Mysterious DNA modification important in fly brain

Drosophila, despite being a useful genetic model of development, have very little DNA methylation on C. What they do have is methylation on A (technically, N6-methyladenine), although little was known about what this modification did for Read more

Where it hurts matters in the gut

What part of the intestine is problematic matters more than inflammatory bowel disease subtype (Crohn’s vs ulcerative colitis), when it comes to genetic activity signatures in pediatric Read more

Overcoming cisplatin resistance

Cisplatin was known to damage DNA and to unleash reactive oxygen species, but the interaction between cisplatin and Mek1/cRaf had not been observed Read more

Department of Cell Biology

When genes forget to forget

In ancient Greek mythology, the souls of the dead were made to drink from the river Lethe, so that they would forget their past lives. Something analogous happens to genes at the very beginning of life. Right after fertilization, the embryo instructs them to forget what it was like in the egg or sperm where they had come from.

This is part of the “maternal-to-zygote transition”: much of the epigenetic information carried on and around the DNA is wiped clean, so that the embryo can start from a clean slate.

Developmental biologist Lewis Wolpert once said: “It is not birth, marriage or death which is
the most important time in your life, but gastrulation,” referring to when the early embryo separates into layers of cells that eventually make up all the organs. Well, the MZT, which occurs first, comes pretty close in importance.

When this process of epigenetic reprogramming is disrupted, the consequences are often lethal. Emory cell biologists David Katz and Jadiel Wasson discovered that when mouse eggs are missing an enzyme that is critical for the MZT, on the rare instances when the mice survive to adulthood, they display odd repetitive behaviors. Read more

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Cancer metastasis: isolating invasive cells with a color change

The capacity of cancer cells to spread throughout the body and metastasize (invade new tissues) makes them deadly. What makes metastatic cells different?

Scientists at Winship Cancer Institute of Emory University have developed a technique for isolating individual cells that display invasive behavior out of a large group in culture by changing their color.

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Growth factor mimics promote recovery after nerve injury

Peripheral nerve injury ranges from chronic irritation like carpal tunnel syndrome to violent trauma. Severe nerve injury can leave patients with lifelong disabilities. Even if nerves regenerate, functional recovery is often poor, because of problems with regeneration of axons, the signal-carrying “stalks” of nerve cells.Figure4.axons

Cell biologist Art English and his colleagues have shown that compounds identified by pathologist Keqiang Ye can promote axon regeneration when mice have injured peripheral nerves. The growth Cheap NFL Jerseys factor-mimicking compounds not only stimulate axons to regenerate twice as quickly (see figure), but also promote the restoration of connections between nerve and muscle. The results were published in September in PNAS.

Ye previously identified compounds that activate the same signals as the neuron growth factor BDNF (brain-derived neurotrophic factor). These compounds – 7,8-dihydroxyflavone and deoxygedunin — have shown promise in experimental models of diseases such as stroke and Parkinson’s disease. They also have been used to tweak learning and memory in animal models.

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What cancer researchers can learn from fruit fly genetics

What can scientists studying cancer biology learn from fruit flies?

Quite a lot, it turns out.  At a time when large projects such as the Cancer Genome Atlas seek to define the changes in DNA that drive cancer formation, it is helpful to have the insight gained from other arenas, such as fruit flies, to make sense of the mountains of data.

Drosophila melanogaster has been an important model organism for genetics because the flies are easy to care for, reproduce rapidly, and have an easily manipulated genome. This NCI newsletter article describes how some investigators have used Drosophila to find genes involved in metastasis.

Emory cell biologist Ken Moberg says that he and postdoctoral fellow Melissa Gilbert crafted a Drosophila-based strategy to identify growth-regulating genes that previous researchers may have missed. Their approach allowed them to begin defining the function of a gene that is often mutated in lung cancer. The results are published online in Developmental Cell.

Part of the developing fly larva, stained with an antibody against Myopic. Groups of cells lacking Myopic, which lack green color, tend to divide more rapidly.

Moberg writes:

Many screens have been carried out in flies looking for single gene lesions that drive tissue overgrowth. But a fundamental lesson from years of cancer research is that many, and perhaps most, cancer-causing mutations also drive compensatory apoptosis, and blocking this apoptosis is absolutely required for cancer outgrowth.

We reasoned that this class of ‘conditional’ growth suppressor genes had been missed in prior screens, so we designed an approach to look for them. The basic pathways of apoptosis are fairly well conserved in flies, so it’s fairly straight forward to do this.

Explanatory note: apoptosis is basically a form of cellular suicide, which can arise when signals within the cell clash; one set of proteins says “grow, grow” and another says “brake, brake,” with deadly results.

Gilbert identified the fruit fly gene Myopic as one of these conditional growth regulators. She used a system where mutations in Myopic drive some of the cells in the fly’s developing eye to grow out more – but only when apoptosis is disabled.

Gilbert showed that Myopic is part of a group of genes in flies, making up the Hippo pathway, which regulates how large a developing organ will become. This pathway was largely defined in flies, then tested in humans, Moberg says. The functions of the genes in this pathway have been maintained so faithfully that in some cases, the human versions can substitute for the fly versions.

Myopic’s ortholog (ie different species, similar sequence and function) is the gene His-domain protein tyrosine phosphatase, or HD-PTP for short. This gene is located on part of the human genome that is deleted in more than 90 percent of both small cell and non-small cell lung cancers, and is also deleted in renal cancer cells.

How HD-PTP, when it is intact, controls the growth of cells in the human lung or kidney is not known. Gilbert and Moberg’s findings suggest that HD-PTP may function through a mechanism that is similar to Myopic’s functions in the fly.

Besides clarifying what Myopic does in the fly, their paper essentially creates a map for scientists studying HD-PTP’s involvement in lung cancer, for example, to probe and validate.

Posted on by Quinn Eastman in Cancer 1 Comment