The role of alpha-synuclein on transcriptional deregulation in Parkinson’s disease
by Isabel Paiva de Castro
Date of Examination:2018-04-24
Date of issue:2018-08-31
Advisor:Prof. Dr. Tiago Fleming Outeiro
Referee:Prof. Dr. André Fischer
Referee:Prof. Dr. Paul Lingor
Referee:Prof. Dr. Steven A. Johnsen
Referee:Dr. Nuno Raimundo
Referee:Prof. Dr. Thomas Meyer
Persistent Address:
http://dx.doi.org/10.53846/goediss-7029
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Description:PhD thesis
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Abstract
English
Parkinson’s disease (PD) is a complex neurodegenerative disorder that manifests through a broad ran ge of motor and non - motor symptoms. Alpha - synuclein (aSyn) is the major protein component of Lewy bodies and Lewy neurites, considered the pathological hallmarks in PD and other synucleinopathies. Some familial forms of PD can be caused by duplication , triplication, or missense mutations in the gene encoding for aSyn. However, the precise molecular mechanisms linking aSyn to the disease are still elusive. Although it has been shown that aSyn plays a role in transcriptional deregulation, the effect of spe cific aSyn mutants associated with familial forms of PD, such as the A30P mutant, remains unclear. This thesis compiles two studies that contain our major findings focused on the role of aSyn on transcriptional deregulation in PD. In the first study, we ai med to investigate the impact of aSyn on transcriptional deregulation using Lund Human Mesencephalic (LUHMES) cells as a model, since they can be differentiated into dopaminergic neurons. To achieve this, we generated two cell lines expressing wild - type (W T) or mutant A30P aSyn and performed gene expression analysis using RNA - sequencing. We observed that both WT and A30P aSyn induced robust transcriptional deregulation, including changes in expression of DNA damage/repair genes. Interestingly, increased DNA damage and was only observed in WT aSyn dopaminergic neurons. Furthermore, WT aSyn affected mitochondrial ROS (miROS) handling, unlike A30P aSyn. In these cells, aSyn expression decreased expression of acetylated histone 3 (acH3) levels that were restored by treatment with sodium butyrate (NaB) , a histone deacetylase inhibitor (HDACi). Interestingly, NaB was able to rescue the DNA damage induced by aSyn expression, possibly by upregulation of DNA repair genes observed upon the treatment. Moreover, treatme nt with NaB was shown to ameliorate miROS handling in WT aSyn cells. In the second study, our main goal was to investigate the role of aSyn on transcriptional deregulation in transgenic mice models of PD. For this purpose , we used transgenic mice overexpr essing human WT aSyn and A30P and conducted gene 16 expression studies. We observed that A30P aSyn promotes stronger transcriptional deregulation and increases DNA binding when compared to endogenous aSyn, consistently with the results obtained previously in LUHMES cells. Importantly, we identified several biological processes affected by A30P mutant aSyn, such as ER - associated pathways. Interestingly, COL4A2, a pro - apoptotic gene, was found to be upregulated in both A30P aSyn transgenic mice and in dopaminerg ic neurons expressing A30P aSyn. Finally, we observed that aSyn A30P alters Golgi morphology and increases endoplasmic reticulum (ER) stress in dopaminergic cells. Our findings suggest that aSyn can impact on transcriptio n , both in dopaminergic neurons an d in transgenic mouse models of PD, and that A30P aSyn has a stronger effect than WT aSyn. These studies provide novel insight into the mechanism underlying aSyn - toxicity, including gene deregulation, histone modification, DNA damage, miROS handling and Golgi - ER systems . Ultimately, our studies open novel avenues for future therapeutic intervention in PD and other synucleinopathies.
Keywords: Alpha-synuclein; Transcription deregulation; DNA damage; Histone deacetylase inhibitors; COL4A2; ER stress; Golgi fragmentation; A30P alpha-synuclein