BGU researchers identify mutation causing severe genetic disease common in Moroccan Jews

Discovery to make it possible for possible carriers of disease that causes epilepsy, severe mental retardation to be tested.

By JUDY SIEGEL-ITZKOVICH
Prof. Ohad Birk. (photo credit: BEN GURION UNIVERSITY OF THE NEGEV)
Prof. Ohad Birk.
(photo credit: BEN GURION UNIVERSITY OF THE NEGEV)
The gene mutation responsible for a disease that causes epilepsy and severe mental retardation has been discovered by researchers at Ben-Gurion University of the Negev, making early detection possible.
The discovery makes it possible for potential carriers of the mutation to be tested, and in cases of in-vitro fertilization, embryos can be tested as well. Those affected by the disease would not be implanted in the womb and this would bring about the eradication of the disease.
Prof. Ohad Birk, head of the genetics institute at Soroka University Medical Center and the affiliated Morris Kahn Lab at BGU’s national institute for biotechnology, discovered the mutation for the disease, which the researchers have called PCCA2 (Progressive cerebello cerebral atrophy type 2).
The disease was shown to be caused by two mutations in the VPS53 gene – both of them common in Jews of Moroccan ancestry, with one of every 37 Moroccan Jews carrying one of the two mutations. The Birk team showed that the mutations cause defective circulation within patients’ cells, leading to detrimental excessive storage of “junk” in the cells.
They recently published their study online in the Journal of Medical Genetics. The research was financed by the Israel Science Foundation and the Legacy Heritage fund.
Babies who are affected by the mutation seem to be perfectly normal when they are born and develop well until about six month, at which point brain atrophy presents itself and the infants begin to deteriorate – reaching severe retardation by age one.
PCCA2 is a recessive disease, this means that if both parents are carriers of a VPS53 mutation there is a 25 percent risk of the disease manifesting in each pregnancy.
Based on the high carrier rate, PCCA2 is the most common severe genetic disease in Moroccan Jews discovered so far, and routine carrier testing for this disease in Moroccan Jews will likely be available within months.
Four years ago, Birk’s group discovered another gene for a similar disease – PCCA – which is common in Jews of Moroccan and Iraqi ancestry (1:40 carrier rate in both cohorts).
Unlike PCCA2, the mutations in PCCA are in a gene called SESPSECS that cancels the body’s ability to utilize the essential micronutrient, selenium.
Thanks to this research, routine, government-funded carrier testing for SESPSECS mutations was introduced in 2011 for all Jews of Moroccan or Iraqi ancestry.
PCCA and PCCA2 are the two most common genetic diseases in Jews of Moroccan heritage, and have never been described before worldwide.
The research into PCCA2 was done as part of the doctoral thesis of Miora Feinstein in Birk’s lab. Dr. Hagit Flusser, Prof. Bruria Ben-Zeev, Prof. Tally Lerman- Sagie and Dr. Dorit Lev contributed to the clinical aspects and Dr. Orly Agamy and others of the Birk lab took part in the molecular studies.
Birk’s research led to the discovery of more than 20 genetic diseases common in Arabs and Sephardi Jews, providing insights into the nature of illness and unraveling molecular pathways of normal human development.