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.