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Journey of the heart

Yale Medicine Magazine, 2004 - Spring


A collaborative bridge between Yale and Iran spanning the genetics of cardiovascular disease is a two-way street for science.

Every medical student must struggle to fight off distractions, but Arya Mani, M.D., had to contend with more than his share. Just before he began medical school in his native Iran in the late 1970s, the nation’s capital, Tehran, was rocked by a massive, student-led uprising that made headlines around the world. The Ayatollah Khomeini ousted Mohammad Reza Pahlavi, who had ruled the nation as the Shah of Iran for nearly 40 years. Khomeini rose to power on the wings of an impassioned revival of Islamic fundamentalism, and toward the end of 1979 he began a nail-biting 444-day standoff with the United States over the capture of hostages from the American embassy, an incident which continues to have profound political repercussions today.

Mani did his best to keep his mind on his studies against the increasingly tense political backdrop in Iran, but in the midst of the upheaval his university was closed, and he fled to the Johannes Gutenberg-University of Mainz in Germany to complete his training. In the last leg of a long journey, he arrived at Yale as a hospital resident in 1992, and he has made New Haven his home ever since.

Mani, now a cardiologist and assistant professor of medicine, had long been convinced that genes play a critical role in many forms of heart disease, but he hadn’t had an opportunity to do serious research in the area until he became a chief resident at Yale in 1993. He then found an enthusiastic and like-minded mentor in Richard P. Lifton, M.D., Ph.D., who has spearheaded an innovative series of genetic research projects around the world, including groundbreaking research on the genetic basis of hypertension. Mani returned to his homeland in 1998 as part of a globe-spanning collaboration between New Haven and Tehran. By bringing Yale’s state-of-the-art genomics initiatives to bear on the time-honored marriage customs of Iran, Mani’s work has put the Lifton lab within striking distance of an elusive gene or genes that act to cause a common congenital heart condition.

A novel approach

In his science, Lifton, the chair and Sterling Professor of Genetics, believes in going to extremes. Find genetic culprits at the pathological and geographical edge, he says, and you can apply your insights to the norm. Thus he has investigated families with the very highest and lowest blood pressure to find clues to treat the everyday hypertension that affects the rest of us.

Populations in which marriages between close relatives are common are particularly ripe for study, says Lifton, a Howard Hughes Medical Institute investigator, because intermarriage keeps the same genes circulating within the group, and genetic diseases occur more frequently. For example, first cousins are much more likely to carry identical defective recessive genes passed down from a grandparent. If these cousins marry, their children run a higher risk of genetic disease than children in more diverse populations. And the more such illnesses arise in a small, discrete population that practices intermarriage, the easier it is to spot recessive genes that may be responsible. On any given day in his third-floor lab in Yale’s new Anlyan Center, Lifton might be found poring over pedigrees of a Saudi Arabian village, a family in the Italian Alps or a close-knit clan in the South Pacific.

The approach has paid off: to date, members of Lifton’s lab have unearthed more than a dozen genes involved in the regulation of blood pressure and several other genes underlying conditions ranging from osteoporosis to vascular disease of the brain.

Mani knew that 25 percent of live births in Iran arise from parents who are closely related, so he thought that the country could provide a uniquely valuable setting to apply Lifton’s methods. He proposed to travel to Iran to conduct a systematic study of disease patterns in families with closely related marriage partners. Lifton advised Mani to first identify any diseases that are markedly more common in the general Iranian population than would be expected from his clinical experience at Yale, and to then look for a subset of those illnesses that occurs frequently among children of closely related parents.

To prepare for the journey, Mani searched the medical literature and discovered a research paper written by Shahrokh Naderi, M.D., an Iranian gynecologist, in 1979. Naderi had catalogued several diseases that were more common in Iranian children of closely related parents, including congenital heart disorders. Neither Mani nor Lifton was aware of any other reported association between intermarriage and cardiovascular disorders, so Mani contacted Naderi, who has also emigrated to the United States, for advice on following up this work in Iran. Mani also consulted with Iranian-born Tayebeh M. Rezaie, M.Sc., at the University of Connecticut Health Center in Farmington, who had been studying genetically based illnesses in Middle Eastern populations. Rezaie provided Mani with a list of candidate illnesses, including the congenital heart defect called patent ductus arteriosis, or PDA.

