LANCL1-AS1 levels decline with muscle aging, increase with human myogenesis By combining the analysis of RNAs expressed in a human cultured model of myogenesis, as well as sequencing and muscle aging biopsies (GESTALT), we identified 48 differentially expressed RNAs shared with these analyses; 5 of these are lncRNAs. Many lncRNAs were shown to correlate with myogenesis and muscle regeneration, but few have known function. We found that LANCL1-AS1 was the most differentially expressed lncRNAs in this combined analysis. Moreover, LANCL1-AS1 is the second most significantly downregulated RNA by negative binomial models analysis during muscle aging. In addition, the linear regression plots showed that LANCL1-AS1 levels were significantly reduced with advancing age. RT-qPCR analysis confirmed a rise in the levels of LANCL1-AS1 during the early stages in human myogenesis, and continuous upregulation of OIP5-AS1 with advancing myogenic differentiation. Those results suggest that LANCL1-AS1 may play an important role for myogenesis, muscle regeneration and muscle aging. LANCL1-AS1 may promote myogenesis, translocates to cytoplasm during myogenesis To begin to study the role of LANCL1-AS1 in myogenesis, we silenced LANCL1-AS1 in AB678 human myoblasts. interestingly, this intervention reduced myogenesis progression in human myoblasts, as determined by measuring myotube formation. To further understand the potential mechanism by which LANCL1-AS1 affected myogenesis, we fractionated RNA through sucrose gradients. LANCL1-AS1 translocated from the nucleus to the cytoplasm during myogenic differentiation, suggesting that LANCL1-AS1 may play the different roles during myogenesis by targeting with different molecular partners on different subcellular spaces. Since the binding partner is critical for lncRNA functions, we used biotinylated antisense oligonucleotides (ASO) RNAs to pull down interacting RNA-binding proteins by mass spectrometry (ChIRP-MS). ChIRP and RT-qPCR analysis revealed that LANCL1-AS1 was very efficiently pulled down by specific LANCL1-AS1 ASOs. Recently, a few examples have been reported of lncRNAs that can be translated partially into small protein products (micropeptides). Interestingly, we also found LANCL1-AS1 is present in small polysome fractions, suggesting that LANCL1-AS1 has protein-coding potential. Notably, differentiated myoblasts have more LANCL1-AS1 is in the heavy polysome fraction, suggesting that LANCL1-AS1 may have functional mcicropeptide during myogenic differentiation. Ongoing Efforts To test the hypothesis that lncRNA LANCL1-AS1 promotes myogenesis and muscle regeneration, we are exploring these three areas: (1) whether LANCL1-AS1 can regulate human myogenesis by (1a) characterizing and annotating lncRNA LANCL1-AS1 in human myoblast and (1b) by determining whether silencing and overexpressing LANCL1-AS1 can regulate myogenesis in myoblasts. (2) the molecular mechanisms by which LANCL1-AS1 regulates gene expression during myogenesis by (2a) identifying and comparing systematically between LANCL1-AS1-driven gene expression changes during myogenesis; (2b) identifying systematically LANCL1-AS1-interacting proteins; and (2c) investigating whether lncRNA LANCL1-AS1 encodes small micropeptide. (3) the role of LANCL1-AS1 in sarcopenia and muscle regeneration in mice by (3a) comparing LANCL1-AS1 expression in muscle biopsy from sarcopenia and healthy donors and (3b) examining whether modulating LANCL1-AS1 levels affects muscle regeneration after exposure to hind limb atrophy.