PubMed · 7633395
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1995. Complex disease genetics gets more complex.. https://doi.org/10.1093/hmg%2F4.4.499
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Hippophae rhamnoides ssp. turkestanica, a subdioecious plant inhabiting the cold desert of the Indian Himalaya, has gained immense recognition for its nutritional and medicinal values. In recent years, the plant species has proven to be a suitable system to understand the evolution of dioecy. Despite its biological significance, the cytogenetics of this dioecious plant is unclear due to various conflicting accounts of its X-Y chromosome system, particularly the length of Y-chromosome. In this study, we resolved these ambiguities through comprehensive cytogenetic analyses across diverse western Himalayan populations. Using morphometric analysis and fluorescence in situ hybridization (FISH) with a gender-specific marker (HRMSSR), we confirmed homomorphic XX chromosomes in females and heteromorphic sex-chromosomes in males with a notably smaller Y-chromosome. The investigation also revealed a predominant somatic chromosome number of 2n = 24, although minor deviations (2n = 18, 20, 22) appeared at the seed level. These findings highlight an evolutionarily advanced sex-chromosome system. This first detailed cytogenetic investigation of Himalayan Seabuckthorn provides critical insights into the chromosomal architecture, laying a crucial foundation for future evolutionary, genomic, and conservation studies in the species.
Translocations affecting the chromosomal region 15q11-13 and various other partners are recurrent in diffuse large-cell lymphomas (DLCL). To identify the putative gene, here named BCL8, involved in these translocations we have cloned the breakpoint region from a DLCL patient with t(14;15)(q32;q11-13) and the corresponding germ-line region from chromosome 15. The genomic locus on chromosome 15 is clonally rearranged in about 4% of DLCL in agreement with the frequency of 15q11-13 translocations. A probe derived from the BCL8 locus on chromosome 15 detected a transcript in human testis and prostate, whereas no expression was found in spleen, thymus, and blood leukocytes. Analysis of the BCL8 cDNA clones isolated from human testis cDNA library showed that the BCL8 gene generates a major transcript of 2.6 kb and a less prominent 4.5-kb species due to differential polyadenylylation. By reverse transcription-PCR analysis of RNA extracted from frozen DLCL samples and lymphoma cell lines, BCL8 expression was detected in all patients carrying 15q11-13 abnormalities and in a fraction of randomly selected DLCL patients. These results suggest that the BCL8 gene is not normally expressed in lymphoid tissues, but its expression can be activated by chromosomal translocation or by other mechanisms in DLCL. Ectopic expression of BCL8 in a significant proportion of DLCL suggests an important role for this gene in the molecular pathogenesis of B cell lymphoma.
In the yeast Saccharomyces cerevisiae, meiotic recombination is initiated by transient DNA double-strand breaks (DSBs) that are repaired by interaction of the broken chromosome with its homologue. To identify a large number of DSB sites and gain insight into the control of DSB formation at both the local and the whole chromosomal levels, we have determined at high resolution the distribution of meiotic DSBs along the 340 kb of chromosome III. We have found 76 DSB regions, mostly located in intergenic promoter-containing intervals. The frequency of DSBs varies at least 50-fold from one region to another. The global distribution of DSB regions along chromosome III is nonrandom, defining large (39-105 kb) chromosomal domains, both hot and cold. The distribution of these localized DSBs indicates that they are likely to initiate most crossovers along chromosome III, but some discrepancies remain to be explained.