1 Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center, The University of Southern California, Los Angeles, CA, USA; Division of Molecular and Computational Biology, Department of Biological Sciences, Dornsife College of Letters, Arts, & Sciences, The University of Southern California, Los Angeles, CA, USA; Department of Biochemistry & Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA. Electronic address: kelvin@usc.edu.