The Sex-Specific VC Neurons Are Mechanically Activated Motor Neurons That Facilitate Serotonin-Induced Egg Laying inC. elegans

Abstract

This work was funded by grants from the NIH (R01-NS086932) and NSF (IOS-1844657) to KMC. RJK 3 rd was supported by a University of Miami Maytag Fellowship. We thank David M. Miller III for sharing plasmids. Some of the strains used in this study were provided by the C.

Muscle-directed mechanosensory feedback activates egg-laying circuit activity and behavior inC. elegans

“…We observed no significant differences in the vulval muscle Ca 2+ response time, peak amplitude, decay time, or efficiency of injection-induced egg release when compared to injected wild-type worms ( Figure 4C – F ). These results indicate the main synaptic inputs into the vulval muscles are not required for the vulval muscle injection response, consistent with previous work showing that worms lacking HSNs and/or VCs still enter egg-laying active states (Waggoner et al, 1998) with robust vulval muscle Ca 2+ activity (Collins et al, 2016; Kopchock et al, 2021; Shyn et al, 2003; Zhang et al, 2008).…”

“…Shifting C. elegans into hypoosmotic or hyperosmotic environments results in inhibition or promotion of egg laying, respectively (Zhang et al, 2010(Zhang et al, , 2008. Given that C. elegans is hydrostatically pressurized (Avery and Thomas, 1997;Gilpin et al, 2015;Harris and Crofton, 1957), and vulval opening is sufficient for egg expulsion from the uterus (Kopchock et al, 2021), changes in osmotic conditions may reflect a physical regulation of egg-laying behavior. Acute shifts of animals to hypoosmotic conditions drives a rapid influx of water into animals (Lamitina et al, 2004) that presumably increases the hydrostatic pressure inside the animal, thus promoting circuit activity and egg-laying based on a physical model.…”

“…To do this, N2 males were crossed with the HSN-deficient LX1938 egl-1(n986dm) V; lite-1(ce314) vsIs164 lin-15(n765ts) X hermaphrodites (Collins et al, 2016). Resulting male cross-progeny were then mated with MIA144 keyIs33; lite-1(ce314) lin15(n765ts) X hermaphrodites (Kopchock et al, 2021) expressing Tetanus Toxin in the VC neurons from a minimal lin-11 enhancer (Bany et al, 2003) which imparts a mild uncoordinated reversal phenotype. Resulting cross-progeny L4s were then picked, allowed to self, and were then selected for mCherry(+), Egl, and Unc reversal phenotypes.…”

“…For example, external vibrations or gentle touches on the tail inhibit egg laying (Sawin, 1996), possibly by activating mechanoreceptors on the PLM neurons that signal to inhibit HSN activity (Zhang et al, 2008). The VC neurons are mechanically activated by the contraction and opening of the vulval muscles, releasing acetylcholine to enhance vulval opening for egg release (Kopchock et al, 2021). The uv1 neuroendocrine cells sit between the vulval canal and uterus, are mechanically deformed and activated in response to passage of eggs through the vulval canal (Collins et al, 2016; Jose et al, 2007), and provide inhibitory feedback following egg laying through the release of tyramine and neuropeptides that inhibit HSN activity (Alkema et al, 2005; Banerjee et al, 2017; Ravi et al, 2021; Zhang et al, 2010).…”

Acetylcholine Signaling Genes are Required for Cocaine-Stimulated Egg Laying inCaenorhabditis elegans

“…Interestingly, recent reports using calcium imaging of the egg laying circuit in freely behaving worms show evidence of coordination between egg laying behavior, body bend, and locomotion (Zhang et al 2008; Collins and Koelle 2013; Collins et al 2016; Kopchock et al 2021). Such detailed analysis of the coordinated function of both circuits in cocaine-treated WT and mutant animals in vivo will be highly valuable to directly describe the neurobiological mechanism of cocaine action in C. elegans .…”