c-Fos is a nuclear phosphoprotein that plays a pivotal role in cell signaling, proliferation, and differentiation. It forms a heterodimer with c-Jun, which then forms the activator protein-1 (AP-1) complex. This complex binds to specific DNA sequences in the promoter and enhancer regions of target genes, transforming extracellular signals into changes in gene expression. c-Fos is crucial in regulating cell development and maintaining skeletal formation. The expression of c-Fos is associated with various biological processes, including cell proliferation, differentiation, and programmed cell death. Additionally, c-Fos is involved in learning and memory processes, with changes in its expression observed in brain regions associated with recognition, working, and fear-related memory. c-Fos is also used as a marker for neural activity, with its expression linked to changes in neuronal function and plasticity. The expression of c-Fos is also related to the occurrence and development of cancer. The c-Fos protein can serve as a marker for tumorigenesis, and its dysregulation is associated with cancer progression. The absence of c-Fos leads to significant neurological abnormalities in mice embryos during development, indicating that c-Fos plays an important role in neurogenesis and brain development.