Ashkenazic? Chances high you carry altered gene
By DEBORAH MOON
article created on: 2009-05-01T00:00:00
Statistics suggest that of the 63 people at a free program about genetic diseases more common among Ashkenazi (eastern European) Jews, 15 are carriers of at least one of those Jewish genetic diseases.
When Rabbi Daniel Isaak read an August 2008 Jewish Review article about Bonnie Davis’ efforts to prevent tragedies such as the death of her 2½-year-old son Adam from Tay-Sachs disease, he wanted to ensure other young couples in the Jewish community knew about such risks. Two decades earlier he had known a family struggling with another JGD and already was aware of the heartache it can bring.
So, on April 19, Congregation Neveh Shalom hosted a free luncheon featuring genetics counselor Gary S. Frohlich and OHSU professor Dr. Robert Steiner. There are now 15 recessive genetic diseases known to be more common among Ashkenazi Jews than in the general population (see box). Several of those diseases, such as Tay-Sachs and Canavans, are fatal in early childhood.
The JGDs are all recessive, single gene mutations on one of human’s 22 non-sex chromosomes. Couples in which both partners have the mutation for the same disease face a 25 percent chance of having a child with the disease. For each pregnancy, there is a one in four chance the child will have the disease, a two in four chance the child will be a carrier for the disease and a one in four chance the child will be a non-carrier.
Frohlich, Genzyme’s senior medical affairs liaison, speaks nationally about genetic diseases and testing. Last year he developed a brochure for distribution to Hillel student groups on campuses to explain those topics and to encourage young Jewish adults to consider genetic testing. The pamphlet is available to individuals or groups by emailing email@example.com.
“My job is tikkun olam and pikkun nefesh,” said Frohlich. “It is our responsibility to maintain our bodies in as healthy states as possible and to improve the world.”
“Testing is a personal decision made in consultation with your rabbi and physician,” he said. “But you don’t know what to consult about unless you have information.”
Steiner, who spoke about some of the specific diseases, agreed with Frohlich on the importance of information.
“The important part is that people of child-bearing age have the education and ideally are screened so they know what the genetics are so they can make educated decisions,” said Steiner.
Davis is also a proponent of spreading information.
“With knowledge, even carrier couples can have healthy, happy kids,” said Davis showing a slide of her two healthy sons Jeremy, 7, and Jordan, 3.
Couples who know they are both carriers have several options. A corionic villi sampling test done at 12 weeks or amniocentesis done at 16 weeks of a pregnancy can screen for the JGDs giving parents the option of terminating a pregnancy of an affected fetus.
For couples who do not want to face the potential of terminating a pregnancy, Pre-implantation Genetic Diagnosis is another option that Frohlich discussed. In PGD, conception occurs outside the uterus and at the 8-cell stage, one cell is removed and tested for the presence of the disease. Then if an embryo is unaffected, it can be implanted in the mother’s uterus.
Adoption and artificial insemination from a non-carrier are other options.
In addition to distributing his and other pamphlets on genetic diseases, Frohlich gave the audience a crash course in biology and Jewish history to explain why the Ashkenazi population has such high carrier rates.
During the large diaspora that followed the destruction of the second Temple, many Jews went to the Iberian Peninsula where they lived in large communities in relative security for about 1,400 years, explained Frohlich. Those Sephardic Jews did not experience a concentration of their genetic pool as did their Ashkenazi brethren who settled in Eastern Europe.
The incidence of the mutated genes in the Ashkenazi population was increased by repeated cycles of that population expanding and then shrinking dramatically several times over 2,000 years. Persecution reduced the Ashkenazi population frequently.
“We were scapegoats for the Black Plague,” he said. “Many Jews were killed in the 10th and 13th centuries. Repeated persecution constricted the population.”
If one person had the changed gene in the original population and 90 percent were killed, then if that one person survived, there was now a 10 percent chance of the changed gene being in the population, explained Frohlich.
Because the Ashkenazi migrated generation after generation, often moving in small groups of one to three families, cousins often married cousins further concentrating the gene pool.
As further proof of the concentration of the Ashkenazi gene pool, Frohlich pointed to studies of mitochondrial DNA, genetic material outside the cell’s nucleus that is inherited entirely from the mother. Analysis of that DNA indicates that nearly half of today’s Ashkenazi Jews are descended from three or four women who lived in the 12th to 13th century.
Carrier frequency of genetic diseases among Ashkenazi Jews
Gaucher disease type 1 1 in 15
Cystic fibrosis* 1 in 26
Tay-Sachs disease 1 in 30
Familial dysautonomia 1 in 30
Canavan disease 1 in 57
Glycogen storage disorder type 1a 1 in 71
Maple syrup urine diease 1 in 81
Fanconi anemia type C 1 in 89
Niemann-Pick disease type A 1 in 90
Bloom’s syndrome 1 in 100
Mucolipidosis type IV 1 in 122
Diseases recently added to list of JGDs (rates unavailable)
Dihydrolipoamide Dehydrogenase Deficiency
Usher syndrome, type IF
Usher syndrome, type 3
* CF is listed because it is primarily a Caucasian disease and far less frequent in Hispanic, Asian or Black populations; it is not more prevalent among Jews than other Caucasions (with the exclusion of Hispanics).
(From Genzyme Corp. publication: “When preparing for your future, there’s one important test schools don’t require.”)
The program was underwritten in part by Genzyme and was co-sponsored by Jewish Family and Child Service and Congregation Neveh Shalom with support from the Mittleman Jewish Community Center.