Fosb, also known as FBJ Murine Osteosarcoma Viral Oncogene Homolog B, is a proto-oncogene and a member of the Fos family of transcription factors. It plays a role in a wide variety of tumourigenic processes and is involved in regulating gene expression. ΔFosB, a product of the FosB gene, accumulates in response to repeated stimulation due to its unusual protein stability, and is associated with pathways related to stress, reward, and neuronal excitability [2].

In mouse models, persistent ΔFosB expression limits recurrent seizure activity and provides neuroprotection in the dentate gyrus of APP mice, acting through discrete modes of hippocampal target gene regulation to modulate neuronal excitability [1]. In mast cell-specific FosB knockout male mice, FOSB/ΔFOSB modulates mast cell functions by limiting reactivity to allergen-like stimuli both in vitro and in vivo, mediated in part by enhanced DUSP4 expression which attenuates MAPK signaling [3].

In conclusion, Fosb and its product ΔFosB are important regulators in multiple biological processes. Mouse knockout models have revealed their role in diseases such as epilepsy and in modulating allergic inflammation, contributing to our understanding of these disease mechanisms and potentially guiding future therapeutic developments.