SPERM-MEDIATED GENE-TRANSFER IN MICE

Sperm-mediated DNA transfer to offspring has the potential to markedly simplify the generation of transgenic animals, but the efficiency in mice has been controversial. To determine the basis of the variability of the procedure in mice, we undertook a large, collaborative study o f sperm-mediated DNA transfer to mouse eggs in well-established labora tory conditions for in vitro fertilization and offspring development f ollowing embryo transfer. Sperm were incubated with plasmid DNA during the capacitation period and then added to freshly ovulated mouse oocy tes for fertilization; cleaved embryos were then transferred to the ov iducts of pseudopregnant recipients for gestation. From a total of 75 experiments, 13 produced 130 transgenic offspring, amounting to 7.4% o f total fetuses. In five experiments, more than 85% of offspring were transgenic, but the factors leading to this high success rate were not discovered. Clustering of such a low frequency event could account fo r the disparate reports of transgenic success with sperm-mediated DNA transfer to mouse offspring. Discovering the factors important to succ ess would not only allow this simplified approach to become an importa nt tool in the generation of transgenic mice, but could also lead to i mportant insights into natural protective mechanisms against sperm-med iated transfer of foreign DNA. Mol. Reprod. Dev. 50.406-409, 1998. (C) 1998 Wiley-Liss, Inc.