The "Other" DNA
New Mitochondrial DNA Lab First in Texas

When Paul Ware was awakened from a drunken sleep, the body of a four-year-old girl, brutalized and lifeless, lay by his side. Ware, 27, who rented a room in the girl's home in Tennessee, pleaded innocence, blaming the child's rape and murder on the male babysitter. The little girl's blood was not found on Ware, nor was his semen found on her body. However, during the autopsy, a small red hair was discovered lodged in the child's throat. Ware, a redhead, professed no knowledge of the crime.

A new technique known as mitochondrial DNA typing confirmed that the hair in the girl's throat belonged to Ware. The State of Tennessee vs. Paul Ware in 1996 became the first case in the United States to introduce mitochondrial DNA evidence at trial. Ware was subsequently convicted of murder and sentenced to life imprisonment.

A Powerful Weapon

The mitochondrial DNA analysis used to convict Ware differs from the type of DNA analysis so often portrayed in the media, for example, the type used in the O.J. Simpson trial. Whereas the Simpson trial analyzed DNA found in the nucleus of cells, the Ware trial analyzed DNA found in the mitochondria - little structures that float about in the cell outside the nucleus. Mitochondria are the only cell structures, other than the nucleus, that contain their own DNA.

Recognized for their role in converting fuel from food into energy for the body, mitochondria have long been called the "powerhouses of the cell." Today, they are powering their way to some of the most intriguing realms of research. Mitochondrial DNA has the potential to reveal why certain diseases occur, how people and animals have evolved from ancient times, and can be used to identify bodily remains, convict criminals or exonerate the wrongly accused.

That's a huge role for such a tiny piece of a cell, says Dr. Ashraf Mozayani, chief toxicologist and director of the forensics laboratory at the Harris County Medical Examiner's Office, located in the Joseph A. Jachimczyk Center. On April 18, Dr. Mozayani presides over the official opening of the new mitochondrial DNA laboratory at the Medical Examiner's Office. The first lab of its kind in Texas, the facility was made possible by a series of three grants from the U.S. Department of Justice totaling $600,000.

Research into mitochondrial DNA testing was initiated at the FBI Crime Lab in 1990 when a feasibility study was performed to determine its usefulness in forensics. In 1995, the lab conducted and published a validation study that set today's standard for the use of mitochondrial DNA in courtroom trials. The study affirms the technique as a "valid and powerful weapon" against crime.

"Today, in addition to the FBI Crime Lab, only a few private laboratories and a handful of government labs are equipped to conduct the procedure, but I predict this number will skyrocket," Dr. Mozayani said.

Chief Medical Examiner Dr. Joye Carter concurs.

"We're extremely fortunate to be among the first in the country to offer such a service. More and more labs are sure to open as awareness of the value of mitochondrial DNA testing increases," she said.

The new laboratory will enable forensic scientists to solve cases that otherwise could forever remain a mystery, Dr. Carter said.

A Different DNA

The advantage of mitochondrial DNA typing over nuclear DNA typing techniques is "strength in numbers," Dr. Mozayani said.

A cell contains only one nucleus, and inside that nucleus are only two copies of DNA, one inherited from the mother, and one passed down from the father. In contrast, a single cell contains thousands of mitochondria, with each of those mitochondria containing numerous DNA molecules.

"The odds are much higher that you can recover more DNA from thousands of mitochondria than you can from only one nucleus," she explained.

But besides being easier to collect, mitochondrial DNA has another advantage over nuclear DNA. Extreme environmental conditions don't appear to negatively impact DNA found in mitochondria, whereas nuclear DNA tends to degrade when the going gets tough. Difficult samples such as skeletonized bones that have been buried for years or badly burned materials have all easily yielded mitochondrial DNA. Aged samples of hair, blood, saliva, or teeth have also been shown to produce mitochondrial DNA.

"Very old samples are much more likely to contain mitochondrial DNA than nuclear DNA, which over time becomes degraded or disappears altogether. Mitochondrial DNA is stronger, longer lasting," said Dr. Mozayani.

In cases where very little or no nuclear DNA is available, mitochondrial DNA is particularly useful. In the Ware case involving the hair in the throat, the hair root (the "living" part of the hair that contains nuclear DNA) was absent. Investigators therefore tested the hair strand (the "dead" part of the hair that contains mitochondrial DNA).

While mitochondrial DNA cannot be matched as precisely as nuclear DNA, the comparisons still can be extremely close - close enough to be allowed as courtroom evidence. There also is the advantage that mitochondrial DNA is passed down the maternal side of families for generations, allowing identifications to be made by comparing a subject's DNA with that of his mother, grandmother, great-grandmother, great-great-grandmother, etc...

Famous Findings

It was mitochondrial DNA that in 1998 helped identify the remains of Air Force Lt. Michael J. Blassie, the Vietnam War pilot placed in the Tomb of the Unknowns at Arlington National Cemetery when his plane was shot down 60 miles north of Saigon in 1972.

