The Disordered Order
Over the years, scientists have come up with the various ways to designate and characterize the molecular and cellular collectives a.k.a. the -OMES. We have experienced the age of the genome to the transcriptome and now onto era of the proteome. A simplified picture of the cell harnesses the nucleus and the cytosol, wherein lies the various traffic avenues of biomolecules, moving forward with the only intent to keep life afloat, as we know it.
In the recent years, researchers have come up with various interesting concepts in the field of chromatin compaction and remodeling, with several accessory proteins enabling the genome to act properly and effectively to maintain normalcy of life in a cell when faced with disorder. Much like in the movie (or book) - Life of a Pi, where the chaos brings the best out of you! The nucleus as we know houses the maximum amount of the DNA within the cell, leaving aside the few other forms of nucleic acids even some in circulation. It can be viewed using nucleic acid stains like 4′,6-diamidino-2-phenylindole (DAPI) or ethidium bromide, as blotches under the microscope, encapsulated by the cell. Several attempts have been made to figure out the actual and full picture and today we are proceeding to check the orientation of the nucleus, how the chromosomes are housed within the nucleus and how the chromatin maintains it’s active and inactive regions.
Fig from the article: doi:10.1038/nature21429
In this paper published in Nature, April (2017) by the Stevens et al., (3D Structures of individual mammalian genomes studied by single cell Hi-C), illustrated the location of the chromosomes, with experiments conducted in haploid mouse embryonic fibroblast cells.
Some interesting features we got to know are:
The chromosomes have particular compartments with the B (inactive zones) towards the periphery and the center and the A-zones (Active) in between the two layers of B zone. A ring like feature that was highlighted in the Figure 2E.
The central inactive zone mainly housed the nucleolus, which was well co-ordinated with the image and the model.
Each chromosome had specifically oriented A/B zones aligned and by the text in the manuscript it was good to realize that the chromosomes were dynamic (at least in the stem cells), to change the A/B zones, by re-aligning their spatial location.
In short, the authors commented that the cells in the G0 phase aligned in form of the Rabl-formation, as shown in the illustration below.
5. This is one of the most pioneering studies where they studied chromatin compaction in the interphase (G0).
With the power of cell imaging and new techniques coming up, there are a lot of discoveries on the horizon!