Roles in elongating long-chain fatty acids. Mammalian fatty acid synthase (FASN) catalyzes the condensation of medium-chain ( C16) SFA or MUFA, but not the elongation of long-chain ( C16) fatty acids (Jensen, 2002). Moreover, fatty acids synthesized by FASN or derived from diets can be further elongated into longchain (16C and 18C) and very long-chain fatty acids by ELOVL (Guillou et al., 2010). To date, 7 ELOVL genes (ELOVL1?7) have been identified in mammals (Leonard et al., 2000; Tvrdik et al., 2000). The rate-limiting enzyme ELOVL6 in the elongation cycle in mammals catalyzes the elongation of longchain SFA and MUFA with 12 to 16 carbons (Green et al., 2010; Green and Olson, 2011). This enzyme plays The elongation of long-chain fatty acid family member 6 (ELOVL6) gene plays an important role in the synthesis of long-chain saturated and monounsaturated fatty acids. Although some studies have revealed that ELOVL6 is the target of sterol regulatory element binding protein 1 (SREBP1; gene name SREBF1) in rodents, the mechanism underlying ELOVL6 regulation during lactation in dairy goats remains unknown. The present study aimed to investigate the transcriptional regulation mechanism of ELOVL6 in goat mammary epithelial cells (GMEC). We used PCR to clone and sequenced a 2,370 bp fragment of the ELOVL6 5? flanking region from goat genomic DNA. Deletion analysis revealed a core promoter region located ?105 to ?40 bp upstream of the transcriptional start site. Mutant sterol regulatory elements (SRE) 1 and 3 significantly reduced the ELOVL6 promoter activities in GMEC. Both SRE1 and SRE3 binding sites were required for the basal transcriptional activity of ELOVL6. Luciferase reporter assays showed that SREBF1 knockdown decreased ELOVL6 promoter activities in GMEC. Furthermore, SRE1 and SRE3 sites were simultaneously mutated completely abolished the stimulatory effect of SREBF1 and the repressive effect of linoleic acid on ELOVL6 gene promoter activities. Furthermore, chromatin immunoprecipitation assays confirmed that SREBP1 directly bound to SRE sites in the ELOVL6 promoter. In conclusion, these results indicate that SREBP1 regulates ELOVL6 transcription via the SRE elements located in the ELOVL6 promoter in goat mammary gland.

Goat milk provides benefits to human health due to its richness in bioactive components, such as polyunsaturated fatty acids (PUFAs). The fatty acid desaturase 2 (FADS2) is the first rate-limiting enzyme in PUFAs biosynthesis. However, its role and transcriptional regulation mechanisms in fatty acid metabolism in dairy goat remain unclear. Here, our study revealed that the FADS2 gene was highly expressed during the peak lactation compared with the dry period, early lactation, and late lactation. The content of triacylglycerol (TAG) was enhanced with the increasing mRNA expression of TAG synthesis genes (diacylglycerol acyltransferase 1/2, DGAT1/2) in FADS2-overexpressed goat mammary epithelial cells (GMECs). Overexpression of FADS2 was positively correlated with the elevated concentrations of dihomo-gamma-linolenic acid (DGLA) and docosahexaenoic acid (DHA) in GMECs. BODIPY staining showed that FADS2 promoted lipid droplet accumulation in GMECs. To clarify the transcriptional regulatory mechanisms of FADS2, 2,226 bp length of FADS2 promoter was obtained. Deletion mutation assays revealed that the core region of FADS2 promoter was located between the −375 and −26 region, which contained SRE1 (−361/−351) and SRE2 (−191/−181) cis-acting elements of transcription factor sterol regulatory element-binding protein 1 (SREBP1). Overexpression of SREBP1 enhanced relative luciferase activity of the single mutant of SRE1 or SRE2, vice versa, and failed to alter the relative luciferase activity of the joint mutant of SRE1 and SRE2. Chromatin immunoprecipitation (ChIP) and site-directed mutation assays further demonstrated that SREBP1 regulated the transcription of the FADS2 gene by binding to SRE sites in vivo and in vitro. In addition, the mRNA levels of FADS2 were significantly decreased by targeting SRE1 and SRE2 sites in the genome via the CRISPR interference (CRISPRi) system. These findings establish a direct role for FADS2 regulating TAG and fatty acid synthesis by SREBP1 transcriptional regulation in dairy goat, providing new insights into fatty acid metabolism in mammary gland of ruminants. The fatty acid desaturase 2 (FADS2) is the first rate-limiting enzyme in polyunsaturated fatty acids (PUFAs) biosynthesis in mammals. This study aimed to investigate the function and transcriptional regulation mechanism of FADS2 in goat mammary epithelial cells (GMECs). The content of triacylglycerol (TAG) was enhanced with lipid droplet accumulation in FADS2-overexpressed GMECs. Overexpression of FADS2 was positively correlated with elevated concentrations of docosahexaenoic acid (DHA) in GMECs. Furthermore, site-directed mutation and chromatin immunoprecipitation (ChIP) assays simultaneously demonstrated that FADS2 was directly regulated by SREBP1 transcriptional factor binding to sterol regulatory element (SRE) in vitro and in vivo. In addition, genetic ablation of SRE1 and SRE2 in the genome resulted in a significant reduction in the mRNA levels of FADS2 via the CRISPR interference (CRISPRi) system. Altogether, this study discovered that the SREBP1 exerts control on FADS2 to regulate milk fatty acids, and provides a theoretical approach for improving milk quality via genetic approaches.

