|DESAULNIERS, AMY - University Of Nebraska|
|CEDERBERG, REBECCA - University Of Nebraska|
|MILLS, GINGER - University Of Nebraska|
|WHITE, BRETT - University Of Nebraska|
Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2017
Publication Date: 8/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5747463
Citation: Desaulniers, A.T., Cederberg, R.A., Mills, G.A., Lents, C.A., White, B.R. 2017. Production of a gonadotropin-releasing hormone 2 receptor knockdown (GnRHR2 KD) swine line. Transgenic Research. 26:567-575. doi:10.1007/s11248-017-0023-4.
Interpretive Summary: An estimated 30 million doses of boar semen are needed every year to artificially inseminate commercial sows. Many boars, however, have poor fertility, which results in a critical need to understand testicular function and develop methods to improve semen production and quality. ARS scientists, in collaboration with researchers from the University of Nebraska, discovered pigs are the only livestock species that produce a hormone called Gonadotropin-releasing hormone 2 (GnRH2) and that the GnRH2 receptor is present in the testes of boars. To understand the role of GnRH2 in regulating reproductive function of boars, Researchers developed a line of pigs in which the expression of the GnRH2 receptor was attenuated or “knocked-down” (KD) by using a small molecule called a hairpin RNA. Reduced expression of GnRH2 receptor made pigs less responsive to the GnRH2 hormone, which caused pigs to develop smaller testes that secreted less testosterone. Researchers are now focused on how to use this information about GnRH2 to improve testicular development and reproductive function of boars.
Technical Abstract: Swine are the only livestock species that produce both the second mammalian isoform of gonadotropin-releasing hormone (GnRH2) and its receptor (GnRHR2). Previously, we reported that GnRH2 and GnRHR2 mediate LH-independent testosterone secretion from porcine testes. To further explore this ligand-receptor complex, a pig model with reduced GNRHR2 expression was developed. Small hairpin RNA sequences targeting porcine GNRHR2 were subcloned into a lentiviral-based vector, lentiviral particles were generated and microinjected into pronuclear zygotes, and embryos were transferred into a recipient. One GnRHR2 knockdown (KD) female was born that subsequently produced 80 piglets from 6 litters with 46 hemizygous progeny (57% transgenic). GnRHR2 KD (n = 10) and littermate control (n = 7) males were monitored at 40, 100, 150, 190, 225 and 300 d of age; body weight and testis size were measured and serum was isolated and assayed for testosterone and luteinizing hormone (LH) concentrations. Body weight of GnRHR2 KD boars was not different from littermate controls (P = 0.14), but testes were smaller (P < 0.05; 331.8 vs. 374.8 cm3, respectively). Testosterone concentrations tended (P = 0.06) to be reduced in GnRHR2 KD (1.6 ng/ml) compared to littermate control (4.2 ng/ml) males, but LH levels were similar (P = 0.47). The abundance of GNRHR2 mRNA was reduced (P < 0.001) by 69% in testicular tissue from mature GnRHR2 KD (n = 5) versus littermate control (n = 4) animals. These swine represent the first genetically-engineered model to elucidate the function of GnRH2 and its receptor in mammals.