Changes inγ-Tubulin Protein Distribution in Zebrafish (Danio rerio) Oocytes and the Early Cleavage-Stage Embryo

We investigated the distribution of -tubulin in zebrafish oocytes and embryos using epifluorescent or confocal microscopy and -tubulin antibodies. During meiotic maturation of zebrafish oocytes, -tubulin begins redistribution from oocyte ooplasm and cortex to the future blastodisc region at the animal pole. In activated eggs, -tubulin was uniformly distributed in the enlarging blastodisc with label emanating from the yolk cell. In newly fertilized eggs, -tubulin was evenly distributed in blastomere cytoplasm, with the presence of pronuclei but initially lacking discernable centrosomes. During early cleavage, especially at the eight-cell stage, striking arc-shaped/rings (A/R) of putative centrosomes were detected. Decreasing -tubulin was seen in yolk cells while early cleavage blastomeres had strong cytoplasmic label along with obvious A/R arrays. In addition, we found the orientation of the A/R array and nuclear division alternated by about 90 degrees for each cell cycle along with alternation of punctate and A/R arrays.