Characterization of seven novel mutations in seven patients with GAMT deficiency.

Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive error of creatine synthesis characterized by cerebral creatine deficiency, accumulation of guanidinoacetate, mental retardation, epilepsy and extrapyramidal signs. So far, six mutations have been identified in seven patients. We investigated seven new patients by screening the promoter, 3'UTR, and six exons and exon/intron boundaries using direct sequencing and denaturing gradient gel electrophoresis.