The ductus arteriosis is a normal fetal structure that joins the aorta to the pulmonary artery; since the fetus obtains oxygen from the placenta, the ductus arteriosis allows blood to bypass the lungs to supply the rest of the body. In PDA, the ductus arteriosis does not fully seal off after birth, and some oxygenated blood in the aorta returns to the lungs via the pulmonary artery instead of entering the general circulation. Many children with PDA experience nothing more than a mild heart murmur or tiredness and are not properly diagnosed for two years or more, but some infants with PDA must be rushed to emergency rooms, where surgeons repair the defect to prevent congestive heart failure.

Mani had seen patients with severe PDA symptoms in his rounds at Yale. But American physicians weren’t certain that the condition had a genetic cause because it appears so sporadically in the United States and, more often than not, does not seem to affect PDA patients’ relatives. Though this clinical picture is typical of recessive illnesses masked by a genetically diverse population, the consensus was that PDA is caused by unknown environmental triggers.

Politics often trumps science, and there were particularly worrisome political hurdles facing Mani in his quest to do research in Iran. Relations between the United States and Iran were severely strained by the 1979 hostage crisis, and have been mixed at best since then. Though there have been instances of cooperation, such as the recent U.S. aid to Iran in the aftermath of the earthquake in the city of Bam (See sidebar), President Clinton instituted a strict trade embargo against the country in 1995, and President Bush famously named the country in his 2002 State of the Union address as part of an “axis of evil.” Fortunately for Mani, Asghar Rastegar, M.D., associate chair for academic affairs in the Department of Internal Medicine, had been building medical partnerships between Yale and countries in need, including Iran, for a dozen years.

After the fall of the Soviet Union, Rastegar, an Iranian by birth, organized collaborative efforts with Russian educators, arranging faculty exchanges and trips to Russia for Yale researchers. With the announcement of Clinton’s trade embargo, Rastegar again sought to build scientific bridges. “I felt that Iran was being isolated politically,” he says, “but that such isolation should not extend academically.” For example, Rastegar has sponsored Iranian faculty members to spend sabbaticals at Yale and more recently he has helped to set up partnerships between Iranian physicians and two Yale researchers—Richard S. Schottenfeld, M.D. ’76, professor of psychiatry and master of Davenport College, and David A. Fiellin, M.D., associate professor of medicine—to study issues related to substance abuse and HIV in Iran.

Introductions in Tehran

Rastegar, who had known Mani from his student days during the Iranian revolution, acted as Mani’s go-between with Iranian physicians and scientists, so when Mani arrived in Iran he was able to quickly team up with internist and nephrologist Behrooz Broumand, M.D., at the Iran University of Medical Sciences in Tehran. Broumand was keenly interested in genetically based kidney diseases and was eager to learn techniques to ferret out the precise genetic defects underlying these conditions. However, he says that he and other physicians at Iran’s top hospitals are handicapped by the country’s economic struggles and political isolation. “We have a shortage of basic science knowledge in Iran because of the lack of facilities,” Broumand says.

According to Broumand, only about 5 percent of Iran’s gross national product goes toward health care (compared to 13 percent in the United States), and many hospitals do not have essential medical equipment such as CT or MRI machines, let alone facilities for basic research. The physicians who staff Iran’s hospitals carry very heavy patient loads but are usually paid only about one-tenth the salary of their colleagues in private practice.

“They really had to be devoted to work in the hospital,” Mani says. But the doctors he met at Tehran’s Shahid-Rajai Cardiovascular Medical Center at the Iran University of Medical Sciences were anxious to help him with his work, and appeared to be motivated more by a thirst for knowledge and a desire to train with new technology than by financial compensation. Such physicians formed the Iran-based part of Mani’s team, and once they provided him with patient records and recounted their clinical experience with Iran’s close-knit families, it didn’t take long for him to conclude that the University of Connecticut’s Rezaie was right—PDA in Iran had all the earmarks of a promising candidate illness for genetic analyses.

