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Newswise Scientists at Penn State College of Medicine, working alongside an international team of researchers, have produced the most complete encyclopedia of functional elements in the mouse genome to date and compared it to the human genome. The findings, published recently in Nature, uphold the mouse model of human disease, but pinpoint important differences in gene expression that will guide future health research.

Mice are the premier model organism for research into human health and disease because they share most of their protein-coding DNA with us. However, only a small fractionless than 2 percentof human and mouse DNA is used to code the building blocks of life. The regulatory elements in our DNA that control the expression of these genes are equally important, if not more so, to disease development and progression, and our understanding of it.

Using high-throughput DNA sequencing techniques, the research team looked at these functional elements in more than 1,000 data sets produced from over 100 mouse cell types and tissues. They were able to assign potential regulatory functions to 12.6 percent of the mouse genome. They then compared these elements and their functions to those of humans.

"This is the most comprehensive effort to do a genomic comparison between humans and mice at this level, including the regulatory elements and gene expression," said Feng Yue, an assistant professor in the department of biochemistry and molecular biology at Penn State College of Medicine. "We looked at regulations of genes, rather than genes themselves, and whether the gene is expressed in certain tissues or how much the gene is expressed there. We wanted to learn which gene expression patterns were conserved between humans and mice during mammalian evolution, and which gene expression patterns diverged."

Major similarities, but also important differences, emerged.

Although much similarity exists, mouse and human gene expression differs significantly in specific biological pathways.

"What we found is that the majority of the gene expression patterns are very similar in human and mouse," Yue said. "That shows that, indeed, the mouse is a good system to use in the study of human disease.

"But there are some genes whose patterns are not quite conserved between human and mouse," he continued. This divergence was most profound for areas of the mouse genome involved in the immune system and metabolic processes. "These genes may function in a different way between human and mouse."

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Mouse Model of Human Disease Still Good, but Significant Differences Exist

BETHESDA, Md., Dec. 4 (UPI) -- Two is often better than one, but not when it comes to the DNA and RNA that make up the human chromosome. Researchers now believe gene duplication in a specific region, key in the regulation of childhood growth, is responsible for the rare disorder known as gigantism.

"Finding the gene responsible for childhood overgrowth would be very helpful, but the much wider question is what regulates growth," Constantine Stratakis, lead author of the new study, said in a press release.

Gigantism is a rare medical condition whereby children grow rapidly. Those affected typically grow to be abnormally tall; gigantism patients may also have delayed puberty, outsized hands and feet, and double vision.

To locate the offending genes, researchers at the National Institutes of Health used whole-genome analysis to study the DNA of 43 people with gigantism. The chromosomes of those afflicted with the rare disorder were then compared to family members who were born without the defect.

The analysis showed that gene duplication varied among the study participants, but researchers were able to narrow down the offending portion of the X chromosome to a stretch containing four duplicated genes. Scientists determined the gene most likely responsible for gigantism was GPR101.

"We believe GPR101 is a major regulator of growth," Stratakis said.

The gene duplication that causes gigantism results in a malfunctioning pituitary, the pea-sized gland that produces growth hormones. Researchers found activity of GPR101 was up to 1,000 times stronger than normal in children with enlarged and overactive pituitary glands.

The research was published this week in the New England Journal of Medicine.

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Duplication of gene on X chromosome causes gigantism