Hypodermal nuclei number reduced

Model Organism: Worms Scientific Discussion
1

Upon request from a reviewer for a paper, we find that, at the adult stage, our mutant worms have about 1/2 as many hypodermal nuclei as wildtype worms These mutants are small and develop slowly.

Quick questions:

  1. Is this phenotype likely caused by less seam cell proliferation, or are there other likely mechanisms?

  2. What other genes or pathway disruptions also reduce hypodermal nuclei number?

Any insight would be helpful.

Thanks,

Keith

2

A lineage problem seems most likely, especially in accord with the slow growth. But for some cell types as they age, nuclei are known to disappear by
phagocytosis (as in intestine) (McGee et al, 2011) or to lose integrity and fade dramatically without completely disappearing (bodywall muscle)
(Herndon et al., 2002). Is there a time point when nuclei reach a maximum number and then begin to vanish, or is there a deficiency
in the number of nuclei at each time point for the mutant?

Dave Hall

3

Let me rephrase what I said here about the disappearance of intestinal cell nuclei. This process occurs by engulfment of the nucleus by an autophagosome
within the intestinal cytoplasm of the aging animal. Thus the organelle is self-eliminated by the intestinal cell itself, and cannot be properly termed
“phagocytosis”, as that term would suggest that the nucleus had been removed by a neighboring scavenger cell.

This still begs the question as to how a mutation may lead to the hypodermal syncytium holding too few nuclei as the mutant animal develops and ages.
Could be a defect in the hyp lineage divisions, a loss of nuclei after their creation, or possibly an effect due to poorer staining properties as the mutant ages.

Dave Hall

4

Thanks so much! I hadn’t considered the possibility of them disappearing.

At this point, we only know that the nuclei number is reduced at the 2-day adult stage. It sound’t like we need to look at this over time to see if they disappear or are never formed. I’m assuming it would be best to measure this at each larval stage and then into the first few days of adulthood.

Are you aware of any other strains with reduced hypodermal nuclei numbers?

Best,
Keith