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

Homeobox A10 (HOXA10) is a well-known transcription factor that plays an important role in directing endometrial differentiation and establishing the conditions required for implantation. Interestingly, the expression level of HOXA10 may be associated with litter size. To study the effects of the porcine HOXA10 promoter fragment on the expression of HOXA10 gene in vivo, we generated a transgenic mouse model using pronuclear microinjection, and measured the expression of HOXA10 in the endometrium. There was no difference in the expression level of HOXA10 between transgenic and wild-type mice in the absence of hormone stimulation. However, following treatment with progesterone and estradiol benzoate, the expression level of HOXA10 was significantly increased in transgenic mice compared with that of wild-type mice. Furthermore, 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. 6.61±1.67; P=0.77) between transgenic and wild-type mice. Therefore, our transgenic mouse model provides exciting insights regarding the actions of HOXA10 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 HOXA10 to alter litter size.