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. Author manuscript; available in PMC: 2014 Feb 20.
Published in final edited form as: Cell. 2013 Jul 18;154(2):325–336. doi: 10.1016/j.cell.2013.06.039

Figure 7.

Figure 7

A three node signaling cascade combined with a feedback signal that generates epigenetic memory (A) Stabilization of OR expression is achieved by an Adcy3-dependent "trap" such that the functional chosen OR cannot be turned off once LSD1 is downregulated by its induction of Adcy3. This trap is caused by removing LSD1 from the signaling circuit which allows stable transcription to ensue (represented by dashed line that reflects the indirect OR stabilization by Adcy3). (B) Pseudogene ORs (ORΨ) are unable to activate Adcy3 and thus OSNs that have chosen these ORs maintain the ability to re-choose and use LSD1 to transcriptionally silence the ORΨ. (C) Alternatively, LSD1 may not silence directly the previously chosen OR, but causes its repression by activating and additional OR allele.