Gabriella Martyn

All Publications

• Phenotypic screen for oxygen consumption rate identifies an anti-cancer naphthoquinone that induces mitochondrial oxidative stress. Redox biology Byrne, F. L., Olzomer, E. M., Marriott, G. R., Quek, L. E., Katen, A., Su, J., Nelson, M. E., Hart-Smith, G., Larance, M., Sebesfi, V. F., Cuff, J., Martyn, G. E., Childress, E., Alexopoulos, S. J., Poon, I. K., Faux, M. C., Burgess, A. W., Reid, G., McCarroll, J. A., Santos, W. L., Quinlan, K. G., Turner, N., Fazakerley, D. J., Kumar, N., Hoehn, K. L. 2020; 28: 101374

  Abstract

  A hallmark of cancer cells is their ability to reprogram nutrient metabolism. Thus, disruption to this phenotype is a potential avenue for anti-cancer therapy. Herein we used a phenotypic chemical library screening approach to identify molecules that disrupted nutrient metabolism (by increasing cellular oxygen consumption rate) and were toxic to cancer cells. From this screen we discovered a 1,4-Naphthoquinone (referred to as BH10) that is toxic to a broad range of cancer cell types. BH10 has improved cancer-selective toxicity compared to doxorubicin, 17-AAG, vitamin K3, and other known anti-cancer quinones. BH10 increases glucose oxidation via both mitochondrial and pentose phosphate pathways, decreases glycolysis, lowers GSH:GSSG and NAPDH/NAPD+ ratios exclusively in cancer cells, and induces necrosis. BH10 targets mitochondrial redox defence as evidenced by increased mitochondrial peroxiredoxin 3 oxidation and decreased mitochondrial aconitase activity, without changes in markers of cytosolic or nuclear damage. Over-expression of mitochondria-targeted catalase protects cells from BH10-mediated toxicity, while the thioredoxin reductase inhibitor auranofin synergistically enhances BH10-induced peroxiredoxin 3 oxidation and cytotoxicity. Overall, BH10 represents a 1,4-Naphthoquinone with an improved cancer-selective cytotoxicity profile via its mitochondrial specificity.

  View details for DOI 10.1016/j.redox.2019.101374

  View details for PubMedID 31743887

  View details for PubMedCentralID PMC6861633

• A natural regulatory mutation in the proximal promoter elevates fetal globin expression by creating a de novo GATA1 site. Blood Martyn, G. E., Wienert, B., Kurita, R., Nakamura, Y., Quinlan, K. G., Crossley, M. 2019; 133 (8): 852-856

  Abstract

  β-hemoglobinopathies, such as sickle cell disease and β-thalassemia, result from mutations in the adult β-globin gene. Reactivating the developmentally silenced fetal γ-globin gene elevates fetal hemoglobin levels and ameliorates symptoms of β-hemoglobinopathies. The continued expression of fetal γ-globin into adulthood occurs naturally in a genetic condition termed hereditary persistence of fetal hemoglobin (HPFH). Point mutations in the fetal γ-globin proximal promoter can cause HPFH. The -113A>G HPFH mutation falls within the -115 cluster of HPFH mutations, a binding site for the fetal globin repressor BCL11A. We demonstrate that the -113A>G HPFH mutation, unlike other mutations in the cluster, does not disrupt BCL11A binding but rather creates a de novo binding site for the transcriptional activator GATA1. Introduction of the -113A>G HPFH mutation into erythroid cells using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) system increases GATA1 binding and elevates fetal globin levels. These results reveal the mechanism by which the -113A>G HPFH mutation elevates fetal globin and demonstrate the sensitivity of the fetal globin promoter to point mutations that often disrupt repressor binding sites but here create a de novo site for an erythroid activator.

  View details for DOI 10.1182/blood-2018-07-863951

  View details for PubMedID 30617196

• Wake-up Sleepy Gene: Reactivating Fetal Globin for β-Hemoglobinopathies. Trends in genetics : TIG Wienert, B., Martyn, G. E., Funnell, A. P., Quinlan, K. G., Crossley, M. 2018; 34 (12): 927-940

  Abstract

  Disorders in hemoglobin (hemoglobinopathies) were the first monogenic diseases to be characterized and remain among the most common and best understood genetic conditions. Moreover, the study of the β-globin locus provides a textbook example of developmental gene regulation. The fetal γ-globin genes (HBG1/HBG2) are ordinarily silenced around birth, whereupon their expression is replaced by the adult β-globin genes (HBB primarily and HBD). Over 50 years ago it was recognized that mutations that cause lifelong persistence of fetal γ-globin expression ameliorate the debilitating effects of mutations in β-globin. Since then, research has focused on therapeutically reactivating the fetal γ-globin genes. Here, we summarize recent discoveries, focusing on the influence of genome editing technologies, including CRISPR-Cas9, and emerging gene therapy approaches.

