genetic diagnosis of epileptic encephalopathy using an extended

GENETIC DIAGNOSIS OF EPILEPTIC ENCEPHALOPATHY
USING AN EXTENDED NGS PANEL
RESULTS
Sousa, S1,2; Sampaio, M3; Silva, P1,2; Ribeiro,
C1,2; Alonso, I1,2,4; Silva, J1,2; Leão, M3,5.
1. Genes included in
the EE-NGS panel
ARX
UBE3A
ST3GAL5
SLC19A3
CDKL5
GABRG2
SLC25A22
GRIN2B
STXBP1
FOXG1
SPTAN1
MECP2
SCN1A
SCN1B
KCNQ2
SLC2A1
ARHGEF9
PNPO
PCDH19
MAGI2
PNKP
DEPDC5
SCN2A
GABRA1
genetically heterogeneous group of severe epilepsies
PLCB1
ALDH7A1
accompanied
SCN8A
CSTB
KCNT1
EPM2A
neurodevelopmental features.
ST3GAL3
FOLR1
Here, we describe the implementation of a NGS gene
TBC1D24
GABRB3
GNAO1
GOSR2
SZT2
NHLRC1
associated genes, including MECP2 and UBE3A.
POLG
NRXN1
Mutations in MECP2 are responsible for Rett syndrome
CHD2
KCTD7
SYNGAP1
SCARB2
1. Centro de Genética Preditiva e Preventiva - CGPP, Instituto de Biologia Molecular
e Celular - IBMC, Universidade do Porto, Porto, Portugal.
2. Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto,
Portugal.
3. Unidade de Neuropediatria - Hospital Pediátrico Integrado - Centro Hospitalar de
S. João.
4. UnIGENe, Instituto de Biologia Molecular e Celular - IBMC, Universidade do Porto,
Porto, Portugal.
5. Unidade de Neurogenética - Serviço de Genética Médica - Centro Hospitalar de S.
João.
INTRODUCTION
Epileptic encephalopathies (EE) are a phenotypically and
by
intellectual
disability
and
other
panel into diagnostic routine, containing 45 EE-
(RTT), which is a rare X-linked neurodevelopmental
seizures in male patients.
MATERIAL & METHODS
Patient:: Here, we report a positive case of a 2 years old
a)
GRIN2A
disorder affecting 1/10,000 to 1/15,000 females and that
can cause a more severe neonatal encephalopathy with
2. Pathogenic mutation in exon 4 of MECP2
gene (c.763C>T; p.Arg255*)
b)
Figure 2:
a) NGS analysis using JSI SeqNext software;
b) Electropherograms of exon 4 (forward) confirmed a heterozygous C-to-T substitution in a patient with EE. This mutation results in the replacement of a arginine by a
stop codon at position 255.
3. MeCp2 protein showing Rett Syndrome disease-causing
mutations
girl with tonic-clonic seizures, acquired microcephaly,
severe development delay with absent speech and
unilateral hand stereotypies, clinically suspected as
having Angelman syndrome but without 15q11.2-q13
deletion.
Laboratory Methodologies: In a group of patients, we
amplified all exons of the 45 genes with conventional
primers, pooled and sheared during library preparation,
and sequenced on the Ion Torrent PGM with a
MBD
Methyl-cytosine-binding domain
TRD
Transcriptional repression domain (mutation in red is the
one detected in our patient)
CTD
Carboxyl terminus domain
minimum coverage of 40x. Sequencing data was
analysed from FASTQ files using JSI SeqNext software.
AT-hook domain
All pathogenic variants were confirmed by Sanger
CONCLUSIONS
sequencing.
o Angelman syndrome can be one of the differential diagnoses of RTT, when the main features are acquired microcephaly,
IBMC – Instituto de Biologia Molecular e Celular
CGPP – Centro de Genética Preditiva e Preventiva
www.testegenetico.com
[email protected]
epilepsy and speech impairment;
o In atypical clinical cases, one of the tools for differential diagnosis can be an extended gene panel, given the genetic and
phenotypic heterogeneity in EE;
o Therefore, our extended panel proved to be a useful diagnostic tool to this patient, thereby allowing a better disease
management and improved genetic counselling for this family.