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Mammalian oocytes store proteins in cytoplasmic lattices

ABSTRACT: Oocytes must accumulate and store maternal factors such as proteins during growth to sustain the first stages of embryonic development. How mammalian oocytes store maternal proteins is not understood. Here, we show that mouse and human oocytes store proteins on cytoplasmic lattices. With super-resolution light microscopy and electron tomography, we demonstrate that cytoplasmic lattices are twisted filament bundles formed by proteins of the subcortical maternal complex, filling the entire ooplasm. The lattices were associated with many proteins that have crucial functions during early embryo development, including proteins controlling genome methylation. Loss of cytoplasmic lattices prevented the accumulation of these proteins and resulted in early embryonic arrest. Thus, cytoplasmic lattices are important for storage of essential maternal proteins and the developmental success of early mammalian embryos.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Oocyte

SUBMITTER: Luisa Welp

LAB HEAD: Melina Schuh

PROVIDER: PXD038575 | Pride | 2023-10-23

REPOSITORIES: Pride

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Project description:In mammals, totipotent pre-implantation embryos are formed by fusion of highly differentiated oocytes and spermatozoa. Acquisition of totipotency concurs with remodeling of chromatin states of parental genomes (M-bM-^@M-^\epigenetic reprogrammingM-bM-^@M-^]), changes in maternally contributed transcriptome and proteome, and zygotic genome activation. Genomes of mature germ cells are more proficient in supporting embryonic development than those of somatic cells. It is currently unknown whether transgenerational inheritance of chromatin states present in mature gametes underlies the efficacy of early embryonic development after natural conception. Here, we show that Ring1 and Rnf2, two core components of the Polycomb Repressive Complex 1 (PRC1), serve redundant gene regulatory functions during oogenesis that are required to support embryonic development beyond the two-cell stage. Numerous developmental regulatory genes that are established Polycomb targets in various somatic cell types are de-repressed in Ring1/Rnf2 double mutant (dm) fully grown germinal vesicle (GV) oocytes. Translation of tested aberrant maternal transcripts is, however, delayed until after fertilization. Exchange of maternal pro-nuclei between control and Ring1/Rnf2 maternally dm early zygotes demonstrates an essential role for Ring1 and Rnf2 during oogenesis in defining cytoplasmic and nuclear maternal contributions that are both essential for proper initiation of embryonic development. A large number of genes up-regulated in Ring1/Rnf2 dm GV oocytes harbor PRC2-mediated histone H3 lysine 27 trimethylation (H3K27me3) in spermatozoa and in embryonic stem cells (ESCs), and are repressed during normal oogenesis and early embryogenesis. These data strongly support the model that Polycomb acts in the female and male germline to silence differentiation inducing genes and to program chromatin states, thereby sustaining developmental potential across generations. Expression profiling of fully grown mouse GV oocytes was performed with the following genotypes: Ring1+/+Rnf2F/F (control), Ring1-/-Rnf2F/F (Ring1 mutant), Ring1+/+Rnf2F/FZp3-cre (Rnf2 mutant) and Ring1-/-Rnf2F/FZp3-cre (Ring1/Rnf2 double mutant). 12 samples were analyzed: 3 biological replicates of each of the 4 genotypes (Ring1+/+Rnf2F/F (control), Ring1-/-Rnf2F/F (Ring1 mutant), Ring1+/+Rnf2F/FZp3-cre (Rnf2 mutant) and Ring1-/-Rnf2F/FZp3-cre (Ring1/Rnf2 double mutant)). Each sample contains 50 GV oocytes.

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Mammalian oocytes store proteins in cytoplasmic lattices

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