Clovis, Yoanne et al. (2019) MicroPubl Biol

Clovis, Yoanne, Turner, Carl, Roberts, Bill, Webb, Alexis

[MicroPubl Biol, 2019]

Chicas-Cruz, Adela et al. (2017) International Worm Meeting "Age-related decline in muscular strength and coordination observed in C. elegans pharynx."

Clovis, Yoanne, Hiebert, Terra, Chicas-Cruz, Adela, McCormick, Kathryn

[International Worm Meeting, 2017]

Aging has been associated with a progressive decline of feeding behavior, but detailed quantification of how this process affects pharyngeal muscle function remains largely unexplored. We profiled the feeding behavior along the lifespan of adult C. elegans worms. Taking advantage of microfluidics combined with whole-body electrophysiology, we found that in older adults, the pharyngeal activity declines, not only in frequency, but also by in pumping regularity and strength. Our data uncover previously undocumented changes in C. elegans feeding behavior associated with age. We show that the duration of pharyngeal contractions (pumps) become more variable as the worm ages. We also show that pumps are interspersed with longer pauses in older worms, as shown by a 35% increase in interpump duration between Day 1 and Day 10. Because of the worms' larger size, we expected to measure a stronger signal in older worms than in young adults. Surprisingly, a decrease in pump amplitude was observed in older worms, showing that despite being larger in size, 10-day old worms produce weaker pumps, consistent with an overall loss of muscle strength in the pharynx. We then exposed aging worms to trehalose, a stress protectant previously shown to increase longevity in C. elegans, and found that trehalose can mitigate the onset of the observed pharyngeal pumping deficiency. In this study, we describe a novel method to reliably quantify the effect of aging on multiple aspects of feeding behavior. We demonstrate that beyond pharyngeal pumping rate, the feeding behavior and muscular activity of C. elegans are strongly impaired by aging. However, such defect can be mitigated by exposure to trehalose.

Chicas-Cruz, Adela et al. (2017) International Worm Meeting "A humanized test system: Using pharyngeal pumping phenotypes as a readout for the serotonergic signaling pathway in C. elegans."

Clovis, Yoanne, Chicas-Cruz, Adela, Hopkins, Chris, McCormick, Kathryn, Hiebert, Terra, Brock, Trisha

[International Worm Meeting, 2017]

The neurotransmitter, serotonin (5HT) has widespread regulatory effects in humans, from contractions of the gut to sensory perception in the brain. Likewise, it is a widespread and important neurotransmitter in C. elegans, where it regulates pharyngeal pumping and feeding behavior. Here, we model this biochemical pathway using pharyngeal pumping phenotypes and provide a reliable readout for serotonergic signaling. We obtained and analyzed electropharyngeogram (EPG) data using a microfluidic device and associated software for tph-1 and mod-5 loss-of-function mutants as well as mod-5 gain-of-function mutants. First, we support previous findings and demonstrate a reduction in pumping rates for tph-1 mutants, which fail to synthesize 5HT. Next, we present new data for worms that have reduced reuptake of 5HT by the mod-5 5HT reuptake transporter. mod-5 null mutants display significantly higher pumping rates than control worms with no exogenous pumping stimulus. Intriguingly, preliminary data using the SSRI fluoxetine (Prozac) exhibits similar results to these mod-5 nulls by blocking the reuptake by the transporter. The mod-5 reuptake transporter is orthologous to the human 5HT transporter SLC6A4. We created an gain-of-function mutant by ectopically expressing human SLC6A4 in the pharynx (mod-5p::hSLC6A4::tbb-2UTR). As expected, the humanized animals retained a pumping defect even when stimulated by food. Only with hyper stimulation of the humanized line by exogenous addition of 10 mM 5HT did the levels of pumping restore to wild type levels. Experiments are underway to move the humanized line into the null background and determine if full rescue of mod-5 function is possible with a human transgene. Combined, these experiments have demonstrated that monitoring pharyngeal pumping is an easy to use platform for exploring the 5HT pathway in C elegans.