LSM14B is essential for oocyte meiotic maturation by regulating maternal mRNA storage and clearance
Ontology highlight
ABSTRACT: Fully grown oocytes remain transcriptionally quiescent, yet many maternal mRNAs are synthesized and retained in growing oocytes. We now know that maternal mRNAs are stored in a structure called the mitochondria associated ribonucleoprotein domain (MARDO). But the components and functions of MARDO remain elusive. Here, we found that LSM14B knockout prevents the proper storage and timely clearance of mRNAs (including Cyclin B1, Btg4, and other mRNAs that are translationally activated during meiotic maturation), specifically by disrupting MARDO assembly during oocyte growth and meiotic maturation. With decreased levels of storage and clearance, the LSM14B knockout oocytes failed to enter meiosis II, ultimately resulting in female infertility. Our results demonstrate the function of LSM14B in MARDO assembly, couple the MARDO with mRNA clearance and oocyte meiotic maturation.
Project description:Fully grown oocytes remain transcriptionally quiescent, yet many maternal mRNAs are synthesized and retained in growing oocytes. We now know that maternal mRNAs are stored in a structure called the mitochondria associated ribonucleoprotein domain (MARDO). But the components and functions of MARDO remain elusive. Here, we found that LSM14B knockout prevents the proper storage and timely clearance of mRNAs (including Cyclin B1, Btg4, and other mRNAs that are translationally activated during meiotic maturation), specifically by disrupting MARDO assembly during oocyte growth and meiotic maturation. With decreased levels of storage and clearance, the LSM14B knockout oocytes failed to enter meiosis II, ultimately resulting in female infertility. Our results demonstrate the function of LSM14B in MARDO assembly, couple the MARDO with mRNA clearance and oocyte meiotic maturation
Project description:The success of human reproduction relies on high quality oocytes. Oocyte quality is manifested by the competence to complete meiosis, to be fertilized, and to support embryonic development. This meiotic and developmental competence is gradually established during the course of oocyte and follicle development, and is determined in large part by the autonomous gene expression program intrinsic to the oocyte. In order to explore the regulatory role of LSM14B in oocyte, we analyzed the effect of Lsm14b KO on gene expression in GV-stage fully-grown oocytes (FGOs) in mice by comparing the corresponding transcriptomes via RNA-Seq Analysis.
Project description:Fully-grown oocytes are transcriptionally silent and must stably maintain mRNAs needed for oocyte meiotic maturation and early embryonic development. However, where and how mammalian oocytes store maternal mRNAs is unclear. Here, we report that mammalian oocytes accumulate mRNAs in a mitochondria-associated ribonucleoprotein domain (MARDO). MARDO assembly around mitochondria was promoted by the RNA-binding protein ZAR1, and directed by an increase in mitochondrial membrane potential during oocyte growth. MARDO foci coalesced into hydrogel-like matrices that clustered mitochondria. Maternal mRNAs stored in the MARDO were translationally repressed. Loss of ZAR1 disrupted the MARDO, dispersed mitochondria, and caused a premature loss of MARDO-localized mRNAs. Thus, a mitochondria-associated membraneless compartment controls mitochondrial distribution and regulates maternal mRNA storage, translation and decay to ensure fertility in mammals.
Project description:A decrease in oocyte developmental potential is a major obstacle for successful pregnancy in women of advanced age. However, the age-related epigenetic modifications associated with dynamic transcriptome changes, particularly meiotic maturation-coupled mRNA clearance, have not been adequately characterized in human oocytes. This study demonstrate a decreased storage of transcripts encoding key factors regulating the maternal mRNA degradome in fully grown oocytes of women of advanced age. A similar defect in meiotic maturation-triggered mRNA clearance was also detected in aged mouse oocytes. Mechanistically, the epigenetic and cytoplasmic aspects of oocyte maturation are synchronized in both the normal development and aging processes. The level of histone H3K4 trimethylation (H3K4me3) was high in fully grown mouse and human oocytes derived from young females but decreased during aging due to the decreased expression of epigenetic factors responsible for H3K4me3 accumulation. Oocyte-specific knockout of the gene encoding CxxC-finger protein 1 (CXXC1), a DNA-binding subunit of SETD1 methyltransferase, caused ooplasm changes associated with accelerated aging and impaired maternal mRNA translation and degradation. These results suggest that a network of CXXC1-maintained H3K4me3, in association with mRNA decay competence, sets a timer for oocyte deterioration and plays a role in oocyte aging in both mouse and human oocytes.
Project description:RNA-binding proteins (RBPs) have essential functions during oocyte development.In order to explore the regulatory role of RNA-binding protein LSM14B in oocyte, we Identified the translatome of WT and Lsm14b KO GV-Stage Oocytes in mice via Scarce Sample Polysome Profiling (SSP-profiling).
