Maternal Oct-4 is a potential key regulator of the developmental competence of mouse oocytes

Background The maternal contribution of transcripts and proteins supplied to the zygote is crucial for the progression from a gametic to an embryonic control of preimplantation development. Here we compared the transcriptional profiles of two types of mouse MII oocytes, one which is developmentally competent (MIISN oocyte), the other that ceases development at the 2-cell stage (MIINSN oocyte), with the aim of identifying genes and gene expression networks whose misregulated expression would contribute to a reduced developmental competence. Results We report that: 1) the transcription factor Oct-4 is absent in MIINSN oocytes, accounting for 2) the down-regulation of Stella, a maternal-effect factor required for the oocyte-to-embryo transition and of which Oct-4 is a positive regulator; 3) eighteen Oct-4-regulated genes are up-regulated in MIINSN oocytes and are part of gene expression networks implicated in the activation of adverse biochemical pathways such as oxidative phosphorylation, mitochondrial dysfunction and apoptosis. Conclusion The down-regulation of Oct-4 plays a crucial function in a sequence of molecular processes that leads to the developmental arrest of MIINSN oocytes. The use of a model study in which the MII oocyte ceases development consistently at the 2-cell stage has allowed to attribute a role to the maternal Oct-4 that has never been described before. Oct-4 emerges as a key regulator of the molecular events that govern the establishment of the developmental competence of mouse oocytes

OCT4 and the acquisition of oocyte developmental competence during folliculogenesis

The role that the transcription factor OCT4 plays during oocyte growth is yet unknown. In this review, we summarise the data on its potential role in the acquisition of oocyte developmental competence in the mouse. These studies describe the presence in MII oocytes and 2-cell embryos of an OCT4 transcriptional network that might be part of the molecular signature of maternal origin on which the inner cell mass and the embryonic stem cell-associated pluripotency is assembled and shaped. The Oct4-gene regulatory network thus provides a connection between eggs, early preimplantation embryos and embryonic stem cells

Transcriptome based identification of mouse cumulus cell markers that predict the developmental competence of their enclosed antral oocytes

BACKGROUND: The cumulus cells (CCs) enveloping antral and ovulated oocytes have been regarded as putative source of non-invasive markers of the oocyte developmental competence. A number of studies have indeed observed a correlation between CCs gene expression, embryo quality, and final pregnancy outcome. Here, we isolated CCs from antral mouse oocytes of known developmental incompetence (NSN-CCs) or competence (SN-CCs) and compared their transcriptomes with the aim of identifying distinct marker transcripts. RESULTS: Global gene expression analysis highlighted that both types of CCs share similar transcriptomes, with the exception of 422 genes, 97.6% of which were down-regulated in NSN-CCs vs. SN-CCs. This transcriptional down-regulation in NSN-CCs was confirmed by qRT-PCR analysis of CC-related genes (Has2, Ptx3, Tnfaip6 and Ptgs2). Only ten of the 422 genes were up-regulated with Amh being the most up-regulated in NSN-CCs, with an average 4-fold higher expression when analysed by qRT-PCR. CONCLUSIONS: The developmental incompetence (NSN) or competence (SN) of antral oocytes can be predicted using transcript markers expressed by their surrounding CCs (i.e., Has2, Ptx3, Tnfaip6, Ptgs2 and Amh). Overall, the regulated nature of the group of genes brought out by whole transcriptome analysis constitutes the molecular signature of CCs associated either with developmentally incompetent or competent oocytes and may represent a valuable resource for developing new molecular tools for the assessment of oocyte quality and to further investigate the complex bi-directional interaction occurring between CCs and oocyte

