An important use for stem cells is the creation of cellular models of human development and disease, critical for uncovering the
molecular roots of illness and testing new drugs. However, a major limitation in achieving these goals is the difficulty in manipulating
human stem cells. We have developed a method of genetically modifying mouse embryonic stem cells that is more efficient than
traditional methods. We took advantage of new methods using the CRISPR/Cas9 system to
develop novel approaches to modifying human embryonic stem cells. We have also created reversible gene trap mutations in a
diversity of human embryonic stem cell genes that can be used to better harness human embryonic stem cells for modeling, or even
treating, human diseases.