Objective: Glucose transporter-1 deficiency syndrome (GLUT1- DS) is defined as a metabolic encephalopathy that is associated with heterozygous and usually de novo pathogenic variations in the SLC2A1 (solute carrier family2 member1) gene.

Materials and Methods: In this study, all coding exons and neighboring intronic regions of SLC2A1 were Sanger sequenced in 12 patients with clinically suspected GLUT1-DS. For de novo variations revealed after sequencing and segregation analysis, we also performed genome wide Single Nucleotide Polymor- phism (SNP) genotyping to confirm parental relatedness with the proband. In patients without any sequence variations, re- al-time quantitative real-time polymerase chain reaction (qPCR) was applied to determine the presence of any copy number vari- ations (CNV).

Results: Sanger sequencing followed by bioinformatics analysis, segregation in the family and SNP array genotyping revealed two novel and de novo pathogenic variations associated with the GLUT1-DS phenotype in 2 patients. qPCR results were compatible with one copy loss of SLC2A1 gene in another patient. All variations identifiedherein are likely to have caused null al- leles and resulted in GLUT1-DS through haplo insufficiency.

Disscussion: In this study we used a series of molecular genetic approaches in order to identify all possible variations in SLC2A1 that may be associated with GLUT1-DS. This collective effort fa- cilitated diagnosis in 3 patients.

Keywords: Glucose transporter-1 deficiency syndrome (GLUT1- DS), SLC2A1, de novo variations, CNV analysis, SNP array