Using extremely fine-grained analytical tools, scientists compared genetic information in three sets of identical twins. One of each pair had Multiple Sclerosis, and the other didn’t — yet their genes proved essentially identical. The research cost $1.5 million, and the scientists took 18 months to sequence 2.8 billion DNA units in each twin, and determine whether they came from the mother or father. Most genomic comparisons look for differences in a just handful of suspect genes, and even whole-genome approaches don’t differentiate between parental contributions. The researchers also analyzed the twins' CD4 cells because of their central role in the development of MS. The absence of genetic differences doesn’t mean that genetics are irrelevant to multiple sclerosis. Identical twins, who are descended from the same egg, are six times more likely to develop MS than non-identical twins, who come from two different eggs. It’s still possible that some as-yet-unknown genetic factor, undetectable by even the most advanced tools, may explain the discordance in the study. However, geneticist Stephen Kingsmore thinks the culprit is probably an unknown environmental influence. This unknown factor could combine with other known genetic risks of developing multiple sclerosis. This study was a pioneering effort and the researchers are looking forward to studying more twins and other cells.
