Chuck Bednar for redOrbit.com Your Universe Online

Scientists at the Baylor College of Medicine Medical Genetics Laboratories and the UCLA Clinical Genomics Center are at the forefront of a new technique that could be a powerful tool for diagnosing rare genetic conditions.

The technique is known as whole-exome sequencing and involves using cutting edge sequencing techniques to analyze the coding regions or exomes of thousands of genes at the same time, Baylor researchers Dr. Yaping Yang, Dr. Christine M. Eng and their colleagues explained in a recent edition of the Journal of the American Medical Association (JAMA).

Sequencing a patients exome and comparing it to a normal reference sequence allows researchers to identify variations in that individuals DNA sequence. Those variations can then be related back to the patients health issues in an attempt to locate the specific genetic cause of that medical condition, the authors added.

The researchers studied a group of 2,000 patients that had been referred for evaluation of suspected genetic conditions, and found that the use of whole-exome sequencing led to the discovery of a molecular diagnosis (meaning that a genetic mutation or variation associated with a specific disease) in roughly 25 percent of them.

The findings in this report, I believe, will forever change the future practice of pediatrics and medicine as a whole, study co-author Dr. James R. Lupski, a professor of molecular and human genetics and pediatrics at Baylor, said in a statement. It is just a matter of time before genomics moves up on the physicians list of things to do and is ordered before formulating a differential diagnosis. It will be the new family history that, better yet, gets you both the important variants inherited from each parent and the new mutations that contribute to disease susceptibility.

In the study, the use of whole-exome sequencing identified ways in which medical professionals could clinically intervene in order to alleviate or eliminate symptoms and give patients families more information about the disease and treatment. Furthermore, many of the diagnoses made using the technique involved patients inheriting a new mutation previously undetected in their parents, the researchers will report Tuesday at the annual meeting of the American Society of Human Genetics (ASHG) in San Diego.

The clinical whole-exome sequencing analyzed as part of the study took place between June 2012 and August 2014, and the tests had been ordered by the patients physician for suspected genetic conditions. The process involved the collection of peripheral blood, tissue, or extracted DNA samples which were collected from patients or their parents, and the majority (87.8 percent) of those analyzed were found to have neurological disorders or developmental delay.

A molecular diagnosis was reported for 504 patients (25.2 percent), with 58 percent of the diagnostic mutations not previously reported, the researchers said. Molecular diagnosis rates for the physical manifestation or phenotypic category was 27.2 percent for the neurological group, 24.6 percent for the neurological plus other organ systems group, 36.1 percent for the specific neurological group, and 20.1 percent for the nonneurological group.

Clinical exome sequencing can assist diagnosis in a wide range of disorders that are diagnostic dilemmas, said Lupski. Rare variants and Mendelian disease are important contributors to disease populations We find rare variants in aggregate actually contribute to disease susceptibility in a big way. The individual diseases may be rare, but there are thousands of such diseases and many more being defined through genomics.

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Exome Sequencing Becoming A Powerful New Diagnostic Tool For Genetic Disorders

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