Chemical mismatch cleavage combined with capillary electrophoresis: detection of mutations in exon 8 of the cystathionine ß-synthase gene

Department of Pharmacology, University of Bergen, Armauer Hansens Hus, 5021 Bergen, Norway.
^a Author for correspondence. Fax 47-55-974605; e-mail Jicun.Ren{at}farm.uib.no.

Mutation detection by chemical mismatch cleavage (CMC) is based on the chemical modification and cleavage at the site of mismatched C or T in heteroduplexes, using hydroxylamine or osmium tetroxide (OsO₄) as chemical probes. In the present study, we evaluated CMC in combination with capillary electrophoresis (CE) by determining the common T833C and G919A mutations in exon 8 of the cystathionine ß-synthase gene in heterozygous and homozygous samples. A 186-bp fragment encompassing exon 8 was amplified by PCR with both primers labeled with 5'-fluorescein. Labeled single strands of 40 and 61 nucleotides (nt) were formed from the coding strand of the T833C sample and non-coding strand from the G919A sample, respectively. These single-stranded DNA (ssDNA) products were analyzed under denaturing conditions by CE with short-chain linear polyacrylamide as the sieving matrix and were detected by laser-induced fluorescence (LIF), using a sensitive, one-channel sheath-flow detector. The CE-LIF format afforded relatively high resolution of ssDNA (down to 1 nt), precise size assessment of CMC products, sensitive detection with small sample requirements, and fast analysis. Thus, CMC combined with CE-LIF is suitable for screening of known mutations, giving expected CMC products, but will also detect unknown mutations, the locations of which are indicated by the fragment sizes.