Precise alteration of the DNA sequence of vertebrate genomes is an important technique for experimental analysis and disease treatment. However, to precisely alter a single nucleotide given some 3 x 10 choices is no small task. Fortunately there are precise cellular mechanisms designed to carry out such modifications and these pathways can be manipulated to favor the changes we wish to make, for studying disease mechanisms, or treatment of genetic diseases. A key hurdle for accomplishing gene targeting efficiently in primary cells has been the delivery of sufficient quantities of template DNA that can be incorporated at the target site by homologous recombination pathways. Adeno-Associated Virus (AAV) is a single stranded DNA virus that can be modified to package and efficiently deliver gene targeting templates to the nucleus of cells. We’re interested in ways to improve the efficiency of recombination once the templates reach the nucleus, and in vector modifications that reduce background integration events, and that allow targeting of non-expressed genes. Source.