Genetic Maps to Diseases

Scientists move a step forward for a better understanding of the connections between genetics and disease by mapping how the genes are turned on or off in different cells as per a study at the University of California San Diego, published online in the issue of Cell.

The study team has produced a single-cell chromatin atlas for the human genome – also called “book of life”. For a long time, scientists have been struggling to discern their functionality.

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‘Scientists move a step forward for a better understanding of the connections between genetics and disease by mapping how the genes are turned on or off in different cells.’

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Chromatin is a complex of DNA and protein found in eukaryotic cells, delineating which would serve as a major step in understanding the role of gene regulatory elements.

The major proteins in chromatin, called histones, help tightly package the DNA in a compact form that fits within the cell nucleus. Changes in how chromatin bundles up DNA are associated with DNA replication and gene expression.

“The human genome was sequenced 20 years ago, but interpreting the meaning of this book of life continues to be challenging. A major reason is that the majority of the human DNA sequence, more than 98 percent, is non-protein-coding, and we do not yet have a genetic codebook to unlock the information embedded in these sequences,” says Bing Ren, Ph.D., director of the Center for Epigenomics, professor of cellular and molecular medicine at UC San Diego School of Medicine and a member of the Ludwig Institute for Cancer Research at UC San Diego.

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Study Atlas of Human Genome

However, an ongoing international effort called the Encyclopedia of DNA Elements (ENCODE) strives to unlock these missing answers. In particular, the study investigated the role and function of chromatin.

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Following this, the team turned their attention to a single-cell atlas of chromatin in the human genome by applying assays to more than 600,000 human cells sampled from 30 adult human tissue types from multiple donors.

The information was then integrated with similar data from 15 fetal tissue types to reveal the status of chromatin at approximately 1.2 million candidates cis-regulatory elements in 222 distinct cell types.

Epigenetics
In the recent years ‘epigenetics’ represents inheritable changes in gene expression that do not include DNA alterations.

“A new paradigm that helps explain how these noncoding variants contribute to diseases posits that these sequence alterations disrupt the function of transcriptional regulatory elements and lead to dysregulation of gene expression in disease-relevant cell types, such as neurons, immune cells or epithelial cells,” says co-first author Kai Zhang, Ph.D., a postdoctoral fellow in the Department of Cellular and Molecular Medicine.

The study anticipates that the chromatin atlas will also allow the scientific community to unravel tissue environment-specific differences of cell types that reside in multiple tissues and facilitate the study of mechanism across a broad spectrum of human diseases for many years to come.

Source-Medindia