Journal: Animals : an Open Access Journal from MDPI
Article Title: The Germline-Restricted Chromosome of Male Zebra Finches in Meiotic Prophase I: A Proteinaceous Scaffold and Chromatin Modifications
doi: 10.3390/ani14223246
Figure Lengend Snippet: Dynamics of GRC structure at prophase I of zebra finch meiosis. Schematic representations of the structure and behavior of meiotic chromosomes are depicted. As the scheme is simplified, it does not capture the chromatin’s loop organization. Abbreviations: GRC, germline-restricted chromosome; SC, synaptonemal complex; AE, axial element; LE, lateral element of SC; TF, transverse filament of central space of SC; as, asynapsis area; ds, desynapsis area. In AEs/LEs of SCs: HORMAD1 (blue dots), cohesins (red dots), and SYCP3 (green dots). Typically, the GRC was found to create a distinct chromatin domain at the nuclear periphery during prophase I ( A – D ). ( A ) Leptotene. At this stage, core proteins (cohesins, HORMAD1 and SYCP3) ( A′ ) are loaded into the chromosome axis; therefore, the nascent proteinaceous scaffolds of the AEs of autosomes and GRC can be observed. ( B ) Zygotene. Chromosomes form a bouquet. Autosomal AEs arise. Two AEs of homologous chromosomes align with each other and begin to form SC segments. SC regions either lack HORMAD1 or contain rare stand-alone signals. Unlike autosomes, where protein assembly of AEs was completed, loading of core proteins continues into the AE of the GRC (protein loading delay) ( B′ ). Asynaptic regions and some regions of the GRC univalent contain a large amount of HORMAD1. ( C ) Pachytene. Autosomes are fully synapsed. Loading of core proteins into the GRC AE is almost complete. Sometimes, some regions of the GRC remain without loaded core proteins (fragmented GRC AEs or GRC with gaps) ( C′ ). Unlike autosomes, the GRC univalent has a lot of HORMAD1. ( D ) Diplotene. Chromosomes are desynapsed. The GRC and desynapsing axes of autosomes undergo protein disassembly. Desynapsing segments of autosomes and GRC are enriched with HORMAD1. ( E ) Explanatory diagram.
Article Snippet: Immunostaining was performed using an anti-SYCP3 (synaptonemal complex protein 3) rabbit polyclonal antibody (Abcam, Cambridge, UK, ab15093), rabbit polyclonal anti-HORMAD1 antibody (Proteintech, Rosemont, IL, USA, 13917-1-AP), rabbit polyclonal anti-RPA32/RPA2 antibody (RPA; Abcam, ab10359), mouse polyclonal anti-RAD51 antibody (Abcam, ab88572), rabbit polyclonal anti-histone H3 antibody (tri methyl K27) (H3K27me3; Abcam, ab195477), mouse monoclonal anti-RNA polymerase II antibody (RNAP II; Abcam, ab5408), mouse monoclonal anti-gammaH2A.X antibody (phospho S139) [9F3] (γH2AFX; Abcam, ab26350), mouse monoclonal anti-SUMO-1 antibody (Zymed, San Francisco, CA, USA #33-2400), mouse monoclonal anti-ubiquityl histone H2A antibody (ubiH2A; Millipore, Billerica, MA, USA, #05-678), rabbit polyclonal anti-H3K9me3 antibody (Abcam, ab8898), rat monoclonal anti-histone H3 antibody (phospho S28) (H3S28ph; Abcam, ab10543), and a human anti-centromere antibody (CREST [calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia]; #90C-CS1058, Fitzgerald Industries International, Concord, MA, USA).
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