Abstract
The signal transducer and activator of transcription 3 of the pStat3 inhibitors, Stattic, and (Stat3) is activated upon phosphorylation at Y705 (pStat3) and serves the dual function of signal transduction and transcription activation. Our previous study suggested that pStat3 is functional during oocyte maturation when transcription is silenced. Therefore, we speculated that pStat3 serves other functions. Immunocytochemical analysis revealed that pStat3 emerges at microtubule asters and spindle and is subsequently localized at the spindle poles along with pericentrin during mouse oocyte maturation. Both Stat3 and pStat3 proteins were detected in conditionally knocked out Stat3−/− mouse oocytes. pStat3 localization was the same in Stat3+/+ and Stat3−/−oocytes, and oocyte maturation proceeded normally, suggesting that pStat3 was still functional. Furthermore, the treatment of oocytes with the Stat3-specific inhibitors stattic and BP-1-102 or anti-pStat3 antibody led to significantly abnormal spindle assembly and chromosome mislocation in a dose-dependent manner, and pStat3 was either absent or improperly localized in these oocytes. Moreover, the development of pre-implantation stage embryos derived from inhibitor-treated oocytes was significantly hampered following in vitro fertilization. These findings indicate a novel function of pStat3 in spindle assembly.
Highlights
Many studies have demonstrated the dual function of signal transducer and activator of transcription 3 (Stat3) in signal transduction and transcription activation
We first assessed the patterns of pStat3 expression in maturing oocytes and pre-implantation stage embryos by western blotting. pStat3 was highly expressed in germinal vesicle (GV) oocytes (Figure 1A, upper panel)
Following germinal vesicle break down (GVBD), pStat3 expression dramatically decreased at 0.5 h, and no signal was detected until 15 h of maturation, when oocytes were at the MII stage
Summary
Many studies have demonstrated the dual function of signal transducer and activator of transcription 3 (Stat3) in signal transduction and transcription activation. Stat is involved in numerous biological processes, such as cell proliferation, differentiation, and survival. Stat is localized to the cytoplasm in its inactive form, stimulation by cytokines or growth factors triggers its phosphorylation (pStat3) at the tyrosine residue (Y705), inducing dimerization, nuclear translocation, and DNA binding [1,2,3]. Janus kinases are one of the best-studied upstream kinases involved in the Jak/Stat pathway [4]. Stat contains the Src homology-2 (SH2) domain required for the dimerization and activation of pStat monomers [5,6,7]. Morris et al [10] have reported that Stat plays a role in the regulation of centrosome clustering in cancer cells
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