Dr. Johnston obtained a PhD in Molecular Systems Pharmacology at Emory University.  As a PhD student, Dr. Johnston analyzed several components of an integrating lentiviral viral vector in order to delineate an optimal transfer vehicle for the delivery of nucleic acids into hematopoietic stem and progenitor cells.  This work yielded a lentiviral vector that became approved by the Recombinant Advisory Committee for potential future gene therapy clinical trials.  Upon graduation, Dr. Johnston continued to pursue gene therapy strategies for blood disorders as a postdoctoral fellow at Stanford University.  However, instead of utilizing a lentiviral vector as a transfer vehicle for transgenes, Dr. Johnston explored the use of transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeat (CRISPR) technology to target transgenes to defined locations in the genome.  For the expression of transgenes not endogenously expressed by the hematopoietic system,  gene addition would need to occur at genomic safe harbors. Yet, she determined that a location can only truly be considered safe if gene disruption does not occur.  Therefore, Dr. Johnston developed an innovative pharmacological strategy that can convert essentially any transcriptionally active genomic location into a safe harbor locus.