Subsequent cleavage of the latter fragment (between residues 38 and 43) by the γ-secretase complex results in the formation of Aβ species, which contain 40–42 amino acids, and the APP intracellular domain (AICD), whose ability to modulate gene expression, apoptosis, and cytoskeletal dynamics has also been linked to AD [18]. This evidence concerns the gene APP and Alzheimer disease.