Sheba Medical Center geneticists have found that a population of Indians in the U.S. state of Colorado has genetic Jewish roots going back to the expulsion of Jews from Spain.

The common marker was a unique genetic mutation on the BRCA1 gene. This mutation, commonly known as the "Ashkenazi mutation," is found in Jews of Ashkenazi origin and is associated with an increased risk of developing breast and ovarian cancer.

The trail began with research conducted by Prof. Jeffrey Weitzel, an oncogenetic (cancer genetics) expert at the City of Hope Hospital in California. Weitzel examined samples from 110 American families of Hispanic origin, and followed them through a computational genetics study, and in 2005 published an article pointing to their common ancestry: People who had immigrated to the United States from Mexico and South America.

Weitzel's discovery of the BRCA1 mutation in these Hispanics led him to suspect that there was a genetic connection between them and European Jews, and he sought to confirm the connection.

A study recently conducted at Sheba Medical Center, Tel Hashomer whose findings have been accepted for publication by the European Journal of Human Genetics has found the missing link: The mutation was also found in a group of Mexican Indians who had immigrated from Mexico to the United States over the past 200 years and settled in western Colorado.

When their samples were submitted to a computational genetic study, it emerged that they, along with Weitzel's original Hispanic subjects, all had a common ancestor: A Jew who immigrated from Europe to South America up to 600 years ago, the period in which Christopher Columbus discovered America and the Jews of Spain were expelled.

The Sheba research was performed by a team headed by Prof. Eitan Friedman, head of the medical center's Oncogenetics Unit, and student Yael Leitman, and sought to identify the original source of the BRCA1 mutation, found in about 1.5 percent of Jews of Ashkenazi origin and 0.5 percent of Iraqi Jews.

To do this, they collected samples from 115 families carrying this mutation from all over the world. These included Jewish families of Ashkenazi and Iraqi origin, and Jews originating from the Indian city of Cochin. They also, with Weitzel's help, collected samples from 16 mutation-carrying families among the Mexican Indians in Colorado, five British families from Manchester, and three families from Malaysia.

The study was based on previous Sheba research from 15 years ago, during which primitive analyses were done on the mutation found in Ashkenazi and Iraqi Jews; at that time, it was thought the mutation had first occurred 2,500 years earlier, during the dispersion after the destruction of the First Temple.

However, the new analysis, which checked 15 different genetic markers associated with the mutation, demonstrated that the Iraqi version of the mutated gene traces back only 450 years, which testifies to a migration of Ashkenazi Jews to Iraq - most probably merchants - that has not been well documented.

Meanwhile, the mutation found in the Colorado Indians was found to be identical to that of Ashkenazi Jews, and dates to a period more than 600 years ago. Researchers say this offers incontrovertible genetic proof that some of the Jews expelled from Spain who reached the New World intermarried with local Indians whose descendants later migrated to the United States.

The mutation identified in the British and Malaysian families, on the other hand, does not come from the same source as the Ashkenazi mutation, indicating that the mutation developed in other communities in parallel.

According to Friedman, the Mexican-Indians of Colorado, who are concentrated in the Mesa Verde area, have never demonstrated any adherence to Jewish customs, nor do they possess any oral traditions that might link them to Jews.