A, Brn3bAP positive deep vibrissal (arrow) and intervibrissal (arrow head) fibers in the mystacial pad are visible as early as E13.5. B1, Brn3bAP positive deep vibrissal (arrow) and intervibrissal (arrow head) as well as general sensory fibers (B2) innervating the lips of E15.5 embryo. C1, Extensive overlap of Brn3b and Isl1 in E12.5 embryos. C2, Brn3bAP positive TGG cells in ROSA26rtTACreERt; Brn3bCKOAP/WT E12.5 mice. D, Sagittal section of a E15.5 cRetCFP/WT maxillary (lines) and mandibular territories (doted lines) of TGG. Insets show combinatorial expression of Brn3b, Isl1, and cRet. E, Box whisker plot for cell populations of E15.5 TGG (D). Scale bars: A,B1,B2,C2,D=100μm, C1=50μm