α_S1-Casein (encoded by the CSN1S1 gene) is associated with food allergy more than other milk protein components. Milk allergy caused by α_S1-casein is derived from cow milk, goat milk and other ruminant milk. However, little is known about the transcription regulation of α_S1-casein synthesis in dairy goats. This study aimed to investigate the regulatory roles of signal transducer and activator of transcription 5 (STAT5) on α_S1-casein in goat mammary epithelial cells (GMEC). Deletion analysis showed that the core promoter region of CSN1S1 was located at −110 to −18 bp upstream of transcription start site, which contained two putative STAT5 binding sites (gamma-interferon activation site, GAS). Overexpression of STAT5a gene upregulated the mRNA level and the promoter activity of the CSN1S1 gene, and STAT5 inhibitor decreased phosphorylated STAT5 in the nucleus and CSN1S1 transcription activity. Further, GAS site-directed mutagenesis and chromatin immunoprecipitation (ChIP) assays revealed that GAS1 and GAS2 sites in the CSN1S1 promoter core region were binding sites of STAT5. Taken together, STAT5 directly regulates CSN1S1 transcription by GAS1 and GAS2 sites in GMEC, and the mutation of STAT5 binding sites could downregulate CSN1S1 expression and decrease α_S1-casein synthesis, which provide the novel strategy for reducing the allergic potential of goat milk and improving milk quality in ruminants.

MicroRNA-26 (miR-26a and miR-26b) plays a critical role in lipid metabolism, but its endogenous regulatory mechanism in fatty acid metabolism is not clear in goat mammary epithelial cells (GMECs). GMECs with the simultaneous knockout of miR-26a and miR-26b were obtained using the CRISPR/Cas9 system with four sgRNAs. In knockout GMECs, the contents of triglyceride, cholesterol, lipid droplets, and unsaturated fatty acid (UFA) were significantly reduced, and the expression of genes related to fatty acid metabolism was decreased, but the expression level of miR-26 target insulin-induced gene 1 (INSIG1) was significantly increased. Interestingly, the content of UFA in miR-26a and miR-26b simultaneous knockout GMECs was significantly lower than that in wild-type GMECs and miR-26a- and miR-26b-alone knockout cells. After decreasing INSIG1 expression in knockout cells, the contents of triglycerides, cholesterol, lipid droplets, and UFAs were restored, respectively. Our studies demonstrate that the knockout of miR-26a/b suppressed fatty acid desaturation by upregulating the target INSIG1. This provides reference methods and data for studying the functions of miRNA families and using miRNAs to regulate mammary fatty acid synthesis.

With the rapid development of omics technologies, metabolomics and lipidomics have become important tools for elucidating the molecular basis of reproductive performance in livestock. These approaches, which focus on small metabolites and lipid species, provide valuable insights into dynamic interactions between genes, proteins, and the environment, offering a high level of sensitivity. This review summarizes key methodological advances in metabolomics and lipidomics and their applications to gametogenesis, oocyte maturation, embryo development, and pregnancy maintenance. It highlights how metabolic and lipid pathways, particularly those involving energy metabolism, redox regulation, lipid remodeling, and cell–cell signaling, affect reproductive cell quality. This review further integrates biomarkers identified from semen, follicular fluid, oocytes, embryos, and uterine tissues, highlighting their potential roles in fertility assessment. Together, these insights enhance our understanding of metabolic regulation in reproduction and support the effective application of metabolomics and lipidomics in improving livestock fertility.