Ontogenic Changes in Hematopoietic Hierarchy Determine Pediatric Specificity and Disease Phenotype in Fusion Oncogene-Driven Myeloid Leukemia.

Fusion oncogenes are prevalent in several pediatric cancers, yet little is known about the specific associations between age and phenotype. We observed that fusion oncogenes, such as ETO2-GLIS2, are associated with acute megakaryoblastic or other myeloid leukemia subtypes in an age-dependent manner. Analysis of a novel inducible transgenic mouse model showed that ETO2-GLIS2 expression in fetal hematopoietic stem cells induced rapid megakaryoblastic leukemia whereas expression in adult bone marrow hematopoietic stem cells resulted in a shift toward myeloid transformation with a strikingly delayed in vivo leukemogenic potential. Chromatin accessibility and single-cell transcriptome analyses indicate ontogeny-dependent intrinsic and ETO2-GLIS2-induced differences in the activities of key transcription factors, including ERG, SPI1, GATA1, and CEBPA. Importantly, switching off the fusion oncogene restored terminal differentiation of the leukemic blasts. Together, these data show that aggressiveness and phenotypes in pediatric acute myeloid leukemia result from an ontogeny-related differential susceptibility to transformation by fusion oncogenes. SIGNIFICANCE: This work demonstrates that the clinical phenotype of pediatric acute myeloid leukemia is determined by ontogeny-dependent susceptibility for transformation by oncogenic fusion genes. The phenotype is maintained by potentially reversible alteration of key transcription factors, indicating that targeting of the fusions may overcome the differentiation blockage and revert the leukemic state.See related commentary by Cruz Hernandez and Vyas, p. 1653.This article is highlighted in the In This Issue feature, p. 1631

Differences in transcription patterns between induced pluripotent stem cells produced from the same germ layer are erased upon differentiation.

Little is known about differences between induced pluripotent stem cells produced from tissues originating from the same germ layer. We have generated human myoblast-derived iPS cells by retroviral transduction of human primary myoblasts with the OCT3/4, SOX2, KLF4 and MYC coding sequences and compared them to iPS produced from human primary fibroblasts. When cultivated in vitro, these iPS cells proved similar to human embryonic stem cells in terms of morphology, expression of embryonic stemness markers and gene promoter methylation patterns. Embryonic bodies were derived that expressed endodermal, mesodermal as well as ectodermal markers. A comparative analysis of transcription patterns revealed significant differences in the gene expression pattern between myoblast- and fibroblast-derived iPS cells. However, these differences were reduced in the mesenchymal stem cells derived from the two iPS cell types were compared

HIV-1 Tat protein induces DNA damage in human peripheral blood B-lymphocytes via mitochondrial ROS production

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Multilayer intraclonal heterogeneity in chronic myelomonocytic leukemia

International audienceThe functional diversity of cells that compose myeloid malignancies, i.e., the respective roles of genetic and epigenetic heterogeneity in this diversity, remains poorly understood. This question is addressed in chronic myelomonocytic leukemia, a myeloid neoplasm in which clinical diversity contrasts with limited genetic heterogeneity. To generate induced pluripotent stem cell clones, we reprogrammed CD34+ cells collected from a patient with a chronic myelomonocytic leukemia in which whole exome sequencing of peripheral blood monocyte DNA had identified 12 gene mutations, including a mutation in KDM6A and two heterozygous mutations in TET2 in the founding clone and a secondary KRAS(G12D) mutation. CD34+ cells from an age-matched healthy donor were also reprogrammed. We captured a part of the genetic heterogeneity observed in the patient, i.e. we analyzed five clones with two genetic backgrounds, without and with the KRAS(G12D) mutation. Hematopoietic differentiation of these clones recapitulated the main features of the patient's disease, including overproduction of granulomonocytes and dysmegakaryopoiesis. These analyses also disclosed significant discrepancies in the behavior of hematopoietic cells derived from induced pluripotent stem cell clones with similar genetic background, correlating with limited epigenetic changes. These analyses suggest that, beyond the coding mutations, several levels of intraclonal heterogeneity may participate in the yet unexplained clinical heterogeneity of the disease

HIV-1 Tat protein induces DNA damage in human peripheral blood B-lymphocytes via mitochondrial ROS production.

International audienc

Expression of myogenic markers.

<p>The indicated markers were analyzed in in differentiated parental cells (<b>A</b>), iPS cells (<b>B</b>) and MSC (<b>C</b>) belonging to the myoblast (grey bar) and fibroblast (white bar) lineages. The experiments were carried out in duplicate. *** P<0.001, * P<0.05. Data were extracted from the 44K+ Agilent transcriptome array and scaled.</p

Venn diagrams.

<p>A representation of the number of genes found upregulated in cells of the myogenic lineage (myo, miPS and mMSC) in comparison with fibroblasts (fibro). The total number of unique genes analyzed after preprocessing was 17,994 with adjusted p value<0.05.</p

Expression analysis of germ layer-specific markers.

<p>Expression patterns of (A) pluripotency, (B) mesoderm, (C) ectoderm and (D) endoderm markers, in parental (P1), myoblast-derived iPS (miPS1), miPS-derived embryonic body (EB1.D4 and EB1.D14) cells and MSC. Data are presented for individual samples. Y axis, expression levels normalized against β-actin expression.</p

Characterization of mMSC1 and mMSC2 surface antigens.

<p>The presence of CD29, CD44, CD73, CD105 and CD166 was detected by FACS analysis performed at passage 5.</p