Overview
The Burgess lab seeks to understand the molecular mechanisms of synapse formation and maintenance at two sites in the nervous system, the peripheral neuromuscular junction and the retina. We are presently examining mutations in agrin, glycyl- and tyrosyl tRNA synthetase, Dscam, and Dscam-Like1. In all of these studies, we are addressing basic molecular mechanisms, but these basic mechanisms also have relevance to a variety of human diseases. Our continued research on these genes, and our continuing effort to identify new genes involved in these processes, will increase our understanding of the molecules required to form and maintain synaptic connectivity in the nervous system.
Scientific report
Genetics of Synapse Formation and Maintenance
The research focus of the Burgess lab is to determine the molecular mechanisms required for the formation and maintenance of synaptic connections in the nervous system. We are using two experimental systems in mice to address these questions. First, we are studying mutations that perturb the neuromuscular junction (NMJ), the connection between motor neurons in the spinal cord and muscle fibers in the periphery. Our second experimental model is the retina, a highly accessible tissue that allows the study of neuron-neuron synapse formation. Our research is directed primarily at understanding the basic biological mechanisms of synapse formation and maintenance. However, there is human disease relevance to this work because defects in these processes cause congenital mysasthenic syndromes and peripheral neuropathies such as Charcot-Marie-Tooth Diseases in the periphery, and neurodevelopmental disorders in the central nervous system.
Neuromuscular Junction Studies
Agrin: Agrin is a signaling protein made in motor neurons that is essential for postsynaptic differentiation at the NMJ. Agrin has been a research focus in the Burgess lab for several years, and previous work has relied primarily on targeted mutations and tagged transgenic alleles. We are now studying a newly identified point mutation in agrin that causes a partial loss of function. This mutation is in the “SEA” domain of agrin, a portion of the protein that was previously unappreciated for its functional significance. In addition to studies at the NMJ, we are also using a conditional knockout and transgenic alleles of agrin to determine if it contributes to the integrity of the blood-brain-barrier, and to examine the relationship between agrin expression in the blood vessels of the brain and the accumulation of beta-amyloid plaque pathology in a transgenic mouse model of Alzheimer’s disease.
Charcot-Marie-Tooth peripheral neuropathies: We are also working to understand how dominant mutations in glycyl tRNA synthetase (Gars) cause Charcot-Marie-Tooth type 2D in humans and a very similar disease in mice. The only known function of GARS is the charging of glycine onto its cognate tRNAgly during translation. Our previous studies on Gars mutant mice indicate that the peripheral neuropathy is not related to this known function of the protein, and suggest that the mutant forms of the protein are assuming novel, pathogenic functions. We are now designing conditional knock-in alleles of Gars to test possible pathogenic mechanisms proposed by our work and by the studies of our collaborators.
In addition to GARS, dominant mutations in tyrosyl tRNA synthetase (YARS) cause Dominant Intermediate Charcot-Marie-Tooth type C (DI-CMTC) in humans. Our early studies suggest that YARS and GARS mutations may share some genetic mechanisms in addition to the related disease phenotypes. Therefore, we are also generating knock-in alleles in the mouse Yars gene to create models of DI-CMTC, and for use in comparative studies on the pathophysiology and mechanisms of Charcot-Marie-Tooth diseases.
In addition to these established projects, the lab is also constantly vigilant for new mutations that present with neuromuscular dysfunction. We currently have several additional novel mutations that affect the NMJ, and these mutations are at various stages of characterization.
Dscams in the retina
To expand our research on synapse formation to the central nervous system, we recently identified a mutation that affects the development of the retina. The mutation is in the gene encoding Down Syndrome Cell Adhesion Molecule (Dscam). In the absence of DSCAM, neurons in the retina fail to arborize their processes, and neurons of the same cell type (dopaminergic amacrine cells for example) fasciculate and clump, destroying their normally even lateral mosaic spacing. We are now examining Dscam’s role in other neuronal populations in the retina, and in other parts of the central nervous system. In addition, we have generated mutations in the closely related gene Dscam-Like1 (Dscaml1). This gene has a phenotype similar to, but distinct from, the Dscam mutation. The role of Dscams in self-recognition and self-avoidance amongst neuronal populations is a fundamentally important aspect of neurodevelopment. Understanding this process is important for basic developmental neurobiology, and has implications for human neurodevelopmental defects.
Lab staff
Principal Investigator: Robert W. Burgess, Ph.D.
Postdoctoral Fellows: Laurent P. Bogdanik, Ph.D.; Morganne Stum, Ph.D.
Research Assistant III: Steven M. Rauch, M.D., M.S.,
Research Assistant II: Kathy Miers
Laboratory Technician IV: Christine Rosales
Research Administrative Assistant: Ashley Stanton
Publication listings
Fuerst PG, Burgess RW. 2009. Adhesion Molecules in establishing retinal circuitry. Curr Opin Neurobiol. 2009 Aug;19(4) 389-394.
Achilli, F., Bros-Facer, V., Williams, H. P., Banks, G. T., AlQatari, M., Chia, R., Tucci, V., Groves, M., Nickols, C. D., Seburn, K. L., Kendall, R., Cader, M. Z., Talbot, K., van minnen, J., Burgess, R. W., Brandner, S., Martin, J. E., Koltzenburg, M., Greensmith, L., Nolan, P. M., and Fisher, E. M. C. 2009. A Novel Mouse Model With a Point Mutation in Glycyl-tRNA Synthetase (Gars) has Sensory and Motor Phenotypes and Profoundly Reduced Enzyme Activity in Homozygotes. Dis Model Mech. Jul-Aug;2(7-8):359-73.
