Publications by authors named "Stanley C Lee"

7 Publications

  • Page 1 of 1

DNA methylation disruption reshapes the hematopoietic differentiation landscape.

Nat Genet 2020 04 23;52(4):378-387. Epub 2020 Mar 23.

New York Genome Center, New York, NY, USA.

Mutations in genes involved in DNA methylation (DNAme; for example, TET2 and DNMT3A) are frequently observed in hematological malignancies and clonal hematopoiesis. Applying single-cell sequencing to murine hematopoietic stem and progenitor cells, we observed that these mutations disrupt hematopoietic differentiation, causing opposite shifts in the frequencies of erythroid versus myelomonocytic progenitors following Tet2 or Dnmt3a loss. Notably, these shifts trace back to transcriptional priming skews in uncommitted hematopoietic stem cells. To reconcile genome-wide DNAme changes with specific erythroid versus myelomonocytic skews, we provide evidence in support of differential sensitivity of transcription factors due to biases in CpG enrichment in their binding motif. Single-cell transcriptomes with targeted genotyping showed similar skews in transcriptional priming of DNMT3A-mutated human clonal hematopoiesis bone marrow progenitors. These data show that DNAme shapes the topography of hematopoietic differentiation, and support a model in which genome-wide methylation changes are transduced to differentiation skews through biases in CpG enrichment of the transcription factor binding motif.
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http://dx.doi.org/10.1038/s41588-020-0595-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7216752PMC
April 2020

Mutations in spliceosome genes and therapeutic opportunities in myeloid malignancies.

Genes Chromosomes Cancer 2019 12 3;58(12):889-902. Epub 2019 Sep 3.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York.

Since the discovery of RNA splicing more than 40 years ago, our comprehension of the molecular events orchestrating constitutive and alternative splicing has greatly improved. Dysregulation of pre-mRNA splicing has been observed in many human diseases including neurodegenerative diseases and cancer. The recent identification of frequent somatic mutations in core components of the spliceosome in myeloid malignancies and functional analysis using model systems has advanced our knowledge of how splicing alterations contribute to disease pathogenesis. In this review, we summarize our current understanding on the mechanisms of how mutant splicing factors impact splicing and the resulting functional and pathophysiological consequences. We also review recent advances to develop novel therapeutic approaches targeting splicing catalysis and splicing regulatory proteins, and discuss emerging technologies using oligonucleotide-based therapies to modulate pathogenically spliced isoforms.
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http://dx.doi.org/10.1002/gcc.22784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6852509PMC
December 2019

Polycomb repressive complex 2 component Suz12 is required for hematopoietic stem cell function and lymphopoiesis.

Blood 2015 Jul 2;126(2):167-75. Epub 2015 Jun 2.

The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; Department of Medical Biology and.

Polycomb repressive complex 2 (PRC2) is a chromatin modifier that regulates stem cells in embryonic and adult tissues. Loss-of-function studies of PRC2 components have been complicated by early embryonic dependence on PRC2 activity and the partial functional redundancy of enhancer of zeste homolog 1 (Ezh1) and enhancer of zeste homolog 2 (Ezh2), which encode the enzymatic component of PRC2. Here, we investigated the role of PRC2 in hematopoiesis by conditional deletion of suppressor of zeste 12 protein homolog (Suz12), a core component of PRC2. Complete loss of Suz12 resulted in failure of hematopoiesis, both in the embryo and the adult, with a loss of maintenance of hematopoietic stem cells (HSCs). In contrast, partial loss of PRC2 enhanced HSC self-renewal. Although Suz12 was required for lymphoid development, deletion in individual blood cell lineages revealed that it was dispensable for the development of granulocytic, monocytic, and megakaryocytic cells. Collectively, these data reveal the multifaceted role of PRC2 in hematopoiesis, with divergent dose-dependent effects in HSC and distinct roles in maturing blood cells. Because PRC2 is a potential target for cancer therapy, the significant consequences of modest changes in PRC2 activity, as well as the cell and developmental stage-specific effects, will need to be carefully considered in any therapeutic context.
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http://dx.doi.org/10.1182/blood-2014-12-615898DOI Listing
July 2015

MOZ regulates B-cell progenitors and, consequently, Moz haploinsufficiency dramatically retards MYC-induced lymphoma development.

Blood 2015 Mar 20;125(12):1910-21. Epub 2015 Jan 20.

The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia; and Department of Medical Biology, and.

The histone acetyltransferase MOZ (MYST3, KAT6A) is the target of recurrent chromosomal translocations fusing the MOZ gene to CBP, p300, NCOA3, or TIF2 in particularly aggressive cases of acute myeloid leukemia. In this study, we report the role of wild-type MOZ in regulating B-cell progenitor proliferation and hematopoietic malignancy. In the Eμ-Myc model of aggressive pre-B/B-cell lymphoma, the loss of just one allele of Moz increased the median survival of mice by 3.9-fold. MOZ was required to maintain the proliferative capacity of B-cell progenitors, even in the presence of c-MYC overexpression, by directly maintaining the transcriptional activity of genes required for normal B-cell development. Hence, B-cell progenitor numbers were significantly reduced in Moz haploinsufficient animals. Interestingly, we find a significant overlap in genes regulated by MOZ, mixed lineage leukemia 1, and mixed lineage leukemia 1 cofactor menin. This includes Meis1, a TALE class homeobox transcription factor required for B-cell development, characteristically upregulated as a result of MLL1 translocations in leukemia. We demonstrate that MOZ localizes to the Meis1 locus in pre-B-cells and maintains Meis1 expression. Our results suggest that even partial inhibition of MOZ may reduce the proliferative capacity of MEIS1, and HOX-driven lymphoma and leukemia cells.
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http://dx.doi.org/10.1182/blood-2014-08-594655DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4440887PMC
March 2015

Polycomb repressive complex 2 (PRC2) suppresses Eμ-myc lymphoma.