An epigenomic biography of the mammalian oocyte

Successful fertilisation and early development depend on the quality of the ovulated oocyte. Even though this is endorsed by both the experimental and clinical practice, our still scarce knowledge of the biology of the mammalian oocyte makes it difficult to identify parameters that define the quality or 'developmental competence' of an oocyte. The many attempts to establish markers of the oocyte's developmental competence have produced divergent results or have worked only in specific experimental contexts. To this respect, the oocyte morphology, the concentration of various factors in the follicular fluid, the role of the oocyte's mitochondria, the telomere length and the transcription profile of cumulus cell-specific genes are some of the most studied aspects of the oocyte and of the ovarian follicle biology. The analysis of the level of cumulus cell-specific transcripts has identified groups of genes that are directly (PTGS2, HAS2, GREM1 and PTX3) [1-3] or inversely (GPX3, CXCR4, CCND2 and CTNND1) [4-5] correlated to human embryo preimplantation quality and pregnancy outcome. Recent studies analysed the whole cumulus cells transcriptome in human [6]and bovine [7] cumulus cell-oocyte complexes bringing up a new set of putative marker transcripts. The concentration in the follicular fluid of myo-inositol (a serum trophic factor), inhibin B [8-9] or AMH have been used for their predictive value of human preimplantation embryonic development, with the latter suggested as a better predictor of oocyte fertilisability [10] and pregnancy rate [11]. Some authors have proposed the presence of a high level of estradiol on the day of hCG administration as a candidate marker of low pregnancy rate [12-13]), but these data are conflicting with others that describe no correlations with the final pregnancy outcome [14-15]. Similarly, a reduction at the time of oocyte collection in the level of progesterone receptor in human cumulus cells was associated with morphologically good oocytes [16]. Mitochondria have been the subject of a large number of studies, but how and whether they contribute to the determination of the oocyte developmental competence is still unclear. The whole preimplantation period is sustained by mitochondria produced during oogenesis and only when the embryo begins implantation, their production is resumed. Therefore, an unbalanced number of these organelles, an incorrect distribution or an altered function may have negative effects on the early stages of development [for a review see 17]. The number of mitochondria in mouse primordial germ cells (PGCs) is very small, being approximately 10-100 per cell, then, by the mature oocyte they sum up to ~ 90.000 [18]. The total number of mitochondria seems to be critical to the developmental competence of an oocyte, since subnormal levels of these organelles correlate with premature maturation arrest of the oocyte and early death of the preimplantation embryo [19-20]. A low mitochondrial complement may determine a bioenergetic/metabolic shortage with consequences on the oocyte’s ability of meiotic resumption, fertilisation and to sustain the early phases of development [reviewed in 20-23]. Along with these studies, ATP values have also been associated with the oocyte’s developmental competence; an ATP content of > 2 pmol seems a threshold to distinguish between developmentally competent and incompetent human oocytes [24]. During folliculogenesis, mitochondria are located in different regions of the oocyte [25-28] and by the mature oocyte they will have an asymmetric polar distribution that will be maintained through segmentation resulting in blastomeres that will own a different number of mitochondria with a different spatial patterning. A number of observations substantiate the involvement of these organelles not only as powerhouse, producing most of the ATP in the cell, but they may also regulate development by modulating Ca2+ signalling, reactive oxygen species (ROS) and intermediary metabolites and through their control of apoptosis. Oxidative stress and intracellular redox potential (IRP) have been shown to regulate the function of a number of transcription factors important in early development. For example, NF-KB (nuclear factor kappa-light-chain-enhancer of activated B cells) and GSK3β (glycogen synthase kinase-3β), expressed during preimplantation development, are activated by mitochondrial ROS production [29-30]. S-glutathionylation of many transcription factors [31] occurs after the oxidation of the IRP, thus, the ability of mitochondria to modulate the IRP will possibly change the activity of these proteins. Altered mitochondrial Ca2+ cycling and ROS production are determinant for the oocyte to enter and accomplish the apoptotic programme [32]. Oxidative stress induces mitochondrial dysfunction that triggers apoptosis in the mouse oocyte and zygote [33]. Specific oocyte morphological features are used to select female gametes of good quality. Oocytes are graded as good, when they posses a cytoplasm with fine granules, a single polar body, a narrow perivitelline space and a ring shaped zona pellucida [34]. On the contrary, they are correlated with low fertilisability and developmental competence, when they own vacuoles and refractile bodies within the ooplasm. Although used in some laboratories that practice human assisted reproduction, these morphological markers have been the subject of many criticisms and are not widely accepted [34-40]. As for nuclear morphological features, a large literature as demonstrated the possibility to select between developmentally competent and incompetent antral oocyte, depending on their chromatin configuration (see below). This selection, however, relies on the use of fluorochromes whose use, for obvious reasons, is not advisable in our species. Up to date, our knowledge lacks of links between the morphological aspects described and the genomic and epigenomic features that work in the backstage. Bringing to light these links would permit the identification of molecular markers of the oocyte developmental competence. In this article, we will review our current understanding of the changes that occur to the oocyte epigenetic signature during folliculogenesis and in mature oocytes

Youth and digital media: risks and opportunities on socialization, sociability and identity

