MicroRNAs (miRNAs) are noncoding RNA molecules that regulate gene expression at the post-transcriptional level to cause translational repression or degradation of targets. The profiles of miRNAs across stages of lactation in small ruminant species such as dairy goats is unknown. In a recent study by researchers from Northwest A&F University, a small RNA library was constructed using tissue samples from mammary gland of Saanen dairy goats harvested at mid-lactation followed by miRNA sequencing service.

A total of 796 conserved miRNAs, 263 new miRNAs, and 821 pre-miRNAs were uncovered. After comparative analyses of their sequence data with published mammary gland transcriptome data across different stages of lactation, a total of 37 miRNAs (including miR-145) had significant differences in expression over the lactation cycle. Further studies revealed that miR-145 regulates metabolism of fatty acids in goat mammary gland epithelial cells (GMEC). Compared with nonlactating mammary tissue, lactating mammary gland had a marked increase in expression of miR-145. Overexpression of miR-145 increased transcription of genes associated with milk fat synthesis resulting in greater fat droplet formation, triacylglycerol accumulation, and proportion of unsaturated fatty acids. In contrast, silencing of miR-145 impaired fatty acid synthesis. Inhibition of miR-145 increased methylation levels of fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), peroxisome proliferator-activated receptor gamma (PPARG), and sterol regulatory element binding transcription factor 1 (SREBF1). Luciferase reporter assays confirmed that insulin induced gene 1 (INSIG1) is a direct target of miR-145.

These findings underscore the need for further studies to evaluate the potential for targeting miR-145 for improving beneficial milk components in ruminant milk. 

 

Reference
H. Wang, H. Shi, J. Luo, Y. Yi, D. Yao, X. Zhang, G. Ma, J. Loor (2017) MiR-145 Regulates Lipogenesis in Goat Mammary Cells Via Targeting INSIG1 and Epigenetic Regulation of Lipid-Related Genes J. Cell. Physiol. 232: 1030–1040 doi: 10.1002/jcp.25499 [abstract]

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