A Long-Range cis-Regulatory Element for Class I Odorant Receptor Genes

Individual olfactory sensory neurons express a single odorant receptor (OR) gene from either class I genes residing in a single cluster on a single chromosome or class II genes spread over multiple clusters on multiple chromosomes. Here, we identify an enhancer element for mouse class I genes, the J element, that regulates class I gene expression of a much larger number of genes and over a much greater genomic distance than known class II gene enhancers. Our data reveal an extraordinary long-range cis-regulatory element that governs the singular class I gene expression and has been phylogenetically preserved to retain a single cluster organization of class I genes in mammals. To comprehensively analyze the effects of deletion of J (ΔJ) on all the OR genes, we directly compared the gene expression profiles in the olfactory epithelia from six wild-type and six ΔJ littermate mice using microarray analysis.