The technique also was used to confirm that the remains found in a shallow grave in Yekaterinburg, Russia, were indeed those of the royal Romanov family, and thereby disproved a claim by a woman named Anna Anderson that she was the missing Princess Anastasia. After comparing Anderson's DNA to that of the female skeletons in the Romanov grave without obtaining a match, investigators dismissed Anderson's claims as fraudulent.

A once-promising effort to identify remains of 866 Korean War veterans, however, failed to meet with the same success. Plans were to exhume the bodies from what is officially the National Memorial Cemetery of the Pacific, nicknamed the "Punch Bowl" for its location in an old volcanic crater in Hawaii. Two bodies were exhumed in 1999, but forensic scientists became puzzled when neither body yielded mitochondrial DNA. The bodies were buried in the traditional military way - wrapped in a sheet and a wool Army blanket, fastened with 20 safety pins, and placed in a metal casket. A strange, light gray powder covered each skeleton. Military scientists analyzed the powder and now suspect that it contained an antiseptic preservative called formalin, which was routinely used in Army burials at the time. Traces of the formalin have since vanished from the powder that was applied almost 50 years earlier, but scientists believe it was present at the time of burial. Formalin has been reported in medical literature to damage DNA and prevent its extraction from tissue.

This January, another four bodies were exhumed . All four were wrapped up in much the same way, and were dusted with the same powder. Scientists once again were unable to extract mitochondrial DNA, and exhumations from the Punch Bowl are on hold indefinitely.

Looking Back - Way Back

In the meantime, anthropologists are abuzz over the recent discovery that isolated ethnic groups contain distinct differences in mitochondrial DNA, allowing researchers to track the migrations, languages, and origins of peoples. One well-known result of such investigations is the identification of the "mitochondrial Eve" or "out of Africa" theory of human origin, based on a group of women who lived about 200,000 years ago in Africa - the mothers of us all, as everyone today carries the progeny of their mitochondrial DNA.

The technique also allowed anthropologists to trace the origin of the waves of people who migrated from Asia across the Bering land bridge to populate North and South America, and be mislabeled "Native" Americans.

And thanks to mitochondrial DNA analysis, it is now known that the 5,300-year-old Tyrolean Iceman, discovered in the Italian Alps during a 1991 ice melt, was not a hoax, but an authentic ice-age European.

A major evolutionary breakthrough occurred in 1997, when a team of U.S. and German scientists extracted mitochondrial DNA from Neanderthal bone, demonstrating that Neanderthals are not the ancestors of modern humans. The researchers used phylogenetic tree reconstruction - a method that uses mitochondrial DNA to group individuals based on similarities in DNA molecules. The trees show that the Neanderthal sequence branches before the divergence of the various human mitochondrial DNA lineages, but after the split from chimpanzees.

Detecting Disease

Medical researchers, like anthropologists, are looking to mitochondrial DNA for answers. It's common knowledge among researchers that defects in mitochondrial DNA play a part in certain diseases. These genetic "errors" are found in tissues that have high demands for energy, such as muscle, heart, brain and eye - relating back to mitochondria's role in converting food into energy for the body. Conditions caused by defective mitochondrial DNA are rare, and include Kerns-Sayre syndrome, characterized by large deletions of mitochondrial DNA in the heart, muscle and brain which cause fatality in young adulthood, and Pearson syndrome, a similar deletion in blood resulting in fatal anemia in infancy. More common disorders are also associated with mutations in mitochondrial DNA. Diabetes is unusually frequent in mitochondrial diseases, and about 2 percent of patients with adult onset (type II) diabetes have mutations in mitochondrial DNA, often with deafness.

A unique approach to detecting cancer by looking for mutations in mitochondrial DNA has been developed by researchers at Johns Hopkins and reported in the journal Science. After analyzing tumor and body fluid samples from cancer patients, they found that mutations in the DNA located in the patients' mitochondria occurred anywhere between 20 and 200 times more than mutations in the patients' nuclear DNA. The Johns Hopkins team envisions the creation of a blood test that will screen for cancer by revealing mutations in mitochondrial DNA, which they say are "much easier to detect based on sheer numbers" than nuclear DNA mutations.

Of all the conditions related to mitochondrial DNA, one in particular spares no one and ultimately affects us all - aging. Scientists are examining the hypothesis that human aging is due in large part to an accumulation of mutations in mitochondrial DNA that build up over a lifetime in the various cells and tissues of the human body. As mutations occur and slip past the repair mechanisms, energy production decreases, and slowly cells lose their ability to carry out their normal functions. So far, this idea appears to be consistent with the data obtained from tissue samples, and "mitochondrial DNA's role in aging" is fast becoming a favored field of study at universities worldwide.

Back in Houston, the Medical Examiner's Office prepares to take on what surely will be an unprecedented number of investigations involving violent crimes and missing persons.

"Maybe now we can help families learn the fate of a lost loved one and provide them with a grave to visit ... now we can offer closure," said Dr. Mozayani.

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©2006 Texas Medical Center

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