Characterization of cystathionine beta-synthase gene mutations in homocystinuric Venezuelan patients: identification of one novel mutation in exon 6

Abstract

This study describes for the first time the cystathionine beta-synthase (CBS) gene mutations in Venezuelan patients. A total of five disease-causing mutations were identified in 9 out of 10 independent chromosomes. Four of the mutations have been previously described (G85R, T191M, D234N, and D444N) and a novel mutation was found (Q243X). Two common polymorphisms (699C/T and 1080C/T) were found in the CBS gene. Mutation analysis was performed using a combined screening approach for CBS mutations: restriction analysis, single-strand conformational polymorphism (SSCP) scanning, and sequencing. All the mutations were detected in homozygous state, except for Q243X, detected in three heterozygous siblings. Each one of the patients studied presented a different mutation. All mutations and polymorphisms detected involved hypermutable CpG sites, except for the novel mutation Q243X. The most common mutations I278T and G307S were not found in any of the patients. The CBS mutations present in each country differ from each other depending on the demographic profile; therefore, specific mutations scanning must be performed in each population for diagnosis and prognosis purposes.