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GDNF and alpha-synuclein in nigrostriatal degeneration
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Histology and Cell Biology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Parkinson’s disease is a common neurological disorder with a complex etiology. The disease is characterized by a progressive loss of dopaminergic cells in the substantia nigra, which leads to motor function and sometimes cognitive function disabilities. One of the pathological hallmarks in Parkinson’s disease is the cytoplasmic inclusions called Lewy bodies found in the dopamine neurons. The aggregated protein α-synuclein is a main component of Lewy bodies. In view of severe symptoms and the upcoming of problematic side effects that are developed by the current most commonly used treatment in Parkinson’s disease, new treatment strategies need to be elucidated. One such strategy is replacing the lost dopamine neurons with new dopamine-rich tissue. To improve survival of the implanted neurons, neurotrophic factors have been used. Glial cell line-derived neurotrophic factor (GDNF), which was discovered in 1993, improves survival of ventral mesencephalic dopamine neurons and enhances dopamine nerve fiber formation according to several studies. Thus, GDNF can be used to improve dopamine-rich graft outgrowth into the host brain as well as inducing sprouting from endogenous remaining nerve fibers. This study was performed on Gdnf gene-deleted mice to investigate the role of GDNF on the nigrostriatal dopamine system. The transplantation technique was used to create a nigrostriatal microcircuit from ventral mesencephalon (VM) and the lateral ganglionic eminence (LGE) from different Gdnf gene-deleted mice. The tissue was grafted into the lateral ventricle of wildtype mice. The results revealed that reduced concentrations of GDNF, as a consequence from the Gdnf gene deletion, had effects on survival of dopamine neurons and the dopamine innervation of the nigrostriatal microcircuit. All transplants had survived at 3 months independently of Gdnf genotype, however, the grafts derived from Gdnf gene-deleted tissue had died at 6 months. Transplants with partial Gdnf gene deletion survived up to 12 months after transplantation. Moreover, the dopaminergic innervation of striatal co-grafts was impaired in Gdnf gene-deleted tissue. These results highlight the role of GDNF for long-term maintenance of the nigrostriatal dopamine system. To further investigate the role of GDNF expression on survival and organization of the nigrostriatal dopamine system, VM and LGE as single or combined to double co-grafts created from mismatches in Gdnf genotypes were transplanted into the lateral ventricle of wildtype mice. Survival of the single grafts was monitored over one year using a 9.4T MR scanner. The size of single LGE transplants was significantly reduced by the lack of GDNF already at 2 weeks postgrafting while the size of single VM was maintained over time, independently of GDNF expression. The double grafts were evaluated at 2 months, and the results revealed that lack of GDNF in LGE reduced the dopamine cell survival, while no loss of dopamine neurons was found in VM single grafts. The dopaminergic innervation of LGE was affected by absence of GDNF, which also caused a disorganization of the striatal portion of the co-grafts. Small, cytoplasmic inclusions were frequently found in the dopamine neurons in grafts lacking GDNF expression. These inclusions were not possible to classify as Lewy bodies by immunohistochemistry and the presence of phospho-α-synuclein and ubiquitin; however, mitochondrial dysfunction could not be excluded. To further study the death of the dopamine neurons by the deprivation of GDNF, the attention was turned to how Lewy bodies are developed. With respect to the high levels of α-synuclein that was found in the striatum, this area was selected as a target to inject the small molecule – FN075, which stimulates α-synuclein aggregation, to further investigate the role of α-synuclein in the formation of cytoplasmic inclusions. The results revealed that cytoplasmic inclusions, similar to those found in the grafts, was present at 1 month after the injection, while impairment in sensorimotor function was exhibited, the number of dopamine neurons was not changed at 6 months after the injection. Injecting the templator to the substantia nigra, however, significantly reduced the number of TH-positive neurons at 3 months after injection. In conclusion, these studies elucidate the role of GDNF for maintenance and survival of the nigrostriatal dopamine system and mechanisms of dopamine cell death using small molecules that template the α-synuclein aggregation.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2014. , 61 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1665
Keyword [en]
Parkinson's disease, GDNF, ventral mesencephalon, lateral ganglionic eminence, alpha-synuclein
National Category
Neurosciences
Research subject
Developmental Neurosciences
Identifiers
URN: urn:nbn:se:umu:diva-91811ISBN: 978-91-7601-098-3 (print)OAI: oai:DiVA.org:umu-91811DiVA: diva2:738352
Public defence
2014-09-18, BiA201, IMB, Biologihuset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2014-08-28 Created: 2014-08-18 Last updated: 2014-12-18Bibliographically approved
List of papers
1. Glial cell line-derived neurotrophic factor is crucial for long-term maintenance of the nigrostriatal system
Open this publication in new window or tab >>Glial cell line-derived neurotrophic factor is crucial for long-term maintenance of the nigrostriatal system
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2010 (English)In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 171, no 4, 1357-1366 p.Article in journal (Refereed) Published
Abstract [en]

