Inducible overexpression of porcine homeobox A10 in the endometrium of transgenic mice

Homeobox A10 （HOXA 10） is a well-known transcription factor that plays an important role in directing endometrial differ- entiation and establishing the conditions required for implantation. Interestingly, the expression level of HOXAIO may be associated with litter size. To study the effects of the porcine HOXAIO promoter fragment on the expression of HOXAIO gene in vivo, we generated a transgenic mouse model using pronuclear microinjection, and measured the expression of HOXAIO in the endometrium. There was no difference in the expression level of HOXAIO between transgenic and wild- type mice in the absence of hormone stimulation. However, following treatment with progesterone and estradiol benzoate, the expression level of HOXAIO was significantly increased in transgenic mice compared with that of wild-type mice. Fur- thermore, the litter size of transgenic females was larger than that of wild-type females （7.02±1.73 vs. 6.48＋1.85; P=0.14）. Moreover, the difference of litter size was greater in the later parities （7.33±1.62 vs. 6.37±2.02; P=0.08） compared with the first parity （6.76±1.81 vs. 6.61v1.67; P=0.77） between transgenic and wild-type mice. Therefore, our transgenic mouse model provides exciting insights regarding the actions of HOXAIO and its hormone-inducible promoter in vivo. The present study offers valuable proof of principle to develop transgenic pigs with a hormone-inducible promoter regulating HOXAIO to alter litter size.

Production of homeobox A10 gene transgenic pigs by somatic cell nuclear transfer

Homeobox A10(Hoxa10) gene is one of the most important candidate genes associated with the reproductive performance of humans and mice. Overexpression of Hoxa10 in mouse endometrium can increase litter size. Moreover, Hoxa10 plays a key role in regulating the embryo implantation of sows. This study aimed to generate transgenic pigs using Hoxa10 via somatic cell nuclear transfer(SCNT). We established seven Hoxa10-transgenic cell lines, and two of the cell lines were selected as nuclear donors for the transfer. A total of 1 270 cloned embryos were generated and transferred to five surrogate mothers(Landrace×Yorkshire). Eight cloned male piglets were produced including one with cryptorchidism. Six transgenic piglets grew up healthy and produced 56 offspring. Finally, we obtained six transgenic male pigs and 26 transgenic positive offspring that can be used to further study the regulatory mechanism of Hoxa10 on the reproductive performance of pigs.