Cover stories: A method for revealing chromatin

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Science  28 Jul 2017:
Vol. 357, Issue 6349, eaao4487
DOI: 10.1126/science.aao4487

Cover stories offer a look at the process behind the art on the cover: who made it, how it got made, and why.

The 28 July 2017 cover highlights the work of Ou et al. in this issue, where we get the first look at a cell’s chromatin in situ. Virtually all previous studies of chromatin structure have been performed in cells in vitro. From this viewpoint, scientists derived the idea that chromatin compacts itself into nicely organized, hierarchically ordered structures; fibers form helices with thicknesses ranging from 30 nanometers all the way to several hundred nanometers. What Ou et al. share, however, is that these textbook-engrained structures were nowhere to be found in situ.

Electron microscopy is needed to visualize structures as tiny as chromatin. Unfortunately, DNA is not accepting of the electron-dense metallic coating needed for detection by an electron microscope. To get around this, the authors identified a dye that binds to DNA and, upon excitation by light, forms a dust-like metallic precipitate around the DNA. It is this metallic dust that allows chromatin to be revealed in its natural environment. This is the concept that drove my creative process.

In an attempt to mimic the research methodology, I wanted the “hidden” chromatin to be revealed from the white of the paper, which would not be possible without the application of a dust-like powder. Instead of processing numbers or pumping out 3D renderings, I visited the local art-supply store, where I picked up some real metallic powder—metallic pigment that is ordinarily combined with water or glue and used for painting.

First, I worked with our Design Director, Beth Rakouskas, to find a composition for the chromatin and a space for the cover headline that would suit the layout. I then headed to our photo studio, where I tapped the metallic dust onto a sheet of paper, following the planned design as closely as possible. After I was satisfied with the job, I experimented with lighting to best display the reflectivity of the powder, then I shot top-down photos of the paper. Finally, I brought these photos into the digital realm, where I used Adobe Photoshop to add the white of the chromatin and fine-tune the dust to selectively follow its edges.

Painting with metallic dust formed the basis for this illustration.Credit: Christina Aycock/Science
The setup for photographing the main part of the illustration.Credit: Valerie Altounian/Science

In the end, we are left with a fun interpretation of the method used to successfully reveal the disordered reality of chromatin’s structure.

Valerie Altounian, Senior Scientific Illustrator at Science

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