2 NOVEL MISSENSE MUTATIONS IN THE CYSTATHIONINE BETA-SYNTHASE GENE IN HOMOCYSTINURIC PATIENTS

Direct sequencing of the coding region of the cystathionine beta-synthase (CBS) gene in two homocystinuric patients revealed the presence of two novel missense mutations. The first mutation, a 1111G --> A transition, resulted in the substitution of the evolutionary conserved valine-371 by a methionine residue (V371M) and created a new NlaIII restriction site. The second mutation, a G --> A transition at base-pair 494, resulted in an amino acid change from cysteine to tyrosine (C165Y) and abolished a BsoFI restriction site. Both mutations were found in a compound heterozygous state with the previously described 833T --> C transition.