Glial cell line-derived neurotrophic factor (GDNF) is a potent factor for the ventral mesencephalic dopamine neurons. However, studies on the Gdnf gene deleted (Gdnf(-/-)) mouse have been limited to fetal tissue since these mice die prematurely. To evaluate long-term effects of Gdnf gene deletion, this study involves co-grafts of ventral mesencephalon (VM) and lateral ganglionic eminence (LGE) derived from different Gdnf genotypes. The VM/LGE co-grafts were evaluated at 3, 6, and 12 months for tyrosine hydroxylase (TH) -positive cell survival and nerve fiber formation in the LGE co-transplant, visualized by dopamine- and cyclic AMP-regulated phosphoprotein relative molecular mass 32,000 (DARPP-32) -immunoreactivity. Cell counts revealed no difference in TH-positive neurons between Gdnf genotypes at 3 months postgrafting. At 6 months, a significant reduction in cell number was observed in the Gdnf(-/-) grafts. In fact, in the majority of the Gdnf(-/-) VM/LGE transplant had degenerated. At 12 months, a reduction in cell number was seen in both Gdnf(-/-) and Gdnf(+/-) compared to wild type transplants. In the Gdnf(-/-) grafts, TH-negative inclusion-like structures were present in the cytoplasm of the TH-positive neurons at 3 months. These structures were also found in the Gdnf(+/-) transplants at 12 months, but not in Gdnf(+/+) controls at any time point. In Gdnf(+/+) grafts, TH-positive nerve fiber innervation of the striatal co-grafts was dense and patchy and overlapped with clusters of DARPP-32-positive neurons. This overlap did mismatch in the Gdnf(+/-) grafts, while the TH-positive innervation was sparse in the Gdnf(-/-) transplants and the DARPP-32-positive neurons were widespread distributed. In conclusion, GDNF is essential for long-term maintenance of both the VM TH-positive neurons and for the striatal tissue, and appears crucial for generation of a proper organization of the striatum.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
GDNF, transplant, substantia nigra, striatum, DARPP-32, Gdnf knockout
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-41351 (URN)10.1016/j.neuroscience.2010.10.010 (DOI)000285231000035 ()20933580 (PubMedID)
Available from: 2011-03-23 Created: 2011-03-23 Last updated: 2017-12-11Bibliographically approved
2. GDNF is important for striatal organization and maintenance of dopamine neurons grown in the presence of the striatum
Open this publication in new window or tab >>GDNF is important for striatal organization and maintenance of dopamine neurons grown in the presence of the striatum
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2014 (English)In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 270, 1-11 p.Article in journal (Refereed) Published
Abstract [en]

