Expression of Skn-1a and Trpm5 in the MOE of Mash1-/-embryos. Expression of Skn-1a and Trpm5 in the Mash1-/- MOE was examined by in situ hybridization at embryonic day 18.5. The MOE of Mash1-/- embryos appeared smaller and thinner than that of wild-type littermates, as observed previously. Expression of either Skn-1a or Trpm5 was observed in both the wild-type and Mash1-/- MOE. Higher-magnification images of the dotted boxes are presented to the right of each image. Scale bars, 100 μm.