HOXB6 and Alzheimer disease: In blood samples from patients with AD and the control subjects, as well as in individuals with MCI, elevated levels of DNA methylation in the homeobox cluster A (HOXA) and homeobox B6 (HOXB6) regions were found to correlate with neuropathology (Figure 2), highlighting the role of epigenetic variations within the homeobox gene family as a potential AD target for future research [138,139].