Circular RNA ACTA1 Acts as a Sponge for miR-199a-5p and miR-433 to Regulate Bovine Myoblast Development through the MAP3K11/MAP2K7/JNK Pathway

Circ_002033 Regulates Proliferation, Apoptosis, and Oxidative Damage of Bovine Mammary Epithelial Cells via the miR-199a-5p-MAP3K11 Axis in Heat Stress

Heat stress is becoming the major factor regarding dairy cow health and milk quality because of global warming. Circular RNAs (circRNAs) represent a special type of noncoding RNAs, which are related to regulating many biological processes. Nonetheless, little is known concerning their effects on heat-stressed bovine mammary epithelial cells (BMECs). Here, this study found a novel circRNA, circ_002033, using RNA sequencing (RNA-seq) and explored the role and underlying regulatory mechanism in proliferation, apoptosis, and oxidative damage in a heat-stressed bovine mammary epithelial cell line (MAC-T). According to the previous RNA-seq analysis, the abundance of circ_002033 in mammary gland tissue of heat-stressed cows increased relative to nonheat-stressed counterparts. This study found that the knockdown of circ_002033 promoted proliferation and alleviated apoptosis and oxidative damage in heat-stressed MAC-T. Mechanistically, circ_002033 localizes to miR-199a-5p in the cytoplasm of MAC-T to regulate mitogen-activated protein kinase kinase 11 (MAP3K11) expression. Meanwhile, miR-199a-5p and MAP3K11 are also involved in regulating the proliferation and apoptosis of heat-stressed MAC-T. Importantly, circ_002033 knockdown promoted the expression of miR-199a-5p while decreasing that of MAP3K11, thereby enhancing proliferation while alleviating apoptosis and oxidative damage in heat-stressed MAC-T. In summary, we found that circ_002033 regulates the proliferation, apoptosis, and oxidative damage of heat-stressed BMECs through the miR-199a-5p/MAP3K11 axis, providing the theoretical molecular foundation for mitigating heat stress of dairy cows.

Biological functions of circRNAs and their advance on skeletal muscle development in bovine

The development of skeletal muscle in animals is a complex biological process, which are strictly and precisely regulated by many genes and non-coding RNAs. Circular RNA (circRNA) was found as a novel class of functional non-coding RNA with ring structure in recent years, which appears in the process of transcription and is formed by covalent binding of single-stranded RNA molecules. With the development of sequencing and bioinformatics analysis technology, the functions and regulation mechanisms of circRNAs have attracted great attention due to its high stability characteristics. The role of circRNAs in skeletal muscle development have been gradually revealed, where circRNAs were involved in various biological processes, such as proliferation, differentiation, and apoptosis of skeletal muscle cells. In this review, we summarized the current studies advance of circRNAs involved in skeletal muscle development in bovine, and hope to gain a deeper understanding of the functional roles of the circRNAs in muscle growth. Our results will provide some theoretical supports and great helps for the genetic breeding of this species, and aiming at improving bovine growth and development and preventing muscle diseases.

CircZFR promotes pancreatic cancer progression through a novel circRNA-miRNA-mRNA pathway and stabilizing epithelial-mesenchymal transition protein

Pancreatic cancer (PC) ranks third in incidence and seventh in mortality among cancers worldwide. CircZFR has been implicated in various human cancers. Yet, how they affect PC progression is understudied. Herein, we demonstrated that circZFR was upregulated in PC tissues and cells, a feature that was correlated with the poor performance of patients with PC. Functional analyses elucidated that circZFR facilitated cell proliferation and enhanced tumorigenicity of PC. Moreover, we found that circZFR facilitated cell metastasis by differentially regulating the levels of proteins related to epithelial-mesenchymal transition (EMT). Mechanistic investigations revealed that circZFR sponged miR-375, thereby upregulating the downstream target gene, GREMLIN2 (GREM2). Additionally, circZFR knockdown resulted in attenuation of the JNK pathway, an effect that was reversed by GREM2 overexpression. Collectively, our findings implicate circZFR as a positive regulator of PC progression through the miR-375/GREM2/JNK axis.

circMEF2D Negatively Regulated by HNRNPA1 Inhibits Proliferation and Differentiation of Myoblasts via miR-486-PI3K/AKT Axis

Circular RNA (circRNA) is a form of endogenous RNA that can regulate gene expression and participate in the regulation of myogenesis. However, the molecular mechanisms and potential roles of circRNAs in bovine muscle development remain largely unknown. Nevertheless, the RNA splicing factors regulating the biogenesis of bovine circRNA have not yet been characterized. In this study, we identified a novel circRNA, circMEF2D, formed by back-splicing of constitutive exons (exons 5-7) of the bovine MEF2D gene. Functional assays showed that circMEF2D inhibited the proliferation and differentiation of bovine myoblasts. Importantly, we showed that circMEF2D regulated the PI3K-AKT signaling pathway through direct and competitive binding to miR-486. Furthermore, to explore the formation mechanism of circMEF2D, we explored the MEF2D gene alternative splicing progress. Four alternative linear variants of MEF2D were found. Due to its role in alternative splicing, the RNA-binding protein HNRNPA1 was selected for further study and the modulation of HNRNPA1 levels showed that it negatively regulated both back-splicing and linear splicing of MEF2D gene. Overall, in addition to the characterization of bovine circRNAs, these findings revealed the crucial role of HNRNPA1 in MEF2D gene alternative splicing and demonstrated a regulatory circMEF2D-miR-486-PI3K-AKT axis.