1 3PS. UK In Drosophila, commitment to a neural face is cantrolled by the Delta-Notch-E(spt) cell-cell signallimg pathway. which mediates lateral inhibilion. In both CNS and PNS, this Serves to single out individual cells for a neural fate and to prevent their neighbours from becoming committed in the same way. Does the same mechanism control neurogenesissimilarly in vertebrates? Multiple vertebrate homologues of the genescoding for the receptor Notch, its ligands Delta and Serrate, and its downstream effcctors of the E(spl) class have been identiied. AlI of these are expressed during neurogenesisboth in the CNS and in the PNS, in pattern suggesting tiat they do Indeedhave a universal role in controlling neurogenesls. both in the CNS and in the PNS, and during late as well as early stages.This view is supported by functional tests in which we have ectopicatly erpmd Delta-l or the antimorphic construct Delta-lSTU, using either mRNA Injection into early blastomeres in Xenopl~sand zebraf=h. or infection with a retrovual vector in the chick. There are, however. some features that conuas~with Drosophila; but in these respects there are also vtiations among verlebrates themselves. For example, where% in the CNS of Xenopus and chick the neural cells transiently expressing Delta-l are postmitotic nascent neurons, in neurogenesis in the otic placode they are proliferative neumbla.sfsas in Drosophila.
Nieel Holder. Caroline Brennan, Julie Cooke, Lindsay Dmbin and Qiling
XII.
Developmental Biology ResearchCentre. Randall Institute, King’s College, 26-29 l?nuy Lane, London WC28 %L We have ,solareJ and charactetisedcDNAr encoding eigbr members of the zbr-.%h Eph related tyrosine kinase family and five members of the B61 related family of Eph receptor ligandsExpression of the receptors during gastrulation and neurulation is dynamic and localised indicating roles in rbe patterning process. This contention is supported by the results of experiments io which the function of one of these receptors. r&l. has beeo analysed using a dominant negative strategy. In these experiments RNA enabling a wnfdrcd receptor prorein Iackrng the inxreilufar kmase domain causes abnormal developmcnl of the bindbraiD rhombomeres and diencephalon. following injection into the fertilised egg, Rtk 1 normally expresses xn these two regions of the developing brain. We are continuing this strategy in the study of a number of the other receptors. Ligmd function has been analysed by ectop~ expression following RNA and DNA injections into the ferlilised egg. It is clear from these experiments chatthe ligands are involved in imp%xrzr developmental processes m the formation of Ihe eye and the retina-~titat cbrmection and in the development of Ihr segmentalstructures. the rhombomeres and lhe somites.
35
36
MOLECULAR MECHANISMS OF AXON GUIDANCE BY DIFFUSIBLE ATTRACTANTS AND REPELLENTS
THE LAMININ GENE FAMLLY LN NEURAL DEVELOPMENT AND REPAIR
Marc Tessier-Lavigne Howard Hughes Medical Institute and Department of Anatomy, University of California San Francisco, CA 94143.0452, USA. An early evem tn the establishment of neuronal connections is the growth of axons to thexr rargets We have been interested in understanding the molecular mechanisms thal are responsible for Ihe accurate guidance of axons, with a particular focus on the identification of diffusrbte factors that attract or repel developing axons. I will discuss our identification of a family of chemoattractants for developing vertebrate axons, the netrins, which have been remarkably conserved across evolution. In viva analysis has demonstrated important roles for the netrins in gutding several different classes of anons m rhe mammaban bram and spinal cord, and recent studies have also provided InsIght into the receptors that mediate their attractive and repulsive effects on axons. To determine whether guidance by diffusible factors is a widespread mechanism of axon guidance, we have also been investigating other cases of chemoatrraction and chemorepulsion. I will discuss our progress in the tdentification and characterization of other chemotropic guidance cues in ihe developmg nervous system.
