Clinical characterization of the mutational landscape of 24,639 real-world samples from patients with myeloid malignancies.

Myeloid neoplasms represent a broad spectrum of hematological disorders for which somatic mutation status in key driver genes is important for diagnosis, prognosis and treatment. Here we summarize the findings of a targeted, next generation sequencing laboratory developed test in 24,639 clinical myeloid samples. Data were analyzed comprehensively and as part of individual cohorts specific to acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and myeloproliferative neoplasms (MPN).

RNA Sequencing Identifies Novel NRG1 Fusions in Solid Tumors that Lack Co-Occurring Oncogenic Drivers.

NRG1 gene fusions are rare, therapeutically relevant, oncogenic drivers that occur across solid tumor types. To understand the landscape of NRG1 gene fusions, 4397 solid tumor formalin-fixed, paraffin-embedded samples consecutively tested by comprehensive genomic and immune profiling during standard care were analyzed. Nineteen NRG1 fusions were found in 17 unique patients, across multiple tumor types, including non-small-cell lung (n = 7), breast (n = 2), colorectal (n = 3), esophageal (n = 2), ovarian (n = 1), pancreatic (n = 1), and unknown primary (n = 1) carcinomas, with a cumulative incidence of 0.

Leukaemia hijacks a neural mechanism to invade the central nervous system.

Acute lymphoblastic leukaemia (ALL) has a marked propensity to metastasize to the central nervous system (CNS). In contrast to brain metastases from solid tumours, metastases of ALL seldom involve the parenchyma but are isolated to the leptomeninges, which is an infrequent site for carcinomatous invasion. Although metastasis to the CNS occurs across all subtypes of ALL, a unifying mechanism for invasion has not yet been determined.

Formin 2 Regulates Lysosomal Degradation of Wnt-Associated β-Catenin in Neural Progenitors.

Although neural progenitor proliferation along the ventricular zone is regulated by β-catenin through Wnt signaling, the cytoskeletal mechanisms that regulate expression and localization of these proteins are not well understood. Our prior studies have shown that loss of the actin-binding Filamin A (FlnA) and actin-nucleating protein Formin 2 (Fmn2) impairs endocytosis of low-density-lipoprotein-receptor-related protein 6 (Lrp6), thereby disrupting β-catenin activation, resulting in decreased brain size. Here, we report that activated RhoA-GTPase disengages Fmn2 N- to C-terminal binding to promote Fmn2 activation and redistribution into lysosomal vesicles.

Afadin controls cell polarization and mitotic spindle orientation in developing cortical radial glia.

Background: In developing tissues, cell polarity and tissue architecture play essential roles in the regulation of proliferation and differentiation. During cerebral cortical development, adherens junctions link highly polarized radial glial cells in a neurogenic niche that controls their behavior. How adherens junctions regulate radial glial cell polarity and/or differentiation in mammalian cortical development is poorly understood.

Filamin A- and formin 2-dependent endocytosis regulates proliferation via the canonical Wnt pathway.

Actin-associated proteins regulate multiple cellular processes, including proliferation and differentiation, but the molecular mechanisms underlying these processes are unclear. Here, we report that the actin-binding protein filamin A (FlnA) physically interacts with the actin-nucleating protein formin 2 (Fmn2). Loss of FlnA and Fmn2 impairs proliferation, thereby generating multiple embryonic phenotypes, including microcephaly.

The role of adherens junctions in the developing neocortex.

The disproportional enlargement of the neocortex through evolution has been instrumental in the success of vertebrates, in particular mammals. The neocortex is a multilayered sheet of neurons generated from a simple proliferative neuroepithelium through a myriad of mechanisms with substantial evolutionary conservation. This developing neuroepithelium is populated by progenitors that can generate additional progenitors as well as post-mitotic neurons.

Clonality assessment of cutaneous B-cell lymphoid proliferations: a comparison of flow cytometry immunophenotyping, molecular studies, and immunohistochemistry/in situ hybridization and review of the literature.

