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The stum Gene Is Essential for Mechanical Sensing in Proprioceptive Neurons

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Science  14 Mar 2014:
Vol. 343, Issue 6176, pp. 1256-1259
DOI: 10.1126/science.1247761

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Touchy-Feely Genes

All animals need accurate proprioceptive sensation to control motor function. Desai et al. (p. 1256) identified a Drosophila mutant with impaired walking coordination. The affected gene, stumble (stum), is conserved throughout the animal kingdom and expressed in a subpopulation of multidendritic neurons. stum-expressing neurons are found proximal to leg joints, and if the angle of the joint shifts, dendritic stretching occurs that in turn elevates cellular calcium. Therefore, it looks as if stum is a transducer for mechanical stimuli.

Abstract

Animal locomotion depends on proprioceptive feedback, which is generated by mechanosensory neurons. We performed a genetic screen for impaired walking in Drosophila and isolated a gene, stumble (stum). The Stum protein has orthologs in animals ranging from nematodes to mammals and is predicted to contain two transmembrane domains. Expression of the mouse orthologs of stum in mutant flies rescued their phenotype, which demonstrates functional conservation. Dendrites of stum-expressing neurons in legs were stretched by both flexion and extension of corresponding joints. Joint angles that induced dendritic stretching also elicited elevation of cellular Ca2+ levels—not seen in stum mutants. Thus, we have identified an evolutionarily conserved gene, stum, which is required for transduction of mechanical stimuli in a specific subpopulation of Drosophila proprioceptive neurons that sense joint angles.

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