MiR‐24‐3p regulates cell proliferation and milk protein synthesis of mammary epithelial cells through menin in dairy cows

Abstract

MiR‐24‐3p, a broadly conserved, small, noncoding RNA, is abundantly expressed in mammary tissue. However, its regulatory role in this tissue remains poorly understood. It was predicted that miR‐24‐3p targets the 3′ untranslated region (3′‐UTR) of multiple endocrine neoplasia type 1 (MEN1), an important regulatory factor in mammary tissue. The objective of this study was to investigate the function of miR‐24‐3p in mammary cells. Using a luciferase assay in mammary epithelial cells (MAC‐T), miR‐24‐3p was confirmed to target the 3′‐UTR of MEN1. Furthermore, miR‐24‐3p negatively regulated the expression of the MEN1 gene and its encoded protein, menin. miR‐24‐3p enhanced proliferation of MAC‐T by promoting G1/S phase progression. MiR‐24‐3p also regulated the expression of key factors involved in phosphatidylinositol‐3‐kinase/protein kinase B/mammalian target of rapamycin and Janus kinase/signal transducer and activators of transcription signaling pathways, therefore controlling milk protein synthesis in epithelial cells. Thus, miR‐24‐3p appears to act on MAC‐T by targeting MEN1. The expression of miR‐24‐3p was controlled by MEN1/menin, indicating a negative feedback loop between miR‐24‐3p and MEN1/menin. The negatively inhibited expression pattern of miR‐24‐3p and MEN1 was active in mammary tissues at different lactation stages. The feedback mechanism is a new concept to further understand the lactation cycle of mammary glands and can possibly to be manipulated to improve milk yield and quality.

Role of miR-24 in Multiple Endocrine Neoplasia Type 1: A Potential Target for Molecular Therapy

“…The regulatory network between miR-24, MEN1, and menin was demonstrated also in other species, than humans, in vitro and in vivo [30][31][32]. Interestingly, Gao et al [30] demonstrated, both by Target Scan algorithm-based prediction and by an in vitro study Figure 1.…”

“…The regulatory network between miR-24, MEN1 , and menin was demonstrated also in other species, than humans, in vitro and in vivo [ 30 , 31 , 32 ]. Interestingly, Gao et al [ 30 ] demonstrated, both by Target Scan algorithm-based prediction and by an in vitro study in neonatal rat cardiac myocytes, that miR-24 targets the CDNK1B mRNA, blocking translation of the encoded p27 kip1 protein, a negative regulator of cell cycle, resulting in a decreased G0/G1 arrest and in cell hypertrophy.…”

Epigenetics: New Insights into Mammary Gland Biology

“…miR-24-3p, which is abundantly expressed in mammary tissue, enhances proliferation. Through luciferase assays in immortalized bovine mammary epithelial cells (MAC-T), miR-24-3p has been shown to target the 3′UTR of Multiple endocrine neoplasia type 1 ( Men1 ) [ 156 ]. miR-101a is also able to regulate cell proliferation by altering Cyclooxygenase 2 ( Cox2 ) expression [ 127 ].…”

“…Studies describing miRNAs involved in the expression of milk protein genes, such as casein ( miR-3031 [ 161 ], miR-15 [ 159 ], miR-139 [ 130 ], miR-101a [ 127 ], miR-142-3p [ 131 ]), have highlighted the aforementioned genes as markers of the differentiation status of mammary epithelial cells (see before) rather than with the goal of understanding the role of miRNAs in their regulation. Indirectly, by showing that miR-24-3p regulates genes involved in the PI3K/Akt/mTOR and JAK/Stat5 pathways, which regulate milk protein synthesis, Qiaoqiao et al [ 156 ] highlighted the importance of this miRNA in this process. miRNAs are also involved in milk calcium concentration.…”

“…genes involved in the PI3K/Akt/mTOR and JAK/Stat5 pathways, which regulate milk protein synthesis, Qiaoqiao et al [156] highlighted the importance of this miRNA in this process. miRNAs are also involved in milk calcium concentration.…”