Attention conservation notice: Basically only interesting if you care about the preservation quality of cells and tissues following formaldehyde treatment.
This past week Jin et al published good evidence that the epigenome of thyroid follicular cells is maintained in at least a subset of single cells.
As you can see in Fig 1b in the original paper, the periodic DNA hypersensitivity pattern is retained in single formaldehyde-fixed postmortem cells.
Just as a nerdy sidenote, as far as I understand, this periodicity is due to DNA wrapping around the histone core particle in nucleosomes.
Notably, this paper does not show that formaldehyde does not alter the epigenome of cells at all — but it does show that the effect is not to radically alter the structure.
I personally am most interested in how these results translate to brain cells and tissue. Here are a couple of points on that front:
1) Formaldehyde-preserved tissue has already shown to preserve epigenomic signals, such as those marked by anti-DNA methylation antibodies.
2) However, there might be differences between the variability of responses from single thyroid follicular cells and single brain cells in their response to formaldehyde, and that (to the best of my knowledge) has not yet been tested.
Anyway, this paper was interesting to me because the epigenome holds a lot of information about the function brain cells, and can even specify some synapse information relevant to memory. The ability to preserve this via formaldehyde is an important point for designing research studies.