Identification of MAL gene splicing isoforms in oral squamous epithelium. (A) Structure of the human MAL gene and PCR primers used to determine expression of MAL variants. The MAL gene has four exons and encodes four major transcripts, namely, full-length isoform a and isoform b which lacks exon 3, isoform c which lacks exon 2, and isoform d which lacks exon 2 and exon 3. Primers MAL-98F and MAL-472R were used to discriminate four variants, namely, a, b, c, and d. (B) Expression of alternatively spliced MAL isoforms in 10 cases of normal oral squamous epithelium using semi-quantitative RT-PCR analysis. β-actin was amplified as a control.