Hematoxylin and eosin (H&E) staining of sections of wild-type (top row) and H1 triple-knockout (bottom row) embryoid bodies. After 14 days in rotary suspension culture, the wild-type embryoid bodies showed more differentiated morphologies with cysts forming (black arrows) and the knockout embryoid bodies failed to form cavities (far right). (Credit: Yuhong Fan)

(Phys.org) — New research findings show that embryonic stem cells unable to fully compact the DNA inside them cannot complete their primary task: differentiation into specific cell types that give rise to the various types of tissues and structures in the body.

Researchers from the Georgia Institute of Technology and Emory University found that chromatin compaction is required for proper embryonic stem cell differentiation to occur. Chromatin, which is composed of histone proteins and DNA, packages DNA into a smaller volume so that it fits inside a cell.

A study published on May 10, 2012 in the journal PLoS Genetics found that embryonic stem cells lacking several histone H1 subtypes and exhibiting reduced chromatin compaction suffered from impaired differentiation under multiple scenarios and demonstrated inefficiency in silencing genes that must be suppressed to induce differentiation.

While researchers have observed that embryonic stem cells exhibit a relaxed, open chromatin structure and differentiated cells exhibit a compact chromatin structure, our study is the first to show that this compaction is not a mere consequence of the differentiation process but is instead a necessity for differentiation to proceed normally, said Yuhong Fan, an assistant professor in the Georgia Tech School of Biology.

Fan and Todd McDevitt, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, led the study with assistance from Georgia Tech graduate students Yunzhe Zhang and Kaixiang Cao, research technician Marissa Cooke, and postdoctoral fellow Shiraj Panjwani.

The work was supported by the National Institutes of Healths National Institute of General Medical Sciences (NIGMS), the National Science Foundation, a Georgia Cancer Coalition Distinguished Scholar Award, and a Johnson & Johnson/Georgia Tech Healthcare Innovation Award.

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Phase contrast images showing that H1 triple-knockout (bottom) embryonic stem cells were unable to adequately form neurites and neural networks compared to wild-type embryonic stem cells (top). (Click image for high-resolution version. Credit: Yuhong Fan)

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