CircFBLN2 regulates duck myoblast proliferation and differentiation through miR-22-5p and MEF2C interaction

The growth and development of duck skeletal muscle significantly affect duck meat production, making it essential to understand the molecular mechanisms underlying these processes. Circular RNAs (circRNAs) and microRNAs (miRNAs) are identified in many species and play essential roles in the regulation of myogenic processes; however, research on circRNAs and miRNAs involved in the duck skeletal muscle development is limited. In prior whole-transcriptome RNA sequencing study, we identified differential expression of miR-22-5p and the novel circular RNA circFBLN2, which arises from the second exon of the FBLN2 gene, in duck primary myoblasts (DPMs). In this study, we confirmed the circular structure of circFBLN2 and explored its expression patterns and functional implications in myogenesis. To elucidate the function of circFBLN2 in the myogenic processes of duck, we conducted experiments involving both the silencing and overexpression of circFBLN2 in DPMs. Our findings indicated that circFBLN2 inhibits DPM proliferation while promoting their differentiation. Conversely, when miR-22-5p was silenced and overexpressed, it exhibited opposing effects by promoting the proliferation of DPMs and inhibiting their differentiation. These results suggest a complex dynamic interplay between circFBLN2 and miR-22-5p in the regulation of DPMs proliferation and differentiation. Additionally, our results revealed that both circFBLN2 and myocyte enhancer factor 2 C (MEF2C) act as sponges for miR-22-5p, as demonstrated by binding predictions and dual-luciferase reporter assays. These results offer novel perspectives on the regulatory pathways underlying the duck embryonic skeletal muscle development, underscoring the pivotal function of circFBLN2 in the regulation of miR-22-5p expression. This research deepens our comprehension of the molecular underpinnings of avian myogenesis, potentially paving the way for more effective approaches to bolster growth and development of livestock.