Accumulation of Bucky ball protein from the oocyte to early cleavage stages (EGK I/II) in chicken embryos. The upper panel represents differential interference (A1) and bright field images (B1,C1,D1) of the germinal vesicle (A1), the total fragment containing the germinal disc (B1) and the germinal disc regions (C1,D1). Frames indicate the region of the higher magnified fluorescent images in the lower panels. Freshly ovulated oocytes are characterized by a diffuse distribution of the Bucky ball protein from a condensed outline of the germinal vesicle (A2). At the outline, a higher Bucky ball concentration at one side (*) is apparent. After zygote formation, when the fertilized oocyte reached the isthmus part of the oviduct 2 to 2.5 h after fertilization, Bucky ball protein concentrates in granular patches in the center of the germinal disc where first cleavage furrows will be formed (B2). The first cleavage furrow is lined by tightly aggregated Bucky ball, and in perpendicular orientation, the Bucky ball granules demarcate the predicted next furrow (C2). During the next furrow divisions of stage I and II, further Bucky ball protein condenses in the cleavage furrows in the center of the forming embryo (D2). There is no clear demarcation of cellular outlines yet. This pattern of protein distribution is highly colocalizing to CVH (A3–C3), one of the first known germ plasm proteins as visualized in the overlay in A4–C4). Scales represent for (A) = 20 µm, (B1) = 200 µm; (C) = 50 µm; (D1) = 200 µm, the panels (B2–B4) = 20 µm, and (D2–D4) = 50 µm.
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