Novel isoforms of periostin expressed in the human thyroid

Periostin is an extracellular matrix protein. Five isoforms of human periostin cDNA have been reported, but the expression of periostin isoforms in the human thyroid tissue is by far unknown. A group of primer sets were designed to amplify the full length of cDNA sequence of periostin. Using human thyroid carcinoma and their paired non-neoplastic tissues together with anaplastic thyroid carcinoma cell lines, we examined the presence of periostin cDNA isoforms by RT-PCR and direct DNA sequence analysis. We identified eight coexisting cDNA isoforms in all the tissue samples and cell lines. Three of them were unique to this study. Especially two of them haven't been previously reported in any species. The eight periostin isoforms differ in the C-terminus from exon XII to exon XXI where alternative splicing usually happens. This is the first report that demonstrates all the eight isoforms of periostin cDNA expressed in the human thyroid gland and identifies three novel isoforms.