ABSTRACT
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. The ß subunit TMEM30A is indispensable for transport and proper function of P4-ATPase. Previous studies have shown that the ATP11A and TMEM30A complex is the molecular switch for myotube formation. However, the role of Tmem30a in skeletal muscle regeneration remains elusive. In the current study, Tmem30a was highly expressed in the tibialis anterior (TA) muscles of dystrophin-null ( mdx) mice and BaCl 2-induced muscle injury model mice. We generated a satellite cell (SC)-specific Tmem30a conditional knockout (cKO) mouse model to investigate the role of Tmem30a 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 BaCl 2-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 Tmem30a in skeletal muscle regeneration.
Subject(s)
Membrane Proteins/metabolism , Muscle, Skeletal/physiology , Regeneration/physiology , Satellite Cells, Skeletal Muscle/metabolism , Animals , Cell Proliferation , Dystrophin/genetics , Dystrophin/metabolism , Estrogen Antagonists/toxicity , Gene Expression Regulation/physiology , Genotype , Membrane Proteins/genetics , Mice , Mice, Inbred mdx , Mice, Knockout , Muscle, Skeletal/drug effects , MyoD Protein/genetics , MyoD Protein/metabolism , Myogenin/genetics , Myogenin/metabolism , Myosin Heavy Chains/genetics , Myosin Heavy Chains/metabolism , PAX7 Transcription Factor/genetics , PAX7 Transcription Factor/metabolism , Regeneration/genetics , Tamoxifen/toxicityABSTRACT
Familial exudative vitreoretinopathy (FEVR) is a hereditary eye disease characterized by defects in the development of periphery retinal vessels. However, the clinical phenotypes of FEVR vary widely from asymptomatic to complete blindness. We analyzed patients from three Chinese families and one sporadic patient with FEVR to investigate the clinical features and disease-causing mutations. Ocular phenotypes included increased ramification of the peripheral retinal vessels, a peripheral avascular zone, inferotemporal dragging of the optic disc and macula, and retinal folds. Peripheral blood DNA samples were obtained from patients with FEVR and their family members. Primers were designed to amplify the coding exons and adjacent intronic regions of the FEVR-causing genes FZD4, LRP5, NDP and TSPAN12. By polymerase chain reactions, each amplicon was subjected to direct Sanger sequencing analysis. Potential pathogenic changes of the sequence variants were analyzed by the orthologous protein sequence alignment and computational prediction software. We identified five LRP5 mutations: three novel heterozygous mutations-p.M181R, p.R399S and p.G503R and two known mutations that were never reported in FEVR patients: p.R494Q and p.G876S. All five mutations involved highly conserved residues and were predicted to be damaging by SIFT and PolyPhen-2. None was present in 500 normal individuals. To assess the pathogenesis of these mutations, wild-type and all five mutant LRP5 proteins were assayed for the ability to activate the Norrin/ß-catenin pathway by established luciferase reporter assays, and all mutants failed to activate the pathway. This study extends the genetic database of the FEVR disease in China and provides a basis for molecular diagnosis of the disease.
