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February 26, 2015
Digest

Tick Genome Reveals Secrets of a Successful Bloodsucker

With tenacity befitting their subject, an international team of nearly 100 researchers toiled for a decade and overcame tough technical challenges to decipher the genome of the blacklegged tick (Ixodes scapularis).

Moderate hyperopia, if not treated, may affect reading ability and grade school readiness among preschoolers.
Ixodes scapularis tick engorged with blood. Some genes allow ticks to quickly expand their stiff outer coats to accommodate a 100-fold increase in total body size during blood feeding.

PHOTO: CDC

The National Institute of Allergy and Infectious Diseases contributed primary support to the research, which appeared in the online journal Nature Communications.

“Ticks spread more different kinds of infectious microbes to people and animals than any other arthropod group,” said NIAID director Dr. Anthony Fauci. “The spiral-shaped bacterium that causes Lyme disease is perhaps the best known microbe transmitted by ticks; however, ticks also transmit infectious agents that cause human babesiosis, anaplasmosis, tick-borne encephalitis and other diseases. The newly assembled genome provides insight into what makes ticks such effective disease vectors and may generate new ways to lessen their impact on human and animal health.”

The researchers’ focus was a creature that is extremely difficult to maintain and that lives a long time—up to 2 years in the wild and 9 months in the lab.

Another challenge was the sheer size of the tick genome—some 2.1 billion DNA base pairs—and expansive regions where sequences are repeated.

“The genome gives us a code book to the inner workings of ticks. With it, we can now begin to hack their system and write a counter-script against them,” said Dr. Catherine A. Hill of Purdue University, who headed the team of investigators.

Hill admits to a grudging admiration for her 8-legged subjects. “I find them almost endearing in the way they stick so firmly to the business of parasitizing their hosts. They are persistent and resilient. In a way, our team took a page from the tick’s book in working together over so many years until we achieved our goal.”

Criminal Justice Alcohol Program Linked to Decreased Mortality

A criminal justice program that requires offenders convicted of alcohol-related offenses to stop drinking and submit to frequent alcohol testing with swift, certain and modest sanctions for a violation was linked to a significant reduction in county-level mortality rates in South Dakota. These results came from a study funded by the National Institute on Alcohol Abuse and Alcoholism.

The 24/7 Sobriety program, launched in South Dakota in 2005, was associated with a 4.2 percent decrease in all-cause mortality over 6 years, with the largest reductions occurring among women and individuals over 40. Deaths from circulatory conditions, which include heart disease and stroke, declined significantly.

“The study suggests that effective programs for alcohol-involved offenders may have benefits, not only for the participants themselves, but [also] for the community as a whole,” said Dr. George Koob, NIAAA director. “If these results are replicated in future studies, it could advance our understanding of how interventions within the criminal justice system can be used to improve public health.”

The study results appeared online in The Lancet Psychiatry.

NIH Researchers Identify Striking Genomic Signature Shared by 5 Types of Cancer

NIH researchers have identified a striking signature in tumor DNA that occurs in 5 different types of cancer. They also found evidence that this methylation signature may be present in many more types of cancer.

The specific signature results from a chemical modification of DNA called methylation, which can control the expression of genes like a dimmer on a light switch. Higher amounts of DNA methylation (hypermethylation), like that found by the researchers in some tumor DNA, decreases a gene’s activity. Based on this advance, the researchers hope to spur development of a blood test that can be used to diagnose a variety of cancers at early stages, when treatments can be most effective. The study appeared Feb. 5 in the Journal of Molecular Diagnostics.

“Finding a distinctive methylation-based signature is like looking for a spruce tree in a pine forest,” said Dr. Laura Elnitski, a computational biologist at NHGRI. “It’s a technical challenge to identify, but we found an elevated methylation signature around the gene known as ZNF154 that is unique to tumors.”

In 2013, her research group discovered a methylation mark (or signature) around ZNF154 in 15 tumor types in 13 different organs and deemed it a possible universal cancer biomarker. Biomarkers are biological molecules that indicate the presence of disease. Elnitski’s group identified the methylation mark using DNA taken from solid tumors.

“No one in my group slept the night after that discovery,” Elnitski said. “We were so excited when we found this candidate biomarker. It’s the first of its kind to apply to so many types of cancer.”

Elnitski will next begin screening blood samples from patients with bladder, breast, colon, pancreatic and prostate cancers to determine the accuracy of detection at low levels of circulating DNA. Tumor DNA in a person with cancer typically accounts for 1 to 10 percent of all DNA circulating in the bloodstream. The group noted that when 10 percent of the circulating DNA contains the tumor signature, the detection rate is quite good. Because the methylation could be detected at such low levels, it should be adequate to detect advanced cancer as well as some intermediate and early tumors, depending on the type.

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