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During meiosis, homologous chromosomes pair to facilitate the exchange of DNA at crossover sites along the chromosomes. The frequency and distribution of crossover formation are tightly regulated to ensure the proper progression of meiosis. Using immunofluorescence techniques, our group and others have studied the meiotic proteins in spermatocytes of infertile men, showing that this population displays a reduced frequency of crossovers compared to fertile men. An insufficient number of crossovers is thought to promote chromosome missegregation, in which case the faulty cell may face meiotic arrest or contribute to the production of aneuploid sperm. Increasing evidence in model organisms has suggested that the distribution of crossovers may also be important for proper chromosome segregation. In normal males, crossovers are shown to be rare near centromeres and telomeres, while frequent in subtelomeric regions. Our study aims to characterize the crossover distribution in infertile men with non-obstructive (NOA) and obstructive azoospermia (OA) along chromosomes 13, 18 and 21. Eight of the 16 NOA men and five of the 21 OA men in our study displayed reduced crossover frequency compared to control fertile men. Seven NOA men and nine OA men showed altered crossover distributions on at least one of the chromosome arms studied compared to controls. We found that although both NOA and OA men displayed altered crossover distributions, NOA men may be at a higher risk of suffering both altered crossover frequencies and distributions compared to OA men. Our data also suggests that infertile men display an increase in crossover formation in regions where they are normally inhibited, specifically near centromeres and telomeres. Finally, we demonstrated a decrease in crossovers near subtelomeres, as well as increased average crossover distance to telomeres in infertile men. As telomere-guided mechanisms are speculated to play a role in crossover formation in subtelomeres, future studies linking crossover distribution with telomere integrity and sperm aneuploidy may provide new insight into the mechanisms underlying male infertility.
Pubmed ID: 27273078 RIS Download
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The Canadian Institutes of Health Research (CIHR) is the Government of Canada''s agency responsible for funding health research in Canada. CIHR was created in 2000 under the authority of the CIHR Act and reports to Parliament through the Minister of Health. CIHR''s budget for 2008-09 is $928.6 million, of which $132 million is allocated to administering the Networks of Centres of Excellence and Canada Research Chair programs. CIHR was created to transform health research in Canada by: * funding more research on targeted priority areas; * building research capacity in under-developed areas such as population health and health services research; * training the next generation of health researchers; and * focusing on knowledge translation, so that the results of research are transformed into policies, practices, procedures, products and services. CIHR consists of 13 virtual institutes, a structure that is unique in the world. These innovative institutes bring together all partners in the research process - the people who fund research, those who carry it out and those who use its results - to share ideas and focus on what Canadians need: good health and the means to prevent disease and fight it when it happens. Each institute supports a broad spectrum of research in its topic areas and, in consultation with its stakeholders, sets priorities for research in those areas.
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