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Thursday, July 22, 2004
SUDDEN INFANT DEATH SYNDROME
Science to aid of justice as 'cot death' gene is found
By ROWAN HOOPER
There can be few things more likely to provoke horrific fascination -- and guarantee massive media coverage -- than a mother who murders her babies.
We find the act repugnant because nothing is more contrary to natural selection.
But there can surely be nothing worse than suffering the tragedy of your babies dying and then being falsely accused of their murders. This is exactly what happened to a woman in Britain last year, but thankfully the story has a happy ending, or at least a just one.
A pharmacist, Trupti Patel, was accused of murdering her three babies, Amar, Jamie and Mia. She was arrested and prosecuted largely on the evidence of Professor Sir Roy Meadow, a consultant pediatrician.
"Sudden, unexpected death does not run in families," Meadow told the court. But he was wrong, as the Patel jury found -- and as scientists have demonstrated this week.
Meadow (now retired and discredited) is the man responsible for the widespread belief that one infant death is a tragedy, two is suspicious and three is murder. As an "expert witness," Meadows came close to reversing the "innocent until proven guilty" creed. Despite this -- or more likely because of it -- he was popular with prosecution lawyers, acting as an expert witness in more than 5,000 cases.
In Britain, where the phenomenon is informally called cot death, around 300 babies a year die from sudden infant death syndrome (SIDS). In around 10 percent of those cases, there may be suspicious circumstances: neglect or murder. But as medical knowledge deepens, we are recognizing explanations other than criminal.
Trupti Patel was saved by her grandmother, who flew from India to testify. Five of her 12 children had died soon after birth, Surajben Patel told the court. In her village in Gujarat there was no hospital, nor even a doctor, but a genetics expert told the jury that there was a strong likelihood of a genetic link to the deaths of babies in the Patel family.
The jury found the hypothesis reasonable and acquitted Patel. She had, by then, spent a year in jail awaiting trial, without access to her 8-year-old daughter.
But hard evidence of a genetic link had to wait until this week, when scientists announced that they have discovered the first gene to be linked with SIDS. The work has been done by a team led by Dietrich Stephan, director of neurogenomics at the Translational Genomics Research Institute in Phoenix, Ariz.
In the United States, some 3,000 infants a year die of the syndrome. The newly described form of SIDS is named sudden infant death with dysgenesis of testes (SIDDT). The announcement was made Monday in the journal Proceedings of the National Academy of Sciences.
"This is one of the first genetic sub-classifications of SIDS," Stephan said. "And it's going to be helpful in offering parents answers for sudden infant deaths, recognizing predisposition early, and hopefully saving a number of these babies."
The researchers were helped in their search for the gene by people with little scientific knowledge, indeed with little desire for any of the trappings of modern life: the Amish. Some 300 years ago, around 200 Amish founders from Europe settled in the United States. A closed population with a fixed gene pool and genealogies dating back 14 generations, the members of this Christian sect are a good natural experiment for geneticists.
The researchers first identified Amish with SIDDT in a small "Old Order" community in central Pennsylvania. Over two generations, nine families from this community had lost 21 babies to sudden death syndrome.
They found that male SIDDT victims tended to have underdeveloped testes, but females appeared to be normal,with normal female hormones in blood and urine. Despite these differences, male and female infants died suddenly of SIDDT at the same age.
As in the Patel family, the familial clustering in the Amish community suggested a genetic basis for the syndrome. The researchers analyzed the DNA from four of the 21 infants, along with their parents, siblings, and extended family members, and found the location of the disorder on a region of chromosome 6.
The scientists then made an educated guess. They looked at which genes were known to reside in the region of chromosome 6 and looked at what happens clinically in babies with the syndrome. This led them to a gene called TSPYL. They then sequenced the DNA of TSPYL (that is, they read the DNA letters that spell the gene) and found that in all four patients there was a mutation. The affected children had two abnormal copies of the TSPYL gene.
Geneticists refer to conditions such as SIDDT as recessive; that is, two mutant copies of the gene are required for the symptoms to develop. All parents were carriers, that is, they had one mutant copy. Although several other genes are known to be associated with SIDS, this is the first gene to have been identified which causes a primary form of SIDS. Infants with two mutant copies of TSPYL suffer organ dysfunction and die in their first year from sudden cardiac and respiratory failure.
Ironically for work carried out with the cooperation of the Amish, a group that shuns modern technology, the discovery is a good demonstration of the speed of modern medical research. The mapping and identification of the gene was performed in less than two months from start to finish. Old Order Amish do not use electricity or cars, but many with diabetes use blood-glucose monitors. Genetics is helping them and will no doubt help many of the women currently imprisoned for murdering their babies.
A book of Natural Selections columns translated into Japanese, "Nou to sekkusu no seibutsugaku," is published by Shinchosha. Rowan Hooper is a biologist at Trinity College, Dublin. He welcomes readers' questions and comments at email@example.com