Alan L. Pearlman - US grants

The long-range objectives of these stuidies is to gain an understanding of the developmental factors that lead to the orderly, laminar arrangement of neurons within the visual cortex, and the complex set of neuronal connections that determine its function. In our recent work we have provided the first description of fibronectin(FN)-like immunoreactivity in the developing neocortex of the mouse in a distribution that suggests a role in guiding the ingrowth of cortical afferents or in the consolidation of the cortical plate. We have developed a monoclonal antibody, 2Al, which recognizes a developmentally regulated cellsurface antigen (2Al-A) specific to CNS neurons that may be involved in cellsubstrate or cell-cell adhesion. In tissue culture, 2A1-A is prcminent on qrowth cones and at points of neurite-neurite contact and fasciculation. In the present application, we propose a series of in vivo and in vitro studies to answer the following questions: 1. Is FN a component of the substrate traversed by growth cones of early-arriving cortical afferents or in the migratory pathway of cells that form the cortical plate? We will carry out an immno-electron microscopic determination of the relationship between FN-like immunoreactivity, growth cones, and migrating neurons in the developing cortex. 2. Which cellular elements in the developing cortex produce or sequester FN? We will identify cortical cells producing FN in vitro with cell-type specific antibodies, and use in situ hybridization to identify cortical cells producing FN mRNA in vivo. 3. Is the epitope recoqnized by 2Al carried on a ganglioside? Does the location of 2Al-A suggest that it forms a link between cells, between fasciculating axons, or between growth cones and their substrate? We will characterized 2Al-A biochemically, use immuno- EM to lccalize 2A1-A in the embryonic cortex, and use in vitro assays to determine whether neurite outgrowth and fasciculation are altered by Fab fragments of 2A1 and whether advancing neurites adhere to or avoid substrates coated with 2Al-A. 4. Do radial glia and early cortical neurons have common precursor? Does the common precursor persist after neuronal and glial phenotypes appear? What is the fate of the transient population of radial glia? We will use a recombinant retroviral lineage marker to determine the early lineage relationships of neurons and glia in vitro, and cell-type specific antibody markers to determine whether radial glia are transformed into astrocytes.

The Neurobiology of Disease Teaching Workshops have been held for the past three years in association with the annual meeting of the Society for Neuroscience. They are aimed at young basic scientists to begin to introduce them to the diseases of the nervous system. Up to 100 students attend each year (PhD students, MD-PhD students, students, post-doctoral fellows, neurology residents and a small number of faculty). The work shop covers two major diseases or disorders each year, and consists of patient presentations, "core" lectures covering relevant clinical and basic science information small group discussions, special technolgy sessions and presentations dealing with the impact of these diseases on patients and their families. A faculty of approximately 20 is gathered for each workshop from outstanding researchers and clinician-researchers in the fields covered. The topics for the 1983 Workshop will be Pain and Affective Disorders.

Neuronal migration is a critical event in the formation of the laminar structure of the cerebral cortex, but the molecular signals that guide migration and determine neuronal position are not known. In prior studies we have shown that the extracellular matrix (ECM) glycoprotein fibronectin (FN) is distributed along the processes of radial glia as they pass through the layers that contain the preplate/subplate neurons and that chondroitin sulfate proteoglycans (CSPG) are closely associated with these neurons. These findings suggest that FN might be involved in glial-guided migration, and that preplate/subplate neurons and their associated ECM may constitute a framework for formation of the cortical plate, which will become definitive cortex. To test these hypotheses we have developed an assay for neuronal migration in an organotypic slice preparation of developing cortex that preserves three-dimensional cortical structure in vitro for several days. We will use this system to perturb the interactions between labeled migrating cells and the ECM experimentally. To analyze these perturbations quantitatively, we will use the Core microscopic and computer resources of the Program Project to automate the acquisition of high resolution images of labeled cells, plot their positions, and perform statistical correlations. We will also use these resources to analyze the distribution of ECM components, their receptors, and matrix proteases on individual migrating cells. These studies will provide a basis for understanding the abnormalities in neuronal migration that are common in the fetal alcohol syndrome and other insults to the cerebral cortex during early human development, and that have been implicated in the pathogenesis of epilepsy and dyslexia.