Additional polgD257A mutation (mutator) does not influence dopaminergic neurodegeneration in aged parkin-deficient mice

Abstract

Background: Parkinson’s disease is a neurodegenerative disease caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. Among the first identified causes of autosomal recessive Parkinson’s disease were mutations in the parkin gene. Independently, we and other groups have developed various parkin knockout mice, and none displayed dopaminergic degeneration in the substantia nigra. Interestingly, dopaminergic degeneration in the substantia nigra has been reported in a parkin knockout line (exon 3 deletion) carrying an additional mutation (D257A) in the mitochondrial DNA polymerase (polg) gene (mutator). The mutator mice show accelerated mutation rates in mitochondrial DNA resulting in a premature-aging phenotype. Methods: To verify this finding, we crossed our parkin-deficient mice with the mutator mice, and characterized phenotypic changes of the parkin/mutator double mutant mice up to one year of age. We examined their locomotion and motor coordination behaviors by using the open field, the rotarod, and the pole test, subsequently investigating their nigrostriatal axis by counting TH-positive cells in every tenth section throughout the entire substantia nigra pas compacta and their termini in the striatum. Results: The double mutants did not display additional deficiencies in locomotion in our behavior tests. We could also not detect dopaminergic neurodegeneration in the substantia nigra pars compacta of aged double mutants measured by levels of tyrosine hydroxylase positive neurons in the substantia nigra pars compacta as well as in striatal terminals. Conclusion: Our results do not support the hypothesis that the polgD257A mutation contributes to the age-related vulnerability of dopaminergic neurons in parkin-deficient mice. Keywords: Parkin, neurodegeneration, polgD257A, mutator, substantia nigra

The deubiquitinase BRCC3 increases the stability of ZEB1 and promotes the proliferation and metastasis of triple-negative breast cancer cells

“…Then sections were incubated for 20 min with horseradish peroxidase (HRP)-labelled Goat anti-Rabbit IgG (ab205718, 1:2000; Abcam) or HRP-labeled Donkey anti-Goat IgG (A0181, 1:1000; Beyotime). Finally, sections were developed with DAB for 2 min, counterstained with hematoxylin for 1 min, and examined under a microscope after sealing [21] . PBS was used instead of the primary antibody as a negative control.…”