Two single nucleotide polymorphisms in the promoter of the ovine myostatin gene (MSTN) and their effect on growth and carcass muscle traits in New Zealand Romney sheep

Myostatin is a negative regulator of muscle growth and development in mammals, and variation in ovine myostatin gene (MSTN) has been demonstrated to be associated with variation in the muscularity of sheep. Polymerase chain reaction-single-stranded conformational polymorphism (PCR-SSCP) was used to look for single nucleotide polymorphisms (SNPs) in a 304-bp amplicon from the promoter region of ovine MSTN. Sequence analyses revealed two previously identified SNPs (c.-2449G/C and c. -2379T/C) that resulted in three haplotypes (H₁ (c.[-2449G; -2379C]), H₂ (c.[-2449C; -2379C]) and H₃ (c.[-2449G; -2379T]). The effect of these SNPs on growth and carcass traits was investigated in 357 NZ Romney lambs. General linear mixed-effect models revealed that sheep with the genotype c.-2449GC had a higher loin meat yield (p = 0.032) and proportion loin yield (p = 0.028), than those with the genotype c.-2449GG. The genotype c.-2379CC was associated with an increase in three weight traits: birthweight (p = 0.003), tailing weight (p = 0.009) and weaning weight (p = 0.028), when compared with the genotype c.-2379TC, but it was not found to have an association with growth rate. This suggests that c.-2379T/C has an effect that originates at, or before birth. Haplotype H₃ was associated with a decrease in birthweight (p = 0.002), tailing weight (p = 0.003) and weaning weight (p = 0.011). Haplotype H₂ was associated with increased loin yield (p = 0.012) and proportion loin yield (p = 0.002). The SNPs may have value as genetic markers for improved Romney breeding