Development of KISS1 knockout pigs is characterized by hypogonadotropic hypogonadism, normal growth, and reduced skatole

Authors: AHERN, DANIEL - University Of Nebraska; MARTINS, KYRA - Acceligen Inc; FLOREZ, JULIO - Acceligen Inc; ROSS, CAITLIN - University Of Nebraska; HUISMAN, ABE - Hendrix Genetics; Cushman, Robert - Bob; SHUPING, SYDNEY - North Carolina State University; NESTOR, CASEY - North Carolina State University; DESAULNIERS, AMY - University Of Nebraska; WHITE, BRETT - University Of Nebraska; SONSTEGARD, TAD - Acceligen Inc; Lents, Clay

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Male piglets destined for pork production are routinely castrated to prevent development of aggressive male behaviors that increase the risk of injures to other pigs and workers, and to meet consumer expectations for pork quality. Gene editing technologies provide opportunity to develop alternatives to castration. Researchers in collaboration with ARS scientists at Clay Center, Nebraska, used gene editing to knockout a key gene in the reproductive system of pigs called KISS1. Scientists measured hormones and evaluated development of the reproductive organs in male (boars) and female (gilts) pigs that had either both copies of the KISS1 gene knocked out or only one copy knocked out and compared them to pigs that had two copies of the KISS1 gene. Researchers found that when only one copy of the KISS1 gene was knocked out, pigs had normal reproductive development, but when both copies of the KISS1 gene were knocked out, they had low levels of reproductive hormones, and their reproductive organs did not develop beyond the adolescent stage. They also found that knocking out both copies of the KISS1 gene in boars caused them to produce very little skatole, a compound that can make meat from boars taste bad. This research is providing critical new understanding of reproduction in pigs and demonstrates the potential to use gene editing for developing alternatives to castration.

Technical Abstract: Kisspeptin is a major regulator of gonadotropin secretion in pigs. Previously, CRISPR/Cas9 knockout of KISS1 was used to develop a mosaic parental line of pigs to generate offspring expected to be castration free due to loss of kisspeptin. The current goal was to characterize growth and reproductive development of F1 pigs from this parental line. Body weights, gonadotropin concentrations and gonadal development were measured from birth through development (boars to 220 d of age, n = 42; gilts to 160 d of age, n = 36). Testosterone, skatole, and androstenone were also measured in boars. Blood samples were collected by jugular venipuncture for quantification of serum hormones, gonadal tissues collected for gross morphology and histology, and a fat biopsy collected (boars) for skatole and androstenone analysis. Body weight did not differ with genotype. There were no differences between KISS1+/+ and heterozygote KISS1+/- animals for most parameters measured. Gonadotropin concentrations were reduced in KISS1-/- boars and gilts compared with KISS1+/+ and KISS1+/- animals (P < 0.05). Concentrations of testosterone in serum and both androstenone and skatole in adipose were less in KISS1-/- boars than in KISS1+/+ and KISS1+/- boars (P < 0.05). Hypogonadism was prevalent in both KISS1-/- gilts and boars, the later which exhibited dysregulation of Sertoli cells. These data indicate that knocking out KISS1 causes hypogonadotropic hypogonadism but does not negatively affected growth in pigs. Only one KISS1 allele is needed for normal gonadotropin secretion and gonadal development, and accumulation of compounds in adipose leading to boar taint.