Glial cell-derived neurotrophic factor (GDNF) exerts neuroprotective and neurorestorative effects on neurons and GDNF plays a significant role in maintenance of the dopamine neurons utilizing grafting to create a nigrostriatal microcircuit of Gdnf knockout (Gdnf(-/-)) tissue. To further evaluate the role of GDNF on organization of the nigrostriatal system, single or double grafts of ventral mesencephalon (VM) and lateral ganglionic eminence (LGE) with mismatches in Gdnf genotypes were performed. The survival of single grafts was monitored utilizing magnetic resonance imaging (MRI) and cell survival and graft organization were evaluated with immunohistochemistry. The results revealed that the size of VM single grafts did not change over time independent of genotype, while the size of the LGE transplants was significantly reduced already at 2weeks postgrafting when lacking GDNF. Lack of GDNF did not significantly affect the survival of tyrosine hydroxylase (TH)-positive neurons in single VM grafts. However, the survival of TH-positive neurons was significantly reduced in VM derived from Gdnf(+/+) when co-grafted with LGE from the Gdnf(-/-) tissue. In contrast, lack of GDNF in the VM portion of co-grafts had no effect on the survival of TH-positive neurons when co-grafted with LGE from Gdnf(+/+) mice. The TH-positive innervation of co-grafts was sparse when the striatal co-grafts were derived from the Gdnf(-/-) tissue while dense and patchy when innervating LGE producing GDNF. The TH-positive innervation overlapped with the organization of dopamine and cyclic AMP-regulated phosphoprotein-relative molecular mass 32,000 (DARPP-32)-positive neurons, that was disorganized in LGE lacking GDNF production. In conclusion, GDNF is important for a proper striatal organization and for survival of TH-positive neurons in the presence of the striatal tissue.

Keyword
GDNF, GDNF knockout, dopamine, substantia nigra, striatum, DARPP-32
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-88075 (URN)10.1016/j.neuroscience.2014.04.008 (DOI)000336624000001 ()24726488 (PubMedID)
Available from: 2014-04-23 Created: 2014-04-23 Last updated: 2017-12-05Bibliographically approved
3. A novel animal model for Parkinson's disease based on in vivo effects of small-molecule of alpha-synuclein
Open this publication in new window or tab >>A novel animal model for Parkinson's disease based on in vivo effects of small-molecule of alpha-synuclein
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Amyloid fibrils of alpha-synuclein are major constituents of Lewy bodies, the pathological hallmark of Parkinson’s disease. Monomeric α-synuclein is involved in synaptic vesicle trafficking and long-term maintenance of neurons. The underlying mechanisms of Parkinson’s disease are not known but it has been proposed that oligomers of α-synuclein, formed during the aggregation process, are toxic to neurons. To search for a new animal model of Parkinson’s disease, here we capitalized on the in vitro discovery of a small-molecule templator of α-synuclein fibrillization, the 2-pyridone, FN075. FN075 and MS382, another 2-pyridone variant that act as an inhibitor of amyloids in vitro, were injected into the striatum or substantia nigra of normal C57Bl/6 mice. No acute toxicity of the compounds was detected, as there was 100 % survival of the injected mice. At 6 months after the striatal injection, sensorimotor functions were impaired with no reduction in TH-positive neurons in the substantia nigra in mice injected with FN075, whereas mice injected with MS382 or vehicle had no dysfunctions. Injection of FN075 into the substantia nigra revealed a significant loss of TH-positive neurons already at 3 months and TH-negative inclusion-like structures were detected in substantia nigra neurons of these mice. Thus, the results suggest that injection of a templator of α-synuclein aggregation into the brain of normal mice can serve as a novel experimental design for an animal model of Parkinson’s disease.

Keyword
Parkinson's disease, alpha-synuclein, small molecules, FN075, MS382
National Category
Neurosciences
Research subject
Developmental Neurosciences
Identifiers
urn:nbn:se:umu:diva-91807 (URN)
Available from: 2014-08-18 Created: 2014-08-18 Last updated: 2014-09-08Bibliographically approved

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