H3Africa PI: Guida Landoure
Institution: University Sciences of Techniques and Technologies of Bamako, Mali
Project Affiliation: Clinical and Genetic Studies of Hereditary Neurological Disorders in Mali
Introduction: Epilepsy is one of the most common neurological disorders worldwide with an important clinical and genetic heterogeneity. Recent advances in genomics technology have enabled the identification of new causal genes and variants causing epilepsy with at 140 genes known to date, nevertheless, many patients remain without a precise genetic diagnosis and genotype-phenotype relationships are not always clear. In this study, we describe a putative candidate gene PCDH8found in a Malian family with generalized epilepsy (GE).
Materials and methods: This study was approved by the institutional ethics committee of the Faculty of Medicine and Dentistry of Mali and written consent/assent was obtained from participants. Blood chemistries, EEG, and brain imaging were performed to rule out acquired causes. DNA was extracted from 10ml peripheral blood for genetic analysis including whole exome sequencing (WES) and Sanger sequencing. Functional studies are performed in Xenopus tropicalis. SgRNA were made for CRISPR/cas9 Knockout of the target gene in frog embyos to further confirm variant pathogenticity.
Results: A nonconsanguineous Malian family was enrolled with two affected females aged 18 and 30-year-old with generalized tonic-clonic seizures. The age at onset was 2 and 8 years, respectively. Patients are born from a normal pregnancy with an uneventful delivery. Early psychomotor milestones acquisition were normal. Seizures are often triggered by emotions, sleeplessness, and sometimes preceded by auditory hallucinations. The oldest patient reported forgetfulness and learning difficulties. The neurological examination were normal. WES identified a compound heterozygous variant (p.A786T and p.G696C) in the PCDH8gene. PCDH8 is not a known epilepsy gene. These variants are predicted to be deleterious by several prediction tools with CADD19.34 and31respectively.
Next step: Additional family members recruitments, and segregation analysis with Sanger sequencing and functional studies using Xenoupus tropicalis models are ongoing to confirm its pathogenicity.
Keywords: Epilepsy, PCDH8,Xenopustropicalis, CRISPR/Cas9, Mali, Africa