dc.description.abstracteng | 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. | de |