EPRS1 and hydrops fetalis: To understand the primary changes of the proteome caused by the loss of Eprs1 at the steady state level (determined by protein synthesis and degradation rates), we performed quantitative mass spectrometry at 2 weeks post-Eprs1 deletion (to avoid secondary effects from the late stage HF) and found a significant decrease of 312 proteins (cutoff: Log2FC < −1 or p < 0.05) and an increase of 616 proteins (cutoff: Log2FC > 1 or p < 0.05) in Eprs1cKO-Homo hearts (Figure 5A, Table S2), indicating a significant compensatory response at this stage.