Facultative heterochromatin

The regions of DNA packaged in facultative heterochromatin are not consistent among cell types within a species, hence the name "facultative." Unlike constitutive heterochromatin, facultative heterochromatin populates both A and B compartments, shows weak correlation with chromatin accessibility measured by ATAC-seq, and does not phase separate into dense domains. Its relation to gene regulation, e.g. how does H3K27me3 coordiante gene silencing is also unclear. An emerging picture is that facultative heterochromatic