While many studies have shown altered expression levels of BDNF in AD patients and AD mouse models at older ages, we did not observe any significant difference in the mRNA expression level of BDNF at 2 months of age, raising the possibility that alterations in BDNF mRNA levels during progression of AD pathology may be through indirect mechanisms rather than by the direct effects of APPswe/PS1ΔE9 mutant expression, or that alterations in BDNF expression are pronounced at a later stage (Figure 3A). The gene discussed is BDNF; the disease is Alzheimer disease.