Mutations in the protocadherin 19 gene cause epilepsy in ... - Illumina

Mutations in the
protocadherin 19 gene
cause epilepsy in females
by a mechanism called
cellular interference
Christel Depienne
UF de neurogénétique & CRicm
Hôpital de la Pitié-Salpêtrière, Paris
Clinical Implications of Arrays & Next Generation Sequencing Technologies
Seminar, Paris, 10/05/2010

Severe myoclonic epilepsy of infancy
or Dravet syndrome
Normal PMD & MRI before the onset of seizures
Onset < 1 yr: seizures +++ triggered by fever
Febrile and afebrile polymorphic seizures
(generalized, partial seizures & absences)
Pharmacoresistant
Psychomotor delay, myoclonic jerks > 2 yrs
Na +
Mental retardation, behavioral disturbances
Sporadic cases
70-80% de novo mutations in the SCN1A gene
(voltage-gated sodium channel alpha 1 or Nav1.1)
β1
α1
P
P
β2
P

Search for new genes responsible for Dravet
syndrome
> 121 SCN1A-negative
patients
Search for microrearrangements
Illumina 370K
arrays

Identification of a male patient with a hemizygous
Xq22.1 deletion
Mother
Patient 1
98.7
98.9
99.1
99.3 99.5
pseudogene pseudogene pseudogene
PCDH19

Function of protocadherins in the CNS
• Highly expressed in CNS
• Cadherin superfamily (δ2 protocadherin)
• Membrane protein (6 extracellular EC
domains, 2 intracellular CM domains)
• Ca+-dependent homophilic/
heterophilic Interactions
Gaitan et Bouchard, 2006
• Potential role in neuronal survival &
migration during development
Screening of PCDH19 in 73 SCN1A-negative DS patients

Identification of 9 different point mutations in
11 unrelated female patients
c.142G>T/
p.Glu48X
c.352G>T/
p.Glu118X
c.859G>T/
p.Glu287X
c.506del/
p.Thr169SerfsX43
c.1036_1040dup/
p.Asn347LysfsX23
A
R
E/X
T
K
V
E/X
I
T
R
E/X
L
L
T/S
P/P
N/T
I
N/K
L/S
L/T
Proband
Control
c.361G>A/
p.Asp121Asn
I K D/N L
c.595 G>C/
p.Glu199Gln
D R E/Q T
c.1019A>G/
p.Asn340Ser
D T N/S D
c.1628T>C/
p.Leu543Pro
P S L/P Q
Proband
Control

Pedigrees & segregation of the mutations in the
families
Family 1
Family 2
Family 3
Family 4
Family 5
Family 6
del = whole gene
deletion
m = p.Glu48X
m = p.Glu118X
m = p.Glu287X
m = p.Glu287X
v = p.Arg1107Gly
m = c.1036_1040dup5
+ +/+ m +/+ + +/+
+/+ del m/+ m/+ +/+ +/+ m/+
2
+/+
m
m/+
+
v
+/+
+/+
m/+
v/+
m
+/+ m m +/+
m/+
m/+
Family 7
Family 8
Family 9
Family 10
Family 11
Family 12
m = c.506delC
m = p.Asp121Asn
m = p.Glu199Gln
m = p.Asn340Ser
m = p.Asn340Ser
m = p.Leu543Pro
+ +/+
m +/+
+ +/+ + +/+ + +/+
m +/+
m/+
m/+
m/+
m/+
m/+
m/+

An unusual X-linked inheritance
Recessive X-linked
X-linked with male sparing
.
. .
.
.
.
PCDH19
Affected
Unaffected
Unaffected
Affected

Principle of cellular interference
Normal individuals
(male/ female)
Mutated males
(hemizygous)
Mutated heterozygous
females
Random Mosaïc mutated X inactivation males
WT protocadherin 19
is expressed in all
neurons
Mutated protocadherin
19 is expressed in all
neurons
Co-existence of
neurons expressing
WT and mutated
protocadherin
Asymptomatic
Asymptomatic
Epilepsy and MR

Mosaïcism in the patient with the PCDH19 deletion
Lymphocytes
A
100%
Fibroblasts
B 47% 53%
Patient
(male)
C
D
Control
(female)

Micro-rearrangements of PCDH19 in females
Deletion of exons 1-3
Whole gene deletions
N07 1329 (family 18)
6.3 Mb
+
+/+
+
+/+
del/+
+/+ del/+
del/+
N07 0897 (family 17)
0.5 Mb
1,20
1,00
0,80
0,60
0,40
Exon1
Exon2
Exon3
Exon4
Exon5
Exon6
N08 0125 (family 16)
65 Kb
0,20
0,00
N 08 0125 N 07 0897 N 07 1329 WT1 WT2
TSPAN6
PCDH11X
NAP1L3
DIAPH2
PCDH19
SRPX2
FAM133A
TNMD
SYTL4

Mutations of PCDH19 in female patients with
epilepsy but without cognitive impairment
Generalized epilepsy with febrile seizures
Cryptogenic partial epilepsy
m/+
m +/+
m/+
m/+
m/+
m/+
m/+
m/+
c.2656 C>T / p.Arg886X
Exon 4
c.437 C>G / p.Thr146Arg
Exon 1
V
N S R/X A H
S
P G T/R R I
Patient
Control
Patient
Control

Conclusions
• High-density SNP arrays are a good tool to identify microrearrangements
and new genes
• PCDH19: new gene responsible for epilepsy +/- mental delay
• Frequent mutations: 15% of female patients with epilepsy and FS
• Unusual X-linked inheritance affecting mainly females
• Familial / sporadic cases (inherited / de novo)
• New pathophysiological mechanism : cellular interference

UF neurogénétique
moléculaire et cellulaire
Oriane Trouillard
Eric Leguern
Thanks to the families!
U975
Delphine Bouteiller
Alexis Brice
Eric Leguern
CRICM
Cytogénétique
Boris Keren
Baya Benyahia
P3S
Wassila Carpentier
Florent Soubrier
Institut Cochin
Karine Poirier
Jamel Chelly
Financements: GIS Maladies rares, AP-HP, INSERM
Cliniciens
Alexandra Afenjar, Paris
Alexis Arzimanoglou, Lyon
Nadia Bahi-Buisson, Paris
Patrick Berquin, Amiens
Marie Bru, Nantes
Claude Cances, Toulouse
Denys Chaigne, Strasbourg
Emmanuel Cheuret, Toulouse
Anne Dusser, Kremlin-Bicêtre
Agnès Gautier, Nantes
Brigitte Gilbert-Dussardier, Poitiers
Isabelle Gourfinkel-An, Paris
Delphine Héron, Paris
Annie Lannuzel, Paris
Gaetan Lesca, Lyon
Hélène Maurey, Kremlin-Bicêtre
Sophie Meyer, Bordeaux
Rima Nabbout, Paris
Isabelle Py, Cholet
Serge Rivera, Bayonne
François Rivier, Montpellier
Agathe Roubertie, Montpellier
Dominique Steschenko, Nancy
Sandra Whalen, Paris
Et les autres...

Craniofrontonasal syndrome
• Another disease with unusual X-linked inheritance
Forward
signaling
Wieland et al, 2004
Twigg et al, 2004
Eph R
Mutations in Ephrin B1 (EFNB1 en Xq12)
Ephrin
• Mouse model supporting cellular
interference as the pathological mechanism
Compagni et al, 2003
Reverse
signaling
D’après Wieacker & Wieland, 2008