Blood 2013 Oct 27;122(15):2654-63. Epub 2013 Aug 27.

The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia; and.

Deregulation of polycomb group complexes polycomb repressive complex 1 (PRC1) and 2 (PRC2) is associated with human cancers. Although inactivating mutations in PRC2-encoding genes EZH2, EED, and SUZ12 are present in T-cell acute lymphoblastic leukemia and in myeloid malignancies, gain-of-function mutations in EZH2 are frequently observed in B-cell lymphoma, implying disease-dependent effects of individual mutations. We show that, in contrast to PRC1, PRC2 is a tumor suppressor in Eµ-myc lymphomagenesis, because disease onset was accelerated by heterozygosity for Suz12 or by short hairpin RNA-mediated knockdown of Suz12 or Ezh2. Accelerated lymphomagenesis was associated with increased accumulation of B-lymphoid cells in the absence of effects on apoptosis or cell cycling. However, Suz12-deficient B-lymphoid progenitors exhibit enhanced serial clonogenicity. Thus, PRC2 normally restricts the self-renewal of B-lymphoid progenitors, the disruption of which contributes to lymphomagenesis. This finding provides new insight regarding the functional contribution of mutations in PRC2 in a range of leukemias.
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http://dx.doi.org/10.1182/blood-2013-02-484055DOI Listing
October 2013

Characterization of proteomic changes in cardiac mitochondria in streptozotocin-diabetic rats using iTRAQ™ isobaric tags.

Proteomics Clin Appl 2007 Jun;1(6):565-76

School of Biological Sciences and Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.

Diabetes now affects more than 5% of the world's population and heart failure is the most common cause of death amongst diabetic patients. Accumulating evidence supports a view that myocardial mitochondrial structural and functional changes are central to the onset of diabetic heart failure, but the exact nature of these changes at the proteomic level remains unclear.Here we report on proteomic changes in diabetic rat heart mitochondria following 120 days of streptozotocin-diabetes using the recently developed iTRAQ™ labeling method, which permits quantification of proteins directly from complex mixtures, bypassing the limitations associated with gel-based methods such as 2-DE. Of 252 unique proteins identified, 144 were represented in at least three of six individual paired experiments. Relative amounts of 65 proteins differed significantly between the groups, confirming that the cardiac mitochondrial proteome is indeed impacted by diabetes. The most significant changes were increased protein levels of enzymes involved in mitochondrial oxidation of long-chain fatty acids, which was also confirmed by enzyme assays, and decreased levels of multiple enzymes involved in oxidative phosphorylation and catabolism of short-chain fatty acids and branched-chain amino acids. We also found significant changes in levels of several enzymes linked to oxidative stress.
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http://dx.doi.org/10.1002/prca.200600831DOI Listing
June 2007

Involvement of TRP-like channels in the acute ischemic response of hippocampal CA1 neurons in brain slices.

Brain Res 2006 Mar 17;1077(1):187-99. Epub 2006 Feb 17.

Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 92-019 Auckland, New Zealand.

During a period of acute ischemia in vivo or oxygen-glucose deprivation (OGD) in vitro, CA1 neurons depolarize, swell and become overloaded with calcium. Our aim was to test the hypothesis that the initial responses to OGD are at least partly due to transient receptor potential (TRP) channel activation. As some TRP channels are temperature-sensitive, we also compared the effects of pharmacological blockade of the channels with the effects of reducing temperature. Acute hippocampal slices (350 mum) obtained from Wistar rats were submerged in ACSF at 36 degrees C. CA1 neurons were monitored electrophysiologically using extracellular, intracellular or whole-cell patch-clamp recordings. Cell swelling was assessed by recording changes in relative tissue resistance, and changes in intracellular calcium were measured after loading neurons with fura-2 dextran. Blockers of TRP channels (ruthenium red, La3+, Gd3+, 2-APB) or lowering temperature by 3 degrees C reduced responses to OGD. This included: (a) an increased delay to negative shifts of extracellular DC potential; (b) reduction in rate of the initial slow membrane depolarization, slower development of OGD-induced increase in cell input resistance and slower development of whole-cell inward current; (c) reduced tissue swelling; and (d) a smaller rise in intracellular calcium. Mild hypothermia (33 degrees C) and La3+ or Gd3+ (100 microM) showed an occlusion effect when delay to extracellular DC shifts was measured. Expression of TRPM2/TRPM7 (oxidative stress-sensitive) and TRPV3/TRPV4 (temperature-sensitive) channels was demonstrated in the CA1 subfield with RT-PCR. These results indicate that TRP or TRP-like channels are activated by cellular stress and contribute to ischemia-induced membrane depolarization, intracellular calcium accumulation and cell swelling. We also hypothesize that closing of some TRP channels (TRPV3 and/or TRPV4) by lowering temperature may be partly responsible for the neuroprotective effect of hypothermia.
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http://dx.doi.org/10.1016/j.brainres.2006.01.016DOI Listing
March 2006