> For example, what amount of transient DNA methylation is transmitted to the next generation via egg or sperm?
I read something recently that was a good primer on this.
The question seems to be not "what amount?", but instead "is there any tangible expression change resulting from methylation?", and/or "does it matter at all?".
So far, not a lot of evidence in support, so while this makes for interesting presentation and magazine article speculation, there just isn’t anything tangible just yet.
https://doi.org/10.3390/insects13020110
"Phenotypic Plasticity: What Has DNA Methylation Got to Do with It?"
Selected quotes:
"The complex relationship between DNA methylation and gene expression is reflected by several studies across a range of insects, including beetles [61], ants [57,59] and bees [62,63,64,65], that show no association between differences in DNA methylation and gene expression."
"...recent reports in ants [57], bumblebees [62] and honey bees [65] (Duncan and Dearden, unpublished data) in which DNA methylation varies significantly between colonies. This indicates that there is a genetic effect on DNA methylation, that colony environment influences DNA methylation, or that DNA methylation is not environmentally responsive in adults (it may be set when individuals are developing). If this ‘colony-level’ effect is a common phenomenon amongst insects, this would be a major confounding factor in many DNA methylation studies."
" Studies to date have not demonstrated an unequivocal role for DNA methylation in phenotypic plasticity. However, there are hints that DNA methylation may function in some examples of phenotypic plasticity. Studies to date have been hampered by technological and analytical limitations that have made it difficult to mechanistically link an environmental cue to changes in DNA methylation, gene expression and ultimately phenotype."
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