[Dynamic changes of γ-tubulin in mouse somatic cell nuclear transferred embryos]

The aim of the present study is to observe the dynamic changes of γ-tubulin in mouse somatic nuclear transferred (SCNT) embryos. The γ-tubulin was detected and analyzed in the enucleated oocyte and SCNT embryos by immunofluorescence and laser confocal microscopy. The results showed that γ-tubulin distributed in the cortex of the enucleated MII oocytes, and decreased in this area during the activation of oocytes. Meanwhile cytoplasmic asters appeared, but there was no spindle formed. Spindle formation could be observed in the enucleated oocytes which were injected with cumulus cells and activated by SrCl2. The spots-like γ-tubulin signals spread between chromosomes at the prophase, and the signals arrayed with spindle or aggregated at two poles of the spindle at the early metaphase. Furthermore, γ-tubulin signals were localized between the segregated sister chromatids at anaphase or telophase. Some reconstructed embryos exhibited advanced activation, showing abnormal spindles and aberrant distribution of γ-tubulin and chromosomes. Two spindles would be formed when the cumulus cell was injected into an intact oocyte, and the distribution of γ-tubulin was similar to that of the normal SCNT. Moreover, advanced activation also occurred in this case and formed either two small spindles or one big barrel-shaped spindle. These results suggest that γ-tubulin plays a pivotal role in spindle assembling in mouse SCNT embryos. The reconstructed oocytes were easily to be activated, and aberrant distribution of γ-tubulin is associated with formation of abnormal spindles and chromosome misalignment.