  View details for DOI 10.1016/j.tig.2018.09.004

  View details for PubMedID 30287096

• Natural regulatory mutations elevate the fetal globin gene via disruption of BCL11A or ZBTB7A binding. Nature genetics Martyn, G. E., Wienert, B., Yang, L., Shah, M., Norton, L. J., Burdach, J., Kurita, R., Nakamura, Y., Pearson, R. C., Funnell, A. P., Quinlan, K. G., Crossley, M. 2018; 50 (4): 498-503

  Abstract

  β-hemoglobinopathies such as sickle cell disease (SCD) and β-thalassemia result from mutations in the adult HBB (β-globin) gene. Reactivating the developmentally silenced fetal HBG1 and HBG2 (γ-globin) genes is a therapeutic goal for treating SCD and β-thalassemia 1 . Some forms of hereditary persistence of fetal hemoglobin (HPFH), a rare benign condition in which individuals express the γ-globin gene throughout adulthood, are caused by point mutations in the γ-globin gene promoter at regions residing ~115 and 200 bp upstream of the transcription start site. We found that the major fetal globin gene repressors BCL11A and ZBTB7A (also known as LRF) directly bound to the sites at -115 and -200 bp, respectively. Furthermore, introduction of naturally occurring HPFH-associated mutations into erythroid cells by CRISPR-Cas9 disrupted repressor binding and raised γ-globin gene expression. These findings clarify how these HPFH-associated mutations operate and demonstrate that BCL11A and ZBTB7A are major direct repressors of the fetal globin gene.

  View details for DOI 10.1038/s41588-018-0085-0

  View details for PubMedID 29610478

• KLF1 drives the expression of fetal hemoglobin in British HPFH. Blood Wienert, B., Martyn, G. E., Kurita, R., Nakamura, Y., Quinlan, K. G., Crossley, M. 2017; 130 (6): 803-807

  Abstract

  β-Hemoglobinopathies are among the most common single-locus inherited diseases. In this condition, high fetal hemoglobin (HbF) levels have been found to be beneficial, and boosting HbF expression is seen as an attractive therapy. Naturally occurring mutations in the fetal globin promoter can result in high HbF persisting into adulthood in a benign condition known as hereditary persistence of fetal hemoglobin (HPFH). Individuals with one form of HPFH, British HPFH, carry a T to C substitution at position -198 of the fetal globin gene promoter. These individuals exhibit HbF levels of up to 20%, enough to ameliorate the symptoms of β-hemoglobinopathies. Here, we use clustered regularly interspaced short palindromic repeat-mediated genome editing to introduce the -198 substitution into human erythroid HUDEP-2 cells and show that this mutation is sufficient to substantially elevate expression of HbF. We also examined the molecular mechanism underlying the increase in fetal globin expression. Through a combination of in vitro and in vivo studies, we demonstrate that the mutation creates a de novo binding site for the important erythroid gene activator Krüppel-like factor 1 (KLF1/erythroid KLF). Our results indicate that introducing this single naturally occurring mutation leads to significantly boosted HbF levels.

  View details for DOI 10.1182/blood-2017-02-767400

  View details for PubMedID 28659276

• The regulation of human globin promoters by CCAAT box elements and the recruitment of NF-Y. Biochimica et biophysica acta. Gene regulatory mechanisms Martyn, G. E., Quinlan, K. G., Crossley, M. 2017; 1860 (5): 525-536

  Abstract

  CCAAT boxes are motifs found within the proximal promoter of many genes, including the human globin genes. The highly conserved nature of CCAAT box motifs within the promoter region of both α-like and β-like globin genes emphasises the functional importance of the CCAAT sequence in globin gene regulation. Mutations within the β-globin CCAAT box result in β-thalassaemia, while mutations within the distal γ-globin CCAAT box cause the Hereditary Persistence of Foetal Haemoglobin, a benign condition which results in continued γ-globin expression during adult life. Understanding the transcriptional regulation of the globin genes is of particular interest, as reactivating the foetal γ-globin gene alleviates the symptoms of β-thalassaemia and sickle cell anaemia. NF-Y is considered to be the primary activating transcription factor which binds to globin CCAAT box motifs. Here we review recruitment of NF-Y to globin CCAAT boxes and the role NF-Y plays in regulating globin gene expression. This article is part of a Special Issue entitled: Nuclear Factor Y in Development and Disease, edited by Prof. Roberto Mantovani.

