We thank Dr. Martha Pyron, Mohammed Alkatan, Mandeep Dhindsa, and Tariq Thannoun for technical assistance. This study was supported in part by grants from the American Federation for Aging Research (8A0024, A.P.H.), the National Institute of Neurological Disorders and Stroke (R01NS75565, A.P.H.), and the National Institute on Aging (F31AG040890, M.M.G.).

Conflicts of interest

The authors declare that they have no conflicts of interest.