Researchers of Vanderbilt and Berkeley of the United States recently dug around the star of the star-nosed mole to see what could be learned about mammalian mechanoreception, sense of touch.
Moles are generally creatures that spend most time underground and therefore have terrible vision. To make up for this they have an excellent sense of touch. The star-nosed mole is classified as an animal with the highest density of touch neurons in one area of any animal on the planet. The star of this creature is where most of the touch receptors are housed. For this reason, this group wanted to test the microbiological and genetic components that make this organ so great for mechanoreception in order to learn about mammalian parallels.
The enhanced tactical acuity of the star led researchers to believe the ability of the mole to detect noxious stimuli of thermal and/or chemical root may be impaired. The enhancement of one sense may come at the expense of another so to speak. This was tested by applying capsaicin to the hind-paw of the mole and mice followed by application to mole nose. The first test elicited a nocifensive response in both mole and mouse, but no behavioral response was seen when applied to mole star.
RNA sequencing revealed a lack of TRPA1 and TRPV1 in the group of neurons immediately associated with the star-nose, but a 10 fold higher detection of these molecules in neurons outside the nose proximity. The aforementioned molecules are associated with nociception, or detection of pain.
Furthermore, 20 fold higher levels of Cnga2 and Cnga4, molecules associated with touch detection, were found in the ganglia associated with the nose (trigeminal ganglia) than found outside the area (dorsal root ganglia). A related ion channel, Fam 38a (Piezo1), was found to be expressed in trigeminal ganglia and dorsal root ganglia. Fam38a was found as a parallel to mouse Piezo1.
The group concluded that genes found to be associated with expression of mechanoreceptor stimuli as well as CNG and Piezo1 ion channels played roles in various aspects of mechano-transduction. Studying animals at the extremes of sensory perception can aid in understanding the senses further. In this case, researchers were guided closer to the answer of “how do humans feel” by a star not in the sky, but on a mole.
Kristin A. Gerhold equal contributor,
Maurizio Pellegrino equal contributor,
Makoto Tsunozaki, Takeshi Morita, Duncan B. Leitch, Pamela R. Tsuruda, Rachel B. Brem, Kenneth C. Catania, Diana M. Bautista. The Star-Nosed Mole Reveals Clues to the Molecular Basis of Mammalian Touch. PLoS ONE, 2013