Chromosome size, morphology, and gene density determine bivalent positioning in metaphase i human spermatocytes

Objective To determine whether there is a preferential bivalent distribution pattern in metaphase I human spermatocytes and to analyze whether this positioning is influenced by chiasmata count, chromosome size, gene density, acrocentric morphology, and heterochromatic blocks. Design Proximity frequencies of bivalents were evaluated with the analysis of meiotic preparations combining sequentially standard techniques and multiplex fluorescence in situ hybridization. Setting University. Patient(s) Twenty-five men consulting for fertility problems. Intervention(s) Unilateral testicular biopsies. Main Outcome Measure(s) Proximity analyses were performed for each bivalent considering as nearby bivalents those that were part of the first ring around the bivalent studied. Data were analyzed using Poisson regression models, multidimensional scaling, and cluster analysis. Result(s) Some bivalents have a preferential relative position. Significant associations among bivalents related to chromosome size, high gene density, and acrocentric morphology were observed. Chiasmata count and heterochromatic blocks were nonconditioning parameters of the bivalent organization. Conclusion(s) This study demonstrates that distribution in metaphase I is nonrandom and influenced by chromosome size, gene density, and acrocentric chromosome morphology. Results support that some features defining chromosome territories are maintained during meiosis. © 2014 American Society for Reproductive Medicine, Published by Elsevier Inc.