Regulation of gene expression is critical for the maintenance of cell state and homeostasis. Aberrant regulation of genes can lead to unwanted cell proliferation or misdirected differentiation. Here we investigate the role of MED31, a highly conserved subunit of the Mediator complex, to determine the role this subunit plays in the maintenance of human mesenchymal stem cell (hMSC) state. Using siRNA-mediated knockdown of MED31 we demonstrate a decrease in self-renewal based on cell assays and monitoring of gene expression. In addition, in the absence of MED31, hMSCs also displayed a reduction in adipogenesis as evidenced by diminished lipid vesicle formation and expression of specific adipogenic markers. These data present evidence for a significant role for MED31 in maintaining adult stem cell homeostasis, thereby introducing potential novel targets for future investigation and use in better understanding stem cell behavior and adipogenesis.
Liposarcomas are the most diagnosed soft tissue sarcoma, with most cases consisting of well-differentiated (WDLPS) or dedifferentiated (DDLPS) histological subtypes. While both tumor subtypes can have clinical recurrence due to incomplete resections, DDLPS often has worse prognosis due to a higher likelihood of metastasis compared to its well-differentiated counterpart. Unfortunately, targeted therapeutic interventions have lagged in sarcoma oncology, making the need for molecular targeted therapies a promising future area of research for this family of malignancies. In this work, previously published data were analyzed to identify differential pathways that may contribute to the dedifferentiation process in liposarcoma. Interestingly, Gli-mediated Hedgehog signaling appeared to be enriched in dedifferentiated adipose progenitor cells and DDLPS tumors, and coincidentally Gli1 is often co-amplified with MDM2 and CDK4, given its genomic proximity along chromosome 12q13-12q15. However, we find that Gli2, but not Gli1, is differentially expressed between WDLPS and DDLPS, with a noticeable co-expression signature between Gli2 and genes involved in ECM remodeling. Additionally, Gli2 co-expression had a noticeable transcriptional signature that could suggest Gli-mediated Hedgehog signaling as an associated pathway contributing to poor immune infiltration in these tumors.
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