Abstract：
Intramuscular fat (IMF) is a critical factor in beef quality. IMF is mainly distributed between muscle fibres and its accumulation can affect the marbling and meat quality of beef. IMF formation and deposition is a complex process and in recent years a group of non-coding RNAs (ncRNAs), known as circRNAs, have been discovered to play an important role in regulating intramuscular fat deposition. CircRNAs form a covalent loop structure after reverse splicing of precursor mRNAs. They can act by adsorbing miRNAs, thereby reducing their repressive effects on downstream target genes. Based on high-throughput sequencing of circRNAs in intramuscular fat of Qinchuan and Japanese black cattle, we identified a novel circSSBP2 that is differentially expressed between the two species and associated with adipogenesis. We show that circSSBP2 knockdown promotes bovine intramuscular preadipocyte proliferation, whereas overexpression inhibits bovine intramuscular preadipocyte proliferation. We also show that circSSBP2 can act as a molecular sponge for miR-2400 and that miR-2400 overexpression promotes bovine intramuscular preadipocyte proliferation. Furthermore, N-myc downstream-regulated gene 1 (NDRG1) was identified as a direct target gene of miR-2400, and NDRG1 interference promoted the proliferation of bovine intramuscular preadipocytes. In conclusion, our results suggest that circSSBP2 inhibits the proliferation of bovine intramuscular preadipocytes by regulating the miR-2400/NDRG1 axis.
摘要：
肌内脂肪(IMF)是影响牛肉品质的关键因素。IMF主要分布在肌肉纤维之间，其积累会影响牛肉的大理石花纹和肉质。IMF的形成和沉积是一个复杂的过程,近年来一组非编码RNA(ncRNAs),被称为circRNAs，已被发现在调节肌内脂肪沉积中起重要作用。CircRNA在前体mRNA的反向剪接后形成共价环结构。它们可以通过吸附miRNAs起作用，从而降低其对下游靶基因的抑制作用。基于对秦川和日本黑牛肌内脂肪中circRNAs的高通量测序,我们确定了一种新的circSSBP2，它在两个物种之间差异表达并与脂肪生成相关。我们显示circSSBP2敲低促进牛肌内前脂肪细胞增殖，而过表达抑制牛肌内前脂肪细胞增殖。我们还显示circSSBP2可以作为miR-2400的分子海绵，并且miR-2400过表达促进牛肌内前脂肪细胞增殖。此外，N-myc下游调节基因1(NDRG1)被鉴定为miR-2400的直接靶基因,NDRG1干扰促进牛肌内前脂肪细胞增殖。总之,我们的结果表明,circSSBP2通过调节miR-2400/NDRG1轴抑制牛肌内前体脂肪细胞的增殖.
