Xu's research focuses on two major mechanisms that are thought to maintain genetic stability in human embryonic stem cells. His research is aimed at identifying pathways that promote efficient DNA repair as well as pathways that regulate self-renewing capabilities of these stem cells in the absence and presence of DNA damage. The goal is to promote efficient self-renewal of human embryonic stem cells with minimum genetic instability - critical for the development of human therapeutics. A major objective of Xu's proposed research is to improve the genetic manipulation technologies of human embryonic stem cells, including transgenic and gene-targeting technologies, in order to significantly improve scientists' capability to generate disease-specific human stem cell lines.