Evidence Rules Out Down Syndrome Suspect

The genes commonly believed to cause Down syndrome may not be the culprit after all, according to a new study in mice in the 22 October 2004 issue of the journal Science.

Circumstantial evidence had supported the hypothesis that the syndrome results from extra genes within a critical region of chromosome 21, which is present in triplicate in people with this condition. But researchers show that this central concept—which underlies most research into the genetic mechanisms of the syndrome—can be refuted by measuring Down-like characteristics in mice that are genetically engineered to possess the suspect genes.

The researchers bred mice with one, two, or three copies of the critical region and compared them to other mice expressing both visible and genetic Down-like characteristics. Based primarily on facial, head, and growth measurements, the mice with three copies of genes in the critical chromosomal region did not appear significantly distinct from those with one or two copies, in contrast to unambiguous features of the established Down syndrome mouse model.

The study provides evidence that Down syndrome may arise from a complex interplay of genetic and developmental factors. A related "Perspective" in the same issue of Science further discusses this research.

22 October 2004