Location: Livestock Bio-SystemsTitle: Use of genetic engineering to elucidate reproductive physiology of the boar
|DESAULNIERS, AMY - University Of Central Missouri|
|CEDERBERG, REBECCA - University Of Nebraska|
|KNOX, ROB - University Of Illinois|
|WHITE, BRETT - University Of Nebraska|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/22/2019
Publication Date: 10/26/2019
Citation: Desaulniers, A., Cederberg, R., Knox, R., Lents, C.A., White, B. 2019. Use of genetic engineering to elucidate reproductive physiology of the boar. In: Missouri Physiological Society 2019 Annual Meeting Abstracts, 26Oct2019, Columbia, MO. pp. 6.
Technical Abstract: The second mammalian form of gonadotropin-releasing hormone (GnRH-II) and its cognate receptor (GnRHR-II) are produced in only one livestock species, the pig. Paradoxically, the interaction of GnRH-II with its receptor does not stimulate gonadotropin secretion. Instead, both are abundantly produced within the gonads and have been implicated in autocrine/paracrine regulation of steroidogenesis. Our data suggests that GnRH-II originating from seminiferous tubules interacts with GnRHR-II on porcine Leydig cells to stimulate testosterone biosynthesis independent of the classical androgen stimulator, luteinizing hormone (LH). To further study the role of this system, our laboratory generated a knockdown (KD) swine line with 70% lower testicular GnRHR-II mRNA levels compared with littermate controls. During pubertal development, serum testosterone concentrations tended to be reduced in transgenic versus littermate control boars (P < 0.06), yet LH concentrations were unaffected (P > 0.10). In mature animals, the diurnal secretory patterns of testosterone and basal circulating concentrations of 9 other gonadal steroids were evaluated using animals fit with indwelling jugular cannulae. Testosterone concentrations were constitutively reduced in GnRHR-II KD compared with littermate control boars (P < 0.05); however, serum LH levels were similar between lines (P > 0.10). Mass spectrometry revealed that gonadal steroids were dramatically ablated by GnRHR-II KD; concentrations of steroids derived from the testis were either significantly decreased (7 hormones) or tended to be reduced (3 hormones) in transgenic boars. In order to determine if reduced androgen secretion affected semen quality, ejaculates were subjected to computer-assisted semen analysis. Both sperm production and motility parameters were reduced in GnRHR-II KD boars (P < 0.05). At euthanasia, testicular tissue from GnRHR-II KD boars secreted less testosterone ex vivo (P < 0.05). Histological analyses revealed that GnRHR-II KD boars had fewer, hypertrophic Leydig cells (P < 0.05). Ultimately, these data demonstrate that GnRH-II and its receptor are critical modulators of steroidogenesis within porcine Leydig cells and may represent novel targets to enhance boar fertility. Partially supported by USDA/NIFA AFRI ELI predoctoral fellowship (2017-67011-26036; ATD) and AFRI (2017-67015-26508; BRW) funds.