LS-13-O-3309 How can the in vitro culture affect the spindle assembly and chromosome segregation in mammalian oocytes?

the chromosomal segregation errors in comparison with mitotically divided cells. This could lead to spontaneous abortion, embryonic lethality and serious congenital malformations. It has been previously shown, in mammalian oocytes, that many of quantitative and qualitative parameters, such a spindle microtubule morphogenesis, structure, assembly, cytoplasmic position and distribution, are affected by in vitro culture. The aim of our study is comparison of the spindle assembly and metaphase plate formation between in vitro and in vivo matured mammalian oocytes. To obtain physiologically relevant results we used multichannel live cell imaging confocal microscopy combined with high-resolution microscopy of fixed samples. Combination of those techniques allowed us to detect and monitor several parallel processes in every single cell. The spindle assembly and spindle bipolarization (the formation of bipolar spindle) are the results of counteraction of the kinesins (plus end-directed motoric proteins) and dyneins (minus end-directed motoric proteins). We discovered that the balance between those two groups of molecules, which is crucial for correct assembly of the spindle in meiosis I and meiosis II, is influenced by maturation in vitro. This was reflected by dramatic changes of spindle morphology and function observed in meiosis II. Since spindle is playing important role in faithful chromosome segregation, our results are suggesting that techniques frequently used in assisted reproduction techniques (ART) might contribute to chromosome segregation errors.