Essay on the nucleoli survey by the alpha- and beta-satellite DNA probes of the acrocentric chromosomes in mitogen-stimulated human lymphocytes

The two constitutive heterochromatin (alpha- and beta-satellite DNA) probes of human acrocentric chromosomes were essayed separately to label the nucl eoli in the phytohemagglutinin (PHA)-stimulated human lymphocytes. Fluoresc ent in situ hybridisation (FISH) results have shown that: a) whole (100 %) signal-nucleoli overlapping was obtained with both heterochromatin probes i n maximally activated nuclei (MANs); b) partial overlapping was observed in non activated or slightly activated nuclei; c) random signal-nucleolus ove rlapping (background level) was found to be similar to 6 % by the NOR-irrel evant euchromatic probe (D5S23); d) Yq-nucleolus association in the MANs wa s found to be similar to 97 % without the subtraction, of the background le vel. We concluded that: a) acrocentric alpha- or beta-satellite DNA probes may be used as nucleolar markers only in the MANs and not in slightly activ ated or non-activated nuclei; b) the distances between rDNA loci and alpha- /beta-satellite DNA on human acrocentrics are short enough to permit their observation on the same nucleolus. (C) 2000 Editions scientifiques et medic ales Elsevier SAS.