Seeking superior stem cells

Researchers from the Wellcome Trust Sanger Institute have discovered a new technique to reprogramme human cells, such as skin cells, into stem cells. Their process increases the efficiency of cell reprogramming by one hundred-fold and generates cells of a higher quality at a faster rate.

Until now cells have been reprogrammed using four specific regulatory proteins. By adding two further regulatory factors, the scientists brought about a dramatic improvement in the efficiency of reprogramming and the robustness of stem cell development. The new streamlined process produces cells that can grow more easily.

“This research is a milestone in human stem cells,” explained Wei Wang, first author on the research from the Wellcome Trust Sanger Institute. “Our technique provides a foundation to unlock the full potential of stem cells.”

With more than 20 years of research, gold standard stem cells are derived from mice, largely because they are easy to work with and provide accurate and reproducible results. The team’s aim was to develop human cells of equivalent quality to mouse stem cells.

“The reprogrammed cells developed by our team have proved to have the same capabilities as mouse stem cells,” states Pentao Liu, senior author from the Sanger Institute. “Our approach will enable researchers to easily engineer and reprogramme human stem cells to generate cell types for cell replacement therapies in humans.”

Retinoic acid receptor gamma and liver receptor homolog, the additional regulatory factors used by Liu and co-workers, were introduced into the skin cells along with the four other regulatory proteins. The team’s technology produced reprogrammed cells after just four days, compared to the seven days required for the four-protein approach. Key indicators of successfully reprogrammed cells, Oct4 and Rex-1 genes, were seen to be switched on much faster in a much higher number of cells, demonstrating increased efficiency in reprogramming.

“This is the most promising and exciting development in our attempt to develop human stem cells that lend themselves in practical applications. It bears comparison to other technologies as it is simple, robust and reliable,” says Allan Bradley, Senior Group Leader and Director of Emeritus at Sanger Institute.

doi: 10.1073/pnas.1100893108



New genetic mutation for amyotrophic lateral sclerosis identified

A team led by scientists from Johns Hopkins and the US National Institutes of Health has discovered a new genetic mutation for amyotrophic lateral sclerosis (ALS) and a related disease called frontotemporal dementia (FTD) that appears to account for more than a third of all inherited cases of these diseases. The researchers show in a new study published online on 21 September 2011 in Neuron that this mutation, found within a gene called C9ORF72, is about twice as common as all the other mutations discovered thus far for the disease combined.

The findings, say study leader Bryan J. Traynor, MD, an assistant professor in the Department of Neurology at the Johns Hopkins University School of Medicine and chief of the Neuromuscular Diseases Research Unit at the NIH, could help scientists develop new animal models of ALS, also known as Lou Gehrig’s disease, and eventually new targets for attacking the more common sporadic form of the disease, which isn’t inherited and appears to crop up in the population at random.

Though a handful of other genetic mutations have been linked to inherited, or familial, ALS and FTD over the past several years, these mutations appear to account for only about a quarter of cases. Knowing that other ALS- and FTD-causing mutations remain undiscovered in the genome, the team focused their search on a place that other studies had suggested might hold promise: the short arm of chromosome 9. While previous research had suggested this as a likely hotbed for genetic problems that cause ALS and FTD, the exact location of the responsible mutation or which genes might be affected was unknown.

“If you think of chromosomes like geographic regions, we knew what city this mutation was located in, and what part of the city, but we didn’t know what street it was located on or which house,” explained Dr Traynor. “We were really looking for the exact address for this mutation.”

To narrow down the mutation’s location, Traynor and his colleagues worked with collaborators around the world, using a next-generation genomic sequencing technique on pieces of chromosome 9 sampled from ALS and FTD patients in unrelated Welsh and Dutch families in which the diseases had been diagnosed in multiple generations. They compared sequences from these affected individuals to healthy people, both unaffected relatives and people outside these families who had never been diagnosed with ALS or FTD.

