Higher expression of KLF15 was detected in slow than in fast muscles.
KLF15 did not regulate myogenic differentiation of C2C12 cells.
KLF15 upregulated slow myosin heavy chain expression in C2C12 myotubes.
KLF15 regulated NFATc1 expression by direct binding and activating Nfatc1 promoter.
KLF15 upregulated slow myosin heavy chain expression through NFATc1.