Single-stranded conformation polymorphism (SSCP)-driven indirect sequencing in detection of short deletion

To seek for novel rare and/or sporadic mutations within genomic neighborhood of common -344 C>T (rs2427827) FCER1A proximal promoter polymorphism, which by its prevalence could have masked the presence of less frequent genetic variants in our previous single-stranded conformational polymorphism (SSCP) mutational search study, SSCP screening was repeated using primers fixing -344 C>T variant. The genomic region surrounding -344 C>T polymorphism was confirmed to be fairly conservative and only a single sporadic mutation (present in 1 out of 196 chromosomes), a 6-bp deletion -262 to 257 del CTAGAC, was found. From the methodological point of view, we demonstrated a successful detection of a short-length polymorphism using SSCP screening in a population, in which the same genomic region contained frequent single-nucleotide polymorphic variant. In conjunction with subsequent cloning of aberrantly migrating PCR products and SSCP-driven indirect sequencing of the clones, this method offers a superior (to direct sequencing of PCR products) detection of rare mutations. The cost-effective method applied by us enables a reliable characterization of infrequent (thus present only in heterozygotic form) short-length variance of the sequence which are difficult to interpret by direct sequencing.