INCREASED CPA6 PROMOTER METHYLATION IN FOCAL

EPILEPSY AND INFEBRILE SEIZURES

Annick Salzmann, PhDService de Médecine Génétique (HUG)Département de Psychiatrie (UNIGE)

7ème Journée de la Recherche Clinique8 mai 2014

• Epilepsy

• Focal Epilepsy & Febrile Seizures

• Carboxypeptidase A6 (CPA6)

• Epigenetics of epilepsy

• CPA6 DNA Methylation & Epilepsy

• Perspectives

EPILEPSY

• Chronic neurological disorder à affects all ages

•Defined by 2 or more unprovoked seizures

• 50 million people worldwide (WHO 2009)

• 0.5–1% world population

• Epileptic phenomenen

‣ Hyperexcitability & Hypersynchrony

FOCAL EPILEPSY

• Most common form of epilepsy (60%)

• Localisation-related – Temporal lobe epilepsy

• Resistance to anti-epileptic drugs

• Surgical resection of anterior temporal lobe structures

• Antecedent of febrile seizures

• Complex disorder = genetic + environment

FEBRILE SEIZURES

• Not considered to be an epileptic condition

• Provoked by fever (>38.5°)

• Prevalence: 2–5%

• Onset age: 3 months and 5 years

• Epilepsy occurs 2–10 times more

• Important genetic predisposition

CONSANGUINEOUS FAMILY

7

Complex Febrile Seizures + Temporal Lobe Epilepsy

Complex Febrile Seizures

One Simple Febrile Seizure

Several Simple Febrile Seizures

1 2

5

3 4 5 6

4

II

III

1 2 3 6 7 8 9 10

I M/– M/–

M/– M/–

Founder mutation = M

M/M M/M M/M M/MM/–or –/–

M/–or –/–

M/–or –/–

M/–or

M/M

Common Ancestor

Autosomal Recessive Model

CARBOXYPEPTIDASE A6 (CPA6) MUTATION

CPA6 Protein

Salzmann et al. Hum Mutat, 2012

CARBOXYPEPTIDASE A6 (CPA6)

• Member of the M14 metallocarboxypeptidase family

• Highly expressed in human embryonic brain and in fetal umbilical cord blood (Wei et al., J. Biol. Chem. 2002)

• 50-kDa pro-CPA6 → 37-kDa active form secreted into the extracellular matrix (Lyons et al., J. Biol. Chem. 2008)

• Cleaves C-terminal hydrophobic residues → role in neuropeptides regulation (Lyons et al., J. Biol. Chem. 2008)

CPA6 MUTATIONS IN EPILEPTIC PATIENTS

CPA6 Protein

7 missense variants

Consanguineous FEB11/ELT5 familyc.809C>T → TT

3 FE patientsc.799G>A → GA1 TLE patient

c.843A>G → AG

1 TLE patientc.875C>G → CG

AssociationStudy

AssociationStudy

AssociationStudy

Sapio et al. J Biological Chemistry, 2012

• Epilepsy

• Focal Epilepsy & Febrile Seizures

• Carboxypeptidase A6 (CPA6)

• Epigenetics of epilepsy

• CPA6 DNA Methylation & Epilepsy

• Perspectives

EPIGENETICS

• Regulation of biological processes from conception to death of an organism

• Mitotically and/or meiotically heritable variations in gene functions, which are not due to changes in DNA sequence

• Essential for normal development, maintenance of cellular homeostasis and functions of an adult organism

LIFE EPIGENETIC PROFIL

Foley et al. Am. J. Epidemiol. 2009

DNA METHYLATION

CCH3 GC

GCH3

METHYLATION HYPOTHESIS IN EPILEPTOGENESIS

Kobow & Blümcke, Epilepsia, 2012

• Epilepsy

• Focal Epilepsy & Febrile Seizures

• Carboxypeptidase A6 (CPA6)

• Epigenetics of epilepsy

• CPA6 DNA Methylation & Epilepsy

• Perspectives

CPA6 CpGs IN PROMOTER

EPILEPTIC PATIENTS & CONTROLS

INCREASED LEVEL OF CPA6 METHYLATION

0 1 2 3 4 5 6 7 8

Controls FE FS Treated Controls

with AEDs Healthy Children with FHE

Young Controls

* ; # ; § ; $

** ; ## ; § § ; $ $

% M

ethy

latio

n

• Epilepsy

• Focal Epilepsy & Febrile Seizures

• Carboxypeptidase A6 (CPA6)

• Epigenetics of epilepsy

• CPA6 DNA Methylation & Epilepsy

• Perspectives

PERSPECTIVES

• In epilepsy field à Beginning of epigenetics research à A few published studies and most related to DNA methylation

•New cohorts of patients

à Blood (DNA) collected after a first seizure

à Blood (DNA) collected after X seizures

à Comparison of DNA methylation level (EpiGenome wide)

Thank you for your attention