Sudden infant death syndrome, or SIDS, is the leading cause of death in babies from one to 12 months, killing about 2,500 infants in the United States each year. Three decades of research have found factors that increase the risk of SIDS-such as letting babies sleep on their stomachs-but no definitive answers as to what causes the condition. Recently, studies have pointed to genetic and brain abnormalities that predispose an infant to SIDS. In an isolated Amish community in southern Pennsylvania, nine families lost 21 babies in two generations to the mysterious condition and scientists from all over the country investigated to try to find a genetic link to the deaths. What the researchers wanted to know: Why did so many seemingly healthy babies in one community die from unexplained causes?

What they did: The researchers, led by neurogeneticist Stephen Dietrich of the Translational Genomics Research Institute in Phoenix, analyzed DNA from four of the infants who died in southern Pennsylvania in the past several years, as well as DNA from their families. They looked for variations in specific chromosomes and in the genes that make up those chromosomes. When they found an abnormal gene in the affected infants, the researchers looked up the function of that gene and searched for any related symptoms the infants had before they died.

What they found: The four infants studied all had two abnormal copies of a gene called TSPYL, which regulates sexual differentiation, testicular development, and brain function. Their parents each had one abnormal TSPYL gene, so they were carriers of the condition, but, because the gene is recessive, the condition appears only in children who got two malformed copies of the gene from their parents. The two boys who died suddenly had underdeveloped testes or ambiguous genitalia, but the girls had no external sexual signs. Autopsy reports from the other 17 babies who died also showed that some of those babies had subtle, and often externally invisible, reproductive abnormalities. The researchers named this new variation of SIDS sudden infant death with dysgenesis of testes (SIDDT). Dysgenesis means disabled development and usually refers to an organ.

As part of the presentation Silicon Genetics will show how researchers at the Translational Genomics Research Institute in Phoenix used Silicon Genetics tool Varia to analyze Genotype data.