Objective: A growing body of evidence suggests a correlation between endothelial cell dysfunction and cancer, as well as facioscapulohumeral dystrophy, both of which are DUX4-related diseases. However, the endogenous expression of DUX4 within endothelial cells (ECs) remains unexplored. This study aims to investigate DUX4 expression in ECs and examine the presence of DUX4-counteracting proteins named PAX3 and PAX7.

Material and Methods: This is a cell study in which human umbilical vein endothelial cells (HUVECs) were selected as an in vitro representative of the EC population. The presence of the DUX4, PAX3 and PAX7 proteins in the HUVECs was examined using immunofluorescence staining. The mRNA levels of these proteins were investigated using qPCR with specific primers for each transcript.

Results: It was observed that 51% of HUVECs expressed the DUX4 protein whereas only a small number of cells were stained with PAX3/PAX7 antibody. At the mRNA level, HUVECs exhibited expression of DUX4, PAX3 and PAX7. The mRNA levels of PAX3 and DUX4 were lower compared to PAX7 mRNA.

Conclusion: The high rate of DUX4 protein expression observed in HUVECs is the first positive data and suggests a potential role for DUX4 protein in endothelial cells. Further analyses including the functional analyses of DUX4, PAX3 and PAX7 in ECs could improve our understanding of a vascular pathogenesis in DUX4-related diseases, particularly in the contexts of cancer and facioscapulohumeral dystrophy.