In just the affected individuals, the sequences turned up an unusual section of chromosome 9 near the C9ORF72 gene in which a six-base DNA sequence (GGGGCC) was repeated over and over. When the researchers looked at DNA samples from other patients with familial ALS and FTD from Finland, the country with the highest incidence of these diseases worldwide, this same unusual segment was present in nearly half of cases, stretching from hundreds to thousands of repeats.

“Together with another mutation in a previously discovered familial ALS gene known as SOD1, this means that we are now able to explain nearly all of familial ALS disease in Finland,” Dr Traynor notes.

Seeking confirmation in other familial ALS and FTD cases around the globe, the researchers tested samples from patients in Italy, Germany, and North America. Sure enough, the repeats were present in about 38% of patients, but never in healthy individuals.

Dr Traynor notes that he and his colleagues don’t yet know how the repeated segments might cause familial ALS and FTD. It could be that they affect the function of C9ORF72, whose purpose is not yet known. However, the team thinks a more likely mechanism is that the repeated segments cause affected cells to manufacture a slew of toxic RNA, genetic material that clogs up cells and eventually leads to their demise. The slow buildup of toxic RNA could be the reason why ALS and FTD tend to show up in middle age, rather than earlier in life. The researchers note that previous work has already shown abnormal RNA metabolism in ALS patients now known to carry this new mutation, lending support for this theory.



Consortium discovers new genes that control blood pressure

In one of the largest genomics studies ever, an international research consortium has identified 29 genetic variations across 28 regions of the human genome that influence blood pressure. This unprecedented effort brought together more than 230 researchers across six continents and scanned the genomes of over 200,000 people. The results appear in the 11 September 2011 edition of Nature.

“It is fitting that a global research group came together to provide new insight into a condition that affects over 1 billion people worldwide,” said Susan B. Shurin, MD, acting director of the US National Institutes of Health’s National, Heart, Lung, and Blood Institute (NHLBI), which was part of the international consortium behind the study. “This is one of the most important studies of the genetics of high blood pressure to date and a significant step toward finding better therapies for it.”

Sixteen of the 29 variations identified in the study were previously unrecognised. Six of the new variations were found in genes already suspected of regulating blood pressure; the other 10, which were found in unexpected locations, provide new clues into how blood pressure is regulated.

Individually, the genetic variations increased the risk of hypertension (high blood pressure) by only a tiny amount. For people with multiple variants, however, the effects were more significant.

The research team developed a blood pressure genetic risk score by combining variant combinations (with someone having many variants toward the top, and someone with very few at the bottom). They found that people in the top 10% of the genetic risk score had blood pressure readings that were 5.8 mm/Hg and 3.7 mm/Hg higher for the systolic and diastolic values, respectively, than the lowest 10% risk score group. Systolic refers to blood pressure as the heart is pumping blood, while diastolic refers to blood pressure between heartbeats.

In line with the increased values, hypertension also increased with risk score; 29% of people in the highest risk group had hypertension, compared to 16% in the lowest risk group. The risk score was also a good indicator of hypertension complications such as increased thickness of heart chambers, heart failure, stroke, and coronary artery disease. The risk score, however, was not a good indicator of the risk of kidney disease, another common hypertension-related problem.

The primary group of 200,000 participants was of European background and included subjects selected from several NHLBI study populations including the Framingham Heart Study (FHS). The research consortium then followed up its analysis on 70,000 people of East Asian, South Asian, and African ancestry. The researchers found that the genetic risk score and several of the individual variants were associated with increased blood pressure in these ethnic groups as well.

“This study demonstrates the continuing value of large cohorts like Framingham, which started in 1948 and is still helping scientists uncover the genetics and biology of diseases today,” said Daniel Levy, MD, one of the co-leaders of this project and director of the FHS.



World’s first neural stem cells fully transplanted in spinal cord injury

StemCells, has announced that the first patient in the company’s Phase I/II clinical trial in chronic spinal cord injury was successfully transplanted with the company’s proprietary HuCNS-SC adult neural stem cells.

