Genetic Testing on the Horizon

January 10, 2019
Kevin Hattori

Technion-led research published recently in European Journal of Human Genetics sheds light on hereditary deafness in the Israel’s Arab population. The findings could one day lead to significant improvements in genetic diagnostics and to the development of genetic therapies targeting hereditary deafness.

Clinical Professor Stavit Allon-Shalev is a faculty member at the Technion’s Rappaport Faculty of Medicine and the director of the Genetics Center at the Technion-affiliated Ha’Emek Medical Center

The study was conducted by Ph.D. student Nada Farran, under the supervision of Clinical Professor Stavit Allon-Shalev, a faculty member at the Technion’s Rappaport Faculty of Medicine and the director of the Genetics Center at the Technion-affiliated Ha’Emek Medical Center.

Professor Shalev, a researcher and genetic diseases specialist, explained that “genetic diseases are one large group of conditions that have a broad impact on human health. There are centers that specialize in specific areas of genetics, but at the Ha’Emek Genetics Center, our activities address all types of genetic problems, reaching out to all families requiring help.”

The researchers’ findings focused on deafness with a genetic etiology. Hereditary diseases, such as deafness, are common in Israel, primarily in the Arab-Muslim sector, due to the high frequency of consanguineous marriages. Consanguinity is a custom with deep historic roots, and is still common  in many regions around the world, including the Middle East.

Nada Farran

The direct impact of relatives’ marriage is the higher rate of hereditary diseases with autosomal recessive inheritance – diseases which are manifested only when there is a defect in both copies of the responsible gene, namely, both the copy inherited from the mother and the copy inherited from the father.  Due to the relatively high genetic similarity between relatives, cousin/other relatives marriage increases the prevalence of this scenario.

“Genetic, laboratory-based diagnosis,” explained Professor Shalev, “is the first and central stage of genetic counseling to families, including risk assessment of reoccurrence of the condition among other family members and their children. In addition, the data serves as a key tool in family planning.  Such diagnoses not only provide a current medical assessment, but also enable educated and informed decision making that might prevent birth of affected babies.”

Family planning can be conducted via various channels, all of which rely on parental will and preferences.  Firstly, a prenatal test can inform if the fetus is affected.  If the fetus is diagnosed with a severe condition, then the parents can decide upon termination of the pregnancy – a procedure that has been approved by religious Muslim leaders, if performed at early stages of pregnancy.

Alternatively, preimplantation genetic diagnosis (PGD) can be chosen. PGD first involves in vitro fertilization and after several days, during which the egg divides into several cells, the genetic composition of a single cell is tested.  If the disease diagnosed in the family is not detected, the fertilized egg is implanted into the mother’s womb.  “We live in an era in which advanced diagnostic and treatment technologies are becoming accessible and relatively affordable,” explained Professor Shalev, “and we must assist parents in reaching the decisions most suitable for them.”

The current study

Advanced genetic mapping techniques were applied to map the genetic basis for deafness in 24 families. According to Professor Shalev, “We found that each family harbored a different genomic variation relating to deafness.  Therefore, each family needs a specifically tailored genetic diagnostic test. In addition, these findings enabled us to better understand the clinical spectrum and the impact of certain genes on human health and the complex genomic mechanisms impacting development of these diseases.”

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