RET signaling does not modulate MPTP toxicity but is required for regeneration of dopaminergic axon terminals.
Activation of the RET (rearranged during transfection) receptor by glial cell-line-derived neurotrophic factor (GDNF) has been identified as an important differentiation and survival factor for dopaminergic neurons of the midbrain in preclinical experiments. These encouraging results have led to clinical trials of GDNF in patients with Parkinson's disease, which have resulted in conflicting findings. To investigate the potential benefit of Ret-dependent signaling on the challenged dopaminergic system, we tested the effect of tissue-selective ablation of the Ret gene on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in mice, the most widely used animal model for Parkinson's disease. Ablation of Ret did not modify the MPTP-induced loss of dopaminergic neurons in the substantia nigra pars compacta and the dopaminergic innervation of the striatum at 14 days. However, Ret ablation abolished the regeneration of dopaminergic fibers and terminals, as well as the partial recovery of striatal dopamine concentrations, that was observed in control mice between days 14 and 90 after MPTP treatment. We therefore conclude that RET signaling has no influence on the survival of dopaminergic neurons in the MPTP model of Parkinson's disease but rather facilitates the regeneration of dopaminergic axon terminals.
Department of Neurodegeneration and Restorative Research, Centers of Molecular Physiology of the Brain and Neurological Medicine, University of Goettingen, Waldweg 33, D-37073 Goettingen, Germany.
Sebastian
S
Kowsky
Charlotte
C
Pöppelmeyer
Edgar R
ER
Kramer
Björn H
BH
Falkenburger
Anja
A
Kruse
Rüdiger
R
Klein
Jörg B
JB
Schulz
D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D005911:Gliosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D020267:MPTP Poisoning / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism*; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D014446:Tyrosine 3-Monooxygenase; D051096:Proto-Oncogene Proteins c-ret; C494999:Ret protein, mouse; D004298:Dopamine