Revealing the Genetic Secret to a Rare Disease
Revealing the Genetic Secret to a Rare Disease
June 6, 2014
Popular Science — Prof. Ohad Birk, head of the Genetics Institute at Soroka University Medical Center and the Morris Kahn Lab at the National Institute for Biotechnology in the Negev at BGU, is helping neurologists in Israel provide families with children suffering from PCCA with a chance at prevention.
PCCA is a genetic disorder that causes severe mental and physical disabilities and brain atrophy – all before the age of three.
The research team first thought the villain behind PCCA would be one mutation in one gene. After all, so far, they’ve only found the disease in families of Moroccan and Iraqi Jewish descent.
Prof. Ohad Birk
That made the scientists think the faulty gene could have stemmed from one founder – the predecessor to these populations – long ago. But they soon realized the picture was much more complex. “That’s not an uncommon discovery,” says Prof. Birk.
“Now, with massive DNA sequencing, diseases that were classified classically as similar are turning out to be different,” he says.
“On the other hand, sometimes you see that diseases that seem to be different and were in different chapters in the textbook, they’re actually caused by different mutations in the same gene.”
In the case of PCCA, the families that have it may have one of two mutations in one gene called SepSecS, or one mutation in an unrelated gene, called VPS53. People with mutated SepSecS genes can’t incorporate the mineral selenium into their bodies.
It doesn’t matter if they have enough selenium in their diet. People with mutations in their VPS53 genes, on the other hand, aren’t able to move cell structures called vacuoles out of their cells. Essentially, their cells can’t take out the trash. Waste accumulates inside them.
Because these mutations are in two unrelated genes, PCCA is actually considered two diseases, PCCA and PCCA2. Birk’s team published a paper defining PCCA2 and its cause in February, in the Journal of Medical Genetics. Team members think it’s likely there’s a “PCCA3,” too. They’re continuing to investigate.
Unfortunately, PCCA and PCCA2 have no cure. Still, knowing their causes is a boon. Clinics can now test parents to see if they’re carriers for the disease, before they have children. Proff. Birk recommends testing among couples who are both of either Moroccan Jewish or Iraqi Jewish descent.
People of those ethnicities have roughly a 1 in 40 chance of being carriers, which means they have one of the gene mutations, but don’t have symptoms. The mutations are much rarer in people of other ethnicities.
Parents who are both carriers are at risk for having children with the disease. But they have options. One relatively new option: Parents may use in vitro fertilization technology to create embryos and choose those that don’t have PCCA or PCCA2.
Read the full article by Francie Diep on the Popular Science website >>
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