Research Article

Rapid molecular evolution of pain insensitivity in multiple African rodents

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Science  31 May 2019:
Vol. 364, Issue 6443, pp. 852-859
DOI: 10.1126/science.aau0236

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How the mole-rat lost its pain

Pain alerts our bodies that something is amiss and typically we stop the pain-causing activity. Numerous species of plants and prey animals take advantage of this response by producing pain-causing substances that are released during predation attempts. In turn, species that encounter these substances often evolve ways of turning off the pain-producing mechanism. Eigenbrod et al. searched RNA transcripts in eight species of subterranean rodents related to pain-resistant naked mole-rats. They found multiple changes to ion channels involved in pain across the different species. Understanding such adaptations could elucidate pain mechanisms and help us develop approaches for pain relief.

Science, this issue p. 852

Abstract

Noxious substances, called algogens, cause pain and are used as defensive weapons by plants and stinging insects. We identified four previously unknown instances of algogen-insensitivity by screening eight African rodent species related to the naked mole-rat with the painful substances capsaicin, acid (hydrogen chloride, pH 3.5), and allyl isothiocyanate (AITC). Using RNA sequencing, we traced the emergence of sequence variants in transduction channels, like transient receptor potential channel TRPA1 and voltage-gated sodium channel Nav1.7, that accompany algogen insensitivity. In addition, the AITC-insensitive highveld mole-rat exhibited overexpression of the leak channel NALCN (sodium leak channel, nonselective), ablating AITC detection by nociceptors. These molecular changes likely rendered highveld mole-rats immune to the stings of the Natal droptail ant. Our study reveals how evolution can be used as a discovery tool to find molecular mechanisms that shut down pain.

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