New Method to Detect Genetic Disorders
April 25, 2013
Genetic disorders such as learning disabilities, autism, epilepsy or heart defects can now be diagnosed faster and more accurately thanks to a new method introduced to Polish medical practice by the Mother and Child Institute in Warsaw.
The method has been developed in a project coordinated by Paweł Stankiewicz, Ph.D. of the Mother and Child Institute.
The innovative array-comparative genomic hybridization (aCGH) technology used in the project makes it possible to more accurately analyze the human genome—the complete set of human genetic information stored in the form of DNA sequences. The information encoded in our genome determines everything from our eye color to whether we are likely to die of cancer.
Array-comparative genomic hybridization makes it possible to examine a patient’s genome in search for defects that may be responsible for a specific disease. With this method, it is also possible to observe submicroscopic changes in DNA—trouble spots that are not visible under a microscope.
“A lot of diseases are caused by such [submicroscopic] changes in the genome,” says Stankiewicz. They occur in at least one birth per every thousand. Until now, genomic disorders could only be diagnosed, however inaccurately, by using traditional methods. In recent years, the use of fluorescence in situ hybridization, and chiefly the aCGH technique, has made it possible to fully identify such disorders, researchers say.
The results of the research conducted as part of the Mother and Child Institute project have shown that the aCGH method should be used in diagnosing diseases in Poland. So far, there was a tendency to mainly examine the patient’s karyotype, that is whether or not the structure of the patient’s chromosomes is correct and how many of them there are. But that was only possible when the chromosomes could be seen under a microscope. The new technology makes it possible to detect tiny changes that may be responsible for various abnormalities such as learning disabilities, autism, epilepsy, dysmorphia (facial abnormalities), as well as congenital disorders, such as heart defects.
In simple words, if a child is not developing normally, either intellectually or physically, and the child has a disorder, using the new technology makes it possible to detect problems that could not be detected by evaluating the karyotype in the traditional way.
“Our project has been successful in helping improve the clinical diagnostics of diseases caused by chromosomal abnormalities,” says Stankiewicz. “[The new method] is mainly designed for families with genetic risks. Doctors working as genetic counselors will be able to make use of our research to provide appropriate genetic advice—that is, evaluate the risk of reoccurrence of a disease in the family, and, in some cases, make decisions related to treatment.”
Compared to traditional techniques, the method developed by Stankiewicz’s team makes it possible to analyze the whole genome in a single test with an unprecedented resolution. The new method is expected to revolutionize clinical diagnostics and become the method of choice in diagnosing genomic disorders. Modern diagnostic techniques make it possible to detect what is responsible for child disorders. Some disorders develop by accident during the fetal development stage; others are inherited. In order to dispel doubts, doctors need to examine the parents’ chromosomes. If these chromosomes are normal, it is possible to assume that the change in the child’s genome occurred at random and the risk of its reoccurrence in the parents’ next child is low. But the situation is radically different if the chromosome abnormality is detected in the genome of one of the parents. Such a family is at an increased risk of having offspring with an unbalanced karyotype (one in which a part of a chromosome is missing or there is an extra part). This way families subject to genetic risks can be identified.
Although microarrays can only detect if the genome is unbalanced (while it cannot identify balanced chromosome abnormalities), by means of detecting tiny changes in the child’s genome, they help focus further diagnostics in the child’s parents. The most frequent method used in such situations is fluorescence in situ hybridization.
Thanks to all these tests, it is possible to evaluate the risk of reoccurrence of the disease in the family and provide appropriate genetic counseling if the parents plan to have more children. And although most genetic disorders cannot be cured, parents can discover the reasons for a child’s disease and make an informed decision on whether to have more children or not.
It has turned out that the demand for detecting abnormalities using the aCGH method is enormous. According to Stankiewicz, learning disabilities affect 2-3 percent of the population, autistic disorders 1 percent, and epilepsy a further 1 percent. Congenital heart disorders occur in five to eight live births out of 1,000 and represent a third of all congenital disorders; they are also the most frequent cause of death among infants.
The microarrays used at the Mother and Child Institute have been produced by the Agilent Technologies company of the United States. The same version of the microarrays has been introduced to parallel diagnostic tests at the Baylor College of Medicine in Houston, Texas, and applied to examine more than 15,000 patients. The problem is that the microarrays are rather expensive, which makes it impossible to use them routinely in Poland. However, that does not mean patients in Poland do not benefit from the experience gained during the project. The Department of Medical Genetics at the Mother and Child Institute in Warsaw has introduced the aCGH method to routine genetic examinations together with other, cheaper microarrays produced by the UK-based company Oxford Gene Technology.
The Mother and Child Institute has already carried out about 1,500 routine diagnostic tests using microarrays. The problem for many laboratories is that such tests are expensive, mainly because they require the use of a special scanner.
The project was carried out between 2008 and 2012 at the Department of Medical Genetics at the Mother and Child Institute under the supervision of Prof. Tadeusz Mazurczak and subsequently Prof. Ewa Bocian.
The researchers obtained zl.4.1 million for their research and equipment from Poland’s National Center for Research and Development (NCBiR).
More than 30 people worked on the project. It was conducted in association with the Department of Molecular and Human Genetics at the Baylor College of Medicine in Houston, Texas; the Department of Medical Genetics, Department of Pediatrics and the Children’s Cardiology Clinic at the Jagiellonian University Medical College in Cracow; the Pediatric Cardiology Ward at the Children’s Memorial Health Institute in Warsaw; the Faculty of Electronics and Information Technology at the Warsaw University of Technology; and the Faculty of Mathematics, Informatics and Mechanics at the University of Warsaw.