Eye colors: Drusen, the yellow flecks in this image of the retina, are common in people with age-related macular degeneration. These flecks are made up of proteins involved in the part of the immune system called the complement system, which has also been implicated in the disease by genetic studies.
National Eye Institute
Genome-wide association studies have generated new insight into the devastating eye disease.
In 2005, two genetic studies of people with age-related macular degeneration (AMD)--the most common cause of blindness in people older than 65--made a surprising discovery. Research showed that defects in a gene that is an important regulator of parts of the immune system significantly increased risk of the disease. Scientists have since identified variants in several related genes that also boost risk, and which collectively account for about 50 to 60 percent of the heritability of the disorder.
At the same time that researchers identified the harmful variation linked to AMD, Gregory Hageman, now at the University of Utah, identified a protective variant found in about 20 percent of the population. "That form is so incredibly protective that people with two copies are almost guaranteed not to develop the disease," he says. Hageman founded Optherion, a startup based in New Haven, CT, and investigated how to translate the findings into new treatments. Optherion is now producing large quantities of an engineered version of the protein and doing preclinical safety and effectiveness testing--for example, examining whether the treatment can reduce ocular deposits in mice that lack the protein, says Colin Foster, Optherion's president. He declined to estimate when the company will begin clinical trials of the drug.
Scientists hope that these developments will prove to be an example of the benefits that can arise from a type of genetic study called genome-wide association. The genome-wide studies of macular degeneration were among the first and perhaps the biggest success for the approach, which employs specially designed chips dotted with markers to cheaply detect hundreds of thousands of the most common variations in the human genome. While these chips have allowed scientists to cheaply scan the genomes of many patients and healthy controls, the approach has come under increasing scrutiny in the last couple of years. Even huge studies of thousands of people have failed to identify the majority of the heritability of common diseases, such as type 2 diabetes or Alzheimer's disease.
But David Altshuler, a physician and geneticist at the Broad Institute, in Cambridge, MA, and one of the primary architects of these studies, argues that this is not the best way to measure their success. Rather than using the results to design diagnostics to predict an individual risk for developing a disease, we should use genome-wide association studies to identify new drug targets, he says. And he points toward macular degeneration as an example.
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Deer Frozen In Vernacular Headlights
Absence of MIT Ophthalmologist curiosity, maybe due to summer vacation or sabbatical considerations bid additional comment on the topic.
a wide array of genome wide association studies may identify genes active in functioning optic nerve pathways. endothelial, epithelial cells of the optic nerve itself are a curiosity, a focal point of interest being the mitochondrial oxygen sensing mechanism in cells of the eye and its component, lens, retina, light sensing cones, rods etc.....
identifying a key protein deficiency, compensating with a drug may be helpful, that still leaves us with a partially functioning process, and unknown side effects to the introduction of pharmaceutical intervention.
"understanding how oxygen levels are adapted to is fundamentally important to dealing with pretty much all major diseases" according to Celeste Simon of U of Penna. a student of cellular oxygen deprivation.
low levels of oxygen, hypoxia as the condition is known, came to the attention of researchers in 1995 when the transcription factor known as HIF, hypoxia-inducible factor was identified as being a major player in activating blood vessel formation enabling aggressive expansion of tumors...
similar variants of metabolic mitochondrial malfunction, are suspect of being at the forefront of degenerative processes, whether the protein isolated by the startup addresses the root cause of the malady remains to be seen
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53 Comments
In the Macular Vernacular
someday when ion channel pathways and ganglia connections of the autonomic nervous system are as well known and understood as the circulatory system, we will be able to detect the presence of vagrant protein molecules, in the makeup of chemical composition of spinal fluids (for lack of better terminology) confirming/denying, or yielding redundant clues clarifying the causes leading to macular degeneration.....translucence of nearby nerves and or nerve endings is limiting present day comprehensive intervention, recent discoveries of parts of cellular anatomy that have been invisible since time immemorial, offer hope that translucence obstacles will be overcome in the field of nerveous system physiology in the not too distant future, aging baby boomers would have it no other way....from the gist of the article, diagnostic understanding genetic involvement in the degenerative process is a boon to healers, previously relying on intuitive skills and palliative half measures when dealing with hopeless conditions....nice article, hope for better personalized medicine is on the way....
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