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Archive - May 16, 2011

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Worm’s Amazing Regenerative Capacity Tied to Ancient Gene

Most people don't think worms are spectacular. But the tiny flatworm that Northwestern University scientist Dr. Christian Petersen studies can do something quite spectacular indeed: it can regenerate itself from nearly every imaginable injury, including decapitation. When cut in half, it becomes two worms. This amazing ability of the planarian flatworm to regenerate its entire body from a small wedge of tissue has fascinated scientists since the late 1800s. The worms can regrow any missing cell or tissue -- muscle, neurons, epidermis, eyes, even a new brain. Now Petersen and colleague Peter Reddien of the Massachusetts Institute of Technology (MIT) have discovered that an ancient and seldom-studied gene is critical for regeneration in these animals. The findings may have important ramifications for tissue regeneration and repair in humans. The gene, called notum, plays a key role in the regeneration decision-making process. Protein from this gene determines whether a head or tail will regrow at appropriate amputation sites, the researchers found. "These worms are superstars in regeneration, and we want to learn how they restore missing body parts," said Dr. Petersen, an assistant professor of molecular biosciences in Northwestern's Weinberg College of Arts and Sciences. "We anticipate that understanding the details of how regeneration occurs in nature will ultimately have a broad impact on the repair of human tissue." The study is published in the May 13, 2011 issue of the journal Science. Dr. Petersen, a former postdoctoral fellow in Dr. Reddien's lab, is the first author. Dr. Reddien, associate professor of biology at MIT and the Whitehead Institute for Biomedical Research, is the other author.

Retina Sections Regenerated and Visual Function Increased Using Skin Stem Cells

Scientists from the Schepens Eye Research Institute, an affiliate of Harvard Medical School, are the first to regenerate large areas of damaged retinas and improve visual function using induced pluripotent stem cells (iPSCs) derived from skin. The results of their study, which was published online on April 29, 2011, in PLoS ONE, hold great promise for future treatments and cures for diseases such as age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and other retinal diseases that affect millions worldwide. "We are very excited about these results," says Dr. Budd A. Tucker, the study's first author. "While other researchers have been successful in converting skin cells into induced pluripotent stem cells and subsequently into retinal neurons, we believe that this is the first time that this degree of retinal reconstruction and restoration of visual function has been detected," he adds. Dr. Tucker, who is currently an Assistant Professor of Ophthalmology at the University of Iowa, Carver College of Medicine, completed the study at Schepens Eye Research Institute in collaboration with Dr. Michael J. Young, the principle investigator of the study, who heads the Institute's regenerative medicine center. Today, diseases such as retinitis pigmentosa and age-related macular degeneration are the leading causes of incurable blindness in the western world. In these diseases, retinal cells, also known as photoreceptors, begin to die and with them the eye's ability to capture light and transmit this information to the brain. Once destroyed, retinal cells, like other cells of the central nervous system have limited capacity for endogenous regeneration. "Stem cell regeneration of this precious tissue is our best hope for treating and someday curing these disorders," says Dr.

Tiny Variation in One Gene May Have Led to Brain Convolutions

The human brain has yet to explain the origin of one its defining features – the deep fissures and convolutions that increase its surface area and allow for rational and abstract thoughts. An international collaboration of scientists from the Yale School of Medicine and Turkey may have discovered an important clue – a tiny variation within a single gene that determines the formation of brain convolutions – they report online on May 15, 2011, in Nature Genetics. A genetic analysis of a Turkish patient whose brain lacks the characteristic convolutions in part of his cerebral cortex revealed that the deformity was caused by the deletion of two genetic letters from three billion in the human genetic alphabet. Similar variations of the same gene, called laminin gamma 3 (LAMC3), were discovered in two other patients with similar abnormalities. "The demonstration of the fundamental role of this gene in human brain development affords us a step closer to solve the mystery of the crown jewel of creation, the cerebral cortex," said Dr. Murat Gunel, senior author of the paper and the Nixdorff-German Professor of Neurosurgery, co-director of the Neurogenetics Program and professor of genetics and neurobiology at Yale. The folding of the brain is seen only in mammals with larger brains, such as dolphins and apes, and is most pronounced in humans. These fissures expand the surface area of the cerebral cortex and allow for complex thought and reasoning without taking up more space in the skull. Such foldings aren't seen in mammals such as rodents or other animals. Despite the importance of these foldings, no one has been able to explain how the brain manages to create them. The LAMC3 gene – involved in cell adhesion that plays a key role in embryonic development – may be crucial to the process.

Chromosome 3 Region Linked to Depression

Researchers at Washington University School of Medicine in St. Louis and King's College London have independently identified a DNA region on chromosome 3 that appears to be related to depression. Major depression affects approximately 20 percent of people at some point during their lives, and family studies have long suggested that depression risk is influenced by genetics. The new studies identify a DNA region containing up to 90 genes. Both studies were published online on May 15, 2011, in the American Journal of Psychiatry. "What's remarkable is that both groups found exactly the same region in two separate studies," says senior investigator Dr. Pamela A. F. Madden, professor of psychiatry at Washington University. "We were working independently and not collaborating on any level, but as we looked for ways to replicate our findings, the group in London contacted us to say, 'We have the same linkage peak, and it's significant.'" Dr. Madden and the other researchers believe it is likely that many genes are involved in depression. While the new findings won't benefit patients immediately, the discovery is an important step toward understanding what may be happening at the genetic and molecular levels, she says. The group at King's College London followed more than 800 families in the United Kingdom affected by recurrent depression. The Washington University group gathered data from 91 families in Australia and another 25 families in Finland. At least two siblings in each family had a history of depression, but the Australian and Finnish participants were studied originally because they were heavy smokers. "Major depression is more common in smokers, with lifetime reports as high as 60 percent in smokers seeking treatment," says lead author Dr. Michele L. Pergadia, research assistant professor of psychiatry at Washington University.