NOR expression increases on metaphase chromosomes of Down syndrome lymphocytes in concordance with mitogen concentration in culture medium.
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.


METHODS
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.


CONCLUSIONS
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.
Imamoglu
Nalan
N
Department of Medical Biology, Medical Faculty, Erciyes University, Kayseri, Turkey. demtas@erciyes.edu.tr
Demirtas
Halil
H
Donmez-Altuntas
Hamiyet
H
Hamurcu
Zuhal
Z
Ilten
Ali
A
D001399:Azure Stains; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D002871:Chromosome Banding; D002891:Chromosomes, Human, Pair 21 / Q000276:immunology / Q000378:metabolism; D004306:Dose-Response Relationship, Immunologic; D004314:Down Syndrome / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008677:Metaphase; D008938:Mitosis / Q000187:drug effects; D009697:Nucleolus Organizer Region / Q000276:immunology / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology; D016622:Silver Staining
D001399:Azure Stains; D010835:Phytohemagglutinins