Biology subjects

Emori, C.

Publications and source records attributed to Emori, C..

7 recordsLinked to original sources

bioRxiv2024

Single-cell and bulk transcriptional profiling of mouse ovaries reveals novel genes and pathways associated with DNA damage response in oocytes.

Immature oocytes enclosed in primordial follicles stored in female ovaries are under constant threat of DNA damage induced by endogenous and exogenous factors. Checkpoint kinase 2 (CHEK2) is a key mediator of the DNA damage response in all cells. Genetic studies have shown that CHEK2 and its downstream targets, p53 and TAp63, regulate primordial follicle elimination in response to DNA damage, however the mechanism leading to their demise is still poorly characterized. Single-cell and bulk RNA sequencing were used to determine the DNA damage response in wildtype and Chek2-deficient ovaries. A low but oocyte-lethal dose of ionizing radiation induces a DNA damage response in ovarian cells that is solely dependent on CHEK2. DNA damage activates multiple ovarian response pathways related to apoptosis, p53, interferon signaling, inflammation, cell adhesion, and intercellular communication. These pathways are differentially employed by different ovarian cell types, with oocytes disproportionately affected by radiation. Novel genes and pathways are induced by radiation specifically in oocytes, shedding light on their sensitivity to DNA damage, and implicating a coordinated response between oocytes and pre-granulosa cells within the follicle. These findings provide a foundation for future studies on the specific mechanisms regulating oocyte survival in the context of aging, as well as therapeutic and environmental genotoxic exposures.

cell biology↗

bioRxiv2023

Age-associated aberrations of cumulus-oocyte interaction and microfilamentous structure in the zona pellucida decline female fertility

One of the major age-related declines in female reproductive function is the reduced quantity and quality of oocytes. Here we demonstrate that structural changes in the zona pellucida (ZP) decrease fertilization rates from 34- to 38-week-old female mice, equivalent to the mid-reproductive of human females. In middle-age ovaries, the decline in the number of transzonal projections was accompanied by a decrease in cumulus cell-oocyte interactions, resulting in a deterioration of the oocyte quality. Scanning electron microscopy showed the ZP surface microfilament structure transitioning from rugged to smooth with age, leading to decreased fertilization rates due to impaired sperm binding to the ZP. Moreover, the fertilization rate of middle-age mice was restored to a comparable level to that of young mice by destabilizing the ZP in the presence of glutathione. These results suggest that the age-related structural changes in the ZP is a key for successful fertilization at reproductive age.

developmental biology↗

bioRxiv2023

FBXO24 ensures male fertility by preventing abnormal accumulation of membraneless granules in sperm flagella

Ribonucleoprotein (RNP) granules are membraneless electron-dense structures rich in RNAs and proteins, and involved in various cellular processes. Two RNP granules in male germ cells, intermitochondrial cement and the chromatoid body (CB), are associated with PIWI-interacting RNAs (piRNAs) and are required for transposon silencing and spermatogenesis. Other RNP granules in male germ cells, the reticulated body and CB remnants, are also essential for spermiogenesis. In this study, we disrupted FBXO24, a testis-enriched F-box protein, in mice and found numerous membraneless electron-dense granules accumulated in sperm flagella. Fbxo24 knockout (KO) mice exhibited malformed flagellar structures, impaired sperm motility, and male infertility, likely due to the accumulation of abnormal granules. The amount and localization of known RNP granule-related proteins were not disrupted in Fbxo24 KO mice, suggesting that the accumulated granules were distinct from known RNP granules. Further studies revealed that RNAs and two importins, IPO5 and KPNB1, abnormally accumulated in Fbxo24 KO spermatozoa and that FBXO24 could ubiquitinate IPO5. In addition, IPO5 and KPNB1 were recruited to stress granules, RNP complexes, when cells were treated with oxidative stress or a proteasome inhibitor. These results suggest that FBXO24 is involved in the degradation of IPO5, disruption of which may lead to the accumulation of abnormal RNP granules in sperm flagella.

developmental biology↗

bioRxiv2023

Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy

Post-fertilization cleavage of glycoprotein ZP2, a major subunit of egg zona pellucida (ZP) filaments, is crucial for mammalian reproduction by irreversibly blocking polyspermy. ZP2 processing is thought to inactivate a sperm-binding activity located upstream of the proteins cleavage site; however, its molecular consequences and connection with ZP hardening are unknown. Here we report X-ray crystallographic, cryo-EM and biochemical studies showing that cleavage of ZP2 triggers its oligomerization. Deletion of the ZP-N1 domain that precedes the cleavage site of mouse ZP2 allows it to homodimerize even without processing, and animals homozygous for this variant are subfertile by having a semi-hardened ZP that allows sperm attachment but hinders penetration. Combined with the structure of a native egg coat filament, which reveals the molecular basis of heteromeric ZP subunit interaction, this suggests that oligomerization of cleaved ZP2 cross-links the ZP, rigidifying it and making it physically impenetrable to sperm.

