Nature Genetics
34, 297 - 302 (2003)
Published online: 1 June 2003; | doi:10.1038/ng1179
AAV serotype 2 vectors preferentially integrate into active genes in miceHiroyuki Nakai1, Eugenio Montini2, 4, Sally Fuess1, Theresa A Storm1, Markus Grompe2, 3
& Mark A Kay11
Departments of Pediatrics and Genetics, Stanford University School of Medicine, 300 Pasteur Dr. Rm G305A, Stanford, California 94305, USA. 2
Departments of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon 97201, USA. 3
Department of Pediatrics, Oregon Health & Science University, Portland, Oregon 97201, USA. 4
Present address: Instituto per la cura e la ricerca del Cancro, Candiolo, Torino 10060, Italy.
Correspondence should be addressed to Mark A Kay markay@stanford.eduRecombinant adeno-associated virus serotype 2 (rAAV2) is a promising vector for gene therapy because it can achieve long-term stable transgene expression in animals and human subjects after direct administration of vectors into various target tissues1. In the liver, although stable transgene expression primarily results from extrachromosomal vector genomes2, a series of experiments has shown that vector genomes integrate into host chromosomes in hepatocytes3,
4,
5 at a low frequency2. Despite the low integration efficiency, recent reports of retroviral insertional mutagenesis in mice6 and two human subjects7,
8 have raised concerns about the potential for rAAV2-mediated insertional mutagenesis. Here we characterize rAAV2-targeted chromosomal integration sites isolated from selected or non-selected hepatocytes in vector-injected mouse livers. We document frequent chromosomal deletions of up to 2 kb at integration sites (14 of 14 integrations, 100%; most of the deletions were <0.3 kb) and preferred integration into genes (21 of 29 integrations, 72%). In addition, all of the targeted genes analyzed (20 of 20 targeted genes, 100%) were expressed in the liver. This is the first report to our knowledge on host chromosomal effects of rAAV2 integration in animals, and it provides insights into the nature of rAAV2 vector integration into chromosomes in quiescent somatic cells in animals and human subjects.
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