The nuclear factor of the activated T cell (NFAT) family of transcription factors regulates cytokine gene expression by binding to the promoter/enhancer regions of antigen-responsive genes, usually in cooperation with heterologous DNA-binding partners. The nuclear factor of activated T lymphocytes (NFATC1) signaling has been demonstrated to play important roles in cardiac valve and septal development. Genetic variants in genes involved in NFATC1 signaling may affect their expression and promote the formation of congenital heart disease (CHD). Nuclear factor of activated T cells (NFATC1) was up-regulated in cancers mediating malignant behaviors. The nuclear factor of activated T cell 1 (Nfatc1) locus is a common insertion site for murine tumorigenic retroviruses, suggesting a role of transcription factor NFATc1 in lymphomagenesis.