Browsing by Author "Edwards, Donna M."

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    A Barth Syndrome Patient-Derived D75H Point Mutation in TAFAZZIN Drives Progressive Cardiomyopathy in Mice
    (MDPI, 2024-07-27) Snider, Paige L.; Sierra Potchanant, Elizabeth A.; Sun, Zejin; Edwards, Donna M.; Chan, Ka-Kui; Matias, Catalina; Awata, Junya; Sheth, Aditya; Pride, P. Melanie; Payne, R. Mark; Rubart, Michael; Brault, Jeffrey J.; Chin, Michael T.; Nalepa, Grzegorz; Conway, Simon J.; Anatomy, Cell Biology and Physiology, School of Medicine
    Cardiomyopathy is the predominant defect in Barth syndrome (BTHS) and is caused by a mutation of the X-linked Tafazzin (TAZ) gene, which encodes an enzyme responsible for remodeling mitochondrial cardiolipin. Despite the known importance of mitochondrial dysfunction in BTHS, how specific TAZ mutations cause diverse BTHS heart phenotypes remains poorly understood. We generated a patient-tailored CRISPR/Cas9 knock-in mouse allele (TazPM) that phenocopies BTHS clinical traits. As TazPM males express a stable mutant protein, we assessed cardiac metabolic dysfunction and mitochondrial changes and identified temporally altered cardioprotective signaling effectors. Specifically, juvenile TazPM males exhibit mild left ventricular dilation in systole but have unaltered fatty acid/amino acid metabolism and normal adenosine triphosphate (ATP). This occurs in concert with a hyperactive p53 pathway, elevation of cardioprotective antioxidant pathways, and induced autophagy-mediated early senescence in juvenile TazPM hearts. However, adult TazPM males exhibit chronic heart failure with reduced growth and ejection fraction, cardiac fibrosis, reduced ATP, and suppressed fatty acid/amino acid metabolism. This biphasic changeover from a mild-to-severe heart phenotype coincides with p53 suppression, downregulation of cardioprotective antioxidant pathways, and the onset of terminal senescence in adult TazPM hearts. Herein, we report a BTHS genotype/phenotype correlation and reveal that absent Taz acyltransferase function is sufficient to drive progressive cardiomyopathy.
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    Mitotic Errors Promote Genomic Instability and Leukemia in a Novel Mouse Model of Fanconi Anemia
    (Frontiers Media, 2021-11-05) Edwards, Donna M.; Mitchell, Dana K.; Abdul-Sater, Zahi; Chan, Ka-Kui; Sun, Zejin; Sheth, Aditya; He, Ying; Jiang, Li; Yuan, Jin; Sharma, Richa; Czader, Magdalena; Chin, Pei-Ju; Liu, Yie; de Cárcer, Guillermo; Nalepa, Grzegorz; Broxmeyer, Hal E.; Clapp, D. Wade; Potchanant, Elizabeth A. Sierra; Pediatrics, School of Medicine
    Fanconi anemia (FA) is a disease of genomic instability and cancer. In addition to DNA damage repair, FA pathway proteins are now known to be critical for maintaining faithful chromosome segregation during mitosis. While impaired DNA damage repair has been studied extensively in FA-associated carcinogenesis in vivo, the oncogenic contribution of mitotic abnormalities secondary to FA pathway deficiency remains incompletely understood. To examine the role of mitotic dysregulation in FA pathway deficient malignancies, we genetically exacerbated the baseline mitotic defect in Fancc-/- mice by introducing heterozygosity of the key spindle assembly checkpoint regulator Mad2. Fancc-/-;Mad2+/- mice were viable, but died from acute myeloid leukemia (AML), thus recapitulating the high risk of myeloid malignancies in FA patients better than Fancc-/-mice. We utilized hematopoietic stem cell transplantation to propagate Fancc-/-; Mad2+/- AML in irradiated healthy mice to model FANCC-deficient AMLs arising in the non-FA population. Compared to cells from Fancc-/- mice, those from Fancc-/-;Mad2+/- mice demonstrated an increase in mitotic errors but equivalent DNA cross-linker hypersensitivity, indicating that the cancer phenotype of Fancc-/-;Mad2+/- mice results from error-prone cell division and not exacerbation of the DNA damage repair defect. We found that FANCC enhances targeting of endogenous MAD2 to prometaphase kinetochores, suggesting a mechanism for how FANCC-dependent regulation of the spindle assembly checkpoint prevents chromosome mis-segregation. Whole-exome sequencing revealed similarities between human FA-associated myelodysplastic syndrome (MDS)/AML and the AML that developed in Fancc-/-; Mad2+/- mice. Together, these data illuminate the role of mitotic dysregulation in FA-pathway deficient malignancies in vivo, show how FANCC adjusts the spindle assembly checkpoint rheostat by regulating MAD2 kinetochore targeting in cell cycle-dependent manner, and establish two new mouse models for preclinical studies of AML.
