Functional roles for AGPAT6 in milk fat synthesis of buffalo mammary epithelial cells

AGPAT6 plays a crucial role in the triglyceride (TG) synthesis pathway in mammals. However, its roles in buffalo lactation remain unknown. Therefore, we investigated the functional roles of AGPAT6 in milk fat synthesis by transfecting overexpression and lentivirus interference vectors in buffalo mammary epithelial cells (BuMECs) in vitro. AGPAT6 overexpression in BuMECs significantly enhanced the mRNA expression of FABP4, SLC27A6, ACSL1, DGAT1, DGAT2, LPIN1, INSIG1, CEBPA and SREBF1 genes, and significantly reduced that of XDH, CPT1A, LIPE, INSIG2 and PPARGC1A, but has no significant influence to the mRNA abundance of FABP3, GPAM, PPARG and SREBF2. However, the interference with AGPAT6, the mRNA expression of FABP4, SLC27A6, ACSL1, DGAT1, DGAT2, INSIG1, CEBPA, SREBF1, XDH, CPT1A, LIPE, INSIG2 and PPARGC1A genes in BuMECs changed contrary to the overexpression experiment, and that of GPAM, PPARG and SREBF2 also did not change significantly, but the expression of FABP3 was significantly decreased. In addition, the overexpression/interference of AGPAT6 gene significantly increased/decreased TG content in BuMECs. The results here indicate that AGPAT6 gene is involved in TG synthesis in BuMECs, and affects the expression of major genes associated with FA transport and activation, TG synthesis and transcription regulation, FA oxidation and TG degradation during the lipogenesis of milk.

Novel Insight into the Potential Role of Acylglycerophosphate Acyltransferases Family Members on Triacylglycerols Synthesis in Buffalo

Acylglycerophosphate acyltransferases (AGPATs) are the rate-limiting enzymes for the de novo pathway of triacylglycerols (TAG) synthesis. Although AGPATs have been extensively explored by evolution, expression and functional studies, little is known on functional characterization of how many members of the AGPAT family are involved in TAG synthesis and their impact on the cell proliferation and apoptosis. Here, 13 AGPAT genes in buffalo were identified, of which 12 AGPAT gene pairs were orthologous between buffalo and cattle. Comparative transcriptomic analysis and real-time quantitative reverse transcription PCR (qRT-PCR) further showed that both AGPAT1 and AGPAT6 were highly expressed in milk samples of buffalo and cattle during lactation. Knockdown of AGPAT1 or AGPAT6 significantly decreased the TAG content of buffalo mammary epithelial cells (BuMECs) and bovine mammary epithelial cells (BoMECs) by regulating lipogenic gene expression (p < 0.05). Knockdown of AGPAT1 or AGPAT6 inhibited proliferation and apoptosis of BuMECs through the expression of marker genes associated with the proliferation and apoptosis (p < 0.05). Our data confirmed that both AGPAT1 and AGPAT6 could regulate TAG synthesis and growth of mammary epithelial cells in buffalo. These findings will have important implications for understanding the role of the AGPAT gene in buffalo milk performance.

Identification, molecular characteristics, and tissue differential expression of DGAT2 full-CDS cDNA sequence in Binglangjiang buffalo (Bubalus bubalis)

It has been found that diacylglycerol acyltransferase-2 (DGAT2) plays a crucial role in the synthesis of triglycerides (TGs) in some mammals, but its role in buffalo lactation is unclear. In the present study, the DGAT2 full-CDS cDNA sequence of Binglangjiang buffalo was isolated, and the physicochemical characteristics and structure of its encoding protein were characterized. Furthermore, the differential expressions of this gene in 10 tissues of lactating and non-lactating buffalo were analyzed by real-time quantitative PCR (RT-qPCR). The results showed that the coding region (CDS) of this gene was 1086 bp in length, encoding a peptide composed of 361 amino acid residues. The deduced amino acid sequence shared more than 98.6 % identity with that of cattle, zebu, yak, and bison in the Bovidae family. Buffalo DGAT2 protein is a slightly hydrophobic protein with a transmembrane region, which functions in membrane of endoplasmic reticulum. Besides, this protein belongs to the LPLAT_MGAT-like family and contains a conserved domain of DAGAT that has a function in the synthesis of TGs. The multi-tissue differential expression analysis demonstrated that DGAT2 was expressed in the heart, liver, mammary gland, and muscle in both non-lactating and lactating buffalo. And its expression level in the heart, liver, and mammary gland during lactation was significantly higher than that during non-lactation. The results indicate that buffalo DGAT2 may be involved in milk fat synthesis. This study can establish a foundation for further elucidating mechanisms of the buffalo DGAT2 gene in milk fat synthesis.

