The enormous diversity of neurons in the mammalian brain and their interspersed arrangement require genetic targeting to study individual subpopulations that have been recognized in various neurological and psychiatric diseases. For example, the selective degeneration of dopaminergic neurons in Parkinson's disease or the involvement of GABAergic neurons in brain development and epilepsies. Therefore, the ability to mutate specific neuronal groups or control their activity directly or via glial modifications, will be a powerful tool for elucidating the contribution of such neurons-and the contribution of individual molecules within these neurons-to diverse brain functions in health and disease. To aid the study of individual subpopulations we plan to generate transgenic mice harboring bacterial artificial chromosome (BAC) based driver-transgenes that express tamoxifen inducible Cre recombinase (CreERT2), which is a fusion protein of the viral Cre recombinase and a human mutated estrogen receptor ligand binding domain developed by Chambon, Metzger and colleagues. Glia cells will be targeted by Gfap and S100b drivers. For GABAergic neurons we will use GAD65 (Gad2) and VGAT (Slc32a1) as drivers. Aminergic neurons will be targeted with the genes for dopamine transporter (Slc6a3), dopamine beta-hydroxylase (Dbh) and tryptophan hydroxylase 2 (Tph2) as drivers. The inducibility of CreERT2 will allow deletion in mature animals and avoid complications that arise from deletion of floxed genes during development. With the focus of genome science shifting from sequencing genomes to functional genomics, numerous mice with genes flanked by loxP sites and loxP stopped rescue transgenes have been generated. The proposed CreERT2 driver lines would provide an invaluable tool to genetically dissect the functions of floxed genes in the nervous system, thus facilitating the identification of disease-linked genes.
. The medical relevance of our proposal is supported by the discovery of an increasing number of disease linked genes, especially in the brain, that can be studied in a closely related animal model. We could provide the transgenic animal models to recapitulate human brain disorders, and thereby facilitate their experimental access to new therapeutic approaches, that would benefit both the pharmaceutical and medical communities.
