A 50% reduction of Fyn expression (Figure 7A,C) was sufficient to reverse the increase in pFyn-Tyr420, pAPP-Tyr compared with corresponding unsilenced controls (31F vs. siFyn #31F; 38F vs. siFyn 38F; 53M vs. siFyn #53M; Figure 7B,D) suggesting that Fyn is involved in the increase in pAPP-Tyr in these AD neurons. The gene discussed is FYN; the disease is Alzheimer disease.