A GHR Polymorphism and Its Associations with Carcass Traits in Hanwoo Cattle

The growth hormone receptor (GHR) is a membrane transmitter for the growth hormone signal transduction pathway that regulates various metabolic activities, including cell growth and expressions of cytokine genes. The presence or absence of a genetic polymorphism for the LINE-1 retroposon in the P1 promoter, which specifically regulates the GIN gene expression in the Ever, was screened by a novel detection method and examined for its relationships with carcass traits in Hanwoo cattle. Hanwoo cattle had taurine type LINE-1 present (allele I) as well as incidine type LINE-1 absent (allele A) promoter sequences. Three genotypes, I/I, I/A and A/A showed frequencies of 49.1, 36.7 and 14.2%, respectively. The effects of allele A were significant on mean differences for final weight, eye muscle area, marbling score and fat color (p < 0.05), but not for carcass weight, backfat thickness, final meat quality grade or meat color (p > 0.05). Most 30-month old Hanwoo steers bearing the LINE-1 absent promoter had whiter fat color, heavier live weight and higher marbling score, reflecting intramuscular fat deposition in M. longissimus dorsi, compared to animals bearing a LINE-1 present promoter. This suggests that a GHR polymorphism could be a potential genetic marker for improving beef production of Hanwoo cattle.