Cutaneous lymphoid infiltrates are diagnostically challenging. Although ancillary techniques to assess clonality can help distinguish between reactive lymphoid hyperplasia and lymphoma, one of the most widely used techniques in hematopathology, flow cytometry immunophenotyping (FCI), has not been routinely applied to skin specimens. We performed FCI on 73 skin specimens from 67 patients clinically suspected of having a cutaneous B-cell lymphoma (CBCL) and compared the results with those obtained from immunoglobulin heavy chain (IGH) gene molecular studies (58 cases, primarily by polymerase chain reaction) and either immunohistochemistry (IHC) or in situ hybridization to evaluate for light chain restriction (22 and 2 cases, respectively).

AKT activation by N-cadherin regulates beta-catenin signaling and neuronal differentiation during cortical development.

Background: During cerebral cortical development, neural precursor-precursor interactions in the ventricular zone neurogenic niche coordinate signaling pathways that regulate proliferation and differentiation. Previous studies with shRNA knockdown approaches indicated that N-cadherin adhesion between cortical precursors regulates β-catenin signaling, but the underlying mechanisms remained poorly understood.

Results: Here, with conditional knockout approaches, we find further supporting evidence that N-cadherin maintains β-catenin signaling during cortical development.

Expansion of a clonal CD8+CD57+ large granular lymphocyte population after autologous stem cell transplant in multiple myeloma.

Clonal expansions of large granular lymphocytes (LGLs) have been identified in patients following stem cell transplants and may represent posttransplant LGL leukemias or reactive immune responses. To differentiate between these 2 possibilities, we assessed peripheral blood and bone marrow of patients with myeloma after autologous stem cell transplant. All patients examined shortly after autologous stem cell transplant had significant increases in the LGLs in the peripheral blood and bone marrow (71% of lymphocytes) as compared with controls (39%).

Early posttransplant lymphoproliferative disease: clinicopathologic features and correlation with mTOR signaling pathway activation.

Early posttransplant lymphoproliferative disorders (EPTLDs) represent the first changes in posttransplant lymphoproliferative disorders (PTLDs) morphologic spectrum. EPTLD data are available mostly from case reports and series that include other types of PTLD. Fifteen EPTLDs were reviewed retrospectively.

Hierarchical clustering of gene expression patterns in the Eomes + lineage of excitatory neurons during early neocortical development.

Background: Cortical neurons display dynamic patterns of gene expression during the coincident processes of differentiation and migration through the developing cerebrum. To identify genes selectively expressed by the Eomes + (Tbr2) lineage of excitatory cortical neurons, GFP-expressing cells from Tg(Eomes::eGFP) Gsat embryos were isolated to > 99% purity and profiled.

Results: We report the identification, validation and spatial grouping of genes selectively expressed within the Eomes + cortical excitatory neuron lineage during early cortical development.

Rapid quantitative detection of the T315I mutation in patients with chronic myelogenous leukemia.

Acquired resistance to tyrosine kinase inhibitors (TKIs) in the treatment of chronic myelogenous leukemia (CML) is frequently caused by point mutations in the ABL kinase domain of the BCR-ABL fusion gene. The T315I mutation is the most common mutation found in the kinase domain and leads to complete resistance to existing TKIs. Sensitive and specific approaches for detecting this mutation in patient specimens can provide valuable information to guide treatment decisions and monitor their effectiveness.

Distribution of CD133 reveals glioma stem cells self-renew through symmetric and asymmetric cell divisions.

Malignant gliomas contain a population of self-renewing tumorigenic stem-like cells; however, it remains unclear how these glioma stem cells (GSCs) self-renew or generate cellular diversity at the single-cell level. Asymmetric cell division is a proposed mechanism to maintain cancer stem cells, yet the modes of cell division that GSCs utilize remain undetermined. Here, we used single-cell analyses to evaluate the cell division behavior of GSCs.

Clinical, morphologic, immunophenotypic, and molecular cytogenetic assessment of CD4-/CD8-γδ T-cell large granular lymphocytic leukemia.

γδ T-cell large granular lymphocytic (T-LGL) leukemia of the CD4-/CD8- subtype is rare, and data are limited in the literature. This study evaluated the clinical, morphologic, immunophenotypic, and molecular cytogenetic features of 7 cases of CD4-/CD8- γδ T-LGL leukemia. Although this variant shares several clinical and morphologic features with the more common T-LGL leukemias, the incidences of autoimmune hemolytic anemia and pure red cell aplasia are higher.

