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Retrovirus in the human genome is active in pluripotent stem cells.

WORCESTER, Mass., January 23, 2013--A retrovirus called HERV-H, which inserted itself into the human genome millions of years ago, may play an important role in pluripotent stem cells, according to a new study.

Pluripotent stem cells are capable of generating all tissue types, including blood cells, brain cells and heart cells. The discovery, which may help explain how these cells maintain a state of pluripotency and are able to differentiate into many types of cells, could have profound implications for therapies that would use pluripotent stem cells to neat a range of human diseases.

"What we've observed is that a group of endogenous retroviruses called HERV-H is extremely busy in human embryonic stem cells," said Jeremy Luban, M.D., a professor of molecular medicine at UMass Medical School and lead author of the study. "In fact, HERV-H is one of the most abundantly expressed genes in pluripotent stem cells and it isn't found in any Other cell types."

In the study, Luban and colleagues describe how RNA from the HERV-H sequence makes up as much as 2 percent of the total RNA found in pluripotent stem cells. The HERV-H sequence is controlled by the same factors that are used to reprogram skin cells into induced pluripotent stem (iPS) cells.

"In other words, HERV-H is a new marker for pluripotency in humans that has the potential to aid in the development of iPS cells and transform current stem cell technology," said Luban.

When a retrovirus infects a cell, it inserts its own genes into the chromosomal DNA of the host cell. As a result, the host cell treats the viral genome as part of its own DNA sequence and begins making the proteins required to assemble new copies of the virus. And because the retrovirus is now part of the host cell's genome, when the cell divides, the virus is inherited by all daughter cells.

In rare cases, it's believed that retroviruses can infect human sperm or egg cells. If this happens, and if the resulting embryo survives, the retrovirus can become a permanent part of the human genome, and be passed down from generation to generation. Scientists estimate that as much as 8 percent of the human genome may be composed of extinct retroviruses left over from infections that occurred millions of years ago. Yet these sequences of fossilized retrovirus were thought to have no discernible functional value.

Citation: "HERV-H RNA is abundant in human embryonic stem cells and a precise marker for pluripotency"; Federico A Santoni, Jessica Guerra, Jeremy Luban. Retrovirology, 2012; 9(1): 111 DOI: 10.1186/1742-4690-9-111

Abstract:

http://dx.doi.org/10.1186/1742-4690-9-111

Contact: Federico A Santoni,

Federico.santoni@unige.ch

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Title Annotation:Basic Research
Publication:Stem Cell Research News
Date:Feb 4, 2013
Words:446
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