RESUMO
BACKGROUND: Heterochromatic variants of pericentromere of chromosome 9 are reported and discussed since decades concerning their detailed structure and clinical meaning. However, detailed studies are scarce. Thus, here we provide the largest ever done molecular cytogenetic research based on >300 chromosome 9 heteromorphism carriers. RESULTS: In this study, 334 carriers of heterochromatic variants of chromosome 9 were included, being 192 patients from Western Europe and the remainder from Easter-European origin. A 3-color-fluorescence in situ hybridization (FISH) probe-set directed against for 9p12 to 9q13~21.1 (9het-mix) and 8 different locus-specific probes were applied for their characterization. The 9het-mix enables the characterization of 21 of the yet known 24 chromosome 9 heteromorphic patterns. In this study, 17 different variants were detected including five yet unreported; the most frequent were pericentric inversions (49.4%) followed by 9qh-variants (23.9%), variants of 9ph (11.4%), cenh (8.2%), and dicentric- (3.8%) and duplication-variants (3.3%). For reasons of simplicity, a new short nomenclature for the yet reported 24 heteromorphic patterns of chromosome 9 is suggested. Six breakpoints involved in four of the 24 variants could be narrowed down using locus-specific probes. CONCLUSIONS: Based on this largest study ever done in carriers of chromosome 9 heteromorphisms, three of the 24 detailed variants were more frequently observed in Western than in Eastern Europe. Besides, there is no clear evidence that infertility is linked to any of the 24 chromosome 9 heteromorphic variants.
RESUMO
BACKGROUND: Small supernumerary marker chromosomes (sSMC) are detected in 0.043% of general population and can be characterized for their chromosomal origin, genetic content and shape by molecular cytogenetic approaches. Even though recently progress was achieved towards genotype-phenotype-correlations of sSMC, nothing is known on the influence that an additional derivative extra chromosome has on the nuclear architecture. RESULTS: Here we present the first three-dimensional interphase fluorescence in situ hybridization (FISH) studies for the nuclear architecture of sSMC. It could be shown that sSMC derived from chromosomes 15, 16 or 18 preferentially colocalized with one of their corresponding sister chromosomes. This was true in B- and T-lymphocytes as well as in skin fibroblasts. Additionally, a case with a complex sSMC with a karyotype 47,XY,+der(18)t(8;18)(8p23.2 ~ 23.1;18q11.1) was studied. Here the sSMC co-localized with one homologous chromosome 8 instead of 18. CONCLUSION: Overall, there is a kind of "attraction" between an sSMC and one of its homologous sister chromosomes. This seems to be transmitted by the euchromatic part of the sSMC rather than its heterochromatic one.
RESUMO
BACKGROUND: Nuclear architecture studies in human sperm are sparse. By now performed ones were practically all done on flattened nuclei. Thus, studies close at the in vivo state of sperm, i.e. on three-dimensionally conserved interphase cells, are lacking by now. Only the position of 14 chromosomes in human sperm was studied. RESULTS: Here for the first time a combination of multicolor banding (MCB) and three-dimensional analysis of interphase cells was used to characterize the position and orientation of all human chromosomes in sperm cells of a healthy donor. The interphase nuclei of human sperm are organized in a non-random way, driven by the gene density and chromosome size. CONCLUSION: Here we present the first comprehensive results on the nuclear architecture of normal human sperm. Future studies in this tissue type, e.g. also in male patients with unexplained fertility problems, may characterize yet unknown mechanisms of infertility.
