NEW YORK (GenomeWeb News) – Jewish populations around the world remain genetically related to one another despite their diverse geographic locations and population histories, a new genetic study reveals.
Researchers from the US and Israel genotyped hundreds of Jewish individuals from seven Jewish groups, comparing these genetic patterns to those found in non-Jewish controls. The research, scheduled to appear online today in the American Journal of Human Genetics, suggests all Jewish populations tested fall into a large genetic cluster that contains population-specific sub-groups with different levels of Middle Eastern ancestry and European and North African admixture.
"It's really cool that Jews have maintained this degree of genetic coherence over time," senior author Harry Ostrer, a human genetics researcher with the New York University School of Medicine, told GenomeWeb Daily News.
Within this larger Jewish group, the team found two main sub-groups: one representing Jewish populations in Europe and Syria and another containing Jewish populations from Iran and Iraq.
Researchers have long been interested in the genetic patterns associated with the so-called Jewish Diaspora, which refers to the Jewish migrations that have taken place over thousands of years, apparently starting with migrations from the Middle East.
But while some genome-wide studies have been done in Ashkenazi Jews, Ostrer said, studies of most Jewish populations have relied on relatively limited Y-chromosome or mitochondrial DNA sequence data.
For the current study, researchers used the Affymetrix 6.0 microarray platform to genotype 305 Jewish participants from New York City, Seattle, Italy, Greece, and Israel. These individuals came from one of seven major Jewish groups, representing Ashkenazi Jews, Sephardic Jews from Italy, Greece, and Turkey, and Mizrahi Jews from Iran, Iraq, and Syria.
After quality control steps, the team was left with data for 237 Jewish individuals, which they compared with hundreds of non-Jewish samples from the Human Genome Diversity Project (genotyped using the Illumina HumanHap650K Beadchips) and Population Reference Sample (genotyped using the Affymetrix 500 K chip).
Overall, the researchers found that the Jewish populations tested shared genetic patterns not found in non-Jewish populations — a pattern that seems to partly reflect Jewish cultural and religious patterns.
"Our study demonstrated that the studied Jewish populations represent a series of geographical isolates or clusters with genetic threads that weave them together," co-lead author Gil Atzmon, a medicine and genetics researcher at the Albert Einstein College of Medicine, said in a statement.
"Thus, over the past 3,000 years, both the flow of genes and the flow of religious and cultural ideas have contributed to Jewishness," Atzmon added.
In particular, Ostrer said, the researchers were surprised to see such a high level of genetic relatedness in European Jewry, with Ashkenazi, Sephardic, Italian, and Syrian Jews clustering more closely to one another than to Jewish populations in Iran and Iraq.
The results argue against the notion that Ashkenazi Jews are descendants of Eastern European groups such as the Slavs or Khazars, Ostrer noted. "There's just no evidence for that."
Instead, Ashkenazi Jews seem to be more genetically similar to non-Jewish populations in Northern Italy, France, and Sardinia. Meanwhile, Jewish populations in Iran and Iraq tended to cluster closer to non-Jewish Palestinian, Druze, and Bedouin populations than to Europeans.
Based on data available so far, the team estimates that Middle Eastern Jewish and European Jewish populations diverged from one another more than 2,500 years ago. Even so, Ostrer cautioned, teasing apart precise population origins and movements is complicated by multiple migratory events between the Middle East and Europe.
Down the road, the team intends to genotype additional populations to get an even more refined view of Jewish population history, relationships between Jewish and non-Jewish populations, and the genetic basis of disease and other traits in Jewish populations, Ostrer said, noting that they also plan to use whole-genome sequencing for an upcoming breast cancer study in Jewish populations.
Those involved say the results may already help provide a better understanding of diseases affecting both Jewish and non-Jewish populations.
"By providing a comprehensive genetic fingerprint of various Jewish subpopulations, it can help us understand genetic links to heart disease, cancer, diabetes and other common diseases," co-author Edward Burns, executive dean of Albert Einstein College of Medicine, said in a statement.