Production of Transgenic Rats and Mice by the Testis-Mediated Gene Transfer

Abstract

Recent reports have shown that sperm cells incubated with foreign DNA in vitro are able to transfer the DNA into eggs at fertilization. The present study examined if an injection of DNA into the testis in vivo could generate transgenic animals via sperm ejaculated. We prepared 3 gene constructs; human growth hormone (hGH), hGH receptor (hGHR) and mouse leptin (mOB) genes fused to the promoter regions of the mouse genes for whey acidic protein (WAP), metallothionein-I (MT) and mouse mammary tumor virus (MMTV), respectively. Each gene construct mixed with cationic liposome was injected into bilateral testes of male rats or mice, and the males mated with females 3 or 4 days later. A female rat mated with a male treated with MT/hGHR gene gave birth to 17 pups, 3 of which were found to carry the transgene. The expression of hGHR mRNA was demonstrated in the liver, kidney, muscle and brain after treating with zinc in drinking water. At present, the transmission of the exogenous gene to the descendants was confirmed up to the F₄ generation. Three female rats mated with 3 different males injected with MMTV/mOB fusion gene produced 10, 14 and 12 pups, respectively. The genome of 2 out of these 36 pups harbored MMTV-mOB gene, though expression of mOB mRNA was not detected. Two female mice were mated with 2 male mice injected with WAP/hGH gene and produced 15 and 16 pups, 3 of which incorporated the gene. The expression of hGH mRNA in the mammary gland in these mice was confirmed. These results indicate that exogenous DNA injected into the testis as a liposome-complex can be transferred into eggs via sperm and expressed in the postpartum progeny.