Down's syndrome in humans is marked by three copies of chromosome 21. The mouse model has three copies of its chromosome 16, which is virtually identical to human chromosome 21. In the study presented in Washington (and also published in the January issue of Developmental Dynamics), the researchers found the same pattern of lengthening and shortening of skull and facial bones-leading to skulls flattened at the back and shorter nose--as that found in humans with Down's syndrome.

Down's syndrome is of interest to Alzheimer's researchers because people with the syndrome eventually develop plaques and tangles such as those seen in Alzheimer's. However, this pathology has not been found in the Ts65Dn mouse. "We used three stains and several plaque-specific antibodies, but identified no corresponding pathology in mice up to three years old (that's a VERY old mouse!)," writes Reeve in an email to the Alzheimer Forum.-Hakon Heimer.

Reference:Richtsmeier JT, Baxter LL, Reeves RH. Parallels of craniofacial maldevelopment in Down's syndrome and Ts65Dn mice. Developmental Dynamics 2000;217:137-145. Abstract

Reeves RH, Irving NG, Moran TH, Wohn A, Kitt C, Sisodia SS, Schmidt C, Bronson RT, Davisson MT. A mouse model for Down's syndrome exhibits learning and behavior deficits. Nat Genet 1995 Oct;11(2):177-84. Abstract

Baxter LL, Moran TH, Richtsmeier JT, Troncoso J, Reeves RH. Discovery and genetic localization of Down's syndrome cerebellar phenotypes using the Ts65Dn mouse. Human Molec Genet 2000 Jan;9:195-202. Abstract