 |
|
Silenced gene in worm shows role in regeneration
November 28, 2005When smedwi-2 gene is silenced, regeneration stopped in planarians
SALT LAKE CITY - Researchers at the University of Utah have discovered that when a gene called smedwi-2 is silenced in the adult stem cells of planarians, the quarter-inch long worm is unable to carry out a biological process that has mystified scientists for centuries: regeneration.
The study published in the Nov. 25 issue of Science was led by Alejandro Sánchez Alvarado, Ph.D., Howard Hughes Medical Institute investigator and professor of neurobiology and anatomy at the U of U School of Medicine, and carried out by members of his laboratory, in particular Helen Hay Whitney Foundation post-doctoral fellow Peter W. Reddien who is now an Associate Member at the Whitehead Institute for Biomedical Research.
Elimination of smedwi-2 not only leads to an inability to mount a regenerative response after amputation, but also to the eventual demise of unamputated animals along a reproducible series of events, that is, regression of the head tip, curling of the body and tissue disintegration. These defects are very similar to what is observed after the planarian stem cells are destroyed by lethal doses of irradiation. The key difference, however, is that the irradiation-like defects observed in animals devoid of smedwi-2 occur even though the stem cells are still present in the organism.
This finding suggests something surprising: the instructions that a daughter stem cell needs to differentiate for regeneration or for maintaining tissue structure begin to be defined at the time of division of its parent cell. "Once the smedwi-2 molecule is eliminated, the animal is destined to die since the functions of the daughter cells are severely compromised" said Sánchez Alvarado.
The study follows a landmark work that he and Reddien published last spring in Developmental Cell, in which, using a method of gene silencing called RNA interference (RNAi), the researchers silenced more than 1,000 planarian genes, some of which they identified as essential for regeneration. The Science study focus on one such gene, smedwi-2, and brings a new level of genetic detail to understanding planarian regeneration.
Planarians long have fascinated biologists with their ability to regenerate. A worm sliced in two forms two new worm s; even a fractional part of a planarian will grow into a new worm. Scientists know that planarian stem cells, called neoblasts, are central to regeneration, but their exact role is only now being learned.
When an animal stem cell divides, two daughter cells are formed: one that is another stem cell and a second one that can differentiate into the cells that form bone, tissue, and other parts of an organism. These second types of cells are essential for regeneration or maintaining the form and function of tissues by replacing cells that die, a process called homeostasis.
By eliminating smedwi-2, the researchers uncovered a role of this protein in regulating the normal differentiation and function of daughter cells.
The researchers postulated three theories why the worms could not regenerate or maintain cells after smedwi-2 was silenced:
- The stem cells were not responding to tissue damage or homeostasis signals.
- The stem cell division progeny failed to migrate to the appropriate tissues.
- The daughter cells didn't know how to differentiate.
The team found that the stem cells were competent to robustly respond to amputation by significantly increasing their proliferation as well as to home to tissues undergoing homeostasis. But the researchers also found that once the daughter cells reach their target tissues, they were unable to properly differentiate.
"The smedwi-2 molecule is doing something early in the specification of stem cell progeny that modulates their ability to differentiate into the proper cell type," Sánchez Alvarado said. How this molecule is modulating stem cells is one of the next steps that he and Reddien are trying to solve. The answer could have far-reaching implications, because genes similar to smedwi-2 are found in plants, animals and human beings.
University of Utah Health Sciences Center
This finding suggests something surprising: the instructions that a daughter stem cell needs to differentiate for regeneration or for maintaining tissue structure begin to be defined at the time of division of its parent cell. "Once the smedwi-2 molecule is eliminated, the animal is destined to die since the functions of the daughter cells are severely compromised" said Sánchez Alvarado.
The study follows a landmark work that he and Reddien published last spring in Developmental Cell, in which, using a method of gene silencing called RNA interference (RNAi), the researchers silenced more than 1,000 planarian genes, some of which they identified as essential for regeneration. The Science study focus on one such gene, smedwi-2, and brings a new level of genetic detail to understanding planarian regeneration.
