Abstracts

Rationale: The mechanistic target of rapamycin (mTOR) complex 1 is a growth regulator highly involved in neuroglial proliferation, differentiation, and migration, through regulation of protein synthesis. mTOR itself is activated or inhibited by a number of other protein complexes, including TSC1/TSC2/TBC1D7, GATOR1, and KICSTOR. Mutations in mTOR pathway genes (MPG) cause various forms of epilepsy and malformations of cortical development (MCD), including focal cortical dysplasia (FCD), megalencephaly (ME), and hemimegalencephaly (HME). To date, there is no established, comprehensive dataset of the existing variants in MPG. Therefore, we created a publicly available database of MPG variants related to epilepsy or MCD. Methods: MPG variants were ascertained from published patient cohorts with epilepsy and MCD, Each MPG variant was cross-referenced with the Online Mendelian Inheritance in Man (OMIM) catalog of genetic disorders and with the ClinVar database in order to ensure all diagnoses associated with each variant were recorded. For each variant, the cDNA and protein change were recorded as well as the genomic build and coordinates for proper identification of the mutation and its position. Following identification of the variant, the type of mutation (e.g., missense, nonsense) was entered with a description of the pathology seen in the patient. Lastly, based on the editing abilities of current technology, we entered whether the variant was CRISPR-Cas9 editable and whether it had been validated in any in vivo or in vitro studies. Results: The resulting database consists of over 250 recorded variants found in AKT3, c12orf66, DEPDC5, KPTN, MTOR NPRL2, NPRL3, PI3K, RHEB, STRADA, SZT2, and TBC1D. We show that AKT3 variants result in megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome (MPPH) and HME, whereas the PIK3 variants were associated with megalencephaly-capillary malformation (MCAP) as well as HME. GATOR 1 variants (DEPDC5, NPRL2, NPRL3) were associated with familial focal epilepsy with variable foci (FFEVF) and FCD type II. Variants in mTOR were associated with Smith-Kingsmore Syndrome (SKS) and FCD type II. Variants in KPTN, SZT2, c12orf66 within the KICSTOR complex result in epileptic encephalopathy and ME/HME. Of the 250 variants assembled, 120 were amenable to CRISPR editing and 5.6% have been previously validated as causing mTOR pathway activation Conclusions: We have established a comprehensive database that encompasses all reported MPG variants to date associated with epilepsy and/or MCD. This database is available on the University of Maryland website (http://mvvp.igs.umaryland.edu) and is accessible to all, making it useful for researchers and clinicians alike. Furthermore, we have defined which variants are editable using current CRISPR/Cas9, thus providing a significant tool for researchers looking to validate MPG variants. Funding: R01NS099452