Changes in -Tubulin Protein Distribution in Zebrafish (Danio rerio) Oocytes and the Early Cleavage-Stage Embryo
Figure 1
-Tubulin in oocytes is generally dispersed as punctate label that becomes increasingly localized to the animal pole during oocyte maturation, egg activation, and early cleavage; bars equal 100 μm. (a)–(e), (i) and (l) labeled for -tubulin with GTU-88; (f)–(h), (j) and (k) brightfield. (a) fully grown late stage III [72] immature oocyte, optical section with confocal microscope. (b) Stage IV oocyte (maturing) after 2 hr of 17-, 20-dihydroxyprogesterone (DHP), optical section with confocal microscope. (c) Stage V oocyte (i.e., mature egg) after 4 hr of DHP treatment, optical section with confocal microscope; forming blastodisc (bl). (d) Artificially activated egg imaged with an epifluorescence microscope; enlarged blastodisc (bl), streams (s) of label emanating from yolk cell. (e) Late stage III immature oocyte, optical section with confocal microscope using higher magnification, arrow heads point to discreet -tubulin foci. (f) Live stage IV oocyte after 2 hr of DHP treatment under bright field (DHP-treated oocytes usually remain opaque from 90–120 minutes then begin to clear). (g) Live stage V oocyte after 4 hr of DHP treatment under brightfield (note the naturally cleared ooplasm and distinct blastodisc forming, bl); (h) artificially activated egg under brightfield (same as (d)). (i) Previtellogenic stages I and II oocytes with large central nucleus (germinal vesicle, GV) show -tubulin in ooplasm. (j) Stage IV oocyte after 2 hr of DHP artificially cleared with 5% acetic acid, revealing the migrating GV. (k) Stage V oocyte (i.e., mature egg) after 4 hr of DHP artificially cleared with 5% acetic acid revealing the absence of the GV (i.e., undergone dissolution or GVD), and the blastodisc (bl) begins to form at the animal pole. (l) 8-cell embryo labeled for -tubulin, optical section with confocal microscope, revealing within the blastomeres (top) punctate centrosome structures (p), diffuse label in cytoplasm of blastomeres and wispy streams (s) of label extending from the yolk cell. “bl” in (c), (d), (g), (h), and (k) represents blastodisc region; all bars represent 100 μm.
