FETAL TISSUE TRANSPLANT AND OTHER GENE EXPRESSION SYSTEMS

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The overall objectives of the experiments described in the component are to characterize the growth, development, and function of fetal tissue fragments isolated from abortuses at risk for schizophrenia, and to determine whether there are functional differences between such tissue and normal control tissue that might reveal some of the biological vases for schizophrenia. There are four basic aims of these experiments. The first objective will be to study transplanted brain regions (e.g. hippocampus and cerebral cortex) obtained from fetal tissue of normal and schizophrenic women into athymic rats, and to examine the mechanisms underlying the reduced growth and rate of maturation that we have observed. These experiments will test for non-genetic (e.g., medication- related) as well as genetic mechanisms underlying these differences. In particular, we will test for specific abnormalities in neurotrophic factors such as NT-3, which is primarily localized to hippocampus, or GDNF, which has specific trophic effects on dopamine neurons. The second major objective will be to record the electrophysiological activity of brain cells in xenotransplants of hippocampus, cerebral cortex, and other brain areas from fetal tissue of normal and schizophrenic women both in oculo and in vitro. Intracellular and extracellular recording will be employed as well as whole cell patch techniques to characterize intrinsic properties of these neurons and their response to neurotransmitters. The transplants will also be studied by immunohistochemistry and by in situ hybridization to assess the development of specific types of neurons. The third major objective will be to establish in oculo and in vitro the circuits hypothesized (on the basis of ongoing studies in other components of the Center) to be responsible for the deficit in sensory gating seen in schizophrenia. Sequential xenografts of human fetal brain areas in oculo will be combined in an attempt to define which neuronal elements must be derived from brain tissue fragments from abortuses of schizophrenics to produce deficits in the development or function of these circuits. The final objective will be to study isolated cells that have been transfected with genetic material derived from normal and adult schizophrenic post mortem brain tissue to characterize possible differences in neurotransmitter receptors. Candidate genes will be expressed in Xenopus oocytes, in a human embryonic kidney cell line (HEK 293 cells), in Schwann cells, and in primary cultures of fibroblasts from normals, schizophrenics and obligate carriers. In all these cell systems, gene expression will be studied by intracellular and patch recording techniques, and the expression of specific receptor subunits will be confirmed biochemically.