AsianScientist (Oct. 19, 2017) – In a study published in Nature Communications, scientists in Japan have identified how the genetic expression of odor receptors is regulated.
Each odor-detecting neuron (olfactory sensory neuron), chooses a single odorant receptor gene from a fairly large number of options that are split into class I (fish-like) and class II (terrestrial-specific) odorant receptors. This strict selectiveness of olfactory sensory neurons is in part due to enhancers, which are DNA sequences that enhance transcription of a gene when bound by specific protein.
Understanding enhancer functions is of great interest due to their importance in gene expression as well as evolution and disease. However, they have not been sufficiently studied because they cannot be easily predicted from DNA sequences or chromosome modifications nor can they be easily identified.
In this study, a group of scientists led by Associate Professor Junji Hirota of the Tokyo Institute of Technology discovered a regulatory sequence, called the J element, that controls the expression of many more class I odorant receptor genes than other regulatory sequences of class II odorant receptor genes. This extraordinary long-range regulation has never been seen before.
The researchers also report that the J element is evolutionarily conserved across mammalian species, ranging from the most primitive mammal, the platypus, to humans. This may be especially useful as it sheds light onto why class I genes remain on a single region on one chromosome during mammalian evolution, while class II genes do not.
Based on genetic evidence, the researchers also highlight the concept of allelic exclusion, or the expression of just one copy of a gene and not the other. This is especially important for the J element, as it shows that its activity determines which copy of a gene is expressed. This is a novel mechanism of expression wherein the gene regulatory region determines if genes will be turned on or off.
The researchers speculate that the investigation of factors that bind this specific element could reveal the molecular mechanisms that drive selective J element-dependent odorant gene receptor expression.
The article can be found at: Iwata et al. (2017) A Long-range Cis-regulatory Element for Class I Odorant Receptor Genes.
———
Source: Tokyo Institute of Technology; Photo: Pixabay.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.