Insertion/deletion polymorphism of the sterol regulatory element-binding protein 1 gene in different cattle breeds

* Correspondence: [email protected] Sterol regulatory element-binding protein 1 (SREBP1) is the main transcription factor linked to lipogenesis regulation. SREBP1 regulates the expression of the FASN and ACACA genes coding for the 2 major lipogenic enzymes involved in de novo fatty acid synthesis, fatty acid synthase and acetyl-CoA carboxylase, respectively (1). The SREBP1 pathway plays a key role in the regulation of milk fat synthesis, and thus the variation within the SREBP1 gene may influence fat content and especially fatty acid composition in bovine milk and meat (2). Hoashi et al. (3) determined the complete sequence of this gene. They discovered an insertion/deletion (ins/del) of 84 bp in intron 5 of the SREBP1 gene. The short (S)and long (L)-type alleles were identified. Recently, several studies have indicated an association between this ins/ del polymorphism and fatty acid composition in the milk and meat of cattle (2,4–6). The aim of this study was to analyze the genotype distribution of the above-mentioned polymorphism in cattle populations of different breeds. The study included a total of 662 individuals of the following breeds: Montbeliard, Limousin, HolsteinFriesian, Angus, Jersey, and Charolais. DNA was extracted from whole peripheral blood, collected from the jugular vein into test tubes containing an anticoagulant (K3EDTA) using the MasterPure DNA Purification Kit for Blood (Epicentre Biotechnology). The primers used for amplification were those described previously (7). PCR amplifications were performed in a 10-μL volume of reaction mixture containing: approximately 60 ng of genomic DNA, 15 pmol of each primer, 1X Taq DNA polymerase buffer with (NH4)2SO4, 1.5 mM MgCl2, 0.2 mM dNTP, 0.4 U of Taq DNA polymerase, and nucleasefree deionized water up to 10 μL. Amplifications were carried out according to the following temperature profile: initial denaturation at 94 °C for 5 min, followed by 35 cycles (denaturation at 94 °C for 30 s, primer annealing at 56 °C for 45 s, extension at 72 °C for 45 s) and final extension at 72 °C for 5 min. PCR products were separated in a 1.5% agarose gel in 1X TBE buffer and stained with ethidium bromide. After electrophoresis, DNA bands were visualized under UV light and photographed. Two alleles (L and S, corresponding to bands of 492 and 408 bp, respectively) and 3 genotypes (LL, LS, and SS) were identified. The analysis included 6 Polish cattle herds consisting of beef (Limousin, Angus, Charolais), dairy (HolsteinFriesian, Jersey), and dual-purpose (Montbeliard) breeds. Allele and genotype frequencies obtained in the present study are given in the Table. There was no polymorphism in the SREBP1 locus in dairy cattle populations. All HolsteinFriesian and Jersey individuals were LL homozygotes. Kaneda et al. (8) also reported monomorphism in Abstract: In the present study, an 84-bp insertion/deletion polymorphism of the sterol regulatory element-binding protein 1 (SREBP1) gene was investigated. The analysis included 6 Polish cattle herds consisting of beef (Limousin, Angus, Charolais), dairy (HolsteinFriesian, Jersey) and dual-purpose (Montbeliard) breeds. The polymorphism was found only in Limousin and Montbeliard animals, in which both the short (S)and long (L)-type alleles occurred. The genotype distribution in Montbeliard cattle was as follows: 0.038, 0.406, and 0.556 for SS, LS, and LL, respectively. To the author’s knowledge, this study was the first to investigate the above-mentioned polymorphic site in the Montbeliard and Jersey cattle populations. As far as SREBP1 function is concerned, the examined locus seems to be a very interesting object for further investigations, such as association studies for fatty acid content and composition in cattle milk.