Beta-catenin signaling negatively regulates intermediate progenitor population numbers in the developing cortex.

Intermediate progenitor cells constitute a second proliferative cell type in the developing mammalian cerebral cortex. Little is known about the factors that govern the production of intermediate progenitors. Although persistent expression of stabilized beta-catenin was found to delay the maturation of radial glial progenitors into intermediate progenitors, the relationship between beta-catenin signaling and intermediate progenitors remains poorly understood.

Cortical neural precursors inhibit their own differentiation via N-cadherin maintenance of beta-catenin signaling.

Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development.

Nestin reporter transgene labels multiple central nervous system precursor cells.

Embryonic neuroepithelia and adult subventricular zone (SVZ) stem and progenitor cells express nestin. We characterized a transgenic line that expresses enhanced green fluorescent protein (eGFP) specified to neural tissue by the second intronic enhancer of the nestin promoter that had several novel features. During embryogenesis, the dorsal telencephalon contained many and the ventral telencephalon few eGFP+ cells.

Beta-catenin signaling levels in progenitors influence the laminar cell fates of projection neurons.

The mechanisms underlying the timing of the laminar fate decisions during cortical neurogenesis remain poorly understood. Here we show that beta-catenin signaling in cortical neural precursors can regulate the laminar fate of their daughters. In ventricular zone neural precursors, beta-catenin signaling is higher when deep-layer neurons are being generated and lower when upper-layer neurons are being generated.

Activity of the beta-catenin phosphodestruction complex at cell-cell contacts is enhanced by cadherin-based adhesion.

It is well established that cadherin protein levels impact canonical Wnt signaling through binding and sequestering beta-catenin (beta-cat) from T-cell factor family transcription factors. Whether changes in intercellular adhesion can affect beta-cat signaling and the mechanism through which this occurs has remained unresolved. We show that axin, APC2, GSK-3beta and N-terminally phosphorylated forms of beta-cat can localize to cell-cell contacts in a complex that is molecularly distinct from the cadherin-catenin adhesive complex.

Focal reduction of alphaE-catenin causes premature differentiation and reduction of beta-catenin signaling during cortical development.

Cerebral cortical precursor cells reside in a neuroepithelial cell layer that regulates their proliferation and differentiation. Global disruptions in epithelial architecture induced by loss of the adherens junction component alphaE-catenin lead to hyperproliferation. Here we show that cell autonomous reduction of alphaE-catenin in the background of normal precursors in vivo causes cells to prematurely exit the cell cycle, differentiate into neurons, and migrate to the cortical plate, while normal neighboring precursors are unaffected.

Wnt/beta-catenin signaling in cerebral cortical development.

The cerebral cortex is the multilayered sheet of neurons that underlies our highest cognitive abilities. Canonical Wnt/beta-catenin signaling has well-known activities in tissue patterning in regulating rostral-caudal and medial-lateral patterning in the developing cortex. In addition, recent studies suggest that Wnt/beta-catenin signaling also plays important roles in establishing the radial inside to outside organization of the cerebral cortex.

A top-NOTCH way to make astrocytes.

During mammalian nervous system development, neural precursor cells first generate neurons and then switch to astrocytes. In this issue of Developmental Cell, Namihira and colleagues show that committed neuronal precursors and young neurons promote the production of astrocytes from the remaining neural precursors by activating Notch signaling, leading to demethylation and upregulation of astrocyte-specific genes via cytokine-mediated JAK-STAT signaling.

A novel transgenic mouse model of fetal encephalization and craniofacial development.

There are surprisingly few experimental models of neural growth and cranial integration. This, and the dearth of information regarding fetal brain development, detracts from a mechanistic understanding of cranial integration and its relevance to the ontogenetic and interspecific patterning of the form of the skull. To address this shortcoming, our research uses transgenic mice expressing a stabilized form of β-catenin to isolate the effects of encephalization on the development of the basi- and neuro-cranium.