Wolfram, T, Spatz, JP, and Burgess, RW. 2008. Cell Adhesion to Agrin Presented as a Nanopatterned Substrate is Characteristic of an Interaction with the Extracellular Matrix and Not Transmembrane Adhesion Molecules. BMC Cell Biology, Epub Dec. 4, 9(1), 64. 19055842
Wooley, CM, Xing, S, Burgess, RW, Cox, GA, and Seburn, KL. 2009. Age, experience and genetic background influence treadmill walking in mice. Physiol. and Behav. 96(2): 350-61. Epub Nov. 6, 2008. 19027767
Patton BL, Wang B, Tarumi YS, Seburn KL, Burgess RW 2008. A single point mutation in the LN domain of LAMA2 causes muscular dystrophy and peripheral amyelination. J Cell Sci. May 22:121(10): 1593-1604.
Fuerst PG, Koizuma A, Masland R, Burgess RW. 2008. Neurite arborization and mosaic spacing in the mouse retina requires DSCAM. Nature Jan 24:451(7177) 2470-2474.
Misgeld T, Kerschensteiner M, Bareyre FM, Burgess RW, Lichtman JW. 2007. Imaging axonal transport of mitochondria in vivo. Nat Methods Jul;4(7):559-61.
Harvey SJ, Jarad G, Cunningham J, Rops AL, van der Vlag J, Berden JH, Moeller MJ, Holzman LB, Burgess RW, Miner JH. 2007. Disruption of Glomerular Basement Membrane Charge through Podocyte-Specific Mutation of Agrin Does Not Alter Glomerular Permselectivity. Am J Pathol Jul;171(1):139-52.
Fuerst PG, Rauch SM, and Burgess RW. 2007. Defects in eye development in transgenic mice overexpressing the heparan sulfate proteoglycan agrin. Dev Biol 303(12):165-180.
Seburn KL, Nangle LA, Cox GA, Schimmel P, and Burgess RW. 2006. An active dominant mutation of Glycyl-tRNA synthetase causes neuropathy in a Charcot Marie Tooth 2D mouse model. Neuron 51(6):715-26.
Burgess RW, Jucius TJ, Ackerman SL. 2006. Motor axon guidance of the mammalian trochlear and phrenic nerves: dependence on the netrin receptor Unc5c and modifier loci. J Neurosci 26:5756-5766.
Stacy RC, Demas J, Burgess RW, Sanes JR, Wong RO. 2005. Disruption and recovery of patterned retinal activity in the absence of acetylcholine. J Neurosci 25(41:9347-9357.
Burgess RW, Peterson KA, Johnson MJ, Roix JJ, Welsh IC, O'Brien TP. 2004. Evidence for a conserved function in synapse formation reveals Phr1 as a candidate gene for respiratory failure in newborn mice. Mol Cell Biol 24(3):1096-1105.
Buffelli M, Burgess RW, Feng G, Lobe C, Lichtman JW, Sanes JR. 2003. Genetic evidence that relative synaptic activity biases the outcome of synaptic competition. Nature 424:430-434.
Bhattacharya S, Stewart BA, Niemeyer BA, Burgess RW, McCabe BD, Lin P, Boulianne
G, O'Kane CJ, Schwarz TL. 2002. Members of the Synaptobrevin/Vesicle Associated
Membrane Protein (VAMP) Family in Drosophila Are Functionally Interchangeable In
Vivo for Neurotransmitter Release and Cell Viability. Proc Nat Acad Sci, 99:13867
13872.
Burgess RW, Dickman DK, Nunez L, Glass DJ, Sanes JR. 2002. Mapping Sites
Responsible for Interactions of Agrin With Neurons. J. Neurochem 83:271-284.
Misgeld T, Burgess RW, Lewis RM, Cunningham JM, Lichtman JW, Sanes JR.
2002. Roles of Neurotransmitter in Synapse Formation: Development of Neuromuscular Junctions Lacking Choline Acetyltransferase. Neuron 36:271-84.
Books, Book Chapters and Reviews:
Burgess RW, Cox GA, Seburn KL. 200_. Neuromuscular Disease Models and Analysis, in Mouse Models forr Drug Discovery, Methods in Molecular Biology Series, Proetzel G, and Wiles M, editors. The Humana Press, Inc., Totowa, New Jersey.(in press)
Bogdanik L, Burgess RW. 2009. Extracellular Matrix Molecules in Neuromuscular junctions and Central Nervous System Synapses, Chapter 20, in The Sticky Synapse, Hortsh M., and Umemori H, editors. Springer Verlag, New York.
Burgess, RW. 2006. The Formation of the Vertebrate Neuromuscular Junction: Roles for the Extracellular Matrix in Synaptogenesis, Chapter 1, in Molecular Mechanisms of Synaptogenesis, El-Husseini, A. and Dityatev, A., editors. Springer Verlag, New York.
Patton B, Burgess RW. 2005. Synaptogenesis in Developmental Neurobiology, 4th ed., edited by Rao MS, Jacobson M. Published by Kluwer Academic/Plenum Publishers, NY.
Sanes JR, Apel ED, Burgess RW, Emereson RB, Feng G, Gautam M, Glass D, Grady RM, Krejci E, Lichtman JW, Lu JT, Massoulie J, Miner JH, Moscoso LM, Nguyen Q, Nichol M, Noakes PG, Patton BL, Son YJ, Yancopoulos GD, Zhou H. 1998 Development of the neuromuscular junction: genetic anaylsis in mice. J Physiol Paris 92:167-172.
