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. Author manuscript; available in PMC: 2014 Jun 1.
Published in final edited form as: Neurochem Res. 2012 Oct 18;38(6):1100–1112. doi: 10.1007/s11064-012-0906-y

Figure 5. Potential roles of the pineal homeobox genes.

Figure 5

A) Development of the pinealocyte: The proliferation, differentiation and maturation processes of the mammalian pinealocyte are driven by homeodomain transcription factors acting sequentially at different developmental stages. B) Tissue-specific gene expression in the mature pinealocyte: Intrinsic pineal factors in the form of homeodomain proteins control pineal-specific gene expression by binding cis-acting photoreceptor conserved elements (PCEs). On top of this, extrinsic factors in the form of norepinephrine released from sympathetic nerve terminals during nighttime drive cAMP-dependent circadian rhythms in pineal gene expression. For simplicity, only one copy of each cis-element is displayed. The rat Aanat promoter contains at least three PCEs; two of these preferentially bind OTX/CRX, whereas the third might prefer RAX, as indicated by Genomatix promoter analysis. The roles of Pax4 and Rax in the pinealocyte are not yet established, as indicated by question marks (?). CRE, cAMP responsive element; CREB, cAMP responsive element binding protein; NE, norepinephrine; PCE, photoreceptor conserved element, this term refers a group of cis-elements with slightly different core sequences including both OTX2/CRX- and RAX-binding sequences [102].