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Cell Biology International (1996) 20, 673–680 (Printed in Great Britain)
A FINE STRUCTURAL STUDY OF THE HIPPOCAMPUS AND DORSAL ROOT GANGLION IN MOUSE TRISOMY 16, A MODEL OF DOWN'S SYNDROME
NANCY J. LANEa, ANDREA BALBObf1 and STANLEY I. RAPOPORTb
bLaboratory of Neurosciences, National Institute of Aging, N.I.H., Bldg 10/6C-103, Bethesda, MD 20892, U.S.A.
aDepartment of Zoology, Downing Street, Cambridge, CB2 3EJ, U.K.


Abstract

Mouse trisomy 16 (Ts16) appears to provide an animal model of Down's syndrome in that a portion of mouse chromosome 16 is syntenic with part of human chromosome 21. Trisomy 21 in human beings leads to the mental retardation of Down's syndrome and in middle age, to some presenile anatomic and clinical features of Alzheimer's disease. Neural tissue from aging Ts16 mice is unavailable, however, as Ts16 mouse embryos die latein utero. We studied these embryos looking at the ultrastructure of neurons from the hippocampus and dorsal root ganglion in normal control mice embryos (diploid) and in Ts16 late embryonic litter mates after day 15 of gestation. The organelles in the Ts16 neurons looked similar to those in control neurons, fixed and processed under similar conditions. No obvious neuropathological structures were observed. These results, when compared to reports on electrophysiological abnormalities of cultured fetal Ts16 neurons and on abnormalities in neurotransmitter markers in the Ts16 fetal brain, lead us to suggest that the mental retardation of Down's syndrome is likely to result from functional and chemical defects not directly related to abnormal neuronal ultrastructure. When related to fine structural studies of transplanted embryonic Ts16 hippocampus which have been maintained for long periods of time, these results indicate that the trisomic mouse brain would not be useful as a structural model for Down's syndrome and hence presenile Alzheimer's disease, as it is not associated with any detectable morphological abnormality.


Key words: hippocampus, model for Down's syndrome, Alzheimer's disease, mouse trisomy 16, neuropathology, dorsal root ganglion.

f1To whom correspondence should be addressed.


doi:10.1006/cbir.1996.0089


ISSN Print: 1065-6995
ISSN Electronic: 1095-8355
Published by Portland Press Limited on behalf of the International Federation for Cell Biology (IFCB)