Specialized connections between nerve cells, called synapses, are the basic units of communication in the brain. We are interested in how nerve cells in the brain make synaptic connections and modify connections with experience. We study these questions of synapse development and synapse plasticity mainly from a cellular and molecular viewpoint.
What are the molecular triggers that initiate central neuron synapse formation? How do neurotransmitter-filled vesicles and associated release and recycling machinery in axons and neurotransmitter receptors and associated signaling molecules in dendrites become precisely aligned at appropriate nerve cell contacts? How do excitatory glutamate and inhibitory GABA receptors traffic to appropriate synapses, and how are such processes regulated by activity? We use neuron culture, molecular biology, live cell fluorescence imaging, mouse molecular genetics and electrophysiology to answer these questions.
This fundamental research bears directly on psychiatric disorders. Genetic variants in multiple synaptic organizing complexes are linked to autism spectrum disorders and schizophrenia. It is our belief that the cellular molecular level studies and animal models we are developing will contribute to rational and effective therapies for these disorders.
Bird on a Wire:
An unbiased expression screen for proteins able to induce presynaptic differentiation in contacting axons identified the leucine-rich repeat transmembrane protein LRRTM1. The image shows LRRTM1-CFP (blue) expressed on a non-neuronal cell inducing clustering of synapsin (red) in contacting axons. These induced presynaptic specializations are similar to specializations marked by synapsin clusters at sites of axon contact with dendrites (green, MAP2).
We developed a unique unbiased expression screen for proteins that induce presynaptic differentiation in contacting axons. Through this screen, we re-isolated postsynaptic neuroligins and identified additional synaptogenic proteins including LRRTMs, the neurotrophin receptor TrkC, and the Slitrk family. Remarkably, all of these postsynaptically localized synaptogenic proteins act via binding two families of presynaptically localized partners, neurexins and type IIA protein tyrosine phosphatases (PTPs). Specific isoforms of neurexins and PTPs generated from different genes and by alternative splicing associate with different postsynaptic partners to regulate synapse development. We are working towards understanding the full significance of the binding code among these synaptic organizing proteins and studying novel candidates.
Many synaptic organizing proteins including neurexins, PTPs, neuroligins, and LRRTMs are linked to neurodevelopmental disorders, most commonly to autism. Collaboratively, we identified novel function-altering variants in neurexin genes in autism and schizophrenia. Using mouse molecular genetics, a major ongoing emphasis is to understand the role of synapse organizing proteins in controlling synaptic structure, composition, and function in specific pathways in vivo.Â Our hope is to develop targeted reagents that may correct imbalances due to loss of specific genes.
Less is known about the molecular composition of inhibitory GABAergic synapses in comparison with excitatory glutamatergic synapses. In addition to studying organizing proteins selective for inhibitory synapses including neuroligin-2 and Slitrk3, we are using a combined genetic and proteomics approach to identify novel GABA receptor interacting proteins and other components of inhibitory synapses. We are also using live cell imaging to study long term dynamics of inhibitory synapses and specification mechanisms for inhibitory versus excitatory synapses.
Over the years, we contributed to identifying several molecular components of glutamatergic postsynaptic sites. Recent studies focus on mechanisms of synaptic targeting of NMDA type glutamate receptors and of a key enzyme calcium/calmodulin-activated kinase CaMKII as well as excitatory-specific synaptic organizing complexes. These studies contribute towards understanding mechanisms of synaptic plasticity associated with and homeostatic regulation and learning and memory.
Ina Ammendrup-Johnsen, Postdoctoral Fellow
Claire Bomkamp, Graduate Student
Steven Connor, Postdoctoral Fellow
Nazarine Fernandes, Research Technician
Yuan Ge, Postdoctoral Fellow
Lin Luo, Graduate Student
Shinichiro Oku, Postdoctoral Fellow
Tabrez Siddiqui, Postdoctoral Fellow
Parisa Karimi Tari, Graduate Student
Ryan Yan, Undergraduate Research Assistant
Peng Zhang, Postdoctoral Fellow
Xiling Zhou, Lab Manager
Pettem KL*, Yokomaku D*, Luo L*, Linhoff MW*, Prasad T*, Connor SA*, Siddiqui TJ, Kawabe H, Chen F,
Zhang L, Rudenko G, Wang YT, Brose N, and Craig AM (*co-first authors). 2013. The specific α-neurexin
interactor calsyntenin-3 promotes excitatory and inhibitory synapse development. Neuron 80:113-128.
