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1 5 I H I G H L I G H T S 2 0 2 3

PRINCIPAL PUBLICATION AND AUTHORS

Biomechanical origins of proprioceptor feature selectivity and topographic maps in the Drosophila leg, A. Mamiya (a), A. Sustar (a), I. Siwanowicz (d), Y. Qi (b,c), T.-C. Lu (b,c), P. Gurang (a), C. Chen (a,d), J.S. Phelps (e,i), A.T. Kuan (e,j), A. Pacureanu (f), W.-C. Allen Lee (e,g), H. Li (b,c), N. Mhatre (h), J.C. Tuthill (a), Neuron 111(20), 3230-3243.e14 (2023); https:/doi.org/10.1016/j.neuron.2023.07.009 (a) Department of Physiology and Biophysics, University of Washington, Seattle (USA) (b) Huffington Center on Aging, Baylor College of Medicine, Houston (USA) (c) Department of Molecular and Human Genetics, Baylor College of Medicine, Houston (USA) (d) Janelia Research Campus, Howard Hughes Medical Institute, Ashburn (USA) (e) Department of Neurobiology, Harvard Medical School, Boston (USA) (f) ESRF (g) F.M. Kirby Neurobiology Center, Boston Children s Hospital, Harvard Medical School, Boston (USA) (h) Department of Biology, University of Western Ontario, London (Canada) (i) Present address: Neuroengineering Laboratory, Brain Mind Institute & Institute of Bioengineering, EPFL, Lausanne (Switzerland) (j) Present address: Department of Neuroscience, Yale School of Medicine, New Haven (USA)

Fig. 3: Peripheral anatomy of the femoral chordotonal (FeCO) organ (top), and schematic of FeCO sensor organisation, based on X-ray holographic nanotomography reconstruction (bottom).

and hook neurons likely contribute to feedback control of leg movements, such as walking and grooming, while club neurons may be used to monitor vibrations in the external environment, such as detecting wingbeats during social interactions. Computer modelling was used to shed light on how the mechanical differences help the sensors detect the angles of the leg joints. The model, combined with calcium imaging, confirmed the existence of maps in each sensor, which help keep track of joint angles or tibia vibration frequency (depending on their role).

The XHN data was combined with RNA sequencing to study the genetic expression of the different FeCO sensory neurons in order to gauge their contribution to sensing movement. The RNA data suggested that there were not large differences in mechanosensitive genetic expression among the different types of FeCO neurons they were

in fact very similar genetically, further suggesting that the way these sensors are built and how they interact with the leg s structure is more important for detecting different types of movement than gene expression.

In conclusion, this work utilised new experimental methods to investigate the relative contributions of molecular and biomechanical mechanisms to proprioceptor feature selectivity and topographic encoding in the Drosophila leg. The findings suggest that biomechanical specialisation is a key determinant of proprioceptor feature selectivity in Drosophila. More broadly, the discovery of proprioceptive maps reveals common organisational principles between proprioception and other topographically organised sensory systems, opening the way for the investigation of peripheral biomechanics and topographic maps in proprioceptors of other limbed animals.