Abstract：
Clarifying the cellular origin and regulatory mechanisms of intramuscular fat (IMF) deposition is crucial for improving beef quality. Here, we used single-nucleus RNA sequencing to analyze the structure and heterogeneity of skeletal muscle cell populations in different developmental stages of Yanbian cattle and identified eight cell types in two developmental stages of calves and adults. Among them, fibro/adipogenic progenitors (FAPs) expressing CD29 (ITGA7)pos and CD56 (NCAM1)neg surface markers were committed to IMF deposition in beef cattle and expressed major Wnt ligands and receptors. LY2090314/XAV-939 was used to activate/inhibit Wnt/β-catenin signal. The results showed that the blockade of Glycogen Synthase Kinase 3 (GSK3) by LY2090314 promoted the stabilization of β-catenin and reduced the expression of genes related adipogenic differentiation (e.g., PPARγ and C/EBPα) in bovine FAPs, confirming the anti-adipogenic effect of GSK3. XAV-939 inhibition of the Wnt/β-catenin pathway promoted the lipid accumulation capacity of FAPs. Furthermore, we found that blocking GSK3 enhanced the paracrine effects of FAPs-MuSCs and increased myotube formation in muscle satellite cells (MuSCs). Overall, our results outline a single-cell atlas of skeletal muscle development in Yanbian cattle, revealed the role of Wnt/GSK3/β-catenin signaling in FAPs adipogenesis, and provide a theoretical basis for further regulation of bovine IMF deposition.
摘要：
明确肌内脂肪（IMF）沉积的细胞起源和调节机制对于提高牛肉质量至关重要。这里,采用单核RNA测序技术对延边牛不同发育阶段骨骼肌细胞群的结构和异质性进行分析,并在小牛和成虫两个发育阶段鉴定出8种细胞类型。其中,表达CD29（ITGA7）pos和CD56（NCAM1）neg表面标记的纤维/成脂祖细胞（FAP）致力于肉牛中的IMF沉积，并表达主要的Wnt配体和受体。LY2090314/XAV-939用于激活/抑制Wnt/β-连环蛋白信号。结果表明，LY2090314对糖原合成酶激酶3（GSK3）的阻断促进了β-catenin的稳定并降低了成脂分化相关基因的表达（例如，牛FAP中的PPARγ和C/EBPα），证实GSK3的抗脂肪生成作用。XAV-939抑制Wnt/β-连环蛋白途径促进FAP的脂质积累能力。此外，我们发现阻断GSK3可增强FAPs-MuSCs的旁分泌效应,并增加肌肉卫星细胞(MuSCs)的肌管形成.总的来说,我们的结果概述了延边牛骨骼肌发育的单细胞图谱，揭示了Wnt/GSK3/β-catenin信号在FAP脂肪形成中的作用，为进一步规范牛IMF沉淀提供理论依据。
