Age-related alterations in fertilization-induced Ca2+ oscillations depend on the genetic background of mouse oocytes†

Abstract

Maternal aging affects various aspects of oocytes’ physiology, including the functionality of their nuclear apparatus and mitochondria. In the present paper, we wished to investigate whether advanced reproductive age impacts also oocytes’ ability to generate proper Ca2+ oscillations in response to monospermic fertilization. We examined three different mouse strains/crosses: inbred C57BL/6Tar, outbred Tar:SWISS, and hybrid F1 (C57BL/6Tar x CBA/Tar). The females were either 2–4 months old (young) or 13–16 months old (aged). We observed that Ca2+ oscillatory pattern is altered in a strain-dependent manner and that changes were more profound in aged C57BL/6Tar and F1 than in aged Tar:SWISS oocytes. We also showed that maternal aging differently affects the size of Ca2+ store and expression of Itpr, Atp2a2, Txndc4 and Pdia3 genes involved in Ca2+ homeostasis in oocytes of C57BL/6Tar, Tar:SWISS and F1 genetic background, which may explain partially the differences in the extent of age-dependent changes in the Ca2+ oscillations in those oocytes. Maternal aging did not have any visible impact on the distribution of the ER cisterns in oocytes of all three genetic types. Finally, we showed that maternal aging alters the timing of the first embryonic interphase onset and that this timing correlates in C57BL/6Tar and Tar:SWISS oocytes with the frequency of fertilization-induced Ca2+ oscillations. Our results indicate that extreme caution is required when conclusions about oocyte/embryo physiological response to aging are made and complement an increasing amount of evidence that mammalian (including human) susceptibility to aging differs greatly depending on the genetic background of the individual.

Dual spindles assemble in bovine zygotes despite the presence of paternal centrosomes

“…These data therefore indicate that NEBD is complete in bovine zygotes and that NE remnants do not appear to contribute to spatial separation of parental genomes or dual spindle formation. The diffuse distribution of calnexin signal in bovine zygotes closely resembles previously published ER labeling data in oocytes and zygotes of other mammalian species, including human ( FitzHarris et al, 2007 ; Payne and Schatten, 2003 ; Audouard et al, 2011 ; Czajkowska et al, 2020 ; Balakier et al, 2002 ; Hölzenspies et al, 2009 ). Our data demonstrate that ER does not form a physical barrier within the metaphase spindle between proximate parental genomes (maximum intensity projections across whole spindle volumes, Fig.…”

Comparison of parthenogenetic oocyte activation in different mouse strains on in vitro development rate and quality

“…Different mouse strains have different properties in Ca 2+ storage area and the post-fertilization (32,34). Our results demonstrated that calcium channels might enhance the parthenogenetic embryo development in certain mouse strains consistent with previous reports (30)(31)(32)34).…”

Effects of an obesogenic diet on the oviduct depend on the duration of feeding

“…Finally, during the late phase, none of the tested genes was significantly affected by diet despite the continued increase in weight gain and hypercholesterolemia. This could be due to the advanced age of the mice at this time point and the relatively shorter reproductive lifespan of the B6 compared to Swiss mice [ 80 ].…”