Everyday relational and communicative practices are increasingly shaped by the digital media and Internet has become pervasive in young people’s daily life (Riva, Scarcelli, 2016), however the consequences of the learning practices, behaviours and social interactions are still under debate (Guzzetti, Lesley, 2016; Pandolfini, 2016). The chapter investigates the relationship between young people and the use of digital media, exploring risks and potentials on youth’s socialization, sociability, identity building (Merico, 2018). It addresses the following topics: the online behaviour and the media consumption in school and nonschool settings; the management of the relationship with friends online and offline; the use of social network and the formation of social capital; the effectiveness of media education courses to limit the potential risks. Such topics are discussed according to data emerged from a research based on a standardised questionnaire administered to the students of upper secondary schools located in the urban and suburban areas of four Italian cities: Como, Genoa, Padua and Salerno. They have been interviewed 771 students attending the second and fourth years of the following fields of study: Lyceum, Technical institutes, Vocational schools. The survey has been carried out in 2015-2016 and 2016-2017 and administered through a CAWI mode in the informatics labs of the selected schools. The choice of schools and classes has been realised by a purposive sampling. The interviewees are distributed as follows: 43,5% are females, while males represent the 56,5% of the sample; 38,9% of students attend a lyceum, 39,2% a technical institute, 21,9% a vocational school. In terms of use of time, activities and consumer purposes, the online behaviour of young people can be grouped into three orientations: (1) the network as an amusement space, wherein the web is interpreted as a space for escape and leisure experienced by the use of content such as music, games, movies and purchases; (2) the network as an extension of opportunities for knowledge, resulting in a more informative orientation that also includes collection of information for school purposes and reading of newspapers and magazines online; (3) the network as a place of social experimentation, representing a particularly active online space characterized by participation in blogs and discussion forums, sharing media content and use of the network in ways intended to expand the user’s social opportunities. A focus is on the relationship between the use of social network sites (mainly Facebook) and the formation and maintenance of social capital; in addition to examine the consumption behaviour and use’ purposes, the chapter reports on the validation of the Internet Social Capital Scales (Williams, 2006), aimed at investigating two different types of social capital – “bridging” and “bonding” - for both online and offline contexts. The data analysis allows to discuss potentialities and risks related to the world of social networking, representing both a postmodern way of relational opportunity, producing multiplication of ties, as well as an expression of fragmentation of sociality itself. Then, the chapter analyses how the adolescents communicate and manage the relationship with friends online and offline. The data analysis highlights an integration between the online and offline modalities, where the online tends to remain on more superficial levels of the interaction, while the more confidential and intimate aspects tend to be managed face to face (with some significant gender differences). From the perspective of the relational skills, the topic of potentiality and risks related to the use of social media will be addressed (Pattaro et al., 2017). Lastly, the teenagers’ risk perception will be discussed based on the section of the questionnaire (adapted from the Eu Kids online survey – Livingstone et al., 2011; Mascheroni, Ólafsson, 2018) devoted to explore the problematic internet experiences. Finally, the responsible use of the media has to be connected with the attendance of media education training programs (Rivoltella, 2017; Garavaglia, 2014). The research highlights the impacts of such courses on the online behaviour of young people and on their perceptions of the risks connected to the use of technology. Moreover, data analysis shows at what extent young people consider parents and teachers as the main point of reference in enabling them to navigate responsibly and in training them about safety on the Web, providing some insights on students’ needs on this topic. The chapter concludes with suggestions for future research and implications for educational policies, by debating critical points of the relation between socio-cultural aspects of society and digitization processes, questioning on the effects (expected and unexpected) on the lives of young people and the associated risks

Youth and Digital Media: Risks and Opportunities

Everyday relational and communicative practices are increasingly shaped by digital media, and the Internet has become pervasive in young people\u2019s daily lives (Riva and Scarcelli 2016). According to Eurostat data (2017), more than 90 % of youth in the EU aged 16\u201329 accessed the Internet on a daily basis in 2016, which was substantially more often than the population as a whole. This youth demographic predominantly accessed the Internet from mobile devices, such as smartphones, tablets, netbooks, and laptops. However, the consequences of the learning practices, behaviors and social interactions resulting from Internet use are still under debate (Pattaro 2015, Guzzetti and Lesley 2016, Pandolfini 2016). Indeed, discourse about the opportunities and risks of youth using the Internet has attracted considerable attention among researchers from different fields (such as education, sociology, and psychology), and teachers, parents and policy makers seek to identify which factors may encourage beneficial uses of digital media and mitigate its associated risks. On one hand, the Internet offers education, communication, community engagement, creativity, self-expression and entertainment; on the other, it can also expose youth to pornography, self-harm, violent or hateful content, inappropriate or harmful contact with others, harassment, and problematic conduct from peers, such as bullying or invasions of privacy (Vanderhoven et al. 2014, Mascheroni and 3lafsson 2018). This chapter investigates the relationship between young people and the use of digital media by exploring its risks and potential effects on youth socialization, sociability, and identity formation (Bennato 2011, Livingstone et al. 2012, Paccagnella and Vellar 2016, Pattaro et al. 2017, Romeo 2017, Merico 2018, Mascheroni and 3lafsson 2018)