Category Archives: Stem Cells

Public release date: 9-May-2013 [ | E-mail | Share ]

Contact: Andy Hoang ahoang@salk.edu 619-861-5811 Salk Institute

LA JOLLA, CA Scientists have long known that control mechanisms known collectively as "epigenetics" play a critical role in human development, but they did not know precisely how alterations in this extra layer of biochemical instructions in DNA contribute to development.

Now, in the first comprehensive analysis of epigenetic changes that occur during development, a multi-institutional group of scientists, including several from the Salk Institute for Biological Studies, has discovered how modifications in key epigenetic markers influence human embryonic stem cells as they differentiate into specialized cells in the body. The findings were published May 9 in Cell.

"Our findings help us to understand processes that occur during early human development and the differentiation of a stem cell into specialized cells, which ultimately form tissues in the body," says co-lead author Joseph R. Ecker, a professor and director of Salk's Plant Molecular and Cellular Biology Laboratory and holder of the Salk International Council Chair in Genetics.

Scientists have established that the gene expression program encoded in DNA is carried out by proteins that bind to regulatory genes and modulate gene expression in response to environmental cues. Growing evidence now shows that maintenance of this process depends on epigenetic marks such as DNA methylation and chromatin modifications, biochemical processes that alter gene expression as cells divide and differentiate from embryonic stem cells into specific tissues. Epigenetic modificationscollectively known as the epigenomecontrol which genes are turned on or off without changing the letters of the DNA alphabet (A-T-C-G), providing cells with an additional tool to fine-tune how genes control the cellular machinery.

In their study, the Salk researchers and their collaborators from several prominent research institutions across the United States examined the beginning state of cells, before and after they developed into specific cell types. Starting with a single cell typethe H1 human embryonic stem cell, the most widely studied stem cell line to datethe team followed the cells' epigenome from development to different cell states, looking at the dynamics in changes to epigenetic marks from one state to another. Were they methylated, an essential process for normal development, or unmethylated? What happened to the cells during development? What regulatory processes occurred in the cell lineage?

The scientists found sections of the DNA that activate regulatory genes, which in turn control the activity of other genes, tend to have different amounts of letters of the DNA alphabet, "C" and "G" specifically, depending on when these regulatory genes are turned on during development. Additionally, regulatory genes that control early development are often located on stretches of DNA called methylation valleys, or DMVs, that are generally CG rich and devoid of epigenetic chemical modifications known as methylation. Consequently, these genes have to be regulated by another epigenetic mechanism, which the authors found were chemical changes called chromatin modifications. Chromatin is the mass of materialDNA and proteinsin a cell's nucleus that helps to control gene expression.

On the other hand, genes active in more mature cells whose tissue type is already determined tend to be CG poor and regulated by DNA methylation. The results suggest that distinct epigenetic mechanisms regulate early and late states of embryonic stem cell differentiation.

"Epigenomic studies of how stem cells differentiate into distinct cell types are a great way to understand early development of animals," says Ecker, who is also a Howard Hughes Medical Institute and Gordon and Betty Moore Foundation Investigator. "If we understand how these cells' lineages originate, we can understand if something goes right or wrong during differentiation. It's a very basic study, but there are implications for being able to produce good quality cell types for various therapies."

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Salk researchers chart epigenomics of stem cells that mimic early human development

Stem Cells, Racist Proms, and Obama
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Stem Cells, Racist Proms, and Obama - Video

Poor circulation in the legs and feet can lead to the loss of limbs or even the loss of life, but hope is on the horizon. A new treatment could help millions of people get their blood flowing again.

Until recently, Derrick Blount was unable to ride his bike. He said the problem was that "being in a sitting position would greatly restrict the blood flow to my left leg.

Blount has Buergers disease, a form of poor circulation brought on by smoking. He quit the habit and almost had to quit his art gallery job because of his leg limitations. Where as tasks like hanging a picture should take no more than 20 minutes, it was taking him and hour-and-a-half.

So, Blount took part in Dr. Omaida Velazquezs clinical trial at the University of Miami. The doctor is taking stem cells from patients hip bones and injecting them into their legs and feet to help restore circulation.

