SPRR2F (small proline rich protein 2F) is a keratinocyte structural protein involved in cornified envelope formation and epidermal differentiation. The protein is synthesized in the cytosol and becomes cross-linked to membrane proteins via transglutaminase, forming an insoluble envelope beneath the plasma membrane. This structural role is critical for maintaining epithelial integrity and barrier function. At the transcriptional level, SPRR2F expression is dynamically regulated in response to various physiological stimuli. SPRR2F is significantly downregulated in smoking-exposed palatal mucosa, suggesting its suppression may compromise innate immune defenses and contribute to increased periodontal disease susceptibility 1. Similarly, the transcription factor Rorα suppresses SPRR2F expression in cutaneous squamous cell carcinoma cells, and this downregulation correlates with enhanced proliferation and migration in cSCC progression 2. In contrast, SPRR2F expression is upregulated following UV radiation exposure in normal mouse skin, alongside other stress-response genes 3. Clinically, SPRR2F has utility as a cell-specific promoter for conditional genetic studies. The BAC-Sprr2f-Cre transgenic line effectively drives epithelial-specific gene deletion in the endometrium, showing variegated expression within the luminal and glandular epithelium while sparing oviducts, ovaries, and kidneys 45. This tool has been instrumental in studying endometrial homeostasis and cancer biology through conditional knockout models of tumor suppressors like MIG-6 and CHD4.