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.
View: Text | PDF
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

×

Figure 7

Coordinated silencing of L3MBTL1 and SGK2 increases MYC transcription.

Options: View larger image (or click on image) Download as PowerPoint
Coordinated silencing of L3MBTL1 and SGK2 increases MYC transcription. ...
(A) qPCR analysis of MYC, RUNX1, and CCNE1 transcript levels in cord blood–derived erythroid cells after lentiviral knockdown of L3MBTL1, SGK2, L3MBTL1 and SGK2 together, or scrambled shRNA control (n = 6). *P < 0.05, ***P < 0.001 versus scrambled control. (B–D) ChIP PCR analysis for binding of the indicated proteins at the MYC promoter (H3K4me3, L3MBTL1, and BRG1) or transcription start site (ph-S2-PolII) in erythroid cells infected with lentiviral shRNA as in A. Representative experiments are shown. Similar results were obtained in 2 further independent experiments (Supplemental Figure 7, B–E). Mean of duplicate qPCR measurements are shown. (E) Western blot from HNT-34 cells after immunoprecipitation with antibody against BRG1. Cells were transfected with retroviral expression constructs as indicated. (F and G) HNT-34 cells infected with retrovirus expressing SGK2 or control and analyzed for binding of BRG1 (as described above) to the MYC promoter (F) or MYC transcript levels (G). *P < 0.05 versus control. (H) Expression of MYC (qPCR) in single-cell clones grown in erythroid conditions. CD34+ cells from patient 13 were infected with retroviruses expressing L3MBTL1 and/or SGK2 as indicated. Each data point represents 1 clone; horizontal lines denote means. n = 10 in each case. ***P < 0.001 versus empty vector–containing 20q deletion clones. (I) Collaboration between L3MBTL1 and SGK2.