TTF‐2, a new forkhead protein, shows a temporal expression in the developing thyroid which is consistent with a role controlling the onset of differentiation

In this paper the cloning of a cDNA encoding a forkhead containing transcription factor, denominated TTF-2, was reported. In Figure 8 we showed the expression of TTF-2 in the developing thyroid at embryonic days (E) 13.5 and 15, demonstrating a down-regulation of TTF-2 expression at E15 (panel D). In repeating these experiments with a novel TTF-2 probe that gives a stronger signal and that includes the sequence used as a probe in the original manuscript, we have been unable to con®rm such down-regulation. The ®gure below, that should substitute panel D in Figure 8 of the original manuscript, shows the hybridization signal that we now routinely obtain on sections of E15 thyroid with the new TTF-2 probe. The presence of TTF-2 in E15 thyroids has also been con®rmed with a newly developed anti-TTF-2 antibody (data not shown). Thus, TTF-2 expression in thyroid development shows no discontinuity. As a consequence, the hypothesis presented in the original manuscript proposing that the onset of differentiation correlated with disappearance of TTF-2 is no longer supported. However, all other data presented in the manuscript have been con®rmed, including the repression activity of TTF-2 (Perrone et al., 2000). Finally, the presence of TTF-2 in the developing thyroid, even if not discontinuous, has since been demonstrated to be of relevance in mice (De Felice et al. (1998) Mutation of the gene encoding human TTF-2 associated with thyroid agenesis, cleft palate and choanla atresia.A mouse model for hereditary thyroid dysgenesis and cleft palate. The thyroid transcription factor 2 (TTF-2) is a promoter-speci®c DNA-binding independent transcriptional repressor. Biochem. Fig. 8. (D) In situ hybridization on a sagittal section of mouse embryo at E15.5 using a TTF-2 speci®c probe. TTF-2 mRNA is clearly expressed in thyroid cells at this stage.