Hi there,
we are trying to do a lifespan assay on daf-6 chemosensory mutants and find that the vast majority of the animals leave the plates and dry out on the side (we use regular NGM plates with OP50)…
Interestingly, this is different with other chemosensory mutants. Does anybody have any suggestions how to keep the animals on the plates?
Many thanks in advance!
copper rings?
I assumed at least some of the Che mutants would ignore the copper?
liquid culture?
A sensible suggestion, Steve, but so much less entertaining than worm balls.
big sample size?
(lifespan in liquid can get funky)
I wonder if crossing an Unc into the strain would work? You’d want to be very careful about which one(s): some really strong Uncs alter passage of food through the gut and are likely to impose a dietary restriction-like phenotype. And of course there are questions about whether the Unc mechanism itself alters lifespan. Maybe get around that by trying multiple Unc types? I’d actually start with some strong Mecs that are strictly mechanosensory cell defective. Some of those really don’t motor around very much. Anybody else have some ideas?
what about…rollers?
Problem with all this: remember the Dpy mutations that would partially suppress loss of a signaling pathway? I think it was Kimble and glp-1. But wasn’t it thought to be tweaking of a stress response? You really don’t want to tweak a stress response when doing aging. Might get a hormetic effect.
yeah, when eleanor maine was a postdoc in the kimble lab she found that lots of different Dpys suppress glp-1(ts). i didn’t know stress response was the mechanism.
here’s an impractical solution that might also work: how about crossing in the halorhodopsin remote worm controller transgene into all strains and then have a ring of repulsive light to keep them away from the edges?
I think the stress response thing was speculation: don’t know if ever formally tested.
What about a ring of fans around the inside of the plate? The worms won’t want to swim into a headwind. 
just thinking about that is stressing me out 
Looks to me like the main practical suggestions are still liquid culture, large enough numbers so you can afford the losses, and - as an outside contender - worm balls.
The light fence appeals to me as a science fiction fan, but the idea of getting the appropriate transgene integrated and homozygous in every strain you want to test is a barrier, even leaving aside the equipment - and then there’s convincing yourself the transgene is not a problem. Fans wouldn’t work because they’d dry out the plate.
Liquid culture is practical, but using it for lifespan appears to have its detractors. For the “large enough numbers so you can afford the losses” approach, I think the question is whether you can safely assume the remnant that didn’t depart are identical to the ones that took a hike, that you haven’t skewed your results by selecting for a lack of wanderlust?
I’m not completely kidding with the worm balls - I think they actually would solve the problem, they might be fun to do, and they don’t require nearly as much development as a light fence, a wall of fans, or some sort of robot prison guard for worms. But either of the other approaches is probably easier to set up.
Well, you could have a man/woman to worm word with the each of worms (in a quiet room somewhere) before the lifespan assay begins, warning them of the consequences should they venture off the viewing area…OR, something just as time-consuming and impractical
how about a ‘hybrid’ solution. You pour an agar plate with the central 20mm diameter kept free with a tube (you then have a 55mm diameter doughnut with a 20mm inner ring and allow it to dry. Then you pour agar into the centre so that it is below the level of the agar surrounding it.
Finally, add some OP50 to the central agar, pop a 25mm coverslip over the 20mm central depression and off you go. You need to let in some fresh air at regular intervals, but most of the worms (if they can read a sat nav) will cross the coverslip and go back onto the agar.
It is hopelessely flawed, but hey…so am I.
Steve
but the worms could still crawl up the side and stick to the glass and die, no?
liquid culture, just do it.
See, I told you it was flawed. Hillel’s space balls seem much more fun if you can focus on the inside of a sphere😎
Lots of good suggestions, some complicated. Did you try growing them on larger plates (e.g. 9cm)? Perhaps that could cut your losses to a more reasonable amount
Ben