Milk fat is the major energy component of milk, and regulation of its production relies on transcription factors sterol regulatory element-binding protein 1 (SREBP1) and peroxisome proliferator-activated receptor gamma (PPARγ). As one of the target genes of SREBP1 and PPARγ, fatty acid-binding protein 3(FABP3) is the main protein allowing for rapid diffusion and selective targeting of long-chain fatty acids toward specific organelles for metabolism. Whether FABP3 plays an important role in milk fat synthesis signaling pathway is largely unknown. In this study, we observed the effects of FABP3 overexpression and gene silencing in dairy cow mammary epithelial cells, as well as the effects of oleic acid, stearic acid, and palmitic acid on the expressions of FABP3 and lipid droplet formation, by using quantitative reverse transcriptase (qRT)-PCR, Western blotting, and fluorescent immunostaining techniques. FABP3 upregulated the expression of SREBP1 and PPARγ to increase lipid droplet accumulation. Oleic acid, stearic acid, and palmitic acid also increased lipid droplet accumulation by affecting expression of FABP3. These findings shed new insights for understanding the mechanism of FABP3 in regulating milk fat synthesis.

Tudor staphylococcal nuclease (Tudor-SN) is a highly conserved and ubiquitously expressed multifunctional protein, related to multiple and diverse cell type- and species-specific cellular processes. Studies have shown that Tudor-SN is mainly expressed in secretory cells, however knowledge of its role is limited. In our previous work, we found that the protein level of Tudor-SN was upregulated in the nucleus of bovine mammary epithelial cells (BMEC). In this study, we assessed the role of Tudor-SN in milk synthesis and cell proliferation of BMEC. We exploited gene overexpression and silencing methods, and found that Tudor-SN positively regulates milk synthesis and proliferation via Stat5a activation. Both amino acids (methionine) and estrogen triggered NFκB1 to bind to the gene promoters of Tudor-SN and Stat5a, and this enhanced the protein level and nuclear localization of Tudor-SN and p-Stat5a. Taken together, these results suggest the key role of Tudor-SN in the transcriptional regulation of milk synthesis and proliferation of BMEC under the stimulation of amino acids and hormones.

Thyroid hormone responsive spot 14 (THRSP, Spot14, S14) is a nuclear protein that regulates milk fat synthesis. To investigate the role of THRSP in lipogenesis in the dairy cow mammary gland, first, we examined the association between milk fat concentration and THRSP expression in the mammary gland. We found that the dairy cow mammary glands that produced milk with high fat had high THRSP mRNA and protein levels. Additionally, the study described the consequences of overexpression or depletion of THRSP on lipogenesis in cultured bovine mammary epithelial cells (BMECs). We found that BMECs with overexpressed THRSP increased triacylglycerol levels and enhanced the expression of FAS, PPARγ, and SREBP1, compared with the control BMECs. Depletion of THRSP produced the opposite effects. Overall, increased mammary expression of THRSP can be a marker of high fat. In addition, our results provide evidence that THRSP may regulate expression of PPARγ and SREBP1 and can regulate milk fat synthesis by directly affecting the activity of some classical lipogenic enzymes.

Background/Aims: SUZ12 and EZH2 are two main components of polycomb repressive complex 2 (PRC2) that is known to be of great importance in tumorigenesis. EZH2 has been reported to play a vital role in pathogenesis of human cancer. However, whether SUZ12 has equivalent roles in tumorigenesis has not been demonstrated. Here, we investigated a possible role of SUZ12 for the proliferation of gastric cancer cells. Methods: Western-blot analysis was used to detected the levels of SUZ12, H3K27me3, EZH2 and p27 in ten gastric cell lines. SUZ12 was depleted by RNA interference. Cell cycle was detected by flow cytometry. Luciferase assays was to analyze whether miR-200b directly regulate SUZ12. Results: We found that SUZ12 depletion mediated by RNA interference (RNAi) led to a reduction of gastric cell numbers and arrested the cell cycle at G1/S point. As an important G1/S phase inhibitory gene, p27 is re-induced to some extent by SUZ12 knockdown. Furthermore, we demonstrated that SUZ12 was directly downregulated by miR-200b. Conclusion: We provide evidence suggesting that SUZ12 may be a potential therapeutic target for gastric cancer.

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