A high throughput analysis of glutamatergic signaling in the mechanosensory processing in C. elegans

Abstract

From humans to worms, a fundamental role of the nervous system is to detect and interpret sensory information in order to generate an appropriate behavioral response. How multiple, often opposing, sensory inputs become integrated to generate a suitable motor output remains an active area of research in systems neuroscience. Although the gentle touch circuit has been extensively studied over the past two decades, it remains unclear how the combined expression of excitatory and inhibitory glutamatergic receptors mediate mechanosensory processing in this circuit. Previous studies have conducted tap experiments to elucidate the behavior of glutamate receptor mutants, but these either have had small sample sizes or only focused on one type of receptors. To address how different mutations in glutamatergic signaling disrupt the reversal behavior evoked from stimulation of the gentle touch circuit, we performed high throughput tap experiments with eat-4, avr-14, glr-1, and nmr-1 mutants to encompass different aspects of glutamatergic signaling. We found that these mutants decreased in the likelihood of reversal in response to stimulation. Furthermore, we performed high through put optogenetic experiments with nmr-1 mutant worms that expressed the excitatory opsin Chrimson across all six touch neurons to address whether a mutation in excitatory glutamatergic receptors disrupt reversal behavior when they are all optogenetically stimulated. Surprisingly, we found the reversal probability of the nmr-1 x mec-4::Chrimson strain to be comparable to that of the original mec-4::Chrimson strain. In sum, the present thesis project had implemented high throughput methods on previous tap experiments while also presenting optogenetic avenues for further investigation of glutamatergic signaling on mechanosensory processing. Future directions might experimentally adjust for different mutant strain characteristics of habituation; genetic crossing of mec-4::Chrimson with different receptor mutant strains; and separate optogenetic targeting of anterior/posterior regions to further unravel sensory integration.