Planarians long have fascinated biologists with their ability to regenerate. A worm sliced in two forms two new worm s; even a fractional part of a planarian will grow into a new worm. Scientists know that planarian stem cells, called neoblasts, are central to regeneration, but their exact role is only now being learned.
When an animal stem cell divides, two daughter cells are formed: one that is another stem cell and a second one that can differentiate into the cells that form bone, tissue, and other parts of an organism. These second types of cells are essential for regeneration or maintaining the form and function of tissues by replacing cells that die, a process called homeostasis.
By eliminating smedwi-2, the researchers uncovered a role of this protein in regulating the normal differentiation and function of daughter cells.
The researchers postulated three theories why the worms could not regenerate or maintain cells after smedwi-2 was silenced:
- The stem cells were not responding to tissue damage or homeostasis signals.
- The stem cell division progeny failed to migrate to the appropriate tissues.
- The daughter cells didn't know how to differentiate.
The team found that the stem cells were competent to robustly respond to amputation by significantly increasing their proliferation as well as to home to tissues undergoing homeostasis. But the researchers also found that once the daughter cells reach their target tissues, they were unable to properly differentiate.
"The smedwi-2 molecule is doing something early in the specification of stem cell progeny that modulates their ability to differentiate into the proper cell type," Sánchez Alvarado said. How this molecule is modulating stem cells is one of the next steps that he and Reddien are trying to solve. The answer could have far-reaching implications, because genes similar to smedwi-2 are found in plants, animals and human beings.
University of Utah Health Sciences Center
Regeneration News and Current Regeneration Events RSSHearing restoration may be possible with cochlear repair after transplant of human cord blood cells
According to an Italian research team publishing their findings in the current issue of Cell Transplantation (17:6), hearing loss due to cochlear damage may be repaired by transplantation of human umbilical cord hematopoietic stem cells (HSC) since they show that a small number migrated to the damaged cochlea and repaired sensory hair cells and neurons.
Cardiac cell transplant studies show promise in cardiac tissue repair
Two studies published in the current issue of CELL TRANSPLANTATION (17:6) examine the efficacy of transplanting bone marrow cells (BMCs) for the repair of heart tissue.
Bone marrow stem cells may help control inflammatory bowel disease
Massachusetts General Hospital (MGH) investigators have found that infusions of a particular bone marrow stem cell appeared to protect gastrointestinal tissue from autoimmune attack in a mouse model.
Hydrogels provide scaffolding for growth of bone cells
Hyaluronic hydrogels developed by Carnegie Mellon University researchers may provide a suitable scaffolding to enable bone regeneration. The hydrogels, created by Newell Washburn, Krzysztof Matyjaszewski and Jeffrey Hollinger, have proven to encourage the growth of preosteoblast cells, cells that aid the growth and development of bone. Doctoral student Sidi Bencherif will present this research, Sunday, Aug. 17 at the 236th national meeting of the American Chemical Society in Philadelphia.
Vine invasion? UWM ecologist looks at coexistence of trees and lianas
Among the hundreds of species of woody vines that University of Wisconsin-Milwaukee ecologist Stefan Schnitzer has encountered in the tropical forests of Panama, the largest has a stalk nearly 20 inches in circumference.
Sugar study is sweetener for stem cell science
Scientists at The University of Manchester are striving to discover how the body's natural sugars can be used to create stem cell treatments for heart disease and nerve damage - thanks to a £370,000 funding boost.
MIT identifies cells for spinal-cord repair
A researcher at MIT's Picower Institute for Learning and Memory has pinpointed stem cells within the spinal cord that, if persuaded to differentiate into more healing cells and fewer scarring cells following an injury, may lead to a new, non-surgical treatment for debilitating spinal-cord injuries.
Stem cell chicken and egg debate moves to unlikely arena: the testes
Logic says it has to be the niche. As air and water preceded life, so the niche, that hospitable environment that shelters adult stem cells in many tissues and provides factors necessary to keep them young and vital, must have emerged before its stem cell dependents.
