Gene Duplication: New Analysis Shows How Extra Copies Split the Work

Word cloudThe human genome contains more than 20,000 protein-coding genes, which carry the instructions for proteins essential to the structure and function of our cells, tissues and organs. Some of these genes are very similar to each other because, as the genomes of humans and other mammals evolve, glitches in DNA replication sometimes result in extra copies of a gene being made. Those duplicates can be passed along to subsequent generations and, on very rare occasions, usually at a much later point in time, acquire additional modifications that may enable them to serve new biological functions. By starting with a protein shape that has already been fine-tuned for one function, evolution can produce a new function more rapidly than starting from scratch.

Pretty cool! But it leads to a question that’s long perplexed evolutionary biologists: Why don’t duplicate genes vanish from the gene pool almost as soon as they appear? After all, instantly doubling the amount of protein produced in an organism is usually a recipe for disaster—just think what might happen to a human baby born with twice as much insulin or clotting factor as normal. At the very least, duplicate genes should be unnecessary and therefore vulnerable to being degraded into functionless pseudogenes as new mutations arise over time

An NIH-supported team offers a possible answer to this question in a study published in the journal Science. Based on their analysis of duplicate gene pairs in the human and mouse genomes, the researchers suggest that extra genes persist in the genome because of rapid changes in gene activity. Instead of the original gene producing 100 percent of a protein in the body, the gene duo quickly divvies up the job [1]. For instance, the original gene might produce roughly 50 percent and its duplicate the other 50 percent. Most importantly, organisms find the right balance and the duplicate genes can easily survive to be passed along to their offspring, providing fodder for continued evolution.

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Precision Medicine: Who Benefits from Aspirin to Prevent Colorectal Cancer?

Aspirin and DNA StethoscopeIn recent years, scientific evidence has begun to accumulate that indicates taking aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs) on a daily basis may lower the risk of developing colorectal cancer. Now, a new study provides more precise information on who might benefit from this particular prevention strategy, as well as who might not.

Published in the journal JAMA, the latest work shows that, for the majority of people studied, regular use of aspirin or NSAIDs was associated with about a one-third lower risk of developing colorectal cancer. But the international research team, partly funded by NIH, also found that not all regular users of aspirin/NSAIDs reaped such benefits—about 9 percent experienced no reduction in colorectal cancer risk and 4 percent actually appeared to have an increased risk [1]. Was this just coincidence, or might there be a biological explanation?

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What Makes Our Brain Human? The Search for Answers

The Thinker

“The Thinker” by Auguste Rodin (photo by Brian Hillegas)

Humans’ most unique traits, such as speaking and abstract thinking, are rooted in the outer layer of our brains called the cerebral cortex. This convoluted sheet of grey matter is found in all mammals, but it is much larger and far more complex in Homo sapiens than in any other species. The cortex comprises nearly 80 percent of our brain mass, with some 16 billion neurons packed into more than 50 distinct, meticulously organized regions.

In an effort to explore the evolution of the human cortex, many researchers have looked to changes in the portion of the genome that codes for proteins. But a new paper, published in the journal Science [1], shows that protein-coding DNA provides only part of the answer. The new findings reveal that an even more critical component may be changes in the DNA sequences that regulate the activity of these genes.

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NIH-Funded Research Makes Science’s “Top 10” List

NIH-funded AAAS/Science Editors' Choice for 2014 Breakthroughs of the YearModeled after Time’s Person of the Year, the journal Science has a tradition of honoring the year’s most groundbreaking research advances. For 2014, the European Space Agency nabbed first place with the Rosetta spacecraft’s amazing landing on a comet. But biomedical science also was well represented on the “Top 10” list—with NIH helping to support at least four of the advances. So, while I’ve highlighted some of these in the past, I can’t think of a better way for the NIH Director to ring in the New Year than to take a brief look back at these remarkable achievements!

Youth serum for real? Spanish explorer Ponce de Leon may have never discovered the Fountain of Youth, but researchers have engineered an exciting new lead. Researchers fused the circulatory systems of young and old mice to create a shared blood supply. In the old mice, the young blood triggered new muscle and more neural connections, and follow-up studies revealed that their memory formation improved. The researchers discovered that a gene called Creb prompts the rejuvenation. Block the protein produced by Creb, and the young blood loses its anti-aging magic [1]. Another team discovered that a factor called GDF11 increased the number of neural stem cells and stimulated the growth of new blood vessels in the brains of older animals [2].

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Snapshots of Life: Wild Outcome from Knocking Out Mobility Proteins

Spiky fibroblast cell

Credit: Praveen Suraneni and Rong Li, Stowers Institute for Medical Research

When biologists disabled proteins critical for cell movement, the result was dramatic. The membrane, normally a smooth surface enveloping the cell, erupted in spiky projections. This image, which is part of the Life: Magnified exhibit, resembles a supernova. Although it looks like it exploded, the cell pictured is still alive.

To create the image, Rong Li and Praveen Suraneni, NIH-funded cell biologists at the Stowers Institute for Medical Research in Kansas City, Missouri, disrupted two proteins essential to movement in fibroblasts—connective tissue cells that are also important for healing wounds. The first, called ARPC3, is a protein in the Arp2/3 complex. Without it, the cell moves more slowly and randomly [1]. Inhibiting the second protein gave this cell its spiky appearance. Called myosin IIA (green in the image), it’s like the cell’s muscle, and it’s critical for movement. The blue color is DNA; the red represents a protein called F-actin.

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