The question of whether gangliosides were essential for humans or whether other glycoconjugates might function in their place was initially answered with identification of an infantile-onset symptomatic epilepsy syndrome caused by a homozygous loss-of-function mutation in the gene encoding GM3 synthase (ST3GAL5) needed for synthesis of the more complex sialylated CNS gangliosides [8]. Here, ST3GAL5 is linked to epilepsy syndrome.