VP.62 DUX4 expression turn on the myogenic program in MSC

Abstract

Muscle tissue degeneration is accompanied by fibrosis in patients with the facioscapulohumeral dystrophy (FSHD). In skeletal muscles, MSCs are present and they can participate in muscles regeneration. When a muscle is injured, MSCs can migrate towards damaged site from blood circulation and neighboring intact tissues and participate in the recovery process also. Since FSHD is a genetic disease associated with aberrant <i>DUX4</i> expression, we hypothesized that MSC involved in the regeneration process may also have overexpressed level of <i>DUX4</i>, and created a model of MSC with inducible <i>DUX4</i> expression (MSC-DUX4) using the Jagannathan's approach and construct pCW57.1-DUX4-WT from Addgen. MSCs were obtained from the Cell culture collection of the IDB RAS. <i>DUX4</i> expression was confirmed in MSC-DUX4 cells by immunofluorescent staining. We conducted a comparative analysis of the differentiation potencies of MSCs and MSCs with inducible <i>DUX4</i> expression (MSCs were from the same donor). It was shown that MSCs with induced <i>DUX4</i> expression have an increased potential for myogenic differentiation, which is not characteristic of normal MSCs. These cells can fuse and form mature myotubes expressing the main markers of late myogenesis (Troponin T, MF20). At the same time, MSCs with induced expression of <i>DUX4</i> have reduced potencies for main MSC differentiations - adipogenic and osteogenic, that was shown using biochemical, immunocytochemical and RT-PCR assays. Thus, upon induction of DUX4 expression, MSCs turn on the myogenic program, while losing the capacity for their main differentiations. This does not seem so counterintuitive, since the genes involved in myogenesis are <i>DUX4</i>-downstream target genes. However, the real contribution of MSC-DUX4 to the regeneration of muscles affected by FSHD remains to be analyzed.