Olfactory receptor enhancers drive expression of the active OR gene in cis and in trans
Intergenic olfactory receptor (OR) enhancers, residing in OR clusters aggregate in cis and in trans to drive the expression of the active OR allele (A) in olfactory sensory neurons (OSNs). Long-range enhancer interactions are mediated by Ldb1, and Ldb1 knockout OSNs don’t form an enhancer hub, precluding the expression of any OR gene (B). Deletion of a single enhancer abolishes its interaction with the enhancer hub and reduces the expression of local OR genes (C), illustrating the principle that OR enhancers are necessary in cis and redundant in trans.