SLC2A1 gene analysis of Japanese patients with glucose transporter 1 deficiency syndrome

Glucose transporter 1 deficiency syndrome (Glut1-DS) is a congenital metabolic disorder characterized by refractory seizures with early infantile onset, developmental delay, movement disorders and acquired microcephaly. Glut1-DS is caused by heterozygous abnormalities of the SLC2A1 (Glut1) gene, whose product acts to transport glucose into the brain across the blood-brain barrier. We analyzed the SLC2A1 gene in 12 Japanese Glut1-DS patients who were diagnosed by characteristic clinical symptoms and hypoglycorrhachia as follows: all patients had infantile-onset seizures and mild to severe developmental delay, and ataxia was detected in 11 patients. For the 12 patients, we identified seven different mutations (three missense, one nonsense, two frameshift and one splice-site) in exons and exon-intron boundaries of the SLC2A1 gene by direct sequencing, of which six were novel mutations. Of the remaining five patients who had no point mutations and underwent investigation by multiplex ligation-dependent probe amplification, a complex abnormality with deletion and duplication was identified in one patient: this is the first case of such recombination of the SLC2A1 gene. Changes in regulatory sequences in the promoter region or genes other than SLC2A1 might be responsible for onset of Glut1-DS in the other four patients (33%) without SLC2A1 mutation.