The synaptonemal complex (SC) is a meiosis-specific nuclear multiprotein complex that is essential for proper synapsis, recombination and segregation of homologous chromosomes. We combined structured illumination microscopy (SIM) with different expansion microscopy (ExM) protocols including U-ExM, proExM, and magnified analysis of the proteome (MAP) to investigate the molecular organization of the SC. Comparison with structural data obtained by single-molecule localization microscopy of unexpanded SCs allowed us to investigate ultrastructure preservation of expanded SCs. For image analysis, we developed an automatic image processing software that enabled unbiased comparison of structural properties pre- and post-expansion. Here, MAP-SIM provided the best results and enabled reliable three-color super-resolution microscopy of the SCs of a whole set of chromosomes in a spermatocyte with 20–30 nm spatial resolution. Our data demonstrate that post-expansion labeling by MAP-SIM improves immunolabeling efficiency and allowed us thus to unravel previously hidden details of the molecular organization of SCs.

突触复合物（SC）是减数分裂特异性核多蛋白复合物，对于同源染色体的正确突触，重组和分离必不可少。我们将结构照明显微镜（SIM）与不同的扩展显微镜（ExM）协议（包括U-ExM，proExM和蛋白质组学（MAP）的放大分析）相结合，以研究SC的分子组织。通过与未扩展的SC的单分子定位显微镜获得的结构数据进行比较，我们可以研究扩展的SC的超微结构保存。对于图像分析，我们开发了一种自动图像处理软件，该软件能够无偏比较膨胀前和膨胀后的结构特性。这里，MAP-SIM可提供最佳结果，并能以20–30 nm的空间分辨率对精母细胞中整个染色体的SC进行可靠的三色超分辨率显微镜检查。我们的数据表明，通过MAP-SIM进行扩增后标记可提高免疫标记效率，从而使我们能够揭示SC分子组织先前隐藏的细节。