Fluorescence-Activated Cell Sorting of Olfactory Sensory Neuron Subpopulations.

The mouse olfactory epithelium is composed of a heterogeneous population of olfactory sensory neurons, where each neuron expresses one single type of odorant receptor gene, out of a repertoire of ~1000 different genes. Fluorescent-activated cell sorting (FACS) is a powerful technique, which can be used to isolate a cellular subpopulation from a heterogeneous tissue. The sorted neurons can then be used in gene expression studies, or analyzed for the presence of different DNA epigenetic modification marks. Here we describe a method to separate a subpopulation of olfactory sensory neurons expressing the odorant receptor Olfr17. In this method, the main olfactory epithelium from transgenic Olfr17-IRES-GFP mice is dissociated into single cells, followed by separation of the GFP positive cells by FACS.

Nuclear architecture and gene silencing in olfactory sensory neurons.

Odorants are discriminated by hundreds of odorant receptor (OR) genes, which are dispersed throughout the mammalian genome. The OR genes are expressed in a highly specialized type of cell, the olfactory sensory neuron. Each one of these neurons expresses one of the 2 alleles from one single OR gene type. The mechanisms underlying OR gene expression are unclear. Here we describe recent work demonstrating that the olfactory sensory neuron shows a particular nuclear architecture, and that the genomic OR loci are colocalized in silencing heterochromatin compartments within the nucleus. These discoveries highlight the important role played by epigenetic modifications and nuclear genome organization in the regulation of OR gene expression.