This contrasts with two other mouse models of night blindness, Bhlhe23−/− mice11 and Prdm8eGFP/eGFP mice12, which are functionally null mutations of the transcription factor genes Bhlhe23 (also known as BHLHB4 or basic helix-loop-helix family member, b4) and Prdm8 (PRDI-BF1 and RIZ homology domain containing 8) respectively. The gene discussed is BHLHE23; the disease is night blindness.