SHH and Alzheimer disease: Although we found no significant differences in expression of SHH, IHH, or DHH, mean expression levels of key components of the pathway, including the nonredundant signal transducer SMO and the Hh coreceptors CDO and GAS1, were lower in nonlesional skin from AD patients than in skin from healthy controls (Figure 8G), suggesting that baseline levels of Hh signaling are indeed lower in humans who suffer from AD.