Type A spermatogonial stem cells are the only immortal diploid cells in the postnatal animal that undergo self-renewal through the lifetime of an animal and transmit genes to subsequent generations. In this paper, the generation and characterization of double-transgenic mice co-expressing the Escherichia coli appA gene and human MxA gene generated via the in vivo transfection of type A spermatogonial cells were reported for the ifrst time. The dicistronic expression vector pcDNA-appA-MxA（AMP） and ExGen500 transfection reagent were injected into the testicular tissue of 7-d-old male ICR mice. The mice that underwent testis-mediated gene transfer were mated with wild-type female mice, and the integration and expression of the foreign genes in the offspring were evaluated. Transgenic mice that co-expressed appA and MxA showed a gene integration rate of 8.89%（16/180）. The transgenic mice were environmentally friendly, as the amount of phosphorous remaining in the manure was reduced by as much as 11.1%by the appA gene （P〈0.05）;these animals also exhibited a strong anti-viral phenotype.
BAI Li-jingJU Hui-mingMU Yu-lianYANG Shu-linREN Hong-yanAO HongWANG Chu-duanLI Kui
Growth hormone （GH） is a polypeptide hormone secreted by the pituitary, which promotes animal growth, muscle development, metabolism regulation and other important physiological functions. In this study, a pair of mGH short hairpin RNA （shRNA） was designed according to mouse （ Mus musculus） GH mRNA sequence; pSingle-tTS-mGH shRNA-RFP, an integrated controllable expression vector of mGH shRNA, was constructed successfully. The recombinant vector was transfected into mouse pituitary tumor cell line AtT-20. After addition of doxycyelin （ DOX）, the expression of red fluorescent protein （RFP） was observed un- der a fluorescent microscope. The expression level of mGH in cells was detected by quantitative Realtime PCR （qRT-PCR） and Western blot. After DOX induction, the relative expression level of GH mRNA in cells transfected with GH shRNA was reduced by about 70% compared with that in DOX-free group and other control groups, exhibiting extremely significant differences （P 〈 0.01 ） ; moreover, the relative expression level of GH protein was reduced by about 90% ; the expression level of GH mRNA and GH protein exhibited no significant difference among other groups （P 〉 0.05）. In this study, a controllable expression vector of GH shRNA with high gene silencing efficiency was constructed successfully, which could be used to reveal GH autocfine / paracrine interactions and analyze functions of GH gene in growth, development and disease occurrence of animals by regulating GH expression levels.