P&vi Liesi, Mieko Matsotawq Jerry Wrighr and Time Kauppiia* National Institute of Alcohol Abuse and Alcoholism. National Institutes of Health, Rockville. MD 20852,‘DeparIment of Physiology, University of Helsinki. Lamininr form a family of extracellular matrix proteins that have both neurotrophic and neumtoxic effects on developing CNS.The presence of laminins in the CNS was ventied more than ten yeaars years before thc role of laminins in ago, but it took several neuronal migraiion and axon guidance was recogni~.Cloning of various isoforms of lhz basement membrane pmtopypc of larrunin further elucidated the complexity of this gene family. Even though the role of laminins in brain development is presently clear, little is known about the molecular mechanisms involved.Recent data indicate that the B2 chain of laminin is directly involved in neuronal migration A neurite outgrowth domain of the 82 chain of laminin has both neurotmphic and neurotoric functions and IS found in excess usbrains af Alzheimcr‘s disease patients and m cer&ella of the mi@on deficient weaver mutanl mice. BZ cl& of laminin is induced in injuries of adult rat spinal cord and promotes regenerabon of peripheral nerves.A neurite outgrowth domain of the B2 chain of laminin affects electrical excitability of primary neurons via a G-protein coupled pathway.This domain of t& B2 chain may have neuromodulatoty functions in the adult brain.This domain may also be an axonal guidance and differentiation factor for hippocampat neum~ Nanomolar emcenlrations of the B2 chain derived Peptides may promoie axon growth and neuronal migmtion whereas high concentrahom of the same peptides a& neurotoxic.The biological effects of 1anuNn in CNS may be mediated via direct contact of neurons to a laminin substrate or via biologically active peptides released by neuronal proteolysis or secreted by neumnal cells.
34
DELTA-NOTCH SIGNALLING IN CENTRAL AND PLACODAL NEURUGENESSS
THE ROLE OF SIGNALLING THROUGH EPH RECEPTORS IN PATTERNING THE ZEBRAFISH NEURAL PLATE.
D. Henrique, J. Adam. A. Myat, C. Haddon, L. Smithers, S. Schneider-Maunoury, T. Ccche. D. Ish-Horowitz, Julian Lewis KFZF Developmental Biology Unit, Dept. of Zoology, University of Oxford, Oxford OX 1 3PS. UK In Drosophila, commitment to a neural face is cantrolled by the Delta-Notch-E(spt) cell-cell signallimg pathway. which mediates lateral inhibilion. In both CNS and PNS, this Serves to single out individual cells for a neural fate and to prevent their neighbours from becoming committed in the same way. Does the same mechanism control neurogenesissimilarly in vertebrates? Multiple vertebrate homologues of the genescoding for the receptor Notch, its ligands Delta and Serrate, and its downstream effcctors of the E(spl) class have been identiied. AlI of these are expressed during neurogenesisboth in the CNS and in the PNS, in pattern suggesting tiat they do Indeedhave a universal role in controlling neurogenesls. both in the CNS and in the PNS, and during late as well as early stages.This view is supported by functional tests in which we have ectopicatly erpmd Delta-l or the antimorphic construct Delta-lSTU, using either mRNA Injection into early blastomeres in Xenopl~sand zebraf=h. or infection with a retrovual vector in the chick. There are, however. some features that conuas~with Drosophila; but in these respects there are also vtiations among verlebrates themselves. For example, where% in the CNS of Xenopus and chick the neural cells transiently expressing Delta-l are postmitotic nascent neurons, in neurogenesis in the otic placode they are proliferative neumbla.sfsas in Drosophila.
Nieel Holder. Caroline Brennan, Julie Cooke, Lindsay Dmbin and Qiling
XII.
