City of Hope's Yanhong Shi, Ph.D., and her colleagues engineered healthy human skin cells containing the functional aspartoacylase (ASPA) gene into induced pluripotent stem cells (iPSCs) and then differentiated the iPSCs into oligodendroglial progenitor cells, the precursor cells that produce myelin, an insulating sheath that wraps around nerve fibers. Like a bullet train, myelin sheaths facilitate the light-speed transport of information along neuronal axons.