Genome-wide analysis of translation reveals a critical role for deleted in azoospermia-like (Dazl) at the oocyte-to-zygote transition

Abstract

Oocyte maturation, fertilization, and early embryonic development occur in the absence of gene transcription. Therefore, it is critical to understand at a global level the post-transcriptional events that are driving these transitions. Here we used a systems approach by combining polysome mRNA profiling and bioinformatics to identify RNA-binding motifs in mRNAs that either enter or exit the polysome pool during mouse oocyte maturation. Association of mRNA with the polysomes correlates with active translation. Using this strategy, we identified highly specific patterns of mRNA recruitment to the polysomes that are synchronized with the cell cycle. A large number of the mRNAs recovered with translating ribosomes contain motifs for the RNA-binding proteins DAZL (deleted in azoospermia-like) and CPEB (cytoplasmic polyadenylation element-binding protein). Although a Dazl role in early germ cell development is well established, no function has been described during oocyte-to-embryo transition. We demonstrate that CPEB1 regulates Dazl post-transcriptionally, and that DAZL is essential for meiotic maturation and embryonic cleavage. In the absence of DAZL synthesis, the meiotic spindle fails to form due to disorganization of meiotic microtubules. Therefore, Cpeb1 and Dazl function in a progressive, self-reinforcing pathway to promote oocyte maturation and early embryonic development.

Histone variant H3.3 maintains a decondensed chromatin state essential for mouse preimplantation development

“…S1A). Inhibition of translation by MOs is a widely used tool in developmental biology and we routinely apply it to study mouse preimplantation development (Chen et al, 2011;Oh et al, 2011). We note that, unlike in Xenopus (Szenker et al, 2012;Lim et al, 2013), 5Ј UTR sequence divergence in mouse allows us to design MOs expected to target H3.3 but not H3.1 or H3.2.…”

“…In mammals, H3.3 is a maternal factor that can arise from both H3f3a and H3f3b genes and is dynamically distributed during oogenesis (Chen et al, 2011) and through fertilization and cleavage stages to the blastocyst stage (Torres-Padilla et al, 2006). Dramatic epigenetic changes occur during this developmental period, and both DNA demethylation (Gu et al, 2011) and the dynamic regulation of histone marks (Erhardt et al, 2003;Puschendorf et al, 2008) are known to be essential for embryogenesis.…”

DAZL and CPEB1 regulate mRNA translation synergistically during oocyte maturation

“…Ribosome RIP as a strategy to monitor ribosome loading onto maternal mRNAs and translation in the oocyte A genome-wide analysis of actively translating mRNA during mammalian oocyte maturation provided a first insight into the mechanisms controlling specific translation from transition from prophase I to MI and MII (Chen et al, 2011). However, the large number of oocytes needed for polysome fractionation on a sucrose density gradient limits the temporal resolution of measurements.…”

RNA-binding proteins, RNA granules, and gametes: is unity strength?

“…These data strongly suggest that in somatic cells, DAZL participates to the storage of its target mRNAs at specific cytoplasmic sites. In oocyte, DAZL seems to be diffusely distributed throughout the oocyte cytoplasm but is also enriched at the poles of both MI and MII metaphase spindles (Chen et al 2011). A careful simultaneous analysis of DAZL and CPEB1 localization throughout oogenesis remains to be undertaken.…”

“…Then, the newly synthesized DAZL protein increases the translation of its own mRNA. This post-transcriptional regulatory cascade leads to a progressive accumulation of DAZL, which in turn promotes the translation of DAZL target mRNAs, including Tpx2, Tex19.1, and other regulators of the cell cycle necessary for spindle assembly, the MI-MII transition, and early embryonic development (Chen et al 2011). In addition, DAZL is known to interact with several other proteins, including Pumilio2 that may act as a translational repressor (Vasudevan et al 2006, Brook et al 2009, MacNicol & MacNicol 2010.…”