  View details for DOI 10.1016/j.bbagrm.2016.10.002

  View details for PubMedID 27718361

• Transcription factors LRF and BCL11A independently repress expression of fetal hemoglobin. Science (New York, N.Y.) Masuda, T., Wang, X., Maeda, M., Canver, M. C., Sher, F., Funnell, A. P., Fisher, C., Suciu, M., Martyn, G. E., Norton, L. J., Zhu, C., Kurita, R., Nakamura, Y., Xu, J., Higgs, D. R., Crossley, M., Bauer, D. E., Orkin, S. H., Kharchenko, P. V., Maeda, T. 2016; 351 (6270): 285-9

  Abstract

  Genes encoding human β-type globin undergo a developmental switch from embryonic to fetal to adult-type expression. Mutations in the adult form cause inherited hemoglobinopathies or globin disorders, including sickle cell disease and thalassemia. Some experimental results have suggested that these diseases could be treated by induction of fetal-type hemoglobin (HbF). However, the mechanisms that repress HbF in adults remain unclear. We found that the LRF/ZBTB7A transcription factor occupies fetal γ-globin genes and maintains the nucleosome density necessary for γ-globin gene silencing in adults, and that LRF confers its repressive activity through a NuRD repressor complex independent of the fetal globin repressor BCL11A. Our study may provide additional opportunities for therapeutic targeting in the treatment of hemoglobinopathies.

  View details for DOI 10.1126/science.aad3312

  View details for PubMedID 26816381

  View details for PubMedCentralID PMC4778394

• Differential regulation of the α-globin locus by Krüppel-like Factor 3 in erythroid and non-erythroid cells. BMC molecular biology Funnell, A. P., Vernimmen, D., Lim, W. F., Mak, K. S., Wienert, B., Martyn, G. E., Artuz, C. M., Burdach, J., Quinlan, K. G., Higgs, D. R., Whitelaw, E., Pearson, R. C., Crossley, M. 2014; 15: 8

  Abstract

  Krüppel-like Factor 3 (KLF3) is a broadly expressed zinc-finger transcriptional repressor with diverse biological roles. During erythropoiesis, KLF3 acts as a feedback repressor of a set of genes that are activated by Krüppel-like Factor 1 (KLF1). Noting that KLF1 binds α-globin gene regulatory sequences during erythroid maturation, we sought to determine whether KLF3 also interacts with the α-globin locus to regulate transcription.We found that expression of a human transgenic α-globin reporter gene is markedly up-regulated in fetal and adult erythroid cells of Klf3-/- mice. Inspection of the mouse and human α-globin promoters revealed a number of canonical KLF-binding sites, and indeed, KLF3 was shown to bind to these regions both in vitro and in vivo. Despite these observations, we did not detect an increase in endogenous murine α-globin expression in Klf3-/- erythroid tissue. However, examination of murine embryonic fibroblasts lacking KLF3 revealed significant de-repression of α-globin gene expression. This suggests that KLF3 may contribute to the silencing of the α-globin locus in non-erythroid tissue. Moreover, ChIP-Seq analysis of murine fibroblasts demonstrated that across the locus, KLF3 does not occupy the promoter regions of the α-globin genes in these cells, but rather, binds to upstream, DNase hypersensitive regulatory regions.These findings reveal that the occupancy profile of KLF3 at the α-globin locus differs in erythroid and non-erythroid cells. In erythroid cells, KLF3 primarily binds to the promoters of the adult α-globin genes, but appears dispensable for normal transcriptional regulation. In non-erythroid cells, KLF3 distinctly binds to the HS-12 and HS-26 elements and plays a non-redundant, albeit modest, role in the silencing of α-globin expression.

  View details for DOI 10.1186/1471-2199-15-8

  View details for PubMedID 24885809

  View details for PubMedCentralID PMC4033687