# Transcriptome Analysis of Egg Yolk Sialoglycoprotein on Osteogenic Activity in MC3T3-E1 Cells
###### Abstract  
In this study, the effects of egg yolk sialoglycoprotein (EYG) on osteogenesis in MC3T3-E1 cells were investigated and the DEGs (differentially expressed genes) were explored by transcriptome analysis. The results found that EYG effectively increased cell proliferation, enhanced ALP activity, promoted the secretion of extracellular matrix protein COL-I and OCN, enhanced bone mineralization activity, exhibiting good osteogenic activity. Further study of the mechanism was explored through transcriptome analysis. Transcriptome analysis showed that 123 DEGs were triggered by EYG, of which 78 genes were downregulated and 45 genes were upregulated. GO (gene ontology) analysis showed that EYG mainly caused differences in gene expression of biological processes and cell composition categories in the top 30 most enriched items. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that EYG inhibited inflammatory factors and downregulated inflammation-related pathways. The results also showed EYG regulated such genes as COL2A1, COL4A1 and COL4A2 to up-regulate pathways including ECM-receptor interaction, focal adhesion and protein digestion and absorption, enhancing the proliferation and differentiation of osteoblasts. Gene expression of COL-I, Runx2, BMP2 and \(\beta\)-catenin was determined by qRT-PCR for verification, which found that EYG significantly increased COL-I, Runx2, BMP2 and \(\beta\)-catenin gene expression, suggesting that BMP-2 mediated osteogenesis pathway was activated. egg yolk; sialoglycoprotein; MC3T3-E1 cells; osteogenesis; transcriptome analysis +
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resorption. As the basic functional units of bone formation, osteoblasts are essential for the balance of bone metabolism [4]. Stimulating the proliferation of osteoblasts and promoting their differentiation and maturation is one of the effective methods to prevent and treat osteoporosis. However, the current drugs have serious side effects [5], food-derived anti-osteoporotic functional factors have become a research hotspot due to their safety. A large number of studies have confirmed that food-derived functional factors, such as soy isoflav [6], fish oil [7], polyphenol [8], saccharides [9; 10], peptide [11], exhibited excellent effects on the treatment of osteoporosis. In vivo, osteoblasts respond to various factors involved in proliferation and differentiation [12]. During differentiation, pre-osteoblasts express extracellular matrix proteins, such as type I collagen (COL-I), alkaline phosphatase (ALP), osteoclast (OCN), and other bone matrix proteins, which help Ca\({}^{2+}\) deposition and mineralization [13; 14; 15]. Osteogenesis is regulated by some transcription factors and cytokines, such as Runx2, osterix, BMP-2 and \(\beta\)-catenin [16]. Runx2, a transcription factor that has similar Runx2 binding and gene expression profiles in mouse and human osteoblasts, is essential for osteoblast differentiation and bone formation [17]. Activated Runx2 induces the expression of osteoblast-specific genes such as COL-I, ALP, OCN, resulting in osteoblast differentiation and mineralization [18]. Osteoblasts are subject to complex gene regulation during differentiation. As a member of the TGF family, BMP-2 plays a vital role in the regulation of bone formation. It has been proved that BMP-2 can accelerate the specific differentiation of osteoblasts [19]. BMP-2 specifically binds to the receptor and activates phosphorylation of downstream Smad proteins to form a hetero-oligomeric complex with a common mediator Smad, thereby regulating downstream target genes such as Runx2 [20; 21]. BMP-2 also interacts with other pathways to regulate osteoblast differentiation. In the osteoblasts lineage, \(\beta\)-catenin can affect osteoblasts and osteoclasts through pathways that increase bone mass [22].