A Myocyte-Enriched Long Non-Coding RNA NRMLncR Enhances Myogenesis in Mouse.

Myogenesis is a stepwise process encompassing myogenic progenitor proliferation, lineage commitment, differentiation, myocyte fusion, and myotube maturation, and it is orchestrated by myogenic regulatory factors (MRFs) together with signaling pathways that coordinate these transitions. Long noncoding RNAs (lncRNAs) have emerged as important regulators of muscle development and regeneration, yet how lncRNAs integrate with canonical signaling networks to shape myogenic progression remains incompletely defined. Here, we identify a novel myocyte-enriched, Notch-repressed myogenic lncRNA (NRMLncR, known as A930003A15Rik), as a previously uncharacterized regulator of mouse myogenesis. The expression of NRMLncR is robustly induced during primary myoblast activation and differentiation. Loss-of-function analyses show that knockdown of NRMLncR impairs myogenic differentiation, accompanied by reduced expression of key myogenic genes. In contrast, adenovirus-mediated overexpression of NRMLncR enhances myogenic differentiation in vitro and is associated with increased muscle fiber size in vivo. Mechanistically, MyoD and MyoG occupy the NRMLncR promoter and promote its transcription during myogenic differentiation. NRMLncR knockdown alerts the transcription of nearby genes, suggesting its function through a cis-regulatory mechanism. RNA pull-down and functional assays further identify an interaction between NRMLncR and the RNA-binding protein CELF1. Together, these findings establish NRMLncR as a novel Notch-associated lncRNA that promotes myogenic differentiation and provide insight into lncRNA-dependent regulation of the myogenic program.