Endocrine Abstracts

The transcription factor Sox9 is a member of the HMG-box-DNA binding family essential for chondrocyte differentiation, sexual determination, and the maintenance of the stem/progenitor cells in several tissues. Furthermore, Sox9 is involved in the development of endoderm-derived-organs. Owing to the endodermic origin of the thyroid, we proposed to study the expression of Sox9 in thyroid follicular cells and its regulation by TSH and TGFβ, two main factors involved in thyroid function. In addition the role of thyroid transcription factors Nkx2-1, FoxE1, and Pax8 was studied. Sox9 mRNA, protein levels and promoter activity were determined by RT-qPCR, western blot, and transient transfection assays after TSH and TGFβ treatment. Forskolin and H89 were used to study the cAMP/PKA pathway. Co-transfections in Hela cells were performed to elucidate the role of the different transcription factors in the regulation of Sox9 as well as its role over other thyroid specific genes. We showed that Sox9 is expressed in thyroid cells and TSH induced the mRNA, protein levels and promoter activity, while TGFβ inhibited the TSH induction. The TSH effect takes place through cAMP/PKA pathway as forskolin mimics its effects and the PKA inhibitor H89 inhibited it. The in silico analysis of Sox9 promoter reveals the presence of CRE, Smad and thyroid transcription factors binding sites. The results obtained have demonstrated that Sox9 promoter is activated by Pax8 and CREB and inhibited by FoxE1. Interestingly, Sox9 activates FoxE1 promoter while inhibited Nkx2-1 and Pax8 ones. These results demonstrate the involvement of Sox9 in the physiology of the thyroid, something hitherto unknown. In addition our results open a new field to study the role of Sox9 in the development and differentiation of the thyroid gland.

Disclosure: SAF2013-44709R from Ministerio de Economia y Competitividad S2011/BMD-2328-Tironet from the Comunidad de Madrid.