Treating Vision Loss with Stem Cells An efficient new method of growing retinal cells from embryonic stem cells shows promise in treating degenerative eye diseases
Retinal progenitor cells (pictured above) can be efficiently generated from human embryonic stem cells, providing a potential source of eye cells for transplant. (Credit: Deepak Lamba and Thomas Reh)
SOURCE: “Efficient Generation of Retinal Progenitor Cells from Human Embryonic Stem Cells” Deepak Lamba et al. Proceedings of the National Academy of Sciences 103(34): 12769-12774
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RESULTS: Thomas Reh, at the University of Washington in Seattle, and his team have developed a reliable way to generate cells known as retinal progenitors, which have the ability to turn into any of the cell types found in the retina, such as photoreceptors or retinal ganglion cells. Preliminary results show that when the cells are transplanted into retinas either in a dish or in live lab animals, the cells migrate to different layers of the retina and begin to express proteins characteristic of the neighboring cells–including photoreceptors, which convert light into electrical signals.
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WHY IT MATTERS: In retinitis pigmentosa and age-related macular degeneration, photoreceptors degenerate over time, leading to loss of vision. Previous research showed that these diseases can be treated by replacing lost cells, but there was no reliable source of replacements.
METHODS: Researchers exposed human embryonic stem cells to a mix of three proteins, called growth factors, that are involved in the development of head and eye tissue. The treated stem cells developed into retinal progenitors.
NEXT STEPS: The researchers will examine whether the cells actually restore vision when transplanted into the eye.
The Gene That Makes Us Human A rapidly evolved piece of DNA that’s unique to humans could be the key to the human brain
SOURCE: “An RNA Gene Expressed during Cortical Development Evolved Rapidly in Humans” Katherine Pollard et al. Nature 443(7108): 167-172
RESULTS: Researchers identified a small piece of DNA that has undergone rapid evolution in humans but not in other species, such as chickens and chimpanzees. The DNA sequence is part of a gene that codes for RNA rather than for a protein; the gene is expressed during development of the cerebral cortex.
WHY IT MATTERS: The human brain is three times the size of a chimp’s–largely because of a bigger cerebral cortex, the outer layer of the brain that is responsible for reasoning and other types of complex thought. Because the newly identified variation is unique to humans, and the gene it is part of is active during cortical development, the finding might help explain how the human brain evolved.
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METHODS: Researchers compared the human genome with the genomes of chimps, dogs, rats, mice, and chickens to find genetic sequences that changed little between species, suggesting that they were functionally important. Within those shared regions, the researchers looked for sequences that had changed significantly between chimpanzees and humans, indicating that those changes played a crucial role in human evolution.
NEXT STEPS: Researchers will try to better understand the RNA gene’s role in brain development and cognition by creating a mouse that expresses the human form of the gene.
