SPP1 and retinitis pigmentosa 1: Additionally, OCT4 was found to recognize and bind to the enhancer of OPN, a key regulator in ectopic calcification, in which there was a palindromic-octamer-recognition element (ATTTGAAATGCAAAT) (Botquin et al. 1998), and thus it is profound to investigate the role of OCT4 in regulating the OPN expression of hRIFs, since OPN was detected in crystalline deposits and was upregulated in RP tissues (Zhu et al. 2020a; Evan et al. 2005b).