Neurons and their targets exchange information of many sorts as synapses are formed, maintained and modified. We use the simple and accessible skeletal neuromuscular junction to identify molecules and mechanisms that mediate this exchange. Initial studies showed that some cues elaborated by motoneurons and myotubes are stably associated with the basal lamina (BL) that occupies the synaptic cleft between these two cells. Subsequently, we and others identified several BL-associated signals, and we then used gene targeting in mice to ask which played critical roles in vivo. In this way, we found that z-agrin is a nerve-derived organizer of postsynaptic differentiation and used agrin as a starting point to elucidate a rudimentary pathway for postsynaptic differentiation. Now, we will focus on presynaptic differentiation, and seek a corresponding retrograde signaling pathway. The starting point here is our finding that beta2 laminins are BL-associated, muscle-derived cues that are required for nerve terminal maturation but dispensable for their initial differentiation. We recently identified several molecules that laminin may interact or cooperate with, and propose to analyze their roles, (i) Because beta2 laminins are important for synapse formation, we sought its synaptic receptors, and found that they include the voltage-gated calcium channels of the nerve terminal. (ii) Because beta2 laminins do not act alone, we sought other presynaptic organizing molecules, and found four: FGF-22, P84/SIRP-alpha, and two novel proteins from Torpedo electric organ. We will now use blocking reagents and gene targeting to find out what roles these components play at the neuromuscular junction in vivo. In addition, so we can properly interpret these mechanistic studies, we will use new imaging methods and transgenic reporters to document the sequence of steps by which a growth cone is transformed into a motor nerve terminal. Through this work, we hope to gain insight into principles that underlie construction of synapses, which are the fundamental information-processing units that underlie all neural function. Our results will be directly relevant to diseases of the motor nerve terminal, such as Lambert-Eaton Syndrome, and will also provide insights into mechanisms that regulate formation of less accessible central nerve terminals, which may be sites of malfunction in both neurological and psychiatric disorders

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Method to Extend Research in Time (MERIT) Award (R37)
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Neurodifferentiation, Plasticity, and Regeneration Study Section (NDPR)
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Talley, Edmund M
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Harvard University
Schools of Arts and Sciences
United States
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Gingras, Jacinthe; Gawor, Marta; Bernadzki, Krzysztof M et al. (2016) ?-Dystrobrevin-1 recruits Grb2 and ?-catulin to organize neurotransmitter receptors at the neuromuscular junction. J Cell Sci 129:898-911
Proszynski, Tomasz J; Sanes, Joshua R (2013) Amotl2 interacts with LL5?, localizes to podosomes and regulates postsynaptic differentiation in muscle. J Cell Sci 126:2225-35
Lilley, Brendan N; Pan, Y Albert; Sanes, Joshua R (2013) SAD kinases sculpt axonal arbors of sensory neurons through long- and short-term responses to neurotrophin signals. Neuron 79:39-53
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Nishimune, Hiroshi; Valdez, Gregorio; Jarad, George et al. (2008) Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction. J Cell Biol 182:1201-15
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