Project description:Zar1 was the first mammalian maternal-effect gene to be identified. Embryos derived from Zar1-null female mice are blocked before zygotic genome activation; however, the underlying mechanism remains unclear. By knocking out Zar1 and its homolog Zar2 in mice, we revealed a novel function of these genes in oocyte meiotic maturation. Zar1/2-deleted oocytes displayed delayed meiotic resumption and polar body-1 emission and a higher incidence of abnormal meiotic spindle formation and chromosome aneuploidy. The grown oocytes of Zar1/2-null mice contained fewer total mRNAs and displayed a reduced level of protein synthesis. Key maturation-associated changes failed to occur in the Zar1/2-null oocytes, including the translational activation of maternal mRNAs encoding the cell cycle proteins cyclin B1 and WEE2, as well as maternal-to-zygotic transition (MZT) licensing factor BTG4. Consequently, maternal mRNA decay was impaired and MZT was abolished. ZAR1/2 bound mRNAs to regulate the translational activity of their 3ʹ-UTRs and interacted with other oocyte proteins, including mRNA-stabilizing protein MSY2 and cytoplasmic lattice components. These results countered the traditional view that ZAR1 only functions after fertilization and highlight a previously unrecognized role of ZAR1/2 in regulating the maternal transcriptome and translational activation in maturing oocytes.
Project description:Mammalian oocyte maturation is driven by strictly translational regulation of maternal mRNAs stored in the cytoplasm. However, the function and mechanism of post-transcriptional chemical modifications especially the newly identified N4-acetylcytidine (ac4C) catalyzed by N-acetyltransferase 10 (NAT10) in this process are previously unknown. In this study, we developed a low-input ac4C sequencing technology - ac4C LACE-seq and mapped 8241 ac4C peaks at the whole transcriptome level using 50 mouse oocytes at the germinal vesicle (GV) stage. We profiled the mRNA landscapes of NAT10-interactions and ac4C modifications. The NAT10-interacted and ac4C modified transcripts displayed association with high translation efficiency in oocytes. Oocyte-specific Nat10 knockout wiped out ac4C signals in oocytes and caused severe defects in meiotic maturation and female infertility. ac4C LACE-seq results indicated that Nat10 deletion led to a failure of ac4C deposition on mRNAs encoding key maternal factors such as MAY2, ZAR1, BTG4 and cyclin B1 that regulate transcriptome stability and maternal-to-zygotic transition. Nat10-deleted oocytes had decreased mRNA translation efficiencies during meiotic maturation, partially due to the direct inhibition ac4C sites on specific transcripts. In sum, we developed low-input, high-sensitivity mRNA ac4C profiling approach and highlighted the important physiological function of ac4C in precise regulation of the oocyte meiotic maturation by enhancing translation efficiency.
Project description:Mammalian oocyte maturation is driven by strictly translational regulation of maternal mRNAs stored in the cytoplasm. However, the function and mechanism of post-transcriptional chemical modifications especially the newly identified N4-acetylcytidine (ac4C) catalyzed by N-acetyltransferase 10 (NAT10) in this process are previously unknown. In this study, we developed a low-input ac4C sequencing technology—ac4C LACE-seq and mapped 8241 ac4C peaks at the whole transcriptome level using 50 mouse oocytes at the germinal vesicle (GV) stage. We profiled the mRNA landscapes of NAT10-interactions and ac4C modifications. The NAT10-interacted and ac4C modified transcripts displayed association with high translation efficiency in oocytes. Oocyte-specific Nat10 knockout wiped out ac4C signals in oocytes and caused severe defects in meiotic maturation and female infertility. ac4C LACE-seq results indicated that Nat10 deletion led to a failure of ac4C deposition on mRNAs encoding key maternal factors such as MAY2, ZAR1, BTG4 and cyclin B1 that regulate transcriptome stability and maternal-to-zygotic transition. Nat10-deleted oocytes had decreased mRNA translation efficiencies during meiotic maturation, partially due to the direct inhibition ac4C sites on specific transcripts. In sum, we developed low-input, high-sensitivity mRNA ac4C profiling approach and highlighted the important physiological function of ac4C in precise regulation of the oocyte meiotic maturation by enhancing translation efficiency.
Project description:We analyzed the functions of BTG family proteins in maternal mRNA degradation in mouse oocytes. By comparing the degradation of transcripts in WT oocytes and KO oocytes, we are able to know the defects in maternal mRNA clearance in BTG4-deleted oocytes, and identified the BTG4 target genes in oocyte cyplasmic maturation. 2 WT oocyte samples at GV stage, 2 WT oocyte samples at MII stage, 2 Btg4-/- oocyte samples at GV stage and 2 Btg4-/- oocyte samples at MII stage?2 WT embryo samples at zygote stage, 2 WT embryo samples at 2-cell stage, 2 Btg4-/- embryo samples at zygote stage and 2 Btg4-/- embryo samples at 2-cell stage , and a WT GV oocyte, a WT MII oocyte, a Erk-/- GV oocyte and a Erk-/- MII oocyte are performed RNA sequencing.