Myostatin inhibitors may improve recovery of wartime limb injuries
Inhibiting a growth factor that keeps muscles from getting too big may optimize recovery of injured soldiers, researchers say.
Novel hydrogel systems for dentin regeneration
Dental caries, or tooth decay, continues to be the most prevalent infectious disease in the world, presenting significant public health challenges and socio-economic consequences.
More Regeneration News Articles
 | Regeneration by Pat Barker Regeneration, one in Pat Barker's series of novels confronting the psychological effects of World War I, focuses on treatment methods during the war and the story of a decorated English officer sent to a military hospital after publicly declaring he will no longer fight. Yet the novel is much more. Written in sparse prose that is shockingly clear -- the descriptions of electronic treatments are... |
 | The Schwarzbein Principle II: The "Transition" - A Regeneration Program to Prevent and Reverse Accelerated Aging by Diana Schwarzbein In her very successful book, The Schwarzbein Principle, renowned endocrinologist Diana Schwarzbein introduced her scientifically proven conclusion that degenerative diseases are not genetic, but acquired. Many studies have supported this, proving that life expectancy is 75 to 90 percent due to habits and only 10 to 25 percent due to genetics. This means that someone who is genetically destined... |
 | Pharmacology and Ototoxicity for Audiologists by Kathleen C. M. Campbell This highly anticipated text is the only publication on pharmacology and ototoxicity written specifically for audiologists. With contributions from leading audiologists, basic scientists, pharmacologists, and otolaryngologists, Pharmacology and Ototoxicity for Audiologists provides both basic and advanced coverage of topics critical to successful clinical practice. Fundamental concepts and... |
 | reGeneration: 50 Photographers of Tomorrow What are young photographers up to at the outset of the twenty-first century? How do they see the world? How much do they respect, build on or reject tradition? Are they busy in the darkroom or in the computer lab--or both? reGeneration sets out to discover answers to these intriguing questions, previewing the work of 50 photographers who may well emerge as some of the finest of their generation.... |
 | The Detox Miracle Sourcebook: Raw Foods and Herbs for Complete Cellular Regeneration by Robert Morse |
 | Body Electronics: Vital Steps for Physical Regeneration by Thomas Chavez Body electronics is a self-healing system that utilizes nutrient saturation through diet and supplementation. Thomas Chavez learned this discipline under its developer, Dr. John Whitman Ray, and in Body Electronics, Chavez expands it to cover every imaginable trauma and illness. The basis for the approach is the melting of melanin protein complexes (crystals) in the body that develop through... |
 | Regeneration: Species Imperative #3 (Species Imperative) by Julie E. Czerneda With the alien Dhryn cutting a pathway through the inhabited spaceways-bringing about the annihilation of many of the races who have the misfortune to lie along the star trail they are following-time is running out for all sentient life-forms. Can biologists Mackenzie Connor and Emily Mamami solve the riddle of the Dhryn before their part of the galaxy becomes as dead as the mysterious region... |
 | Designing Sustainable Communities: Learning From Village Homes by Michael Corbett, Judy Corbett |
 | Death and the Regeneration of Life It is a classical anthropological paradox that symbols of rebirth and fertility are frequently found in funerary rituals throughout the world. The original essays collected here re-examine this phenomenon in the light of new information from China, India, New Guinea, Latin America, and Africa. The contributors, each a specialist in one of these areas, have worked in close collaboration to produce... |
 | Anatomy of an Illness as Perceived by the Patient: Reflections on Healing and Regeneration by Norman Cousins A special gift edition of Norman Cousins's phenomenal bestseller on illness overcome and the triumph of the human spirit. The premise of Norman Cousins's enormously influential work is that the human mind is capable of promoting the body's capacity for combating illness and healing itself even when faced with a seemingly hopeless medical predicament. The author recounts his personal experiences... |
| © 2008 BrightSurf.com |