Ž . Biochimica et Biophysica Acta 1354 1997 171–181 Transfection of TTF-1 gene induces thyroglobulin gene expression in undifferentiated FRT cells Anna Mascia a , Mario De Felice b , Concetta Lipardi a , Raffaele Gentile a , Gaetano Calı a , ` Mariastella Zannini a , Roberto Di Lauro a,b , Lucio Nitsch a, ) a Centro di Endocrinologia ed Oncologia Sperimentale del CNR – Dipartimento di Biologia e Patologia Cellulare e Molecolare, UniÕersita degli Studi di Napoli ‘Federico II’, Via Pansini 5, 80131 Naples, Italy ` b Stazione Zoologica ‘ Anton Dohrn’, Villa Comunale, 80121 Naples, Italy Received 25 June 1997; accepted 3 July 1997 Abstract The thyroglobulin gene, the substrate for thyroid hormone biosynthesis, is not expressed in the FRT cell line, which, even though it manifests the polarised epithelial phenotype, does not express any of the thyroid functional properties. Two transcription factors, TTF-1 and Pax-8, have been implicated in thyroid specific expression of the thyroglobulin gene. FRT cells contain Pax-8 but they lack TTF-1. In this paper, we show that transfection of TTF-1 expression vectors in FRT cells results in activation of thyroglobulin gene expression. If the expression vector encoded for TTF-1–ER, a fusion gene coding for the entire TTF-1 protein fused to the hormone-binding domain of the steroid receptor, under the control of the RSV promoter, thyroglobulin gene expression was controlled by estrogen. These data provide a direct demonstration that TTF-1 activates the chromosomal thyroglobulin promoter. Since transfection of TTF-1 expression vectors in non-thyroid cell types did not result in thyroglobulin gene expression, it is suggested that Pax-8, in addition, perhaps, to a specific cellular environment, might be required for thyroid specific expression of the thyroglobulin gene. q 1997 Elsevier Science B.V. Keywords: TTF-1; Thyroglobulin; FRT cell; Transfection; Transcription factor 1. Introduction The determination and maintenance of the differ- entiated phenotype appears to be mainly under the control of a combination of transacting factors which are able to promote the transcription of tissue specific w x genes 1,2 . In thyroid follicular cells three tissue specific transactivators have been described: TTF-1, w x TTF-2 and Pax-8 3–7 . These factors, in concert ) Corresponding author: Fax: q39-81-7701016; E-mail: nitsch@cds.unina.it with ubiquitous factors, regulate the transcriptional Ž . activity of thyroglobulin Tg and other thyroid- wx specific genes 8 . TTF-1 is a 42 kDa, homeodomain containing pro- tein that plays a pivotal role in thyroid gland develop- wx ment 9 and in the activation of the Tg gene pro- w x moter 4,10 . TTF-1 also binds to and activates the promoters of other thyroid-specific genes such as w x thyrotropin receptor 11,12 and, to less extent, thy- w x roperoxidase 13 . The presence of TTF-1 protein is w x essential for the expression of the Tg gene 4,14 but its presence does not always correlate with active Tg 0167-4781r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved. Ž . PII S0167-4781 97 00127-9