Siddiqui TJ, Karimi Tari P, Connor S, Zhang P, Dobie FA, She K, Kawabe H, Wang YT, Brose N#, Craig
AM# (#co-corresponding authors). 2013. An LRRTM4-HSPG complex mediates excitatory synapse
development on dentate gyrus granule cells. Neuron 79:680-695.
[highlighted by Song YS and Kim E. 2013. Presynaptic proteoglycans: Sweet organizers of synapse development. Neuron 79:609-611.]
Takahashi H, Craig AM. 2013. Protein tyrosine phosphatases PTP , PTP and LAR: presynaptic hubs for
synapse organization. Trends Neurosci. 36:522-534.
Woo J*, Kwon SK*, Nam J*, Choi S,* Takahashi H*, Krueger D, Park J, Lee Y, Bae JY, Lee D, Ko J, Kim
H, Kim MH, Bae YC, Chang S, Craig AM#, Kim E# (*co-first authors, #co-corresponding authors). 2013.
IgSF9b, an inhibitory synaptic adhesion molecule coupled to neuroligin 2 via S-SCAM, forms a distinct
subsynaptic domain promoting synaptic development. J. Cell Biol. 201:929-944.
Pettem KL*, Yokomaku D*, Takahashi H, Ge Y, Craig AM. (*co-first authors). 2013. Interaction between
autism-linked MDGAs and neuroligins suppresses inhibitory synapse development. J. Cell Biol. 200:321-
[highlighted by J. Cell Biol. “In Focus” jcb.rupress.org/content/200/3/237 & journal cover ]
Xu W, Tse Y C, Dobie F, Baudry M, Craig AM, Wong TP, Wang YT. 2013. Simultaneous monitoring of
presynaptic transmitter release and postsynaptic receptor trafficking reveals an enhancement of
presynaptic activity in mGluR-LTD. J. Neurosci., 33:5867-77.
Bleckert A, Parker ED, Kang Y, Pancaroglu R, Soto F, Lewis R, Craig AM, and Wong ROL. 2013. Spatial
relationships between GABAergic and glutamatergic synapses on the dendrites of distinct types of
mouse retinal ganglion cells across development. PLOS One 8:e69612.
She K, Rose JK, Craig AM. 2012. Differential stimulus-dependent synaptic recruitment of CaMKIIalpha by intracellular determinants of GluN2B. Mol. Cell. Neurosci., 51(3-4):68-78.
She K, Ferreira J, Carvalho AL, Craig AM. 2012. Glutamate binding to GluN2B controls surface trafficking of N-Methyl-D-aspartate (NMDA) receptors. J. Biol. Chem. 287:27432-45.
[highlighted as J. Biol. Chem. Paper of the Week http://www.jbc.org/content/287/33/27446.full with cover photo http://www.jbc.org/content/287/33.cover-expansion]
Takahashi H, Katayama K, Sohya K, Miyamoto H, Prasad T, Matsumoto Y, Ota M, Yasuda H, Tsumoto T, Aruga J# Craig AM# (# co-corresponding authors). 2012. Selective control of inhibitory synapse development by Slitrk3-PTPd trans-synaptic interaction. Nat. Neurosci. 15:389-398.
Kaufman A, Milnerwood A, Sepers M, Coquinco A, She K, Wang L, Lee H, Craig AM, Cynader M, Raymond L. 2012. Opposing roles of synaptic and extrasynaptic NMDA receptor signaling in co-cultured striatal and cortical neurons. J Neurosci 32:3992-400.
Takahashi H, Arstikaitis P, Prasad T, Bartlett T, Wang YT, Murphy TH, Craig, AM. 2011. Postsynaptic TrkC and presynaptic PTPs function as a bidirectional excitatory synaptic organizing complex. Neuron 69:287-303.
