The major goals of my project are to determine if there are developmentally regulated changes in dendritic/axonal arborization and synaptogenesis of GABAergic interneurons and pyramidal neurons in normal PFC, and whether NCAM dysregulation interferes withdevelopment in NCAM-EC and null mutant mice. NCAM shedding will be assessed during development in post-mortem human brain and from individuals with schizophrenia. Cortical neuron cultures will be exploited to identify the ADAM protease(s) responsible for normal NCAM shedding, to localize the NCAM cleavage site, and to ascertain the role of NCAM shedding on neuronal process outgrowth and branching. Finally, behavioral testing in mice will assess whether NCAM-EC overexpression impairs executive functions such as working memory, decreases gamma oscillatory activity, and alters sensitivity to GABA agonists in anxiety-like behavior and sensorimotor gating.
Project Goals:
(1) To define the area and layer V-specific distribution of cortical neurons in CHL1 mice and CHL1/L1 double mutants.
Role for CHL1 interaction with Sema3A in dendritic development will be studied in cortical slices.
(2) To determine the mechansim of CHL1 in radial migration of cortical neurons by BrdU labeling and time lapse recording
in CHL1 knockout mice, and effect of inhibitory integrin antibodies and peptides on migration of wild type neurons in vitro.
(3) To investigate the CHL1 intracellular signaling pathway in neuronal cultures.
(4) To identify topographic mapping defects in the thalamocortical projection of mice deficient in CHL1(homo- and heterozygotes)
and to assess a potential interaction with L1 in axon guidance in CHL1/L1 double mutants.
To investigate the function of L1 adhesion molecule in topographic axon targeting in the retinocollicular pathway in regard to L1 interaction with the neuronal cytoskeleton through ankyrin binding. Cellular and biochemical assays will identify the intracellular signaling mechanism regulating L1-ankyrin binding important for retinal axon branch attraction in response to attractant B-class Eph receptors. ALCAM will be studied as a substrate bound ligand for L1 in the superior colliculus by axon tracing in ALCAM knockout mice and retinal cell cultures.
This grant will study NrCAM knockout mice to investigate the hypothesis that NrCAM mediates guidance of retinal axons to the superior colliculus and thalamic axons to the cortex, as a new model for visual processing deficits in autism spectrum disorder (ASD). Abnormalities in visual processing may impair social communication and motor responses, thus NrCAM mutant mice will be analyzed for behaviors relevant to ASD (sociability, reversal learning, locomotion,stereotypy, and sensory gating).