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Summary T/myeloid mixed phenotype acute leukaemia (MPAL) is a rare aggressive acute leukaemia with poorly understood pathogenesis. Herein, we report two cases of T/myeloid MPAL harbouring BCL11B‐associated structural variants that activate TLX3 (TLX3::BCL11B‐TLX3‐activation) by genome sequencing and transcriptomic analyses. Both patients were young males with extramedullary involvement. Cooperative gene alterations characteristic of T/myeloid MPAL and T‐lymphoblastic leukaemia (T‐ALL) were detected. Both patients achieved initial remission following lineage‐matched ALL‐based therapy with one patient requiring a lineage‐switched myeloid‐based therapy. Our study is the first to demonstrate the clinicopathological and genomic features of TLX3::BCL11B‐TLX3‐activated T/myeloid MPAL and provide insights into leukaemogenesis. [ABSTRACT FROM AUTHOR]

Pancytopenia was detected significant for leukopenia (3.2 × 10 SP 9 sp /L) with an absolute neutrophil count of 0.26 × 10 SP 9 sp /L, thrombocytopenia (8 × 10 SP 9 sp /L), and a normocytic normochromic anaemia with a haemoglobin of 90 g/L. Given the concern for congenital bone marrow failure, a bone marrow evaluation was performed. A 19-week-old infant born at term from an uncomplicated pregnancy with a short postnatal hospital stay for anaemia requiring blood transfusion, and anaemia and neutropenia noted at 6 weeks of age, presented for follow up. ETHICS APPROVAL STATEMENT Ethics approval was not required for this image study. [Extracted from the article]

The coexpression of the MLL partial tandem duplication (PTD) and the FLT3 internal tandem duplication (ITD) mutations associate with a poor outcome in cytogenetically normal acute myeloid leukemia (AML). In mice, a double knock-in (dKI) of MIIPTD/wt and FIt3ITD/wt mutations induces spontaneous AML with an increase in DNA methyltransferases (Dnmt1, 3a, and 3b) and global DNA methylation index, thereby recapitulating its human AML counterpart. We determined that a regulator of Dnmts, miR-29b, is downregulated in bone marrow of dKI AML mice. Bortezomib exerted a dose-dependent increase in miR-29b expression in AML blasts ex vivo, followed by decreased Dnmts, reduced proliferation, and increased apoptosis. In vivo, bortezomib was not active against dKI AML, yet liposomal-encapsulated bortezomib, as a single agent, reversed downregulation of miR-29b in vivo and induced a long-term (90-day) disease-free remission in 80% of dKI AML mice that exhibited high leukemic burden at the start of therapy, yet showed no signs of relapse at autopsy. Taken together, these data support that liposomal bortezomib, as a single agent, eradicates MIIPTD/wt and FIt3ITD/wt AML in mouse and may represent a powerful and potentially curative approach to high-risk human disease. [ABSTRACT FROM AUTHOR]

The ubiquitously expressed G protein a-subunit Gsα is required for receptor-stimulated intracellular cAMP responses and is an important regulator of energy and glucose metabolism. We have generated skeletal muscle-specific Gsα-knockout (KO) mice (MG5KO) by mating Gsα-floxed mice with muscle creatine kinase-cre transgenic mice. MGsKO mice had normal body weight and composition, and their serum glucose, insulin, free fatty acid, and triglyceride levels were similar to that of controls. However, MGsKO mice were glucose intolerant despite the fact that insulin sensitivity and glucose-stimulated insulin secretion were normal, suggesting an insulin-independent mechanism. Isolated muscles from MGsKO mice had increased basal glucose uptake and normal responses to a stimulator of AMP-activated protein kinase (AMPK), which indicates that AMPK and its downstream pathways are intact. Compared with control mice, MG-sKO mice had reduced muscle mass with decreased cross-sectional area and force production. In addition, adult MGsKO mice showed an increased proportion of type I (slow-twitch, oxidative) fibers based on kinetic properties and myosin heavy chain isoforms, despite the fact that these muscles had reduced expression of peroxisome proliferator-activated receptor coactivator protein-1α (PGC- 1α) and reduced mitochondrial content and oxidative capacity. Therefore Gsα deficiency led to fast-to-slow fiber-type switching, which appeared to be dissociated from the expected change in oxidative capacity. MGsKO mice are a valuable model for future studies of the role of Gsα signaling pathways in skeletal muscle adaptation and their effects on whole body metabolism. [ABSTRACT FROM AUTHOR]

Summary Cis -regulatory elements (CREs) are commonly recognized by correlative chromatin features, yet the molecular composition of the vast majority of CREs in chromatin remains unknown. Here, we describe a CRISPR affinity purification in situ of regulatory elements (CAPTURE) approach to unbiasedly identify locus-specific chromatin-regulating protein complexes and long-range DNA interactions. Using an in vivo biotinylated nuclease-deficient Cas9 protein and sequence-specific guide RNAs, we show high-resolution and selective isolation of chromatin interactions at a single-copy genomic locus. Purification of human telomeres using CAPTURE identifies known and new telomeric factors. In situ capture of individual constituents of the enhancer cluster controlling human β-globin genes establishes evidence for composition-based hierarchical organization. Furthermore, unbiased analysis of chromatin interactions at disease-associated cis -elements and developmentally regulated super-enhancers reveals spatial features that causally control gene transcription. Thus, comprehensive and unbiased analysis of locus-specific regulatory composition provides mechanistic insight into genome structure and function in development and disease. [ABSTRACT FROM AUTHOR]