Cooperativity of imprinted genes inactivated by acquired chromosome 20q deletions
Athar Aziz, … , Anne C. Ferguson-Smith, Anthony R. Green
Athar Aziz, … , Anne C. Ferguson-Smith, Anthony R. Green
Published April 1, 2013
Citation Information: J Clin Invest. 2013;123(5):2169-2182. https://doi.org/10.1172/JCI66113.
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Research Article Oncology

Cooperativity of imprinted genes inactivated by acquired chromosome 20q deletions

Abstract

Large regions of recurrent genomic loss are common in cancers; however, with a few well-characterized exceptions, how they contribute to tumor pathogenesis remains largely obscure. Here we identified primate-restricted imprinting of a gene cluster on chromosome 20 in the region commonly deleted in chronic myeloid malignancies. We showed that a single heterozygous 20q deletion consistently resulted in the complete loss of expression of the imprinted genes L3MBTL1 and SGK2, indicative of a pathogenetic role for loss of the active paternally inherited locus. Concomitant loss of both L3MBTL1 and SGK2 dysregulated erythropoiesis and megakaryopoiesis, 2 lineages commonly affected in chronic myeloid malignancies, with distinct consequences in each lineage. We demonstrated that L3MBTL1 and SGK2 collaborated in the transcriptional regulation of MYC by influencing different aspects of chromatin structure. L3MBTL1 is known to regulate nucleosomal compaction, and we here showed that SGK2 inactivated BRG1, a key ATP-dependent helicase within the SWI/SNF complex that regulates nucleosomal positioning. These results demonstrate a link between an imprinted gene cluster and malignancy, reveal a new pathogenetic mechanism associated with acquired regions of genomic loss, and underline the complex molecular and cellular consequences of “simple” cancer-associated chromosome deletions.

Authors

Athar Aziz, E. Joanna Baxter, Carol Edwards, Clara Yujing Cheong, Mitsuteru Ito, Anthony Bench, Rebecca Kelley, Yvonne Silber, Philip A. Beer, Keefe Chng, Marilyn B. Renfree, Kirsten McEwen, Dionne Gray, Jyoti Nangalia, Ghulam J. Mufti, Eva Hellstrom-Lindberg, Jean-Jacques Kiladjian, Mary Frances McMullin, Peter J. Campbell, Anne C. Ferguson-Smith, Anthony R. Green

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Figure 6

Coordinated silencing of L3MBTL1 and SGK2 increases proliferation of early erythroid progenitors.

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Coordinated silencing of L3MBTL1 and SGK2 increases proliferation of ear...
(A) Biphasic erythroid culture of CD34+ cells. (B) In vitro cell count after shRNA-mediated knockdown of L3MBTL1, SGK2, L3MBTL1 and SGK2 together, or scrambled control. Error bars indicate SEM of 5 independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001 versus scrambled control. (C) Hemin-induced erythroid differentiation of HNT-34 cells after retroviral (RV) infection. FACS analysis of hemin-induced GPA expression is also shown, summarized as MFI of GPA in 3 independent experiments. EV, empty vector. Error bars indicate SEM. ***P < 0.001 versus empty vector. (D) Erythroid differentiation of 20q deletion clones obtained from patient 13. Single-cell clones were grown in erythroid conditions from CD34+ cells retrovirally infected with L3MBTL1, SGK2, L3MBTL1 and SGK2 together, or empty vector. Shown are representative 20q deletion clones and MFI of GPA expression in 20q deletion clones (n = 39 [empty vector]; 37 [L3MBTL1]; 27 [SGK2]; 21 [L3MBTL1 and SGK2 together]). ***P < 0.001 versus empty vector. (E) LTC-IC assay of lentivirus infected cord blood CD34+ cells. CFC, colony-forming cell. The number of colony-forming cells after 5 weeks is also shown. Error bars indicate SEM of 3 independent experiments. (F) Competitive reconstituted mice were analyzed for 16 weeks for peripheral blood mononuclear cell donor/competitor ratios. CD45.2+ donors — with shRNA-mediated knockdown of murine (m-) L3mbtl1, Sgk2, L3mbtl1 and Sgk2 together, or scrambled control — were competed with equal numbers of CD45.1+CD45.2+ F1 competitors (n = 5) and injected into CD45.1+ hosts.