Figure 7

Autophagosome markers are accumulated in the micronuclei. Immunofluorescence staining of paraffin sections from gonads of diploid female at 35 Gosner stage: LC3 autophagosome marker (red), DNA counterstained with DAPI (blue) (a,b). (a) Dotted and linear aggregates of LC3 (arrowhead) on the surface of highly condensed micronuclear chromatin may represent the early stage of autophagosome formation. (b) Large LC3 aggregate (arrowhead) on the micronucleus and between the chromatin clumps. Note that DNA is less condensed and fragmented with an empty interior which may represent the later stage of autophagic process connected with DNA degradation. Second micronucleus (arrow) is highly heterochromatinized and apparently not autophagic. (c) Immunofluorescence of frozen tissue sections of an ovary from diploid female at 29 Gosner stage showing wheat germ agglutinin (WGA, red) staining of cellular membranes, DNA counterstained with DAPI (blue). Note the cap-shaped WGA aggregates (arrowheads) at the surface of micronuclei which we interpret as staining of fusion site of autophagosome membranes. The irregular shape of the left micronucleus could reflect chromatin degradation. Additional strong intra-cytoplasmic agglomerates or dots, visible in upper and lower cells, could be trans-Golgi cisternae and post-Golgi membranes, e.g. lysosomal membranes. Confocal images represent projection of 9 z-sections (a) or single z-section (b,c) (0.46 µm). N – nucleus. Scale bars 5 µm.