T gene isoform expression pattern is significantly different between chordomas and notochords.

The T gene plays a key role in chordoma pathology. To investigate the role of T gene isoforms in chordoma, 22 skull base chordomas, three chordoma cell lines and 9 infant notochords, which were used as normal controls, were collected. We first conducted droplet digital PCR to quantify the absolute expression levels of the long and short isoforms of the T gene (T-long and T-short, respectively) and revealed that T-long was dominantly expressed in all chordomas and chordoma cell lines, but not in the notochords. The T-long/T-short ratio was significantly different between the chordomas and the notochords. Next, we validated the isoform expression pattern at protein expression level using Western blot in 9 chordomas. Furthermore, the T gene single nucleotide polymorphism site rs2305089, which is the only marker reported to be associated with chordomas, was sequenced in all of the chordoma samples. Association between rs2305089 and T-long/T-short ratio was not significant, indicating it was not involved in T gene alternative splicing. In conclusion, two T gene isoforms were investigated in skull base chordomas and chordoma cell lines, and the longer isoform was dominantly expressed. The distinct expression patterns of these T gene isoforms may contribute to the pathogenesis of skull base chordomas. However, further studies on the function of these isoforms are needed.