The mature body size of sheep is a polygenic trait that is used as a main selection criterion for increasing meat production through genetic selection. The purpose of this study was to characterize polymorphisms of the follistatin gene (FST locus), which is known to regulate muscle hypertrophy by inhibiting both myostatin and activin. Using single-strand conformation polymorphism analysis (SSCP) and Sanger sequencing, we examined polymorphisms of the ovine FST gene (OAR_v.3.1; Chr 16, NC_019473.1) in Iranian Mehraban sheep (n = 100, seven-month-old male lambs) with records of body measurements, fat-tails, and head morphometry. Among the nine SSCP patterns A to I, we identified five single nucleotide polymorphisms (SNPs), including g.25632659 G>C, g.25632701 G>A, g.25633069 A>G, g.25633069 A>T, and g.25634085 G>C. The only amino acidaltering variant was g.25632659 G>C in exon 3 (p.216Thr > Ser). According to a subsequent statistical analysis, SSCP patterns A (g.25632659 G/C, g.25632701 G/G), B (g.25632659 C/C, g.25632701 G/A), C (g.25632659 C/C, g.25632701 A/A), D (homozygous reference; g.25633069 A/A), E (heterozygous; g.25633069 A/G) and F (homozygous variant; g.25633069 T/T) were significantly (P < 0.05) connected with body measurements. Furthermore, patterns A and B had significantly (P ≤ 0.05) longer forehead lengths than the lambs with the pattern C. Pattern I (homozygous variant; g.25634085 C/C) was significantly associated with an increased mouth width, and decreased eye length compared to patterns H (heterozygous; g.25634085 G/C) and G (homozygous reference; g.25634085 G/G). The findings of this study provide primary evidence of linking between the polymorphisms of the FST gene and body size in a small panel of Iranian Mehraban sheep population.
