The protein-tyrosine kinase receptor Tyro-3 is expressed in postnatal brain where it is abundant in cortex, hippocampus and the granule cells of the cerebellum. We have generated a rabbit polyclonal antiserum which recognized the cytoplasmic tail region of this receptor. This antibody specifically stains apparent dendritic structures in CAl hippocampal neurons. we are interested in identifying the precise location of the Tyro-3 protein within these dendrites in order to determine if it is restricted in expression to the synapse or to other specialized structures such as dendritic spines. The molecule gas6 has been identified as a possible ligand for Tyro-3. We are also intersted in determining the location of this ligand in relationsh to that of its receptor. We will be using the confocal and EM facilities and the expertise of the NCMIR staff to carry out the light and EM localization. We will use a combination of single and double labeling light microscopy to first map the distribution of Tyro-3. Work on this part of the project is underway. This work will be followed by high resolution EM mapping using colloidal gold or photo-oxidation approaches.