Novel Technique Reveals Hidden Chromatin Dynamics in Live Cells

A new study demonstrated how interferometric scattering correlation spectroscopy (iSCORS) can help scientists obtain data on chromatin behavior, which represents an advancement in biological analysis. The findings of this study were published in the journal Communications Biology (1).

Chromatin is a combination of proteins and DNA (2). When scientists study chromatin, they have traditionally used fluorescent labeling, but the technique does have limitations (1). In particular, it has been known to alter the native state of chromatin (1). Further complicating the study of chromatin is that because of its diffusive nature, as well as the fact that it is in constant motion, these factors make it hard to study it in living cells (1). As a result, there is room for improvement when it comes to developing methods that can study chromatin without damaging it.

3D rendering image illustrating the process of DNA packaging into chromatin fibers, highlighting the role of histone proteins in regulating gene expression and chromosome condensation. Generated with AI. | Image Credit: © G.Go - stock.adobe.com

Researchers at National Taiwan University, led by Chia-Lung Hsieh, recently proposed a solution. By using iSCORS, the researchers demonstrated in their study that it addresses much of the limitations traditional methods have. iSCORS uses label-free imaging to detect linear scattering signals generated by chromatin motion (1). The result is that by following chromatin in real-time, iSCORS can collect data to the millisecond, all without damaging its native state.

iSCORS is a highly sensitive analytical technique used to study the dynamics of molecules in solution. It combines interferometric scattering detection with correlation spectroscopy to analyze particles at the nanometer scale. In iSCORS, a coherent light source, typically a laser, illuminates the sample, and the scattered light is collected and interfered with a reference beam to enhance the detection sensitivity. By analyzing the temporal correlation of the scattered light intensity fluctuations, iSCORS can provide detailed information for measuring particle size, diffusion coefficients, and interaction kinetics,

In their study, the research team used iSCORS to measure significant temporal fluctuations and cellular heterogeneity in global chromatin condensation states. This capability is crucial for understanding how chromatin organization impacts cellular functions and how it is regulated during different cellular states and processes (1).

Although the researchers were pleased with the success of the technique and how iSCORS overcame limitations associated with traditional methods, the researchers also pointed to other areas that require future study. As an example, the researchers noted that the iSCORS signals can occasionally originate from non-chromatin structures within the nucleus, such as nuclear bodies and nuclear scaffolds (1). Nonetheless, the strong correlation between iSCORS maps and fluorescence chromatin images suggests that the majority of iSCORS signals do indeed stem from chromatin (1).

By eliminating the need to use a chemical label, iSCORS can observe nanoscopic chromatin configurations over a period of time. By capturing time-varying scattering signals, the researchers can deduce how tightly chromatin is packed and how it fluctuates (1).

One of the significant findings of the study is the observation of changes in iSCORS signals of chromatin upon transcription inhibition. This indicates that iSCORS can probe nanoscopic chromatin structures and dynamics associated with transcriptional activities without fluorescent labels (1).

The biggest benefit to using iSCORS microscopy is because of its noninvasive and nondestructive nature. As a result, it has the capability to study chromatin reprogramming in primary cells, where fluorophore labeling is often challenging (1). And because iSCORS requires minimal light, phototoxicity is not a concern.

The study's conclusions are drawn from the analysis of global chromatin condensation states, which were determined by calculating the spatial median intensity across the images (1). This approach provides a comprehensive view of chromatin dynamics without the need to interpret subnuclear structures depicted in iSCORS maps, which could include unrelated scattering signals (1). Future studies would look to build upon the iSCORS technique.

With the development of iSCORS, studying chromatin and how it influences living cells became easier. Going forward, this new approach could be used to discover and learn more about how chromatin structure influences gene expression and vice versa.

References

(1) Hsiao, Y.-T.; Liao, I.-H.; Wu, B.-K.; et al. Probing Chromatin Condensation Dynamics in Live Cells Using Interferometric Scattering Correlation Spectroscopy. Commun. Biol. 2024, 7, 763. DOI: 10.1038/s42003-024-06457-2

(2) National Human Genome Research Institute, Chromatin. Available at: https://www.genome.gov/genetics-glossary/Chromatin (accessed 2024-07-11).