The hTH-GFP Reporter Rat Model for the Study of Parkinson's Disease

Abstract

Parkinson disease (PD) is the second leading neurodegenerative disease in the US. As there is no known cause or cure for PD, researchers continue to investigate disease mechanisms and potential new therapies in cell culture and in animal models of PD. In PD, one of the most profoundly affected neuronal populations is the tyrosine hydroxylase (TH)-expressing dopaminergic (DA) neurons of the substantia nigra pars compacta (SNpc). These DA-producing neurons undergo degeneration while neighboring DA-producing cells of the ventral tegmental area (VTA) are largely spared. To aid in these studies, The Michael J. Fox Foundation (MJFF) partnered with Thomas Jefferson University and Taconic Inc. to generate new transgenic rat lines carrying the human TH gene promoter driving EGFP using a 11 kb construct used previously to create a hTH-GFP mouse reporter line. Of the five rat founder lines that were generated, three exhibited high level specific GFP fluorescence in DA brain structures (ie. SN, VTA, striatum, olfactory bulb, hypothalamus). As with the hTH-GFP mouse, none of the rat lines exhibit reporter expression in adrenergic structures like the adrenal gland. Line 12141, with its high levels of GFP in adult DA brain structures and minimal ectopic GFP expression in non-DA structures, was characterized in detail. We show here that this line allows for anatomical visualization and microdissection of the rat midbrain into SNpc and/or VTA, enabling detailed analysis of midbrain DA neurons and axonal projections after toxin treatment in vivo. Moreover, we further show that embryonic SNpc and/or VTA neurons, enriched by microdissection or FACS, can be used in culture or transplant studies of PD. Thus, the hTH-GFP reporter rat should be a valuable tool for Parkinson's disease research.

Spiking and Membrane Properties of Rat Olfactory Bulb Dopamine Neurons

“…The increasing availability of transgenic mice over the past few decades has caused mice to assume a greater role in biomedical science compared to rats. However, the advent of transgenic rats such as this hTH-GFP rat line (Iacovitti et al, 2014) allows for further characterization of OB DA neurons from a different rodent species. This adds to the collective knowledge of the function of OB DA neurons, as well as how these neurons may be affected by neurodegenerative diseases such as PD, and is of particular interest to those in the fields of pathology and neurology.…”

“…Transgenic hTH-GFP Sprague Dawley rats (Iacovitti et al, 2014) were used for all experiments (Taconic Biosciences, United States). Rats were housed in an animal vivarium facility at Florida State University, exposed to a 12-h light and dark cycle, and provided ad libitum access to food and water.…”

“…Rats offer some clear advantages over mice (e.g., easier to handle, lower susceptibility to stress, larger brain size facilitates brain surgery and imaging) and are better models for the study of some human behaviors and conditions (Ellenbroek and Youn, 2016). For these experiments, we used a transgenic rat line -the TH green fluorescent protein (hTH-GFP) line (Iacovitti et al, 2014) -which expresses GFP in all TH + (DA) neurons in the OB and other regions of the brain. The advent of this transgenic rat model has important implications to future research and facilitates the exploration of species differences (see section "Discussion").…”

New Developments in Genetic rat models of Parkinson's Disease

“…Recently, a strain of Berlin‐Druckrey rats bearing a synuclein gene promoter mutation was identified that results in accumulation of synuclein in the mesencephalic area, striatum, and frontal cortex, with altered dopaminergic neuron electrophysiology . Together with transgenic rats, these provide valuable research tools that can be combined through breeding with other animal models relevant to PD, including transgenic rats that express green fluorescent protein (GFP) exclusively in dopaminergic neurons …”

“…74 Together with transgenic rats, these provide valuable research tools that can be combined through breeding with other animal models relevant to PD, including transgenic rats that express green fluorescent protein (GFP) exclusively in dopaminergic neurons. 75…”