NOVEL ASSOCIATION BETWEEN GnRHR GENE AND GROWTH TRAITS IN AWASSI AND KARAKUL SHEEP: GnRHR genetic polymorphism in sheep

This study was conducted to investigate the association of the Gonadotropin-Releasing Hormone Receptor (GnRHR) gene with growth traits in Awassi (n= 123) and Karakul (n= 78) sheep. Starting from the birth-day to 12 months of age, several growth traits were investigated, namely body weight and length, wither and rump height, chest, and abdominal circumferences. Four fragments were designed to amplify three exons of GnRHR gene, P1 and P2 for exon 1, P3 for exon 2, and P4 for exon 3.  The polymorphisms in these amplicons were analyzed by single-strand conformation polymorphism (SSCP) method. Genotypic and allele frequency of GnRHR gene were computed after sequence alignment. The results detected two different SSCP banding patterns GG and GA for both P2 and P3 amplicons, and two novel mutations were observed in GA genotype of P2 and P3 amplicons respectively, p.N87= and p.L242F. The identified p.N87= exhibited no relationship with all measured growth traits, while p.L242F showed significant association with the body weight, length, and abdominal circumference in month-6 and month-9. This association was increasingly observed in month-12 with all growth traits, in which individuals with GA genotype exhibited higher growth traits measurements than individuals with GG genotype (P < 0.01). In conclusion, the detected polymorphism of GnRHR gene exon-2 may be useful in marker-assisted selection for growth traits in Awassi and Karakul breeds. This study is the first one to describe the effect of GnRHR polymorphisms on growth traits, which confirm the potential usefulness of this gene in marker-assisted selection in sheep.