Role of Mutant TBP in Regulation of Myogenesis on Muscle Satellite Cells

LncRNA-TBP mediates TATA-binding protein recruitment to regulate myogenesis and induce slow-twitch myofibers

BACKGROUND

Skeletal muscle is comprised of heterogeneous myofibers that differ in their physiological and metabolic parameters. Of these, slow-twitch (type I; oxidative) myofibers have more myoglobin, more mitochondria, and higher activity of oxidative metabolic enzymes compared to fast-twitch (type II; glycolytic) myofibers.

METHODS

In our previous study, we found a novel LncRNA-TBP (for "LncRNA directly binds TBP transcription factor") is specifically enriched in the soleus (which has a higher proportion of slow myofibers). The primary myoblast cells and animal model were used to assess the biological function of the LncRNA-TBP in vitro or in vivo. Meanwhile, we performed a RNA immunoprecipitation (RIP) and pull-down analysis to validate this interaction between LncRNA-TBP and TBP.

RESULTS

Functional studies demonstrated that LncRNA-TBP inhibits myoblast proliferation but promotes myogenic differentiation in vitro. In vivo, LncRNA-TBP reduces fat deposition, activating slow-twitch muscle phenotype and inducing muscle hypertrophy. Mechanistically, LncRNA-TBP acts as a regulatory RNA that directly interacts with TBP protein to regulate the transcriptional activity of TBP-target genes (such as KLF4, GPI, TNNI2, and CDKN1A).

CONCLUSION

Our findings present a novel model about the regulation of LncRNA-TBP, which can regulate the transcriptional activity of TBP-target genes by recruiting TBP protein, thus modulating myogenesis progression and inducing slow-twitch fibers. Video Abstract.

A Longitudinal Study of T2 Mapping Combined With Diffusion Tensor Imaging to Quantitatively Evaluate Tissue Repair of Rat Skeletal Muscle After Frostbite

Purpose: T2 mapping and diffusion tensor imaging (DTI) enable the detection of changes in the skeletal muscle microenvironment. We assessed T2 relaxation times, DTI metrics, performed histological characterization of frostbite-induced skeletal muscle injury and repair, and provided diagnostic imaging biomarkers.

Design and Methods: Thirty-six Sprague Dawley rats (200 ± 10 g) were obtained. Thirty rats were used for establishing a skeletal muscle frostbite model, and six were untreated controls. Functional MR sequences were performed on rats on days 0, 3, 5, 10, and 14 (n = 6 per time point). Rats were then sacrificed to obtain the quadriceps muscles. Tensor eigenvalues (λ1, λ2, and λ3), mean diffusivity (MD), fractional anisotropy (FA), and T2 values were compared between the frostbite model and control rats. ImageJ was used to measure the extracellular area fraction (EAF), muscle fiber cross-sectional area (fCSA), and skeletal muscle tumor necrosis factor α (TNF-α), and Myod1 expression. The correlation between the histological and imaging parameters of the frostbitten skeletal muscle was evaluated. Kolmogorov–Smirnoff test, Leven’s test, one-way ANOVA, and Spearman coefficient were used for analysis.

Results: T2 relaxation time of frostbitten skeletal muscle was higher at all time points (p < 0.01). T2 relaxation time correlated with EAF, and TNF-α and Myod1 expression (r = 0.42, p < 0.05; r = 0.86, p < 0.01; r = 0.84, p < 0.01). The average tensor metrics (MD, λ1, λ2, and λ3) of skeletal muscle at 3 and 5 days of frostbite increased (p < 0.05), and fCSA correlated with λ1, λ2, and λ3, and MD (r = 0.65, p < 0.01; r = 0.48, p < 0.01; r = 0.52, p < 0.01; r = 0.62, p < 0.01).

Conclusion: T2 mapping and DTI imaging detect frostbite-induced skeletal muscle injury early. This combined approach can quantitatively assess skeletal muscle repair and regeneration within 2 weeks of frostbite. Imaging biomarkers for the diagnosis of frostbite were suggested.

CTRP1 Attenuates UUO-induced Renal Fibrosis via AMPK/NOX4 Pathway in Mice

C1q/TNF-related protein 1 (CTRP1), a conserved protein of the C1q family, plays a key role in cardiovascular and metabolic diseases. However, the role of CTRP1 in renal injury is unclear. The purpose of this study is to explore the role of CTRP1 in unilateral ureteral obstruction (UUO)-induced renal fibrosis and to elucidate the underlying mechanism. Using gene delivery system, CTRP1 was overexpressed in the kidney, then the mice were operated to induce UUO model after adenovirus transfection. It was found that the expression of CTRP1 in the renal tissue was decreased in mice after UUO. CTRP1 overexpression decreased the kidney function and kidney weight index. Moreover, CTRP1 reduced oxidative stress and renal collagen deposition in vivo. As expected, we found that CTRP1 activated AMP-activated kinase (AMPK) and decreased NOX4 expression, while silencing AMPKα1 abolished the protective effects of CTRP1 overexpression in mice after UUO. In conclusion, CTRP1 may protect against UUO-induced renal injury via AMPK/NOX4 signaling. Our results indicate that CTRP1 exhibits potential effects to treat renal fibrosis caused by UUO.