Abstract
BackgroundIn bovine maturing oocytes and cleavage stage embryos, gene expression is mostly controlled at the post-transcriptional level, through degradation and deadenylation/polyadenylation. We have investigated how post transcriptional control of maternal transcripts was affected during in vitro and in vivo maturation, as a model of differential developmental competence.ResultsUsing real time PCR, we have analyzed variation of maternal transcripts, in terms of abundance and polyadenylation, during in vitro or in vivo oocyte maturation and in vitro embryo development. Four genes are characterized here for the first time in bovine: ring finger protein 18 (RNF18) and breast cancer anti-estrogen resistance 4 (BCAR4), whose oocyte preferential expression was not previously reported in any species, as well as Maternal embryonic leucine zipper kinase (MELK) and STELLA. We included three known oocyte marker genes (Maternal antigen that embryos require (MATER), Zygote arrest 1 (ZAR1), NACHT, leucine rich repeat and PYD containing 9 (NALP9)). In addition, we selected transcripts previously identified as differentially regulated during maturation, peroxiredoxin 1 and 2 (PRDX1, PRDX2), inhibitor of DNA binding 2 and 3 (ID2, ID3), cyclin B1 (CCNB1), cell division cycle 2 (CDC2), as well as Aurora A (AURKA). Most transcripts underwent a moderate degradation during maturation. But they displayed sharply contrasted deadenylation patterns that account for variations observed previously by DNA array and correlated with the presence of a putative cytoplasmic polyadenylation element in their 3' untranslated region. Similar variations in abundance and polyadenylation status were observed during in vitro maturation or in vivo maturation, except for PRDX1, that appears as a marker of in vivo maturation. Throughout in vitro development, oocyte restricted transcripts were progressively degraded until the morula stage, except for MELK ; and the corresponding genes remained silent after major embryonic genome activation.ConclusionAltogether, our data emphasize the extent of post-transcriptional regulation during oocyte maturation. They do not evidence a general alteration of this phenomenon after in vitro maturation as compared to in vivo maturation, but indicate that some individual messenger RNA can be affected.
Highlights
In bovine maturing oocytes and cleavage stage embryos, gene expression is mostly controlled at the posttranscriptional level, through degradation and deadenylation/polyadenylation
Our results show a moderate degradation of most transcripts during maturation, and evidence contrasted deadenylation patterns that mostly account for variations observed previously by DNA array
Characterization of four bovine genes preferentially expressed in the oocyte We characterized transcripts represented by five distinct EST in our library of EST preferentially represented in bovine oocyte as compared to somatic tissues [23]
Summary
In bovine maturing oocytes and cleavage stage embryos, gene expression is mostly controlled at the posttranscriptional level, through degradation and deadenylation/polyadenylation. The fully grown oocyte (FGO) ability to sustain genome reprogramming and embryo development is associated with a specific and complex pattern of gene expression. This has prompted high-throughput studies of the mammalian oocyte transcriptome in mouse [1,2], in human [3] or bovine [4]. The transcriptome reflects the contemporary pattern of RNA synthesis and protein synthesis In this respect, the fully grown and maturing oocytes are atypical models, since at these stages the oocyte is essentially transcriptionally quiescent. During maturation most maternal transcripts are expected to follow a default deadenylation and degradation pathways [8,9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