The stem cells were administered at Balgrist University Hospital, University of Zurich.

The transplant surgery was performed by a team of surgeons led by Dr Raphael Guzman, a visiting staff neurosurgeon also on faculty at Department of Neurosurgery, Stanford University, and Dr K. Min, an orthopaedic surgeon at Balgrist University Hospital.

“I am pleased to be a part of this innovative clinical trial designed to help us assess the safety and potential efficacy of HuCNSSC stem cells for spinal cord injury,” explained Dr Armin Curt, Principal Investigator. “The preclinical data underlying this trial provided compelling rationale to conduct a study of this nature in spinal cord-injured patients.”

StemCells, has published numerous preclinical studies demonstrating the therapeutic potential of the company’s human neural stem cells for the treatment of acute and chronic spinal cord injury. These studies were conducted in close collaboration with Drs Aileen Anderson and Brian Cummings of the University of California, Irvine.

The first patient transplanted in the trial, a 23-year-old German man, suffered a spinal cord injury in an automobile accident in April of this year. He sustained a complete loss of sensation and mobility from the waist down.

When asked about his decision to enrol in this leading-edge study, he said: “This terrible injury crossed out almost all my life plans, and has led me to an unexpected path. Participating in this clinical trial not only gives me a sense of hope, but it also helps move this important research forward.”

“With this first patient enrolled and dosed, we remain on track to meet our goal of treating the first cohort of patients by the end of this year,” said Stephen Huhn MD, FACS, FAAP, Vice President and Head of the CNS Program at StemCells, Inc.

Huhn added: “While the trial’s first cohort will consist of patients with the most severe, complete injury, the second and third cohorts will progress to patients with less severe, incomplete injury. This unique trial design will allow us to evaluate the potential of our HuCNS-SC cells as a treatment for a broad spectrum of spinal cord injury patients. Even a small improvement could have a marked impact on quality of life for the millions of people who suffer from this debilitating condition.”



New technique identifies first events in tumour development

A novel technique that enables scientists to measure and document tumourinducing changes in DNA is providing new insight into the earliest events involved in the formation of leukemias, lymphomas and sarcomas, and could potentially lead to the discovery of ways to stop those events.

Developed by a team of researchers at the US National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and the US National Cancer Institute (NCI), both parts of the National Institutes of Health, and The Rockefeller University, the technology focuses on chromosomal rearrangements known as translocations. Translocations occur when a broken strand of DNA from one chromosome is erroneously joined with that of another chromosome. Sometimes these irregularities can be beneficial in that they enable the immune system to respond to a vast number of microorganisms and viruses. However, translocations can also result in tumours.

The findings are reported in the 30 September 2011 issue of the Cell. Translocations can take place during the course of normal cell division, when each chromosome – a single strand of DNA containing many genes – is copied verbatim to provide genetic information for the daughter cells. Sometimes, during this process, byproducts of normal metabolism or other factors can cause breaks in the DNA.

“The cell expresses specific enzymes whose primary purpose is to repair such lesions effectively, but when the enzymes mistakenly join pieces of two different chromosomes, the cell’s genetic information is changed,” said Rafael C. Casellas, PhD, senior investigator in the Genomics and Immunity Section at the NIAMS.

Casellas likens the phenomenon to breaking two sentences and then rejoining them incorrectly. For example, “The boy completed his homework.” and “The dog went to the vet.” might become “The dog completed his homework.” or “The boy went to the vet.” When a cell gets nonsensical information such as this, it can become deregulated and even malignant.

Scientists have known since the 1960s that recurrent translocations play a critical role in cancer. What was unclear was how these genetic abnormalities are created, since very few of them were studied, and only within the context of tumours, said Casellas. To better understand the nature of these tumour-inducing rearrangements, the authors had to create a system to visualise their appearance in normal, nontransformed cells.