[highlighted by Faculty of 1000 multiple citations http://f1000.com/8186978]
Gauthier J*, Siddiqui TJ*, Huashan P, Yokomaku D, Hamdan FF, Champagne N, Spiegelman D, Noreau A, Lafreniere RG, Fathalli F, Joober R, Krebs MO, DeLisi LE, Mottron L, Fombonne E, Michaud JL, Drapeau P, Carbonetto S, Craig AM#, Rouleau GA# (*co-first authors; # co-corresponding authors). 2011. Truncating mutations in NRXN2 and NRXN1 in autism spectrum disorders and schizophrenia. Human Genet.130:563-73.
Dobie F, Craig AM. 2011. Inhibitory synapse dynamics: Coordinated presynaptic and postsynaptic mobility and the major contribution of recycled vesicles to new synapse formation. J. Neurosci. 31:10481-93.
[highlighted by Faculty of 1000 http://f1000.com/12176956]
Ferreira J, Rooyakkers A, She K, Ribeiro L, Carvalho AL#, Craig AM# (# co-corresponding authors). 2011. Activity and protein kinase C regulate synaptic accumulation of NMDA receptors independently of GluN1 splice variant. J. Biol. Chem. 286:28331-28342.
She K, Craig AM. 2011. NMDA receptors mediate synaptic competition in culture. PLoS One 6:e24423.
Siddiqui TJ, Craig AM. 2011. Synaptic organizing complexes. Curr. Opin. Neurobiol. 21:132-143.
Soto F, Bleckert A, Lewis R, Kang Y, Kerschensteiner D, Craig AM, Wong ROL. 2011. Coordinated increase in inhibitory and excitatory synapses onto retinal ganglion cells during development. Neural Dev. 6:31.
Siddiqui TJ, Pancaroglu R, Kang Y, Rooyakkers A, Craig AM. 2010. LRRTMs and neuroligins bind neurexins with a differential code to cooperate in glutamate synapse development. J. Neurosci.30:7295-7506
[highlighted by Simons Foundation for Autism Research https://sfari.org/news-and-opinion/news/2010/neurexin-found-to-have-diverse-partners-at-synapse]
Linhoff, MW, Lauren, J, Cassidy RM, Dobie FA, Takahashi H, Nygaard HB, Airaksinen MS, Strittmatter SM, Craig, AM. 2009. An unbiased expression screen for synaptogenic proteins identifies the LRRTM protein family as synaptic organizers. Neuron 61:734-749.
[highlighted by Brose, N. (2009) Synaptogenic proteins and synaptic organizers: "Many hands make light work". Neuron 61:650-652. and by Faculty of 1000 http://f1000.com/1158322]
Rose, J., Jin, S.X., Craig AM. 2009. Heterosynaptic molecular dynamics: Locally-induced propagating synaptic accumulation of CaM kinase II. Neuron 61:351-358.
[highlighted by Klassen, MP and Shen, K (2009) The curious case of a wandering kinase: CaMKII spreads the wealth. Neuron 61:331-332. and by Faculty of 1000 http://f1000.com/1158816].
Kang Y, Zhang X, Dobie F, Wu H, Craig AM. 2008. Induction of GABAergic postsynaptic differentiation by alpha-neurexins. J. Biol. Chem. 283:2323-2334.
Liu Y, Wong TP, Aarts M, Rooyakkers A, Liu L, Lai TW, Wu DC, Lu J, Tymianski M, Craig AM, Wang YT. 2007. NMDA receptor subunits have differential roles in mediating excitotoxic neuronal death both in vitro and in vivo. J Neurosci. 27:2846-2857.
Craig AM, Kang Y. 2007: Neurexin-neuroligin signaling in synapse development. Curr .Opin. Neurobiol. 17:43-52.
Graf ER, Kang Y, Hauner A, Craig AM. 2006: Structure-Function and Splice Site Analysis of the Synaptogenic Activity of the Neurexin-1beta LNS Domain. J. Neurosci. 26:4256-65.
[highlighted by Rowan, A. Synaptogenesis: Neurexins and new synapses. Nature Rev Neurosci, 2006, 7:418]
Craig AM, Graf ER, Linhoff MW. 2006. How to build a central synapse: Clues from cell culture. Trends Neurosci., 29:8-20.
Harms KJ, Tovar KR, Craig AM. 2005. Synapse-specific regulation of AMPA receptor subunit composition by activity. J. Neurosci. 25:6379-88.
