Factors determining the risk of inadvertent retroviral transduction of male germ cells after in utero gene transfer in sheep

Paul J. Park, Evan Colletti, Ferhat Ozturk, Joshua Wood, Joe Tellez, Graça Almeida-Porada, Christopher D. Porada

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The possibility of permanent genetic changes to the germline is central to the bioethics of in utero gene therapy (IUGT) because of the concern of inadvertent potentially deleterious alterations to the gene pool. Despite presumed protection of the male germline due to early germ cell (GC) compartmentalization, we reported that GCs within the developing ovine testes are transduced at low levels after retrovirus-mediated IUGT, thus underscoring the need for a thorough understanding of GC development in clinically predictive models to determine the optimal time to perform IUGT and avoid germline modification. In the present studies, we used the fetal sheep model to analyze GCs for phenotype, location, proliferation, and incidence of transduction after IUGT at various fetal ages to learn when during development the nascent germline is likely to be at greatest risk of retrovirus-mediated alteration. Our studies show that although GCs were transduced at all injection ages, the levels of transduction varied by nearly 700-fold as a function of the age at transfer. After remaining largely quiescent as they migrated to/settled within nascent sex cords, GCs began active cycling before cord closure was complete, suggesting this is likely the point at which they would be most susceptible to retroviral transduction. Furthermore, we observed that compartmentalization of GCs continued into early postnatal life, suggesting the male germline may be vulnerable to low-level inadvertent retroviral vector modification throughout fetal life, but that this risk can be minimized by performing IUGT later in gestation.

Original languageEnglish (US)
Pages (from-to)201-215
Number of pages15
JournalHuman Gene Therapy
Issue number3
StatePublished - Mar 1 2009
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Medicine
  • Molecular Biology
  • Genetics


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