Abstract
Purpose
In this study we hypothesized that the mRNA vector Staufen mediates RNA relocalization during meiotic maturation, and by virtue of its interactions with endoplasmic reticulum, provides a possible mechanism by which protein synthesis is regulated.
Methods
We assessed the expression of staufen (STAU) and calreticulin (CALR), the latter adopted as a marker of the endoplasmic reticulum, in human oocytes at different stages of maturation: GV, metaphase MI and MII. Oocytes were subjected to polymerase chain reaction in order to investigate the expression of STAU and CALR. The corresponding protein products were identified by immunofluorescence and confocal laser scanning microscopy.
Results
STAU and CALR were constantly expressed and selectively localized during oocyte maturation. At the GV stage the both proteins displayed a dispersed distribution localization throughout the cytoplasm. Progressing to the MII stage, STAU tended to compartmentalize towards the cortical area of the oocyte clustering in granules of larger sizes. At the MII stage, CALR assumed a pattern reminiscent and possibly coincident with the position of the meiotic spindle.
Conclusions
The changing pattern of STAU distribution during meiotic maturation of human oocytes implicates a novel mechanism for the regulation of protein synthesis based on mRNA localization. Moreover, the unique disposition of CALR at the MII spindle uncovers a physical interaction with endoplasmic reticulum that may mediate cytoskeletal remodelling during oocyte maturation.
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Acknowledgments
F.G., G.P., S.M., and T.A.L.B. are members of the COST Action FA1201 Epiconcept: Epigenetics and Periconception environment. Part of the experiments are supported by Carraresi Foundation. L.D.S. thanks the “ Alembic” microscopy facility for supporting confocal analysis.
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Capsule Staufen RNA-binding protein undergoes a specific rearrangement during meiotic maturation in human oocytes implying an involvement in the process of mRNA translation. Calreticulin, adopted as a marker for the endoplasmic reticulum, shows a specific localization in association with the meiotic spindle suggesting a regulative function of Ca2+.
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De Santis, L., Gandolfi, F., Pennarossa, G. et al. Expression and intracytoplasmic distribution of staufen and calreticulin in maturing human oocytes. J Assist Reprod Genet 32, 645–652 (2015). https://doi.org/10.1007/s10815-015-0437-y
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DOI: https://doi.org/10.1007/s10815-015-0437-y