VTA greatly enriches the proportion of DA neurons that can be isolated from each of these midbrain regions for culture and transplant studies. With further FACS analysis, DA neurons from each of these regions can be purified to near homogeneity. Thus, the hTH-GFP reporter rat should be a valuable tool for Parkinson disease research. The results of this study indicate the hTH-GFP reporter rat should serve as an important new model, adding to our arsenal of tools used to study and treat PD. Employing the hTH-GFP reporter construct used previously to create both a transgenic reporter mouse and reporter human embryonic stem cells, we demonstrate here that the hTH-GFP rat, particularly line 12141, exhibits high level specific GFP fluorescence in DA brain structures with minimal ectopic expression elsewhere in the brain. The pattern of GFP expression driven by the hTH-promoter matches/ overlaps the expression pattern of endogenous TH. These hTH-GFP rats provide several major benefits over their wild type counterparts. First, they allow for the microdissection of the embryonic mesencephalon in a fluorescence microscope, making it possible to segregate PDsusceptible DA neurons of the SNpc from PD-resistant DA neurons of the VTA for studies of disease pathogenesis in culture. The importance of this advantage cannot be over-emphasized as currently midbrain cultures contain a mixture of DA neurons, predominantly LEE011 comprised of VTA DA neurons which greatly outnumber DA neurons of the SNpc, significantly confounding data analysis. Our studies using the DA-specific toxins MPP+ further indicate that it will be possible to accurately model PD-like neurodegeneration in culture and further dissect the role of environmental modifiers of disease. A second and related benefit of the hTH-GFP reporter rat is the ability to further purify GFP+ DA neurons by FACS sorting, dramatically enriching their yield in culture from 1-5% seen after dissection of wild type rats versus approximately 90% after microdissection and FACS. By isolating homogeneous rat SNpc or VTA DA neurons, it will be possible to develop high throughput screens to test potential new PD drugs and to automate GFP fluorescence as a quantifiable readout. Thirdly, our developmental studies indicate that hTH-GFP rat midbrain neurons develop as predicted from murine studies, arising from a population of Foxa2+ floor plate cells and ultimately giving rise to TH+GFP+ DA neurons. Importantly, because GFP expression is more easily detected than TH immunostaining at early developmental stages, the reporter rat may be particularly useful for early embryonic studies. Furthermore, the ability to isolate developing SNpc and/or VTA DA neurons also made possible their study in the brain following transplantation into wild type rats. As further proof that hTHGFP+ DA neurons develop normally, transplanted GFP+ midbrain cells coexpressed Foxa2 and TH and produced functional motor recovery in the lesioned rat. Finally, the hTH-GFP reporter rat will facilitate studies on the most widely used in vivo model of PD, the 6-OHDA rat. The large size of the rat versus mouse brain makes stereotaxic procedures easier.