Studies on the role of CCAAT/enhancer binding protein (C/EBP) family of bZIP transcription factors (particularly C/EBPβ) in mammary gland development and breast cancer have shown that targeted deletion of C/EBPβ isoforms results in severe inhibition of lobuloalveolar development, blocks functional differentiation, and induces changes in ductal morphogenesis. The gene discussed is CEBPB; the disease is breast cancer.