Updated project metadata. We recently identified C18ORF25 as a new exercise-regulated phophoprotein. To investigate potential in vivo functions of C18ORF25, we used CRISPR/Cas9 to generate a whole-body knock-out (KO) mouse model on a C57BL/6J background. Proteomic analysis was performed to identify potental changes in the proteome. To gain further insights into the possible signalling pathways regulated by C18ORF25, Soleus muscles from WT and KO mice (n=4) were isolated, and the muscle from one leg was maintained at resting tension with no stimulation as a control while the muscle from the contralateral leg was subject to electrical stimulation ex vivo. Muscles were quickly snap frozen and subject to single-shot label-free phosphoproteomic analysis to compare the signalling responses between the genotypes.