Deletion of phosphatidylserine flippase β-subunit Tmem30a in satellite cells leads to delayed skeletal muscle regeneration

Phosphatidylserine(PS)is distributed asymmetrically in the plasma membrane of eukaryotic cells.Phosphatidylserine flippase(P4-ATPase)transports PS from the outer leaflet of the lipid bilayer to the inner leaflet of the membrane to maintain PS asymmetry.TheβsubunitTMEM30 Ais indispensable for transport and proper function of P4-ATPase.Previous studies have shown that the ATP11 A and TMEM30 A complex is the molecular switch for myotube formation.However,the role of Tmem30 a in skeletal muscle regeneration remains elusive.In the current study,Tmem30 a was highly expressed in the tibialis anterior(TA)muscles of dystrophin-null(mdx)mice and BaCl2-induced muscle injury model mice.We generated a satellite cell(SC)-specific Tmem30 a conditional knockout(cKO)mouse model to investigate the role of Tmem30 a in skeletal muscle regeneration.The regenerative ability of cKO mice was evaluated by analyzing the number and diameter of regenerated SCs after the TA muscles were injured by BaCl2-injection.Compared to the control mice,the cKO mice showed decreased Pax7+and MYH3+SCs,indicating diminished SC proliferation,and decreased expression of muscular regulatory factors(MYOD and MYOG),suggesting impaired myoblast proliferation in skeletal muscle regeneration.Taken together,these results demonstrate the essential role of Tmem30 a in skeletal muscle regeneration.

Overexpression of Twist1 in vascular endothelial cells promotes pathological retinal angiogenesis in mice

Retinal angiogenesis is a critical process for normal retinal function.However,uncontrolled angiogenesis can lead to pathological neovascularization(NV),which is closely related to most irreversible blindness-causing retinal diseases.Understanding the molecular basis behind pathological NV is important for the treatment of related diseases.Twist-related protein 1(TWIST1)is a well-known transcription factor and principal inducer of epithelial-mesenchymal transition(EMT)in many human cancers.Our previous study showed that Twist1 expression is elevated in pathological retinal NV.To date,however,the role of TWIST1 in retinal pathological angiogenesis remains to be elucidated.To study the role of TWIST1 in pathological retinal NV and identify specific molecular targets for antagonizing pathological NV,we generated an inducible vascular endothelial cell(EC)-specific Twist1 transgenic mouse model(Tg-Twist1iEC+).Whole-mount retinas from Tg-Twist1iEC+mice showed retarded vascular progression and increased vascular density in the front end of the growing retinal vasculature,as well as aneurysm-like pathological retinal NV.Furthermore,overexpression of Twist1 in the ECs promoted cell proliferation but disturbed cell polarity,thus leading to uncontrolled retinal angiogenesis.TWIST1 promoted pathological NV by activating the Wnt/β-catenin signaling pathway and inducing the expression of NV formation-related genes,thereby acting as a‘valve’in the regulation of pathological angiogenesis.This study identified the critical role of TWIST1 in retinal pathological NV,thus providing a potential therapeutic target for pathological NV.