MiR-204-5p and MiR-211 Synergistically Downregulate the α-Casein Content and Contribute to the Lower Allergy of Goat Milk

α-Casein (encoded by the 11 gene) is associated with higher rates of allergy than other milk protein components for humans. microRNAs (miRNAs) as small noncoding RNA molecules regulate gene expression and influence diverse biological processes. However, little is known about the regulation of milk protein synthesis by miRNAs in ruminants. In this study, we aim to investigate the regulatory roles of miR-204 family members (miR-204-5p and miR-211) on α-casein in goat mammary epithelial cells (GMEC). Here, we observed that the 11 mRNA level is upregulated, while miR-204-5p and miR-211 (miR-204-5p/-211) abundance is downregulated during peak lactation compared with middle lactation of dairy goats. We found that miR-204-5p/-211 synergistically inhibit α-casein expression via directly binding to the 3'-untranslated region (3'UTR) of 11 in GMEC. miR-204-5p/-211 increase β-casein mRNA (2) and protein abundance, as well as the signal transducer and activator of transcription 5a (STAT5a) activity. Further, miR-204-5p/-211 enhance β-casein expression via the 11-STAT5a signaling axis and promote β-casein transcription by activating the STAT5 response element located in the 2 promoter. In conclusion, miR-204-5p/-211 regulate α-casein and β-casein synthesis via targeting 11 in GMEC, which provide the strategy for manipulating miR-204 family members to reduce milk allergy potential and improve ruminant milk quality for human consumption.