Sexually dimorphic mechanosensory neurons regulate copulation duration and persistence in male Drosophila

Peripheral sensory neurons are the gateway to the environment across species. In Drosophila, olfactory and gustatory senses are required to initiate courtship, as well as for the escalation of courtship patterns that lead to copulation. To be successful, copulation must last long enough to ensure the transfer of sperm and seminal fluid that ultimately leads to fertilization. The fly genitalia contain sex-specific bristle hairs innervated by mechanosensory neurons. To date, the role of the sensory information collected by these peripheral neurons in male copulatory behavior is unknown. Here, we employed genetic manipulations that allow driving gene expression in the male genitalia as a tool to uncover the role of these genitalia specific neurons in copulation. We found that the sensory information received by the mechanosensory neurons (MSNs) at the male genitalia plays a key role in copulation duration. We confirmed that these MSNs are cholinergic and co-express both fru and dsx. Moreover, our results show that the function of these fru/dsx cholinergic MSNs is required for copulation persistence, which ensures copulation is undisrupted in the presence of environmental stress before sperm transfer is complete.

Patch-seq of mouse DRG neurons reveals candidate genes for specific mechanosensory functions

A variety of mechanosensory neurons are involved in touch, proprioception and pain. Many molecular components of the mechanotransduction machinery subserving these sensory modalities remain to be discovered. Here, we combined recordings of mechanosensitive (MS) currents in mechanosensory neurons with single cell RNA sequencing. In silico combined analysis with a large-scale dataset enables assigning each transcriptome to DRG genetic clusters. Correlation of current signatures with single-cell transcriptomes provides a one-to-one correspondence between mechanoelectric properties and transcriptomically-defined neuronal populations. Moreover, gene expression differential comparison provides a set of candidate genes for mechanotransduction complexes. Piezo2 was expectedly found to be enriched in rapidly adapting MS current-expressing neurons, whereas Tmem120a and Tmem150c, thought to mediate slow-type MS currents, were uniformly expressed in all neuron subtypes, irrespective of their mechano-phenotype. Further knock-down experiments disqualified them as mediating DRG MS currents. This dataset constitutes an open-resource to explore further the cell-type-specific determinants of mechanosensory properties.

Mechanotransduction channel Piezo is widely expressed in the spider, Cupiennius salei, mechanosensory neurons and central nervous system

Mechanosensory neurons use mechanotransduction (MET) ion channels to detect mechanical forces and displacements. Proteins that function as MET channels have appeared multiple times during evolution and occur in at least four different families: the DEG/ENaC and TRP channels, as well as the TMC and Piezo proteins. We found twelve putative members of MET channel families in two spider transcriptomes, but detected only one, the Piezo protein, by in situ hybridization in their mechanosensory neurons. In contrast, probes for orthologs of TRP, ENaC or TMC genes that code MET channels in other species did not produce any signals in these cells. An antibody against C. salei Piezo detected the protein in all parts of their mechanosensory cells and in many neurons of the CNS. Unspecific blockers of MET channels, Ruthenium Red and GsMTx4, had no effect on the mechanically activated currents of the mechanosensory VS-3 neurons, but the latter toxin reduced action potential firing when these cells were stimulated electrically. The Piezo protein is expressed throughout the spider nervous system including the mechanosensory neurons. It is possible that it contributes to mechanosensory transduction in spider mechanosensilla, but it must have other functions in peripheral and central neurons.

Mechanotransduction Channel Piezo is Widely Expressed in the Spider, Cupiennius Salei, Mechanosensory Neurons and Central Nervous Systems

Mechanosensory neurons use mechanotransduction (MET) ion channels to detect mechanical forces and displacements. Proteins that function as MET channels have appeared multiple times during evolution and occur in at least four different families; the DEG/ENaC and TRP channels, and the TMC and Piezo proteins. We found twelve putative members of MET channel families in two spider transcriptomes, but detected only one, the Piezo protein, by in situ hybridization in their mechanosensory neurons. In contrast, probes for orthologs of TRP, ENaC or TMC genes that code MET channels in other species did not produce any signals in these cells. An antibody against C. salei Piezo detected the protein in all parts of their mechanosensory cells and in many neurons of the CNS. Unspecific blockers of MET channels, Ruthenium Red and GsMTx4, had no effect on the mechanically activated currents of the mechanosensory VS‑3 neurons, but the latter toxin reduced action potential firing when these cells were stimulated electrically. It is possible that the Piezo protein contributes to mechanosensory transduction in spider mechanosensilla, but it must have other functions in peripheral and central neurons.

Distinct subpopulations of mechanosensory chordotonal organ neurons elicit grooming of the fruit fly antennae

Diverse mechanosensory neurons detect different mechanical forces that can impact animal behavior. Yet our understanding of the anatomical and physiological diversity of these neurons and the behaviors that they influence is limited. We previously discovered that grooming of the Drosophila melanogaster antennae is elicited by an antennal mechanosensory chordotonal organ, the Johnston’s organ (JO) (Hampel et al., 2015). Here, we describe anatomically and physiologically distinct JO mechanosensory neuron subpopulations that each elicit antennal grooming. We show that the subpopulations project to different, discrete zones in the brain and differ in their responses to mechanical stimulation of the antennae. Although activation of each subpopulation elicits antennal grooming, distinct subpopulations also elicit the additional behaviors of wing flapping or backward locomotion. Our results provide a comprehensive description of the diversity of mechanosensory neurons in the JO, and reveal that distinct JO subpopulations can elicit both common and distinct behavioral responses.

Convergence of distinct subpopulations of mechanosensory neurons onto a neural circuit that elicits grooming

Diverse subpopulations of mechanosensory neurons detect different mechanical forces and influence behavior. How these subpopulations connect with central circuits to influence behavior remains an important area of study. We previously discovered a neural circuit that elicits grooming of the Drosophila melanogaster antennae that is activated by an antennal mechanosensory chordotonal organ, the Johnston’s organ (JO) (Hampel et al., 2015). Here, we describe anatomically and physiologically distinct JO mechanosensory neuron subpopulations and define how they interface with the circuit that elicits antennal grooming. We show that the subpopulations project to distinct zones in the brain and differ in their responses to mechanical stimulation of the antennae. Each subpopulation elicits grooming through direct synaptic connections with a single interneuron in the circuit, the dendrites of which span the different mechanosensory afferent projection zones. Thus, distinct JO subpopulations converge onto the same neural circuit to elicit a common behavioral response.