HDAC4 and bone disorder: Since Klotho functions as a coreceptor of FGF receptors (FGFRs) to activate a specific fibroblast growth factor 23 (FGF23) signal pathway and FGF23 exerts its biological effects in a Klotho-dependent manner (Lu and Hu, 2017; Navarro-Garcia et al., 2021), it is possible that HDAC4-mediated regulation of Klotho may also indirectly influence the biological functions of FGF23 such as mineral homeostasis and CKD-related bone disorders and cardiovascular problems.