The goal of this project is to characterize the signaling pathways that regulate synaptogenesis in the developing brain. Previous studies have demonstrated that synapses differentiate in a series of steps, one of which is the clustering of postsynaptic neurotransmitter receptors. In the neuromuscular junction, clustering of the cholinergic receptors is induced by a proteoglycan (agrin), which activates a receptor tyrosine kinase (MuSK). In the central nervous system, it is not clear what regulates the clustering of postsynaptic receptors such as the NMDA receptors at excitatory synapses. Preliminary data from the Sponsor's laboratory indicate that activation of Eph receptor tyrosine kinases on cultured hippocampal neurons induces the clustering of a NMDA receptor subunit, NR1. Furthermore, Eph receptor ligands (ephrins) induce a biochemical interaction between the Eph and NMDA receptors. This study will examine the protein-protein interactions that mediate ephrin-induced NMDA receptor clustering through three specific aims. First, we will identify the domains of Eph and NR1 receptors that are critical for ephrin-induced receptor clustering. Then, we will investigate the role of tyrosine phosphorylation on the clustering of NMDA receptors by Eph tyrosine kinases. Finally, the cellular mechanisms of NMDA receptor clustering will be examined through two sets of experiments. We will present the ephrin ligands on the cell membrane and determine their effect on the NMDA receptors on neighboring neurons. Mechanisms of synapse formation are of particular interest to pediatric neurologists because aberrant synapse formation is likely to underlie common developmental disorders such as mental retardation and epilepsy. Through intensive training in basic science under the supervision of Dr. Michael Greenberg and clinical practice in pediatric neurology at the Children's Hospital in Boston, the candidate expects to become a physician- scientist equipped with the molecular and cellular tools to study neuronal dysgenesis in children.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HD001384-04
Application #
6608829
Study Section
Pediatrics Subcommittee (CHHD)
Program Officer
Vitkovic, Ljubisa
Project Start
2000-08-01
Project End
2005-07-31
Budget Start
2003-08-01
Budget End
2004-07-31
Support Year
4
Fiscal Year
2003
Total Cost
$125,429
Indirect Cost
Name
Children's Hospital Boston
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115
Fu, Wing-Yu; Chen, Yu; Sahin, Mustafa et al. (2007) Cdk5 regulates EphA4-mediated dendritic spine retraction through an ephexin1-dependent mechanism. Nat Neurosci 10:67-76
Cowan, Christopher W; Shao, Yu Raymond; Sahin, Mustafa et al. (2005) Vav family GEFs link activated Ephs to endocytosis and axon guidance. Neuron 46:205-17
Sahin, Mustafa; Greer, Paul L; Lin, Michael Z et al. (2005) Eph-dependent tyrosine phosphorylation of ephexin1 modulates growth cone collapse. Neuron 46:191-204
Shamah, S M; Lin, M Z; Goldberg, J L et al. (2001) EphA receptors regulate growth cone dynamics through the novel guanine nucleotide exchange factor ephexin. Cell 105:233-44