Hello heterochromatin, my old friend; CRISPR has come to edit you again; And echo in the sound of silence. As reported in a resounding new study, CRISPR-EChO comes at you from the lab Stanley Qi (Stanford University, California) and amplifies the sounds of silent chromatin.
Following on from avant-garde studies describing CRISPR-GO and CasDrop, which evaluate perturbations to nuclear organization in real-time, this newly developed CRISPR-engineered chromatin organization technique (or CRISPR-EChO for short) combines live-cell CRISPR imaging and the large-scale inducible recruitment of chromatin proteins. In this case, the lab-based maestros explored the function of Heterochromatin Protein 1 (HP1), a heterochromatin-associated transcriptionally-repressive factor that helps to generate large swathes of silent chromatin domains throughout the genome.
So let’s “hear” more from Gao and colleagues about how CRISPR will surely echo through the epigenetic ages.
- CRISPR-EChO makes use of dCas9-HP1α (one of the three HP1 orthologs) to promote HP1α tiling across kilobase-scale genomic DNA in live cells in response to an abscisic acid stimulus
- CRISPR-EChO represses distal gene expression in a highly active region through the dimerization and oligomerization ability of HP1α; however, the silencing does not rely on H3K9me3 as with other HP1α-tethered genes
- Targeting a tandem repeat on Chr3q29 silences genes lying 35 kb (ACAP2), 36 kb (PPP1R2), and 575 kb (TFRC) away
- Newly formed large-scale silent chromatin domains also make long-range interactions with naturally heterochromatic HP1α-enriched regions
- CRISPR-EChO constructs a silent chromatin domain that possesses structural stability and reversibility
These silence-inducing findings highlight the enormous potential of CRISPR-EChO in the study of large-scale silent chromatin organization in living cells and underscore the vitally important role of HP1 in the formation of vast regions of heterochromatin.
We could wax lyrical about this study all day – but instead, listen in on more of the sounds of silent chromatin over at Molecular Cell, August 2021.