Identification of thyroid transcription factor-1 in C cells and parathyroid cells.

We have identified thyroid transcription factor-1 (TTF-1) mRNA in parafollicular C cells of the adult rat thyroid and in parathyroid cells; in each case the signal is stronger than in the thyrocytes themselves. We additionally identify TTF-1 RNA in other adult rat tissues not previously recognized to contain TTF-1 in developmental or knockout studies: basal layer cells of flattened squamous epithelium in skin and esophagus, three layers of the retina, i.e. pigmented epithelium, inner granular layer, and ganglion cell layer, and three areas of the brain, i.e. anterior pituitary, cerebellum, and hippocampus. Based on the array of cells that are shown to contain TTF-1 in this report, we speculate that TTF-1 may have a role in the regulation of genes important in calcium homeostasis in the intact organism as well as different tissues.