Developmental Biology ResearchCentre. Randall Institute, King’s College, 26-29 l?nuy Lane, London WC28 %L We have ,solareJ and charactetisedcDNAr encoding eigbr members of the zbr-.%h Eph related tyrosine kinase family and five members of the B61 related family of Eph receptor ligandsExpression of the receptors during gastrulation and neurulation is dynamic and localised indicating roles in rbe patterning process. This contention is supported by the results of experiments io which the function of one of these receptors. r&l. has beeo analysed using a dominant negative strategy. In these experiments RNA enabling a wnfdrcd receptor prorein Iackrng the inxreilufar kmase domain causes abnormal developmcnl of the bindbraiD rhombomeres and diencephalon. following injection into the fertilised egg, Rtk 1 normally expresses xn these two regions of the developing brain. We are continuing this strategy in the study of a number of the other receptors. Ligmd function has been analysed by ectop~ expression following RNA and DNA injections into the ferlilised egg. It is clear from these experiments chatthe ligands are involved in imp%xrzr developmental processes m the formation of Ihe eye and the retina-~titat cbrmection and in the development of Ihr segmentalstructures. the rhombomeres and lhe somites.
35
36
MOLECULAR MECHANISMS OF AXON GUIDANCE BY DIFFUSIBLE ATTRACTANTS AND REPELLENTS
THE LAMININ GENE FAMLLY LN NEURAL DEVELOPMENT AND REPAIR
Marc Tessier-Lavigne Howard Hughes Medical Institute and Department of Anatomy, University of California San Francisco, CA 94143.0452, USA. An early evem tn the establishment of neuronal connections is the growth of axons to thexr rargets We have been interested in understanding the molecular mechanisms thal are responsible for Ihe accurate guidance of axons, with a particular focus on the identification of diffusrbte factors that attract or repel developing axons. I will discuss our identification of a family of chemoattractants for developing vertebrate axons, the netrins, which have been remarkably conserved across evolution. In viva analysis has demonstrated important roles for the netrins in gutding several different classes of anons m rhe mammaban bram and spinal cord, and recent studies have also provided InsIght into the receptors that mediate their attractive and repulsive effects on axons. To determine whether guidance by diffusible factors is a widespread mechanism of axon guidance, we have also been investigating other cases of chemoatrraction and chemorepulsion. I will discuss our progress in the tdentification and characterization of other chemotropic guidance cues in ihe developmg nervous system.
P&vi Liesi, Mieko Matsotawq Jerry Wrighr and Time Kauppiia* National Institute of Alcohol Abuse and Alcoholism. National Institutes of Health, Rockville. MD 20852,‘DeparIment of Physiology, University of Helsinki. Lamininr form a family of extracellular matrix proteins that have both neurotrophic and neumtoxic effects on developing CNS.The presence of laminins in the CNS was ventied more than ten yeaars years before thc role of laminins in ago, but it took several neuronal migraiion and axon guidance was recogni~.Cloning of various isoforms of lhz basement membrane pmtopypc of larrunin further elucidated the complexity of this gene family. Even though the role of laminins in brain development is presently clear, little is known about the molecular mechanisms involved.Recent data indicate that the B2 chain of laminin is directly involved in neuronal migration A neurite outgrowth domain of the 82 chain of laminin has both neurotmphic and neurotoric functions and IS found in excess usbrains af Alzheimcr‘s disease patients and m cer&ella of the mi@on deficient weaver mutanl mice. BZ cl& of laminin is induced in injuries of adult rat spinal cord and promotes regenerabon of peripheral nerves.A neurite outgrowth domain of the B2 chain of laminin affects electrical excitability of primary neurons via a G-protein coupled pathway.This domain of t& B2 chain may have neuromodulatoty functions in the adult brain.This domain may also be an axonal guidance and differentiation factor for hippocampat neum~ Nanomolar emcenlrations of the B2 chain derived Peptides may promoie axon growth and neuronal migmtion whereas high concentrahom of the same peptides a& neurotoxic.The biological effects of 1anuNn in CNS may be mediated via direct contact of neurons to a laminin substrate or via biologically active peptides released by neuronal proteolysis or secreted by neumnal cells.