"It is believed that these cells release some growth factors and proteins that help in regeneration of blood vessels," explained Velazquez, chief of the Division of Vascular and Endovascular Surgery at the University of Miami Miller School of Medicine.

Velazquez said the treatment could help millions of people with dangerous circulation problems, like peripheral arterial disease.

Blounts not sure if hes getting the stem cells in the double blind study, but said, "These blood pressures are very significantly improved on his left toes, and clinically, almost to a miraculous level.

Right now, the trial is recruiting participants across the country. See the research summary for information about the trials.

DOWNLOAD and VIEW the full-length interview with Dr. Omaida Velazquez about using your own stem cells for circulation

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Health Beat: Using your own stem cells for circulation

India, May 5 -- Ophthalmologists are hoping that Preeti Rathi, 25, who lost vision in her right eye after an unknown man threw acid on her face at Bandra Terminus, may be able to regain her vision after undergoing stem cell therapy.

On Saturday morning, Rathi, who was admitted inside the burns intensive care unit at Masina Hospital at Byculla, scribbled a note pleading her ophthalmologist Dr Yasmin Bhagat to help her see with both eyes again.

"We have helped patients of acid attack to regain vision by using stem cell therapy in the past. Once she (Rathi) recovers fully we can look at harvesting stem cells from her parents' eye and transplanting them in her right eye as the cornea is damaged by the acid," said Dr Bhagat.

Doctors said that her condition is stable and she was put on ventilator support for a few hours to give her rest. According to doctors, Rathi's face is fully bandaged while her eyes are stil shut. "She cannot see but her left eye is showing improvement." added Bhagat who has treated numerous such acid attack victims in the past.

Rathi's father Amarsingh is planning to meet officials from INHS Asvini, where Preeti was supposed join as a nurse, to postpone her joining date. "If they postpone her joining, she would be very happy," said Amarsingh

Meanwhile, The Bandra Government Railway Police (GRP), who are probing the acid attack, have scanned the passenger list of train in which the accused was travelling. Further probe is underway.

Published by HT Syndication with permission from Hindustan Times.

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Stem cells may help Mumbai acid attack victim regain vision: doctors

Newswise ANN ARBORThe human body contains trillions of cells, all derived from a single cell, or zygote, made by the fusion of an egg and a sperm. That single cell contains all the genetic information needed to develop into a human, and passes identical copies of that information to each new cell as it divides into the many diverse types of cells that make up a complex organism like a human being.

If each cell is genetically identical, however, how does it grow to be a skin, blood, nerve, bone or other type of cell? How do stem cells read the same genetic code but divide into very different types?

Researchers at the University of Michigan have found the first direct evidence that cells can distinguish between seemingly identical copies of chromosomes during stem cell division, pointing to the possibility that distinct information on the chromosome copies might underlie the diversification of cell types.

Scientists in the lab of Life Sciences Institute researcher Yukiko Yamashita explained how stem cells can distinguish between two identical copies of chromosomes and distribute them to the daughter cells in a process called nonrandom chromosome segregation. They also described the genes responsible. Their work is scheduled to be published online May 5 in Nature.

"If we can figure out how and why cells are dividing this way, we might be able to get a glimpse of how we develop into a complete human, starting from a single cell," Yamashita said. "It is very basic science, but understanding fundamental biological processes always has wide-ranging implications that could be exploited in therapeutics and drug discovery."

During the cell division cycle, the mother cell duplicates its chromosomes, generating two identical sets. When the cell divides to become two cells, each cell inherits one set of chromosome copies. In many divisions, the daughter cells are identical to the motherone skin cell becomes two, for instance.

But in a process called asymmetric division, a cell divides into two daughters that are not identicala skin stem cell divides into another skin stem cell and a regular skin cell, for example. In that case, the genetic information within the chromosome copies remains the same, but the type of cell, or "cell fate," is different.

The Yamashita lab used stem cells from the testes of the fruit fly Drosophila to study the process of cell division.

"The Drosophila germ line stem cell can be identified at a single-cell resolution, so they are an ideal model," Yamashita said.

The stem cells cluster and are easy to identify; they divide to produce another germ line stem cell and a differentiating cell called a gonialblast, which goes on to eventually become a sperm cell.

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Divide and Define: Clues to Understanding How Stem Cells Produce Different Kinds of Cells