circMAPKBP1 functions as a miR-143-y sponge to regulate quail myoblast proliferation and differentiation

Abstract

The quail (Coturnix japonica) is an economically important poultry species and a useful avian model for muscle biology. Although circular RNA (circRNA)–miRNA competitive endogenous RNA (ceRNA) networks have been described in chicken and duck skeletal muscle, their roles in quail remain poorly defined. We identified circMAPKBP1, generated from the mitogen-activated protein kinase binding protein 1 (MAPKBP1), as highly expressed in quail skeletal muscle and myoblasts. Gain- and loss-of-function experiments in quail myoblast 7 (QM7) cells showed that circMAPKBP1 promotes proliferation while inhibiting differentiation. Dual-luciferase reporter assays demonstrated direct binding between circMAPKBP1 and miR-143-y. Overexpression of miR-143-y promoted both proliferation and differentiation, and its expression pattern was reciprocal to that of circMAPKBP1 during differentiation. RNA-seq of miR-143-y-overexpressing cells revealed significant enrichment of downregulated genes in the mitogen-activated protein kinase (MAPK) signaling pathway. These results establish, for the first time, that the circMAPKBP1/miR-143-y axis modulates quail myogenesis, with the sponge mechanism most clearly explaining the opposing effects on differentiation. The findings provide molecular targets and a mechanistic framework for genetic improvement of muscle traits in poultry.