Transcription regulatory network (TRN) for retinal photoreceptor cell development. Multipotent, photoreceptor precursor cells differentiate into individual photoreceptor cell types via three separate pathways. Thin lines indicate protein-promoter interactions; solid lines indicate published data and dotted lines are from unpublished data of Hennig et al 2008 [145]. Reprinted from Brain Research 1192, Hennig, A.K., Peng, G-H., Chen, S., Regulation of photoreceptor gene expression by Crx-associated transcription factor network, 114–133, (2008) with permission from Elsevier.