[highlighted by Rumbaugh G (2005) Synapses fight over glutamate receptor 1. J. Neurosci 25:8347-8.]
Waites CL, Craig AM, Garner CC: 2005. Mechanisms of vertebrate synaptogenesis. Annu. Rev. Neurosci. 28:251-74.
Graf E, Zhang X, Jin SX, Linhoff M, Craig AM: 2004. Neurexins induce differentiation of GABA and glutamate postsynaptic specializations via neuroligins. Cell, 119:1013-1026.
[highlighted by Hussain NK and Sheng M (2005) Making synapses: A balancing act. Science 307:1207-8. and by Cline H (2005) Synaptogenesis: A balancing act between excitation and inhibition. Curr Biology 6:R203-5 and by Sci. STKE (2005) 265:tw8]
Levi S, Logan SM, Tovar KR, Craig AM: 2004. Gephyrin is critical for glycine receptor clustering but not for the formation of functional GABAergic synapses in hippocampal neurons. J. Neurosci. 24:207-217.
Levi S, Grady RM, Henry MD, Campbell KP, Sanes JR, Craig AM: Dystroglycan is selectively associated with inhibitory GABAergic synapses but is dispensable for their differentiation. J Neurosci. 2002; 22:4274-85.
Fong DK, Rao A, Crump FT, Craig AM: Rapid synaptic remodeling by protein kinase C: reciprocal translocation of NMDA receptors and calcium/calmodulin-dependent kinase II. J. Neurosci. 2002; 22:2153-64.
Crump FT, Dillman KS, Craig AM: cAMP-dependent protein kinase mediates activity-regulated synaptic targeting of NMDA receptors. J. Neurosci. 2001; 21:5079-88.
Craig AM and Boudin H. 2001. Molecular heterogeneity of central synapses: afferent and target regulation. Nat. Neurosci., 4:569-78.
Boudin H, Doan A, Xia J, Shigemoto R, Huganir RL, Worley P, and Craig AM: Presynaptic clustering of mGluR7 requires the PICK1 PDZ domain binding site. Neuron, 2000: 28:485-97.
Rao A, Cha EM and Craig AM: Mismatched appositions of presynaptic and postsynaptic elements in isolated hippocampal neurons. J. Neurosci., 2000; 20:8344-53.
Allison DW, Chervin AS, Gelfand VI and Craig AM: Postsynaptic scaffolds of excitatory and inhibitory synapses in hippocampal neurons: maintenance of core components independent of actin filaments and microtubules. J. Neurosci., 2000; 20:4545-4554.
Stowell JN and Craig AM: Axon / dendrite targeting of metabotropic glutamate receptors by their cytoplasmic carboxy terminal domains. Neuron, 1999; 22:525-536.
Allison DW, Spector I, Gelfand VI and Craig AM: Role of actin in anchoring postsynaptic receptors in cultured hippocampal neurons: Differential attachment of NMDA versus AMPA receptors. J. Neurosci. 1998; 18:2423-2436.
Rao A, Kim E, Sheng M and Craig AM: Heterogeneity in the molecular composition of excitatory postsynaptic sites during development of hippocampal neurons in culture. J. Neurosci. 1998; 18:1217-1229.
Rao A. and Craig AM: Activity regulates the synaptic localization of the NMDA receptor in hippocampal neurons. Neuron 1997; 19:801-812.
Craig AM, Wyborski RJ and Banker G: Preferential addition of newly synthesized membrane protein at axonal growth cones. Nature 1995; 375:592-594.
Craig AM and Banker G: 1994. Neuronal polarity. Annu. Rev. Neurosci. 17:267-310.
Craig AM, Blackstone CD, Huganir RL and Banker G: Selective clustering of glutamate and g-aminobutyric acid receptors opposite terminals releasing the corresponding neurotransmitters. Proc. Natl. Acad. Sci. USAÂ 1994; 91:12373-12377.
Craig AM, Blackstone CL, Huganir RL and Banker G: The distribution of glutamate receptors in cultured rat hippocampal neurons: Postsynaptic clustering of AMPA-selective subunits. Neuron 1993; 10:1055-1068.