MOLECULAR NEUROPHYSIOLOGY OF SENSORY ADAPTATIONS and BEHAVIOR

How do changes in gene structure and expression produce physiological changes that underlie complex behaviors? My lab addresses this question by investigating the molecular and physiological mechanisms of sensory and neuromuscular adaptations underlying predatory behavior (risk assessment, prey choice, prey-specific attack behavior, adaptation to prey defenses, learning, aversive conditioning). We study predator-prey interactions because they rely on fast, specialized sensory inputs and neuromuscular responses, and we focus on ion channels because they encode sensory information and regulate responses to stimuli. Interactions between carnivorous scorpion mice (a.k.a. grasshopper mice) and their chemically defended prey (scorpions, darkling beetles, centipedes, tarantulas) provide a powerful, ecologically relevant model for examining the role of neurotoxins and their ion channel targets in the evolution of adaptations that mediate predatory behavior.

Model System: Scorpions, darkling beetles, centipedes and tarantulas produce complex mixtures of neurotoxins (peptides, chemical compounds) that bind ion channels in sensory and neuromuscular systems, disrupting neuronal signaling and muscle contraction. Toxins that target ion channels (Na⁺, K⁺, TRPA1, TRPV1) in sensory systems induce burning pain and sensitivity to touch, while toxins that target channels in motor neurons and skeletal muscle cause paralysis, seizures and death. Pain and death impose strong selection on predators, thus driving the evolution of adaptations that mediate interactions between chemically defended arthropods and their opponents. For example, scorpion mice have evolved resistance to multiple toxins via changes to ion channels in their sensory and motor neurons, and skeletal muscle.

Current projects: 1) Characterize peptides and chemicals that target ion channels, with a focus on Na⁺, K⁺, TRPA1, TRPV1; 2) determine how changes in the structure, function and expression of channels impart toxin resistance to predators; 3) determine how modifications to sensory and neuromuscular systems shape predatory behavior. Our system is highly tractable because we study interactions between grasshopper mice and their prey in both natural habitats and the laboratory. We use biochemical techniques to isolate peptides and chemicals, and then combine electrophysiology of ion channels and tissues with behavioral analyses to characterize the effects of toxins on sensory and neuromuscular systems. Because toxins act as stimuli that select for variants of genes encoding ion channels in grasshopper mice, we use cloning, site-directed mutagenesis and an expression system to assess the functional consequences of structurally modified channels. Moreover, we can measure the fitness consequences and physiological tradeoffs associated with toxin resistance­. 

My lab is currently accepting applications for graduate students and postdocs excited by sensory systems and behavior! 

• **Niermann, C.N., **Tate, T.G., **Suto, A.L., **Barajas, R., **White, H.A., **Guswiler, O.D., Secor, S.M., Rowe, A.H. and Rowe, M.P. (2020). Defensive venoms: is pain sufficient for predator deterrence? Toxins 12, 260:1-17. doi:10.3390/toxins12040260
• Campbell, P., Arevalo, L., Martin, H., Chen, C., Sun, S., Rowe, A.H., Webster, M.S., Searle, J.B. and Pasch, B. (2019). Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys). Ecology and Evolution 00:1-11. doi:10.1002/ece3.5770
• Walcher, J., Ojeda-Alonso, J., Haseleu, J., Oosthuizen, M.K., Rowe, A.H., Bennett, N.C. and Lewin, G.R. (2018). Specialized mechanoreceptor systems in rodent glabrous skin. Journal of Physiology 596.20:4995-5016. doi:10.1113/JP276608
• Holford, M., Daly, M. and Rowe, A. (2018). The intoxicating science of animal venom: what you need to know. World Economic Forum, Article part of the Annual Meeting of the Global Future Councils, Future Challenges in Science. https://www.weforum.org/agenda/2018/11/animal-venom-biochemical-science-kill-cure/