Morphological manifestation of unique DNA segments in human meiotic prophase I

• Published in: Cell and tissue biology Vol. 6; no. 5-6; pp. 407 - 411
• Main Authors: Bogdanov, Yu. F., Spangenberg, V. E., Dadashev, S. Ya, Vityazeva, I. I., Bogoliubov, S. V., Kolomiets, O. L.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 2012
• Subjects: Biomedical and Life Sciences; Cell Biology; Life Sciences; fluorescent hybridization in situ; lateral chromatin loops; meiosis; prophase I; synaptonemal complex
• ISSN: 1990-519X; 1990-5203
• DOI: 10.1134/S1990519X12050033

DNA attachment to the lateral elements of the synaptonemal complex (SC) in human spermatocytes was studied by the FISH technique using a commercial probe. The probe is a 160-kbp fragment from the 17p11.2 region containing the RAII gene and D17S620 marker (the probe for the deletion in human chromosome 17 causing Smith-Magenis syndrome). It was found that the DNA probe produced lateral chromatin protrusions in contact with SC stained with antibodies to SYCP3 protein. The morphological configuration of lateral chromatin protrusions depended on the substages of meiotic prophase I. At the zygotene, FISH probe forms two sticks with lengths about 6 μm perpendicular to the SC longitudinal axis, one stick at each SC side. At the early pachytene, each stick transforms into a globule, again one globule at each SC side. At the late pachytene, each globule transforms into two crumbly globules composed of short threads and clumps. At the diplotene, globules finally transform into thin DNA (chromatin) loops up to 10 μm from the base to the top with periodic thickenings (beads) along their length. As a result of this dynamic transformation, two chromatin loops with beads have been formed on each side of the SC of chromosome 17. These loops are most probably the loops of sister chromatides. Thereby, four loops of the full set of four chromatides were observed in the particular site of chromosome 17 bivalent, i.e., representing two pairs of chromatides. Thus, we are the first to have visualized true “open” lateral chromatin loops in human male meiotic prophase I rather than the usually postulated “loops” in reports on condensed road- or brushlike chromatin protrusions attached to the lateral elements of synaptonemal complexes. The open configuration of chromatin loops presumably depends on activation of transcription during the late pachytene-early diplotene. They resemble mini lateral loops of lampbrush chromosomes.