The researchers focused on the Vmn2r family of genes, which encode proteins that function as olfactory receptors in mammals. These receptors detect odor molecules in the nose and transmit signals to the brain, enabling us to perceive different scents. Interestingly, the Vmn2r genes share a remarkable similarity to a group of immune receptor genes called the Vmn1r genes.
Through evolutionary analysis and functional studies, the researchers demonstrated that the Vmn2r genes evolved from an ancestral Vmn1r immune receptor gene. This gene duplication event occurred approximately 150 million years ago, coinciding with the divergence of mammals from other vertebrates.
The duplicated Vmn2r gene underwent several changes in its genetic sequence over time, acquiring mutations that specifically enhanced its ability to bind to odor molecules. These mutations led to the evolution of distinct olfactory receptor repertoires in different mammalian species, enabling them to detect and discriminate between a wide range of scents.
The researchers further showed that the Vmn2r genes became selectively expressed in the olfactory sensory neurons of the nose, while their ancestral Vmn1r counterparts remained expressed in immune cells. This functional shift was likely driven by changes in gene regulation that restricted Vmn2r expression to the olfactory system.
The co-option of Vmn2r genes from the immune system highlights the remarkable plasticity of gene function during evolution. Genes that originally evolved for one purpose can be repurposed to serve entirely new functions in different contexts. This evolutionary process underlies the complexity and diversity of biological systems, allowing organisms to adapt to changing environments and develop new sensory capabilities.
