Expression of nk2.1a during early development of the thyroid gland in zebrafish

We show here that a zebrafish orthologue of the Thyroid Transcription Facto r-1 (TTF-1), nk2.1a, is expressed in the developing thyroid gland. Using a fate mapping approach we found that an early nk2.1a expression domain in th e endoderm adjacent to the heart follows morphogenetic movements of the low er jaw, ending up in the region in which the mature thyroid gland is locate d. We therefore suggest that nk2.1a labels the thyroid precursor cells from somitogenesis stages onwards. (C) 2000 Elsevier Science Ireland Ltd. All r ights reserved.