biophysics↗

bioRxiv2021

CHEK2 SIGNALING IS THE KEY REGULATOR OF OOCYTE SURVIVAL AFTER CHEMOTHERAPY

Radiation and chemotherapy can damage the primordial follicle reserve in female cancer patients leading to ovarian failure and infertility. Preservation of ovarian function requires treatment strategies that prevent loss of immature oocytes in primordial follicles during cancer therapy. Checkpoint kinase 2 (CHEK2) inhibition prevents loss of primordial oocytes caused by DNA damage and thus is a promising target for ovoprotective treatment against genotoxic agents. To determine which cancer treatments could benefit from ovoprotective activity of CHEK2 inhibition we investigated oocyte survival in Chek2-/- mice exposed to different chemotherapy drugs. Here, we show that loss of CHEK2 function prevents elimination of primordial oocytes damaged by cisplatin, cyclophosphamide, mafosfamide, doxorubicin, and etoposide, suggesting it could be used to reduce ovarian damage caused by wide range of drugs. Using genetic knockouts we reveal a critical role for TRP53 in oocyte response to chemotherapy drugs and show that both targets of CHEK2--TAp63 and TRP53-- are activated by cisplatin and cyclophosphamide. Furthermore, we show that checkpoint kinase inhibitor and radiation- and chemotherapy sensitizer AZD7762 reduces oocyte elimination after radiation and chemotherapy treatments, despite its cytotoxic effect on ovarian somatic cells. Altogether, these findings demonstrate the role for CHEK2 as the master regulator of primordial oocyte survival or death and credential its targeting for ovoprotective treatments. SIGNIFICANCEChemotherapy and radiation are ovotoxic and increase the risk of premature ovarian insufficiency and infertility in women cancer survivors. Development of treatment strategies preserving ovarian function and ensuring future reproductive health of female cancer patients depends on better understanding of the mechanisms underlying ovarian toxicity caused by different chemotherapy treatments. Preservation of long-term ovarian function can only be achieved by preventing the loss of immature oocytes in primordial follicles during toxic cancer therapies. Checkpoint kinase 2 (CHEK2) inhibition is an attractive strategy for protecting ovarian reserve with a potential additional benefit of sensitizing cancer cells to radiation and chemotherapy. Using a genetic approach, we show that blocking CHEK2 function is sufficient to prevent elimination of primordial oocytes damaged by chemotherapy drugs such as cisplatin, cyclophosphamide, mafosfamide, doxorubicin and etoposide. Many chemotherapy drugs are used in combination (e.g. cyclophosphamide with doxorubicin), thus the protective effect of CHEK2 inhibition is likely to be beneficial for a broad spectrum of patient treatments.

developmental biology↗

bioRxiv2021

Sperm membrane proteins DCST1 and DCST2 are required for the sperm-egg fusion process in mice and fish

The process of sperm-egg fusion is critical for successful fertilization, yet the underlying mechanisms that regulate these steps have remained unclear in vertebrates. Here, we show that both mouse and zebrafish DCST1 and DCST2 are necessary in sperm to fertilize the egg, similar to their orthologs SPE-42 and SPE-49 in C. elegans and Sneaky in D. melanogaster. Mouse Dcst1 and Dcst2 single knockout (KO) spermatozoa are able to undergo the acrosome reaction and show normal relocalization of IZUMO1, an essential factor for sperm-egg fusion, to the equatorial segment. While both single KO spermatozoa can bind to the oolemma, they rarely fuse with oocytes, resulting in male sterility. Similar to mice, zebrafish dcst1 KO males are subfertile and dcst2 and dcst1/2 double KO males are sterile. Zebrafish dcst1/2 KO spermatozoa are motile and can approach the egg, but rarely bind to the oolemma. These data demonstrate that DCST1/2 are essential for male fertility in two vertebrate species, highlighting their crucial role as conserved factors in fertilization.

developmental biology↗

bioRxiv2020

Sexual dimorphism in the meiotic requirement for PRDM9: a mammalian evolutionary safeguard

In many mammals, genomic sites for recombination are determined by histone methyltransferase PRMD9. Mice lacking PRDM9 are infertile, but instances of fertility or semi-fertility in the absence of PRDM9 have been reported in mice, canines and a human female. Such findings raise the question of how the loss of PRDM9 is circumvented to maintain reproductive fitness. We show that genetic background and sex-specific modifiers can obviate the requirement for PRDM9 in mice. Specifically, the meiotic DNA damage checkpoint protein CHK2 acts as a modifier allowing female-specific fertility in the absence of PRDM9. We also report that in the absence of PRDM9, a PRDM9-independent recombination system is compatible with female meiosis and fertility, suggesting sex-specific regulation of meiotic recombination, a finding with implications for speciation. One Sentence SummarySex-specific modulation of a meiotic DNA damage checkpoint limits the requirement for PRDM9 in mammalian fertility.

genetics↗