Novel human PDGFA gene transcripts derived by alternative mRNA splicing

The polymerase chain reaction (PCR) has been used to amplify sequences coding for the platelet-derived growth factor A chain (PDGFA) using mRNA populations derived from two transformed cell lines (a human osteosarcoma, U-2OS, and a human glioma, U-343) and from human umbilical vein cells. The primers used for PCR were designed to amplify both of the two transcripts previously reported for the PDGFA gene. These transcripts differ from each other by the presence or absence of sequences from a sixth exon located near the 3' end of the gene. The PCR procedure revealed not only these expected transcripts, but additional RNAs that were shown by cloning and sequencing to lack exon 2. These species were present at variable levels in the three cell types examined. We propose that this novel splicing pattern, generating mRNAs encoding truncated and non-functional polypeptides, signals an additional, post-transcriptional mechanism for modulation of PDGFA gene expression.