October 2012 – Page 6

10.08.2012

nobel prize in medicine

The Nobel prize in medicine was awarded today to John B. Gurdon and Shinya Yamanaka for the discovery that led to stem cell research. From the Nobel press release:

The Nobel Prize in Physiology or Medicine 2012 goes jointly to John B. Gurdon and Shinya Yamanaka for the discovery that mature cells can be reprogrammed to become pluripotent

Summary

The Nobel Prize recognizes two scientists who discovered that mature, specialised cells can be reprogrammed to become immature cells capable of developing into all tissues of the body. Their findings have revolutionised our understanding of how cells and organisms develop.

John B. Gurdon discovered in 1962 that the specialisation of cells is reversible. In a classic experiment, he replaced the immature cell nucleus in an egg cell of a frog with the nucleus from a mature intestinal cell. This modified egg cell developed into a normal tadpole. The DNA of the mature cell still had all the information needed to develop all cells in the frog.

Shinya Yamanaka discovered more than 40 years later, in 2006, how intact mature cells in mice could be reprogrammed to become immature stem cells. Surprisingly, by introducing only a few genes, he could reprogram mature cells to become pluripotent stem cells, i.e. immature cells that are able to develop into all types of cells in the body.

Check the link for the whole release.

10.06.2012

“awesome” synthesis

Scientists have made amazing progress in the synthesis of biologics

Scientists have created a way to add a uniform coating of sugars to the protein erythropoietin. Erythropoietin is a protein that induces production of red blood cells. In the body, the sugars coating the surface of the protein are essential to its function. Samuel Danishefsky, who is a synthetic chemist at Sloan Kettering, has developed a synthesis of the protein which has smaller sugar chains, but still allow the protein to carry out its function. From Science:

Last week, the MSKCC-Columbia team reported online in Angewandte Chemie that for the first time they had synthesized EPO with a uniform coating of sugar chains that decorate the outside of the natural molecule. EPO is a hormone produced by the kidneys that stimulates the production of red blood cells. It’s also administered as a drug, sometimes called a biologic, to anemia patients, as well as those with cancer who have undergone radiation and chemotherapy treatments that can damage red blood cells.

“EPO is the most complex biologic synthesized to date,” says Laura Kiessling, a chemist at the University of Wisconsin, Madison, who calls the accomplishment “remarkable.” Peng George Wang, a synthetic chemist at Georgia State University in Atlanta, agrees that the new synthetic ascent is “an awesome achievement,” because the researchers not only synthesized a complex protein but also decorated it with a uniform set of sugars—a feat that has long been out of reach. A decade ago, “we could not imagine it could be a target. It was just too complicated,” Wang says. Danishefsky notes that the feat rests on a decade of advances in fabricating portions of the protein, linking them together, and then coming up with novel chemical techniques to tie sugar chains on at precise locations. Although the version of EPO the group made has shorter sugar chains than those typically found in organisms, biochemical studies showed that it carried out the same function of stimulating the production of red blood cells.

10.06.2012

stem cells yield eggs

Mouse stem cells yield viable eggs that produce fertile offspring

This week brought big news on the stem cell front. A research group in Japan, under the leadership of Mitntori Saitou, has produced viable eggs from mouse stem cells, producing a healthy set of baby mice. Stem cells have produced eggs and sperm before, but this is the first report of viable cells yielding fertile offspring. The breakthrough is in the October 4 issue of Science magazine. A summary from Science News:

In the new study, Saitou and colleagues started with stem cells from very early mouse embryos as well as stem cells reprogrammed from fetal cells, known as induced pluripotent stem cells. Saitou’s team manipulated the activity of a few genes in the stem cells to turn them into cells that resemble precursors of gametes, as eggs and sperm are sometimes known.

These primordial germ cell–like cells, as they are called, were mixed with support cells from an embryonic ovary and then transplanted into adult mice. Once the precursor cells had developed into oocytes, the researchers pulled them out and fertilized them in the lab before implanting the resulting embryos in female mice.

The oocytes made from either type of stem cell produced mouse pups 3.9 percent of the time. That rate is lower than for primordial germ cells taken directly from mouse embryos, which the researchers found produced pups 17.3 percent of the time. Oocytes taken from the ovaries of 3-week-old mice generated offspring 12.7 percent of the time. Female pups resulting from stem cell–derived eggs grew up to become fertile adults, the researchers report.

About half of the stem–cell derived oocytes had an extra set of chromosomes, the researchers discovered. That indicates a breakdown in meiosis, the process of halving the genetic material doled out to eggs and sperm. Saitou acknowledges there is room for improvement in his group’s technique.

GOLLYGEE!

Month: October 2012 (page 6 of 10)

nobel prize in medicine

“awesome” synthesis

stem cells yield eggs