SELENON-Related Myopathy (SELENON-RM) is caused by recessive mutations of the SELENON gene and is characterized by spinal and axial muscle weakness with progressive respiratory insufficiency. There are no effective treatments for SELENON-RM. A challenge has been the lack of cellular or animal models that exhibit disease-related abnormalities. The SELENON gene encodes selenoprotein N, a reductase enzyme involved in redox reactions located at the sarcoplasmic/endoplasmic reticulum membrane. Selenoprotein N has been shown to colocalize with mitochondria-associated membranes (MAMs) and participate in mitochondrial function. However, the molecular mechanism(s) by which selenoprotein N deficiency cause SELENON-RM are undetermined. Selenoprotein N expression peaks during embryogenesis, specifically in somites and presomitic mesoderm cells (skeletal muscle precursors), with weaker expression during adulthood. However, the role that selenoprotein N plays during embryonic development remains to be explored. Here we present three cellular and animal model assays suited for studying the mechanism(s) of disease and therapeutic development. Firstly, we demonstrate reduced spontaneous coiling in selenon-KO zebrafish embryos. Analysis of single cell RNAseq data in a zebrafish embryo-atlas reveals coexpression between selenon and multiple genes involved in the glutathione redox pathway. These data support a hypothesis that selenoprotein N plays a role in modulating the redox environment in conjunction with glutathione redox reactions. Secondly, we show that week-old selenon-KO zebrafish larvae exhibit reduced swimming activity. Electron microscopy of these larvae revealed enlargement of muscle mitochondria in KO-fish. Lastly, we report abnormalities of glycolytic and cellular respiration in myotubes from selenoprotein N deficient C2C12 and primary cells isolated from adult mice when seeded at high confluency. Together, these data enable a path toward disease mechanism discovery that encompasses different aspects of disease (i.e., embryonic, larval, and adult stages) as well as providing a basis for three assays of use for therapeutic testing.