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    SIK2 kinase synthetic lethality is driven by spindle assembly defects in FANCA‐deficient cells
    (Wiley, 2022-02) Chan, Ka‐Kui; Abdul‐Sater, Zahi; Sheth, Aditya; Mitchell, Dana K.; Sharma, Richa; Edwards, Donna M.; He, Ying; Nalepa, Grzegorz; Rhodes, Steven D.; Clapp, D. Wade; Potchanant, Elizabeth A. Sierra; Pediatrics, School of Medicine
    The Fanconi anemia (FA) pathway safeguards genomic stability through cell cycle regulation and DNA damage repair. The canonical tumor suppressive role of FA proteins in the repair of DNA damage during interphase is well established, but their function in mitosis is incompletely understood. Here, we performed a kinome‐wide synthetic lethality screen in FANCA −/− fibroblasts, which revealed multiple mitotic kinases as necessary for survival of FANCA‐deficient cells. Among these kinases, we identified the depletion of the centrosome kinase SIK2 as synthetic lethal upon loss of FANCA. We found that FANCA colocalizes with SIK2 at multiple mitotic structures and regulates the activity of SIK2 at centrosomes. Furthermore, we found that loss of FANCA exacerbates cell cycle defects induced by pharmacological inhibition of SIK2, including impaired G2‐M transition, delayed mitotic progression, and cytokinesis failure. In addition, we showed that inhibition of SIK2 abrogates nocodazole‐induced prometaphase arrest, suggesting a novel role for SIK2 in the spindle assembly checkpoint. Together, these findings demonstrate that FANCA‐deficient cells are dependent upon SIK2 for survival, supporting a preclinical rationale for targeting of SIK2 in FA‐disrupted cancers.
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    The Loss of Tafazzin Transacetylase Activity Is Sufficient to Drive Testicular Infertility
    (MDPI, 2024-11-26) Snider, Paige L.; Sierra Potchanant, Elizabeth A.; Matias, Catalina; Edwards, Donna M.; Brault, Jeffrey J.; Conway, Simon J.; Pediatrics, School of Medicine
    Barth syndrome (BTHS) is a rare, infantile-onset, X-linked mitochondriopathy exhibiting a variable presentation of failure to thrive, growth insufficiency, skeletal myopathy, neutropenia, and heart anomalies due to mitochondrial dysfunction secondary to inherited TAFAZZIN transacetylase mutations. Although not reported in BTHS patients, male infertility is observed in several Tafazzin (Taz) mouse alleles and in a Drosophila mutant. Herein, we examined the male infertility phenotype in a BTHS-patient-derived D75H point-mutant knockin mouse (TazPM) allele that expresses a mutant protein lacking transacetylase activity. Neonatal and adult TazPM testes were hypoplastic, and their epididymis lacked sperm. Histology and biomarker analysis revealed TazPM spermatogenesis is arrested prior to sexual maturation due to an inability to undergo meiosis and the generation of haploid spermatids. Moreover, TazPM testicular mitochondria were found to be structurally abnormal, and there was an elevation of p53-dependent apoptosis within TazPM seminiferous tubules. Immunoblot analysis revealed that TazPM gamete genome integrity was compromised, and both histone γ-H2Ax and Nucleoside diphosphate kinase-5 protein expression were absent in juvenile TazPM testes when compared to controls. We demonstrate that Taz-mediated transacetylase activity is required within mitochondria for normal spermatogenesis, and its absence results in meiotic arrest. We hypothesize that elevated TazPM spermatogonial apoptosis causes azoospermia and complete infertility.