Biology subjects

Bolcun-Filas, E.

Publications and source records attributed to Bolcun-Filas, E..

5 recordsLinked to original sources

bioRxiv2025

Functional Equivalence of Gamma- and X-Ray Irradiation for Long-Term Hematopoietic and AML Transplant Outcomes in Mice

Total-body irradiation (TBI) is routinely used for myeloablation prior to mouse hematopoietic cell transplant. Widespread transition from 137Cs{gamma} -irradiators to X-ray systems has raised questions about whether these modalities yield equivalent biological outcomes. Although prior studies compared{gamma} and X-ray irradiation in healthy syngeneic transplants, their performance in reciprocal congenic models and in primary acute myeloid leukemia (AML) transplant remains unclear. Here, we systematically evaluated{gamma} and X-ray irradiation across dose and dose-rate conditions, and tested dose equivalents in CD45.1/CD45.2 reciprocal transplants and in AML transplant models. While each modality exhibited distinct early effects, both ultimately supported comparable long-term donor chimerism in congenic transplants and equivalent AML engraftment, leukemic burden, and disease progression. These findings indicate that, with proper dose calibration, X-ray irradiation is a functionally effective alternative to{gamma} -irradiation for normal and malignant transplant studies.

cell biology↗

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↗

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↗

bioRxiv2017

A Single Checkpoint Pathway Eliminates Mouse Oocytes With DNA Damage Or Chromosome Synapsis Failure

Pairing and synapsis of homologous chromosomes during meiosis is crucial for producing genetically normal gametes, and is dependent upon repair of SPO11-induced double stranded breaks (DSBs) by homologous recombination. To prevent transmission of genetic defects, diverse organisms have evolved mechanisms to eliminate meiocytes containing unrepaired DSBs or unsynapsed chromosomes. Here, we show that the CHK2 (CHEK2)-dependent DNA damage checkpoint culls not only recombination-defective mouse oocytes, but also SPO11-deficient oocytes that are severely defective in homolog synapsis. The checkpoint is triggered by spontaneous DSBs that arise in late prophase I, accumulating above the checkpoint activation threshold ([~]10 DSBs) because presence of HORMAD1/2 on unsynapsed chromosome axes prevents their repair. Furthermore, Hormad2 deletion rescued fertility and meiotic DSB repair of oocytes containing a synapsis-proficient, non-crossover recombination defective mutation in a gene (Trip13) required for removal of HORMADs from synapsed chromosomes, indicating that a substantial fraction of meiotic DSBs are normally repaired by intersister recombination in mice.

genetics↗

bioRxiv2017

Pharmacological inhibition of the DNA damage checkpoint prevents radiation-induced oocyte death

Ovarian function is directly correlated with survival of the primordial follicle reserve. Women diagnosed with cancer have a primary imperative of treating the cancer, but since the resting oocytes are hypersensitive to the DNA-damaging modalities of certain chemo- and radiotherapeutic regimens, such patients face the collateral outcome of premature loss of fertility and ovarian endocrine function. Current options for fertility preservation primarily include collection and cryopreservation of oocytes or in vitro fertilized oocytes, but this necessitates a delay in cancer treatment and additional assisted reproductive technology (ART) procedures. Here, we evaluated the potential of pharmacological preservation of ovarian function by inhibiting a key element of the oocyte DNA damage checkpoint response, checkpoint kinase 2 (CHK2; CHEK2). Whereas non-lethal doses of ionizing radiation (IR) eradicate immature oocytes in wild type mice, irradiated Chk2-/- mice retain their oocytes and thus, fertility. Using an ovarian culture system, we show that transient administration of the CHK2 inhibitor 2-(4-(4-Chlorophenoxy)phenyl)-1H-benzimidazole-5-carboxamide-hydrate (\"CHK2iII\") blocked activation of the CHK2 targets TRP53 and TRP63 in response to sterilizing doses of IR, and preserved oocyte viability. After transfer into sterilized host females, these ovaries proved functional and readily yielded normal offspring. These results provide experimental evidence that chemical inhibition of CHK2 is a potentially valid treatment for preserving fertility and ovarian endocrine function of women exposed to DNA-damaging cancer therapies such as IR.\n\nSummary sentenceOocytes, which are highly sensitive to DNA damage caused by certain cancer treatments, can be protected from radiation-induced death by an inhibitor of the checkpoint protein CHK2.

cancer biology↗