Effect of differentiation on microRNA expression in bovine skeletal muscle satellite cells by deep sequencing

Background

The differentiation of skeletal muscle-derived satellite cells (MDSCs) is important in controlling muscle growth, improving livestock muscle quality, and healing of muscle-related disease. MicroRNAs (miRNAs) are a class of gene expression regulatory factors, which play critical roles in the regulation of muscle cell differentiation. This study aimed to compare the expression profile of miRNAs in MDSC differentiation, and to investigate the miRNAs which are involved in MDSC differentiation.

Method

Total RNA was extracted from MDSCs at three different stages of differentiation (MDSC-P, MDSC-D1 and MDSC-D3, representing 0, 1 and 3 days after differentiation, respectively), and used to construct small RNA libraries for RNA sequencing (RNA-seq).

Results

The results showed that in total 617 miRNAs, including 53 novel miRNA candidates, were identified. There were 9 up-expressed, 165 down-expressed, and 15 up-expressed, 145 down-expressed in MDSC-D1 and MDSC-D3, respectively, compared to those in MDSC-P. Also, 17 up-expressed, 55 down-expressed miRNAs were observed in MDSC-D3 compared to those in MDSC-D1. All known miRNAs belong to 237 miRNA gene families. Furthermore, we observed some sequence variants and base edits of the miRNAs. GO and KEGG pathway analysis showed that the majority of target genes regulated by miRNAs were involved in cellular metabolism, pathways in cancer, actin cytoskeleton regulation and the MAPK signaling pathway. Regarding the 53 novel miRNAs, there were 7 up-expressed, 31 down-expressed, and 8 up-expressed, 26 down-expressed in MDSC-D1 and MDSC-D3, respectively, compared to those in MDSC-P. The expression levels of 12 selected miRNA genes detected by RT-qPCR were consistent with those generated by deep sequencing.

Conclusions

This study confirmed the authenticity of 564 known miRNAs and identified 53 novel miRNAs which were involved in MDSC differentiation. The identification of novel miRNAs has significantly expanded the repertoire of bovine miRNAs and could contribute to advances in understanding muscle development in cattle.

Electronic supplementary material

The online version of this article (doi:10.1186/s11658-016-0009-x) contains supplementary material, which is available to authorized users.

<i>AGPAT6</i> gene EX1_303T > C and EX12_299G > A mutations and associations with economic traits of Chinese Simmental-cross cattle

Abstract. One of the 11 members in the family of 1-acylglycerol-3-phosphate-O- acyltransferases (AGPATs), AGPAT6, is responsible for the second step in the biosynthesis of triacylglycerol in eukaryotes. The AGPAT6 gene is highly expressed in brown adipose tissue, mammary gland epithelial cells and many other tissues. In this study, the PCR-restriction fragment length polymorphism technique was applied to detect sites of polymorphism in the bovine AGPAT6 gene, and two single nucleotide polymorphisms (SNPs) were detected in the exon 1 and exon 12. Thirty-three traits associated with the meat quality and the carcass were also measured in Chinese Simmental-cross steers. The association between the two SNPs and the traits was then analyzed. The polymorphism site EX1_303T > C was significantly associated with the omasum weight, liver weight, pH value of the beef (carcass), fat coverage rate of the carcass, fat color score, kidney weight and back fat thickness. The polymorphism site EX12_299G > A was significantly associated with bone net weight, forehoof weight, hind feet weight, the fat coverage rate of the carcass, the head and heart weight and the marbling score. Thus, the polymorphisms in the AGPAT6 gene might be important genetic factors that influence the carcass yield and meat quality of beef cattle and may be useful markers of meat quality traits in future marker-assisted selection programs for the breeding and production of beef cattle.