FCER1A gene exon 1A polymorphisms in Japanese and Polish subjects--a comparative analysis of haplotypes

Genetic variability of the high-affinity IgE receptor alpha-subunit (FcepsilonRIalpha)

Our knowledge on the variability of FCER1A gene encoding for alpha-subunit of the high-affinity immunoglobulin E receptor (FcepsilonRI) that plays a central role in the pathogenesis of allergy and related disorders, has been recently much extended. Last findings from FCER1A mutational screening and genetic association studies, followed by functional analyses of the polymorphisms, are briefly summarized in this mini-review. The association between FCER1A gene variants and total serum IgE levels seems especially interesting and, supported by functional analyses of polymorphisms, may provide a rationale for pharmacogenetic studies on anti-IgE therapy that indirectly suppresses FcepsilonRI expression.

FcepsilonRIalpha gene -18483A>C polymorphism affects transcriptional activity through YY1 binding

Three frequent genetic polymorphisms in the human high-affinity IgE receptor alpha-subunit (FcepsilonRIalpha) were shown to be associated with allergic disorders and/or total serum IgE levels in allergic patients. Two of these were previously demonstrated to affect FcepsilonRIalpha expression while the third -18483A>C (rs2494262) has not yet been subjected to functional studies. We hypothesized that the -18483A>C variant affects transcriptional activity of the FcepsilonRIalpha distal promoter in monocytes in which FcepsilonRIalpha transcription is driven through that regulatory region. Indeed, we confirmed preferential binding of the YY1 transcription factor to the -18483C allele, resulting in lower transcriptional activity when compared with the -18483A allele.

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.