SREBF1 expression and genetic polymorphism significantly affect intramuscular fat deposition in the longissimus muscle of Erhualian and Sutai pigs

¹ Key Laboratory of Animal Physiology & Biochemistry, Nanjing Agricultural University, Nanjing 210095, China
² Research Institute for the Biology of Farm Animals, D-18196 Dummerstorf, Germany
³ Department of Animal Sciences, Washington State University, Pullman, WA 99164-6351

^* To whom correspondence should be addressed. E-mail: zhao.ruqian{at}gmail.com.

	Abstract

Two experiments were performed to elucidate the role of sterol regulatory element binding transcription factor 1 (SREBF1) in intramuscular fat (IMF) deposition in pigs. In Exp. 1, LM samples were removed from 4 male and 4 female Erhualian (EHL) piglets at 3, 20 and 45 d of age and SREBF1 mRNA expression level and IMF content were measured. Intramuscular fat content and expression of SREBF1 mRNA was greater (P < 0.05) in females than males at all three stages of age, providing initial evidence that the level of SREBF1 mRNA expression is related to IMF deposition in muscle of suckling pigs. Additionally, in Exp. 2 there was a significantly positive correlation between the SREBF1 mRNA level and IMF content (r = 0.67, P < 0.01) in 100 Sutai finishing pigs, a synthetic line produced by crossing EHL and Duroc pigs. Single strand conformation polymorphism (SSCP) analysis of the reverse transcription PCR (RT-PCR) products of SREBF1 gene revealed 3 genotypes in Sutai pigs with frequencies of 50% for AA, 36% for AB and 14% for BB, respectively. Both SREBF1 mRNA level and IMF content in muscle were greater (P < 0.05) in AB and BB animals than in AA animals, while no difference in backfat thickness was observed among the 3 genotypes. Sequencing analysis identified two single nucleotide polymorphisms (SNP) at T1006C and C1033T within the open reading frame of SREBF1 gene (NM_214157). Although both are silent mutations, they affected the secondary structure of SREBF1 mRNA. These results suggest that SREBF1 might play an important role in regulation of muscle fat deposition during postnatal growth of pigs. The SNP identified in the SREBF1 gene suggest that it could be used as a genetic marker to improve IMF content in pigs.

Key Words: association, intramuscular fat content, mutations, mRNA expression, pig, sterol regulatory element binding transcription factor 1

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