The system the teams created involved introducing enzymes that recognise and cause damage at a particular sequence in the DNA into cells from mice, thereby constructing a genome where a unique site is broken continuously. The group then used a technique called polymerase chain reaction – which allows scientists to quickly amplify short sequences of DNA – to check all the sites in the genome that would get translocated to this particular break. Using this technique, they were able to examine more than 180,000 chromosomal rearrangements from 400 million white blood cells, called B cells.

Based on this large data set, the scientists were able to make several important observations about the translocation process. They learned that most of the translocations involve gene domains, rather than the space on the DNA between the genes. They also found that most translocations target active genes, with a clear bias for the beginning of the gene, as opposed to its middle or end. The team also showed that a particular enzyme that normally creates DNA breaks in B cells dramatically increases the incidence of translocations during the immune response. This feature explains the longstanding observation that more than 95% of human lymphomas and leukemias are of B cell origin.

“This knowledge is allowing us to understand how tumours are initiated,” said Casellas. “It is the kind of information that in the near future, might help us prevent the development of cancer.”



Uterine stem cells used to treat diabetes in mice

Researchers funded by the US National Institutes of Health (NIH) have converted stem cells from the human endometrium into insulin-producing cells and transplanted them into mice to control the animals’ diabetes.

The endometrium, or uterine lining, is a source of adult stem cells. Normally, these cells generate uterine tissue each month as part of the menstrual cycle. Like other stem cells, however, they can divide to form other kinds of cells.

The study's findings suggest the possibility that endometrial stem cells could be used to develop insulin-producing islet cells. These islet cells could then be used to advance the study of islet cells transplantation as a treatment for people with diabetes. If the transplantation of islet cells derived from endometrial cells is perfected, the study authors write that women with diabetes could provide their own endometrial tissue for such a transplant, sidestepping the chance of rejection posed by tissue from another person. Endometrial stem cells are readily available and can be collected easily during a simple outpatient procedure. Endometrial tissue could also be collected after hysterectomy, the surgical removal of the uterus.

“The study findings are encouraging,” said Louis V. DePaolo, PhD, chief of the Reproductive Sciences Branch at the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), which funded the study. “Research to transplant insulin-producing cells into patients with diabetes could proceed at a much faster pace with a relatively accessible source of donor tissue.”

The study authors note that such a treatment would be more useful for people with Type 1 diabetes, in which no insulin is produced. The treatment would be less useful for Type 2 diabetes, in which insulin is usually produced, but in which cells have difficulty using the insulin that is available.

The findings appear in Molecular Therapy, 30 August 2011.

The study authors write that endometrial tissue samples could be warehoused in a tissue bank. A large number of samples would make it comparatively easy to find compatible tissue for transplant to women who no longer have a uterus and to men.

doi: 10.1038/mt.2011.173



Researchers find genetic code for regulating liver

Researchers have identified a large number of areas in the human genetic code that are involved in regulating the way in which the liver functions, in a new study of over 61,000 people, published 16 October 2011 in Nature Genetics.

The work is an international collaboration led by Imperial College London and it identifies 42 genetic regions associated with liver function, 32 of which had not been linked to liver function before. The work should lead to a better understanding of precisely what goes wrong when the liver ceases to work normally. Ultimately, it could point the way to new treatments that can improve the function of the liver and help to prevent liver damage.

Dr John Chambers, the lead author of the study from the School of Public Health at Imperial College London, said: “The liver is a central hub in the body and because it has so many diverse functions, it is linked to a large number of conditions. Our new study is a big step towards understanding the role that different genes play in keeping the liver working normally, and towards identifying targets for drugs that can help prevent the liver from functioning abnormally or becoming susceptible to disease.”

Professor Jaspal S Kooner, the senior author of the study from the National Heart and Lung Institute at Imperial College London, said: “This massive international research effort provides indepth new knowledge about the genes regulating the liver. We are particularly excited about the genes whose precise role we don’t yet know. Investigating these further should help us to fill in the gaps in our understanding about what happens when the liver ceases to function normally and how we might be able to tackle this.”

doi: 10.1038/ng.970



 

                                   
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