Lifton still recalls a phone call Mani made to Yale from Tehran. “He told me, ‘I have seen 20 cases of PDA here in two weeks but only half a dozen in my entire clinical experience at Yale.’” The patient records painted a startling picture: at Shahid-Rajai, PDA accounted for 15 percent of 13,000 congenital heart defects, while the best estimates say that PDA makes up only 2 to 7 percent of congenital heart disorders in the United States. And the disease showed up far more frequently in children whose parents were first cousins. When the researchers looked closely at 338 recent cases of babies born with PDA, nearly two-thirds had closely related parents. These data indicated that, at least in Iran, the disease is almost certainly caused by a defect in one or more recessive genes.

Mani collected blood samples from 21 PDA patients born to parents who were first cousins for genetic analysis back at Yale. Members of Lifton’s lab combed through the patients’ DNA and compared it to samples from unaffected children, performing analyses that mark stretches of the genome where genetic defects might lie. The lab’s preliminary analyses pointed toward three chromosomes as culprits, but more intensive number crunching eventually steered the group toward a section of chromosome 12; nine PDA patients had sequences in this region that were so similar that the odds of the matches occurring by chance are less than one in a million. In a November 2002 paper in the Proceedings of the National Academy of Sciences, Mani and Lifton proposed that a gene mutation somewhere in this section of chromosome 12, which they have christened PDA1, causes at least one-third of the PDA cases in Iran, and may be responsible for as many cases in other populations throughout the world. The study is further vindication of the cross-cultural methods that Lifton has so profitably used thus far.

“This is a very interesting approach, and one that will be even more powerful in the near future,” says molecular geneticist David M. Altshuler, M.D., Ph.D., of the Broad Institute in Cambridge, Mass. In particular, Altshuler says that the approach of Mani and Lifton benefits from a new genetic tool called a haplotype map—in essence, an exhaustive inventory of common DNA variations within human populations. Knowing those variations will give geneticists such as Lifton a head start in identifying dna patterns that might be linked to diseases.

Putting science over politics

Members of the Yale-Iran PDA collaboration still work together, but they are also heading in different directions. Lifton and his colleagues are whittling away at millions of base pairs on chromosome 12 to find the gene that carries the mutation that causes PDA. So far, they have ruled out three promising candidates, but there are 31 more to test. Lifton is also applying his methods to other diseases found in different isolated populations; for example, he is now on a hunt for the genes that confer a high risk of heart attack among the people of the Kosrae Islands in the South Pacific. Meanwhile, Mani and Lifton have begun work to uncover the genetic underpinnings of the high risk of early heart attack in Indian men, which seems to persist even if these men leave India to live elsewhere.

As for Broumand and his Iranian colleagues, they are building on the training Mani gave them by collecting tissue samples from adult heart disease patients born of closely related parents in the hopes of finding genes related to that ailment. In the end, the New Haven-Tehran collaboration was a win-win situation, Broumand says—America has cutting-edge genomic technology, and Iran has unique study populations. If the two countries continue to join forces, he says, science can more rapidly find the treatments that patients so desperately need.

But Broumand does voice one note of caution. Many of the Iranian patients who participated in the study did so, he says, because they hope that they or their descendants will eventually benefit from any treatments that emerge. Similarly, Iranian physicians donated their time to expand their knowledge and to better treat their patients. Broumand fears that those in poorer nations who help to make cross-cultural medical collaborations possible could be forgotten once the necessary data are gathered. “If the studies stop at the point when the paper is published, then the fruit is dead and nothing else will happen,” he says. For his own part, Lifton has been inviting researchers from Iran and other countries to spend time training in his lab and to take knowledge back to their home countries.

Broumand believes that everyone can benefit if Western researchers maintain strong contacts with colleagues in other regions, not simply by reading each others’ papers, but by engaging in regular discussions with each other. And this is particularly true where the United States and Iran are concerned. “I believe that if we go through cooperation in science,” he says, “we will create an environment to soften the politics and the violence, which is based on politics. That is the hope.” YM

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