Fos-P2A-iCreERT2 Mouse

The Fos gene (Fos proto-oncogene) encodes the Fos protein, also known as c-Fos, which is a nuclear transcription factor belonging to the immediate early gene (IEG) family. Fos can be rapidly and transiently induced in neurons in brain tissue following stimuli such as sensory stimulation, synaptic activity, or stress, and can also be expressed in other tissues and cells in response to growth factors and various external signals. The Fos protein can form heterodimers with Jun family proteins to constitute the transcription factor AP-1, which regulates transcription of downstream genes and participates in the regulation of gene expression related to cell proliferation, differentiation, and neural activity. Because Fos expression can reflect the activation state of cells within a specific time window, it is commonly used in neuroscience research to identify activated cells; however, its expression is not neuron-specific and should be interpreted in conjunction with experimental conditions and other markers ^[1-2].

Fos-P2A-iCreERT2 mice are constructed using gene editing technology by inserting a "P2A-iCreERT2" cassette at the stop codon of the mouse endogenous c-Fos gene. In the absence of tamoxifen treatment, iCreERT2 recombinase is mainly localized in the cytoplasm; after tamoxifen induction, iCreERT2 recombinase can enter the nucleus and exert its recombination activity. When Fos-P2A-iCreERT2 mice are crossed with mice carrying loxP sites, after tamoxifen induction, the offspring are expected to achieve iCreERT2 recombinase-mediated sequence recombination between loxP sites in Fos-positive cells.