ATOH1 and Alzheimer disease: To express Aβ or its truncated or mutated forms in mouse cochlear hair cells, we established Tg mouse lines carrying an expression vector for Aβ, a truncated form of Aβ (Aβ42), or Aβ with a familial AD mutation (Aβ42Arc, E22G substitution) downstream of the minimal enhancer region of mouse Math1 (Math1E), which drives gene expression in many types of sensory neurons including cochlear hair cells [24] (Fig. 1A).