Our long-term goal is to understand the molecular basis of synapse formation in vertebrates. Currently, no target-derived signals have been firmly established as regulators of nerve terminal formation in vertebrates. This application focuses on a muscle-derived cue that controls nerve terminal formation at the neuromuscular junction, the most-studied synapse. Previous studies identified an activity in the basal lamina lining the synaptic cleft that induces presynaptic differentiation in reinnervating axons. The best candidate for mediating that activity is laminin-11, a muscle-derived component of the synaptic basal lamina. Laminin-11 is a heterotrimer, composed of three homologous laminin """"""""chains"""""""": a5, b2, and g1. Mice lacking laminin-11 through targeted deletion of b2 (s-laminin) die of neuromuscular failure at one month of age. Motor nerve terminals in the b2-knock-out are poorly differentiated, and cut axons fail to reinnervate b2-deficient synaptic sites properly. Purified laminin-11 (but not other laminins) acts as a """"""""stop"""""""" signal to cultured motor neurites, suggesting laminin-11 directly regulates axons in vivo. Previously, laminin-b2 was thought to contain the active sites in laminin-11. However, this simple hypothesis is now insufficient, because another b2-containing laminin (laminin-3, a2b2g1) was found to promote rather than stop neurite outgrowth. We now hypothesize that laminin-a5 bears much of the inhibitory activity of laminin-11, and that presynaptic defects in b2-knock-out mice are largely due to the accompanying loss of laminin-a5 at b2-deficient synapses. We propose to test this hypothesis in three ways. We will determine if laminin-a5 is required in vivo for synapse formation by characterizing laminin a5-knock-out mice. We will determine if laminin-a5 directly regulates axons, using in vitro assays of neurite outgrowth on substrates containing purified laminin trimers that contain a5 (but not b2). Finally, because Schwann cells that surround nerve terminals are also regulated by laminin-11, we will determine whether laminin-a5 directly regulates nerve terminal formation by assaying synaptogenesis in nerve-muscle co-cultures, where Schwann cells can be eliminated. These studies will provide insight into the mechanisms by which neuronal targets foster and control the pattern of innervation they receive, and these insights will advance methods of treating neuromuscular disorders and injuries.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS040759-01
Application #
6227578
Study Section
Special Emphasis Panel (ZRG1-MDCN-7 (01))
Program Officer
Nichols, Paul L
Project Start
2001-02-09
Project End
2005-01-31
Budget Start
2001-02-09
Budget End
2002-01-31
Support Year
1
Fiscal Year
2001
Total Cost
$302,000
Indirect Cost
Name
Oregon Health and Science University
Department
Neurosciences
Type
Schools of Medicine
DUNS #
009584210
City
Portland
State
OR
Country
United States
Zip Code
97239
Abrass, Christine K; Hansen, Kim M; Patton, Bruce L (2010) Laminin alpha4-null mutant mice develop chronic kidney disease with persistent overexpression of platelet-derived growth factor. Am J Pathol 176:839-49
Kazanis, Ilias; Lathia, Justin D; Vadakkan, Tegy J et al. (2010) Quiescence and activation of stem and precursor cell populations in the subependymal zone of the mammalian brain are associated with distinct cellular and extracellular matrix signals. J Neurosci 30:9771-81
Yurchenco, Peter D; Patton, Bruce L (2009) Developmental and pathogenic mechanisms of basement membrane assembly. Curr Pharm Des 15:1277-94
Patton, Bruce L; Wang, Bing; Tarumi, Yukie S et al. (2008) A single point mutation in the LN domain of LAMA2 causes muscular dystrophy and peripheral amyelination. J Cell Sci 121:1593-604
Lathia, Justin D; Patton, Bruce; Eckley, D Mark et al. (2007) Patterns of laminins and integrins in the embryonic ventricular zone of the CNS. J Comp Neurol 505:630-43
Miner, Jeffrey H; Go, Gloriosa; Cunningham, Jeanette et al. (2006) Transgenic isolation of skeletal muscle and kidney defects in laminin beta2 mutant mice: implications for Pierson syndrome. Development 133:967-75
Yang, Dongren; Bierman, Jesse; Tarumi, Yukie S et al. (2005) Coordinate control of axon defasciculation and myelination by laminin-2 and -8. J Cell Biol 168:655-66
Miner, Jeffrey H; Li, Cong; Patton, Bruce L (2004) Laminins alpha2 and alpha4 in pancreatic acinar basement membranes are required for basal receptor localization. J Histochem Cytochem 52:153-6
Yurchenco, Peter D; Amenta, Peter S; Patton, Bruce L (2004) Basement membrane assembly, stability and activities observed through a developmental lens. Matrix Biol 22:521-38
Patton, Bruce L (2003) Basal lamina and the organization of neuromuscular synapses. J Neurocytol 32:883-903