ABSTRACT
Progressive chromosome 21 loss in individuals with trisomy 21 or Down syndrome (DS) is supposedly related to their premature senescence. In addition, the telomere hypothesis of cellular aging involving telomere shortening in normal and accelerated aging in vivo and in vitro is well documented. This study investigated the integrity of two chromosome 21 regions (the 21q telomere and the 21q22.13-q22.2 region) and their relationship with aging by means of fluorescence in situ hybridization (FISH) in lymphocytes and gingival fibroblasts cells. The use of tissues from different germ layers allows detection of mosaicism. Chromosome variations in tissue from the neuroectoderm layer could explain the variable phenotype of DS. This approach is original in the literature. Lymphocyte and gingival fibroblast nuclei from 18 affected individuals aged 5-54 years were analyzed. Although not significant (P = 0.06), analysis from 11 tissue-matched individuals as well as the comparison between lymphocytes and fibroblasts from different subjects (P = 0.05) suggested that lymphocyte cells are more likely to miss 21q telomere signals. Hence, gingival fibroblasts are probably capable of more efficient cell repair, and the occurrence of mosaicism is more related to cell proliferation than to germ layer origin. Investigation of the 21q22.13-q22.2 region from six tissue-matched individuals and from different DS patients revealed no significant differences between the tissues.
