SCCs are present to a different extent in the lower airways of TrpM5- and Tas1R3-GFP mice. A. Micrograph of whole-mounted larynx and trachea opened laterally to show the distribution of the SCC cells (exhibiting green TrpM5-driven GFP fluorescence). Some SCCs are present in the hypoglossal portion of the larynx just below the arytenoids. Numerous TrpM5 GFP+ SCCs are present throughout the length of the trachea although at a lower density in the bronchi. L1, L2, L3, L4 refer to the levels of the micrographs of panels B-K of this figure. L1 = hypoglottis, L2 = proximal trachea, L3 = distal trachea, L4 = bronchi. B-I. Whole mount en face views of epithelium from different levels of the trachea in the two transgenic lines, TrpM5-GFP and Tas1R3-GFP B. & C. SCCs in the hypoglossal region. D. - G. Numerous SCCs are present in the proximal (L2) and distal (L3) portions of the trachea in the TrpM5-GFP line, while fewer are evident in the Tas1R3-GFP line. H. & I. SCCs are still evident in the bronchi of the TrpM5-GFP mouse while virtually none express Tas1R3-driven GFP. J & K. Tissue section through the lung showing SCCs in bronchioles of more than 400 ± 100 μm in diameter (I), but none in smaller bronchioles or alveoli. J. Green channel fluorescent image. K. Identical image field showing a Normarski image along with the fluorescence image. An SCC is indicated by a blue arrow in panel K. BV = blood vessel, LP = lung parenchyma, Bro = bronchioles.