AI Article Synopsis
- The process of meiotic division in mammalian oocytes involves several key steps: germinal vesicle breakdown, spindle formation, chromosome segregation, and polar body extrusion, with a halt at metaphase of the second division.
- Previous research indicated that Fyn, a type of protein kinase, plays a role in the oocyte's progression out of metaphase II, and this study explored its involvement in the entire resumption of meiosis.
- The findings showed that Fyn is degraded during germinal vesicle breakdown and is crucial for processes like spindle positioning and polar body extrusion; inhibiting Fyn led to larger polar bodies but did not affect chromosome alignment or migration.
Article Abstract
The process of resumption of the first meiotic division (RMI) in mammalian oocytes includes germinal vesicle breakdown (GVBD), spindle formation during first metaphase (MI), segregation of homologous chromosomes, extrusion of the first polar body (PBI) and an arrest at metaphase of the second meiotic division (MII). Previous studies suggest a role for Fyn, a non-receptor Src family tyrosine kinase, in the exit from MII arrest. In the current study we characterized the involvement of Fyn in RMI. Western blot analysis demonstrated a significant, proteasome independent, degradation of Fyn during GVBD. Immunostaining of fixed oocytes and confocal imaging of live oocytes microinjected with Fyn complementary RNA (cRNA) demonstrated Fyn localization to the oocyte cortex and to the spindle poles. Fyn was recruited during telophase to the cortical area surrounding the midzone of the spindle and was then translocated to the contractile ring during extrusion of PBI. GVBD, exit from MI and PBI extrusion were inhibited in oocytes exposed to the chemical inhibitor SU6656 or microinjected with dominant negative Fyn cRNA. None of the microinjected oocytes showed misaligned or lagging chromosomes during chromosomes segregation and the spindle migration and anchoring were not affected. However, the extruded PBI was of large size. Altogether, a role for Fyn in regulating several key pathways during the first meiotic division in mammalian oocytes is suggested, particularly at the GV and metaphase checkpoints and in signaling the ingression of the cleavage furrow.
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| http://dx.doi.org/10.4161/cc.9.8.11299 | DOI Listing |
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