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Browsing by Author "Sun, Zejin"
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Item 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 MedicineCardiomyopathy 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.Item FANCA safeguards interphase and mitosis during hematopoiesis in vivo(Elsevier, 2015-12) Abdul-Sater, Zahi; Cerabona, Donna; Potchanant, Elizabeth Sierra; Sun, Zejin; Enzor, Rikki; He, Ying; Robertson, Kent; Goebel, W. Scott; Nalepa, Grzegorz; Department of Pediatrics, IU School of MedicineThe Fanconi anemia (FA/BRCA) signaling network controls multiple genome-housekeeping checkpoints, from interphase DNA repair to mitosis. The in vivo role of abnormal cell division in FA remains unknown. Here, we quantified the origins of genomic instability in FA patients and mice in vivo and ex vivo. We found that both mitotic errors and interphase DNA damage significantly contribute to genomic instability during FA-deficient hematopoiesis and in nonhematopoietic human and murine FA primary cells. Super-resolution microscopy coupled with functional assays revealed that FANCA shuttles to the pericentriolar material to regulate spindle assembly at mitotic entry. Loss of FA signaling rendered cells hypersensitive to spindle chemotherapeutics and allowed escape from the chemotherapy-induced spindle assembly checkpoint. In support of these findings, direct comparison of DNA crosslinking and anti-mitotic chemotherapeutics in primary FANCA-/- cells revealed genomic instability originating through divergent cell cycle checkpoint aberrations. Our data indicate that FA/BRCA signaling functions as an in vivo gatekeeper of genomic integrity throughout interphase and mitosis, which may have implications for future targeted therapies in FA and FA-deficient cancers.Item INPP5E Preserves Genomic Stability through Regulation of Mitosis(American Society for Microbiology, 2017-03-15) Sierra Potchanant, Elizabeth A.; Cerabona, Donna; Sater, Zahi Abdul; He, Ying; Sun, Zejin; Gehlhausen, Jeff; Nalepa, Grzegorz; Department of Pediatrics, IU School of MedicineThe partially understood phosphoinositide signaling cascade regulates multiple aspects of cellular metabolism. Previous studies revealed that INPP5E, the inositol polyphosphate-5-phosphatase that is mutated in the developmental disorders Joubert and MORM syndromes, is essential for the function of the primary cilium and maintenance of phosphoinositide balance in nondividing cells. Here, we report that INPP5E further contributes to cellular homeostasis by regulating cell division. We found that silencing or genetic knockout of INPP5E in human and murine cells impairs the spindle assembly checkpoint, centrosome and spindle function, and maintenance of chromosomal integrity. Consistent with a cell cycle regulatory role, we found that INPP5E expression is cell cycle dependent, peaking at mitotic entry. INPP5E localizes to centrosomes, chromosomes, and kinetochores in early mitosis and shuttles to the midzone spindle at mitotic exit. Our findings identify the previously unknown, essential role of INPP5E in mitosis and prevention of aneuploidy, providing a new perspective on the function of this phosphoinositide phosphatase in health and development.Item Leukemia and chromosomal instability in aged Fancc-/- mice(Elsevier, 2016-05) Cerabona, Donna; Sun, Zejin; Nalepa, Grzegorz; Department of Pediatrics, IU School of MedicineFanconi anemia (FA) is an inherited disorder of genomic instability associated with high risk of myelodysplasia and acute myeloid leukemia (AML). Young mice deficient in FA core complex genes do not naturally develop cancer, hampering preclinical studies on malignant hematopoiesis in FA. Here we describe that aging Fancc(-/-) mice are prone to genomically unstable AML and other hematologic neoplasms. We report that aneuploidy precedes malignant transformation during Fancc(-/-) hematopoiesis. Our observations reveal that Fancc(-/-) mice develop hematopoietic chromosomal instability followed by leukemia in an age-dependent manner, recapitulating the clinical phenotype of human FA and providing a proof of concept for future development of preclinical models of FA-associated leukemogenesis.Item Leukemia and chromosomal instability in aged Fancc−/− mice(Elsevier, 2016-05) Cerabona, Donna; Sun, Zejin; Nalepa, Grzegorz; Department of Pediatrics, IU School of MedicineFanconi anemia (FA) is an inherited disorder of genomic instability associated with high risk of myelodysplasia and acute myeloid leukemia (AML). Young mice deficient in FA core complex genes do not naturally develop cancer, hampering preclinical studies on malignant hematopoiesis in FA. Here we describe that aging Fancc−/− mice are prone to genomically unstable AML and other hematologic neoplasms. We report that aneuploidy precedes malignant transformation during Fancc−/− hematopoiesis. Our observations reveal that Fancc−/− mice develop hematopoietic chromosomal instability followed by leukemia in an age-dependent manner, recapitulating the clinical phenotype of human FA and providing a proof of concept for future development of preclinical models of FA-associated leukemogenesis.Item 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 MedicineFanconi 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.Item Pak2 regulates hematopoietic progenitor cell proliferation, survival and differentiation(Wiley, 2015-05) Zeng, Yi; Broxmeyer, Hal E.; Chitteti, Brahmananda Reddy; Park, Su-Jung; Hahn, Seongmin; Cooper, Scott; Sun, Zejin; Jiang, Li; Yang, XianLin; Yuan, Jin; Kosoff, Rachelle; Sandusky, George; Srour, Edward F.; Chernoff, Jonathan; Clapp, Wade; Department of Medicine, IU School of Medicinep21-Activated kinase 2 (Pak2), a serine/threonine kinase, has been previously shown to be essential for hematopoietic stem cell (HSC) engraftment. However, Pak2 modulation of long-term hematopoiesis and lineage commitment remain unreported. Using a conditional Pak2 knockout mouse model, we found that disruption of Pak2 in HSCs induced profound leukopenia and a mild macrocytic anemia. Although loss of Pak2 in HSCs leads to less efficient short- and long-term competitive hematopoiesis than wild-type cells, it does not affect HSC self-renewal per se. Pak2 disruption decreased the survival and proliferation of multicytokine stimulated immature progenitors. Loss of Pak2 skewed lineage differentiation toward granulocytopoiesis and monocytopoiesis in mice as evidenced by (a) a three- to sixfold increase in the percentage of peripheral blood granulocytes and a significant increase in the percentage of granulocyte-monocyte progenitors in mice transplanted with Pak2-disrupted bone marrow (BM); (b)Pak2-disrupted BM and c-kit(+) cells yielded higher numbers of more mature subsets of granulocyte-monocyte colonies and polymorphonuclear neutrophils, respectively, when cultured in the presence of granulocyte-macrophage colony-stimulating factor. Pak2 disruption resulted, respectively, in decreased and increased gene expression of transcription factors JunB and c-Myc, which may suggest underlying mechanisms by which Pak2 regulates granulocyte-monocyte lineage commitment. Furthermore, Pak2 disruption led to (a) higher percentage of CD4(+) CD8(+) double positive T cells and lower percentages of CD4(+) CD8(-) or CD4(-) CD8(+) single positive T cells in thymus and (b) decreased numbers of mature B cells and increased numbers of Pre-Pro B cells in BM, suggesting defects in lymphopoiesis.