861B Poster - 13. Neural development and physiology
Friday April 08, 2:00 PM - 4:00 PM

Authors:
Vanessa Puñal ¹; Najia Elkahlah ¹; Jackson Rogow ²; Jamal Jenkins ¹; E. Josie Clowney ¹; Mark Lewis ¹; Mona Saeed ¹; E. Josie Clowney ¹

Affiliations:
1) University of Michigan; 2) The Rockefeller University

Keywords:
r. sensory cell development; o. olfaction

Detection of environmental stimuli is essential for survival. The total number of sensory stimuli encountered by an organism is unpredictable and nearly limitless, making genetic coding of detectors for all possible stimuli impossible. How then does development build neural circuits capable of processing unforeseen and expansive arrays of sensory input? One strategy is to harness the power of combinations. Consider a palette of 100 colors: when combined, this limited number of colors can paint a rich picture containing ~10¹⁵⁸ hues. Similarly, evolution has selected for amplifying the number of discriminable stimuli from a limited number of genetically encoded sensors to the number of combinations among them. This is achieved by expanding sensory neuron inputs via sparse, combinatorial wiring to higher order neurons involved in perceptual processing. It is not understood in any species what developmental mechanisms give rise to the input sparseness necessary for sensory amplification. To address this knowledge gap, I use the fly olfactory system where 50 odor channels are dispersed, via Projection Neurons, among ~2,500 higher order neurons called Kenyon Cells in the mushroom body calyx. Previous work in the lab demonstrated that in the absence of Kenyon Cells during development, adult Projection Neuron axons no longer provide input to the calyx. We have subsequently found that this is because developing Projection Neurons never initiate collateral formation when Kenyon Cells are not present. These results have led to the hypothesis that Kenyon Cells dictate their input density via retrograde feedback to Projection Neurons. To test this hypothesis, we generated a bulk RNA sequencing dataset for developing Kenyon Cells and used this as the basis for a candidate screen to search for Kenyon Cell-derived retrograde signals required for the production of odor channel inputs. Results suggest a role for a variety of molecules secreted by Kenyon Cells as part of a molecular pathway that drives Projection Neurons to meet Kenyon Cell demands to generate odor channel inputs.