Novel alpha-fetoprotein-V messenger RNA isoforms in humans.

It has been demonstrated that several messenger RNA (mRNA) isoforms have been transcribed from the alpha-fetoprotein (AFP) gene. In rats, it was reported that the novel exon, termed the exon V, exists between the exons 7 and 8, and the novel mRNA isoform (termed AFP-V mRNA) is synthesized using the exon V. In this study, a reverse transcription-polymerase chain reaction was performed and quantitative analysis was done on the AFP mRNA to identify the exon V and the AFP-V mRNA in humans. As a result, 2 novel exons, the exons VA and VB, were identified. Furthermore, 3 novel AFP mRNAs, the AFP-V1, -V2, and -V3 mRNA, were demonstrated to be expressed through alternative splicing. Expression of the AFP-V2 mRNA isoform and the wild-type mRNA was differentially regulated, implying that the AFP-V mRNA isoforms could be used in diagnosis and classification of hepatocellular carcinoma and ovarian carcinoma.