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NOR expression increases on metaphase chromosomes of down syndrome lymphocytes in concordance with mitogen concentration in culture medium
Author(s) -
Imamoglu Nalan,
Demirtas Halil,
DonmezAltuntas Hamiyet,
Hamurcu Zuhal,
Ilten Ali
Publication year - 2005
Publication title -
cytometry part b: clinical cytometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 61
eISSN - 1552-4957
pISSN - 1552-4949
DOI - 10.1002/cyto.b.20050
Subject(s) - metaphase , trisomy , biology , microbiology and biotechnology , autosome , nucleolus , chromosome , nucleolus organizer region , lymphocyte , in utero , andrology , down syndrome , concordance , karyotype , immunology , genetics , fetus , medicine , gene , pregnancy , cytoplasm
Background Regulation of nucleolus organizer region (NOR) expression in trisomy 21 (Down syndrome [DS]) cells is not fully explained. This work compared NOR expression on metaphase chromosomes in gradiently stimulated lymphocytes from DS patients with those from healthy controls. Method Conventional peripheral blood culture (72 h) and chromosomal preparation procedures were used except that blood samples from each individual were cultivated in the same but gradiently increasing concentrations (0.37, 0.75, 1.48, and 2.21 ml) of phytohemagglutinin (PHA) per 100 ml of medium. One hundred consecutive metaphases per concentration were analyzed for scoring the means of the active NORs bearing chromosomes (AgNOR + chromosome) per individual and per concentration. Results In contrast to healthy controls (n = 24), AgNOR + chromosomal number in lymphocytes from 30 DS patients increased in concordance to the gradient of PHA concentration in the culture medium. Conclusion DS lymphocytes do not downregulate their NOR expression in the limit of control cells. This in vitro result may serve as a clue for the explanation of the DS phenotype due to the wasted energy in producing unnecessary rRNA transcripts and AgNOR proteins in utero during organogenesis. These results also indicate that precautions must be used in routine work of NOR evaluation/interpretation in DS lymphocytes. © 2005 Wiley‐Liss, Inc.