1/3. A case of elevated spontaneous micronucleus frequency derived from chromosome 2.This work tested the hypothesis that the content of spontaneous micronuclei in lymphocytes in an apparently healthy normal human subject, who exhibited an unusually high micronucleus frequency, was non-random. Several dna probes were used in fluorescent in-situ hybridization (FISH), beginning with a probe generated from the subject's micronuclei. Micronuclei obtained from peripheral blood lymphocytes by microdissection were subjected to random amplification of polymorphic DNA (RAPD-PCR), and a unique PCR product was then used to isolate a cosmid clone from a human genomic library. This clone hybridized to chromosome 2. Subsequently, commercial probes were included in FISH analyses of micronuclei from the subject and age- and sex-matched controls. No significant differences were found between subject and controls in the percentages of micronuclei hybridizing with a centromere probe for the x chromosome or a painting probe for chromosome 3. However, the subject had a very highly significant increase (p<0.0001) in chromosome 2 in micronuclei over a level that might be expected to be present by chance. Characterization of micronuclei may be a promising tool in studies of mechanisms of inherited or induced chromosome instability. The strength of the strategy employed in this study is that, by characterizing the chromosomes present in micronuclei, this work has advanced from an observation of chromosomal instability to a foundation for study of the mechanism underlying the observation.- - - - - - - - - - ranking = 1keywords = hybridization (Clic here for more details about this article) |
2/3. Chromosome instability in ICF syndrome: formation of micronuclei from multibranched chromosomes 1 demonstrated by fluorescence in situ hybridization.We report on a new patient with immunodeficiency, centromeric heterochromatin instability, and facial anomalies (the ICF syndrome). Studies with traditional cytogenetic methods demonstrate that aberrations in this syndrome primarily involve the centromeric regions of chromosomes 1 and 16. We applied fluorescence in situ hybridization (FISH) using "painting" probes for chromosomes 1 and 16 to document the progression of centromeric instability from simple decondensation aberrations to the subsequent formation of complex multibranched chromosomes 1, and finally to the interphase aberrations of nuclear projections and micronuclei involving both chromosomes 1 and 16. The loss of the large multibranched chromosome 1 configurations from the cells as micronuclei suggests that the centromeric aberrations subsequently interfere with normal chromosome movement at anaphase in ICF syndrome. Circular areas of counterstained chromatin were observed by FISH in the micronuclei corresponding to the intertwined segments of centromeric heterochromatin seen involving multibranched chromosomes 1 in the patient's G-banded chromosome study. The current hypothesis of recessive inheritance for this disorder suggests that the chromosomal aberrations are not a causative event in this syndrome; however, the chromosome aberrations are clearly an important basic diagnostic criterion.- - - - - - - - - - ranking = 5keywords = hybridization (Clic here for more details about this article) |
3/3. Centromeric instability of chromosome 1 resulting in multibranched chromosomes, telomeric fusions, and "jumping translocations" of 1q in a human immunodeficiency virus-related non-Hodgkin's lymphoma.BACKGROUND. acquired immunodeficiency syndrome-related non-Hodgkin's lymphomas are associated with the B-cell chromosomal translocation t(8;14)(q24; q32). The most common secondary chromosome aberrations in these patients involve 1q and are believed to be associated with tumor progression. A mechanism for the origin of these 1q aberrations has not been demonstrated. To their knowledge, the authors report the first human immunodeficiency virus (hiv)-positive patient to have centromeric decondensation and multibranched chromosome aberrations of chromosomes 1 and 16 resulting in telomeric associations and "jumping translocations" of 1q. methods. Tumor cells from peritoneal fluid of an hiv-positive patient were cultured for 24, 48, and 72 hours and analyzed by both conventional G-banding and fluorescence in situ hybridization. RESULTS. G-band analysis showed a stemline with t(8;14)(q24;q32), but also showed the progression from centromeric decondensation to multibranched chromosome configurations of chromosomes 1 and 16. The interchange and duplications of chromosome arms resulted in the gain of extra copies of 1q material on a number of different chromosomes, but also the loss of 16q in at least one sideline and the formation of micronuclei. fluorescence in situ hybridization analysis demonstrated that micronuclei predominantly involved chromosome 1 and, to a lesser extent, chromosome 16. CONCLUSIONS. The cytogenetic findings in this unique case suggest that immunodeficiency may be a factor involved in centromeric instability, multibranching, and the progression to the subsequent formation of telomeric fusions and multiple unbalanced translocations of 1q (jumping translocations). The striking similarity of the centromeric instability in this patient to those with ICF syndrome (variable immunodeficiency, centromeric heterochromatin instability, and facial anomalies) suggests hypomethylation as the etiologic mechanism for the chromosome instability.- - - - - - - - - - ranking = 2keywords = hybridization (Clic here for more details about this article) |