Loss of MEF2D expression inhibits differentiation and contributes to oncogenesis in rhabdomyosarcoma cells.

BACKGROUND: Rhabdomyosarcoma (RMS) is a highly malignant pediatric cancer that is the most common form of soft tissue tumors in children. RMS cells have many features of skeletal muscle cells, yet do not differentiate. Thus, our studies have focused on the defects present in these cells that block myogenesis. METHODS: Protein and RNA analysis identified the loss of MEF2D in RMS cells. MEF2D was expressed in RD and RH30 cells by transient transfection and selection of stable cell lines, respectively, to demonstrate the rescue of muscle differentiation observed. A combination of techniques such as proliferation assays, scratch assays and soft agar assays were used with RH30 cells expressing MEF2D to demonstrate the loss of oncogenic growth in vitro and xenograft assays were used to confirm the loss of tumor growth in vivo. RESULTS: Here, we show that one member of the MEF2 family of proteins required for normal myogenesis, MEF2D, is largely absent in RMS cell lines representing both major subtypes of RMS as well as primary cells derived from an embryonal RMS model. We show that the down regulation of MEF2D is a major cause for the failure of RMS cells to differentiate. We find that MyoD and myogenin are bound with their dimerization partner, the E proteins, to the promoters of muscle specific genes in RMS cells. However, we cannot detect MEF2D binding at any promoter tested. We find that exogenous MEF2D expression can activate muscle specific luciferase constructs, up regulate p21 expression and increase muscle specific gene expression including the expression of myosin heavy chain, a marker for skeletal muscle differentiation. Restoring expression of MEF2D also inhibits proliferation, cell motility and anchorage independent growth in vitro. We have confirmed the inhibition of tumorigenicity by MEF2D in a tumor xenograft model, with a complete regression of tumor growth. CONCLUSIONS: Our data indicate that the oncogenic properties of RMS cells can be partially attributed to the loss of MEF2D expression and that restoration of MEF2D may represent a useful therapeutic strategy to decrease tumorigenicity

Alternative splicing of MEF2C pre-mRNA controls its activity in normal myogenesis and promotes tumorigenicity in rhabdomyosarcoma cells.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Many cellular disruptions contribute to the progression of this pediatric cancer, including aberrant alternative splicing. The MEF2 family of transcription factors regulates many developmental programs, including myogenesis. MEF2 gene transcripts are subject to alternate splicing to generate protein isoforms with divergent functions. We found that MEF2Cα1 was the ubiquitously expressed isoform that exhibited no myogenic activity and that MEF2Cα2, the muscle-specific MEF2C isoform, was required for efficient differentiation. We showed that exon α in MEF2C was aberrantly alternatively spliced in RMS cells, with the ratio of α2/α1 highly down-regulated in RMS cells compared with normal myoblasts. Compared with MEF2Cα2, MEF2Cα1 interacted more strongly with and recruited HDAC5 to myogenic gene promoters to repress muscle-specific genes. Overexpression of the MEF2Cα2 isoform in RMS cells increased myogenic activity and promoted differentiation in RMS cells. We also identified a serine protein kinase, SRPK3, that was down-regulated in RMS cells and found that expression of SRPK3 promoted the splicing of the MEF2Cα2 isoform and induced differentiation. Restoration of either MEF2Cα2 or SPRK3 inhibited both proliferation and anchorage-independent growth of RMS cells. Together, our findings indicate that the alternative splicing of MEF2C plays an important role in normal myogenesis and RMS development. An improved understanding of alternative splicing events in RMS cells will potentially reveal novel therapeutic targets for RMS treatment

A Survey of Foreign Students’ Cross-cultural Adaptation in Chongqing Normal University—A Case Study of Sri Lankan Students

Cross-cultural adaptation research is an important part of study for foreign students. With theories of Searle & Ward and John W. Berry, mainly from two aspects: psychological adaptation and social-cultural adaptation, the research investigates Sri Lankan students’ cross-cultural adaptation in Chongqing Normal University and analyzes the problems of Sri Lankan students’ cross-cultural adaptation in Chongqing Normal University in four aspects: Chinese reading and vocabulary, communication and exchange, adaptation of learning and teaching styles and knowledge of Chinese culture. Combined with the survey and problems of Sri Lankan students’ adaptation, the research will be used to give relevant suggestions to help Sri Lankan students adapt Chinese culture better

Finite element simulation of pressing fabric switch at low speed

The partial weave of a through-interlocking fabric switch has been simplified, and the 1/3 twill woven fabric model is set up. Finite element software Workbench has been used to simulate the dynamic response of 1/3 twill woven fabric compressed at a low speed by a sphere and to analyse the compressive deformation process of the 1/3 twill woven fabric. The influence of yarn material properties, the friction coefficient among yarns at crossovers, the friction coefficient between sphere and fabric, and the compression traverse of sphere on the compressibility of through-interlocking fabric switch are studied. The results reveal that the pressing pressure of the fabric switch increases with the increase in elastic modulus of insulating yarns, the friction coefficient among the yarns at crossovers, the friction coefficient between sphere and fabric, and the height of supporting part