Castro, Isabel Paiva de

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

Georg-August-University Göttingen

The role of alpha-synuclein on transcriptional deregulation in Parkinson’s disease

https://ediss.uni-goettingen.de/bitstream/11858/00-1735-0000-002E-E497-F/1/Thesis_IsabelPaiva.pdf

The role of alpha-synuclein on transcriptional deregulation in Parkinson’s disease

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