Abner Louissaint

Coordinated Interaction of Neurogenesis and Angiogenesis in the Adult Songbird Brain

Neurogenesis proceeds throughout life in the higher vocal center (HVC) of the adult songbird neostriatum. Testosterone induces neuronal addition and endothelial division in HVC. We asked if testosterone-induced angiogenesis might contribute importantly to HVC neuronal recruitment. Testosterone upregulated both VEGF and its endothelial receptor, VEGF-R2/Quek1/KDR, in HVC. This yielded a burst in local HVC angiogenesis. FACS-isolated HVC endothelial cells produced BDNF in a testosterone-dependent manner. In vivo, HVC BDNF rose by the third week after testosterone, lagging by over a week the rise in VEGF and VEGF-R2. In situ hybridization revealed that much of this induced BDNF mRNA was endothelial. In vivo, both angiogenesis and neuronal addition to HVC were substantially diminished by inhibition of VEGF-R2 tyrosine kinase. These findings suggest a causal interaction between testosterone-induced angiogenesis and neurogenesis in the adult forebrain.

High-yield selection and extraction of two promoter-defined phenotypes of neural stem cells from the fetal human brain

Neural stem and precursor cells reside in the ventricular lining of the fetal forebrain, and may provide a cellular substrate for brain repair. To selectively identify and extract these cells, we infected dissociated fetal human brain cells with adenoviruses bearing the gene for green fluorescence protein (GFP), placed under the control of enhancer/promoters for two genes (nestin and musashi1) that are expressed in uncommitted neuroepithelial cells. The cells were then sorted by fluorescence-activated cell sorting (FACS) on the basis of E/nestin- or P/musashi1-driven GFP expression. Both P/musashi1:hGFP- and E/nestin:EGFP-sorted cells were multipotent: limiting dilution with clonal expansion as neurospheres, in tandem with retroviral lineage analysis and xenograft to E17 and P0-2 rat forebrain, revealed that each phenotype was able to both self-renew and co-generate neurons and glia. Thus, fluorescent genes placed under the control of early neural promoters allow neural stem cells to be specifically targeted, isolated, and substantially enriched from the fetal human brain.

A targeted mutational landscape of angioimmunoblastic T-cell lymphoma

The genetics of angioimmunoblastic T-cell lymphoma (AITL) are very poorly understood. We defined the mutational landscape of AITL across 219 genes in 85 cases from the United States and Europe. We identified ≥2 mutations in 34 genes, nearly all of which were not previously implicated in AITL. These included loss-of-function mutations in TP53 (n = 4), ETV6 (n = 3), CCND3 (n = 2), and EP300 (n = 5), as well as gain-of-function mutations in JAK2 (n = 2) and STAT3 (n = 4). TET2 was mutated in 65 (76%) AITLs, including 43 that harbored 2 or 3 TET2 mutations. DNMT3A mutations occurred in 28 (33%) AITLs; 100% of these also harbored TET2 mutations (P < .0001). Seventeen AITLs harbored IDH2 R172 substitutions, including 15 with TET2 mutations. In summary, AITL is characterized by high frequencies of overlapping mutations in epigenetic modifiers and targetable mutations in a subset of cases.

Physiologic Medium Rewires Cellular Metabolism and Reveals Uric Acid as an Endogenous Inhibitor of UMP Synthase

A complex interplay of environmental factors impacts the metabolism of human cells, but neither traditional culture media nor mouse plasma mimic the metabolite composition of human plasma. Here, we developed a culture medium with polar metabolite concentrations comparable to those of human plasma (human plasma-like medium [HPLM]). Culture in HPLM, relative to that in traditional media, had widespread effects on cellular metabolism, including on the metabolome, redox state, and glucose utilization. Among the most prominent was an inhibition of de novo pyrimidine synthesis-an effect traced to uric acid, which is 10-fold higher in the blood of humans than of mice and other non-primates. We find that uric acid directly inhibits uridine monophosphate synthase (UMPS) and consequently reduces the sensitivity of cancer cells to the chemotherapeutic agent 5-fluorouracil. Thus, media that better recapitulates the composition of human plasma reveals unforeseen metabolic wiring and regulation, suggesting that HPLM should be of broad utility.

Infectious mononucleosis mimicking lymphoma: distinguishing morphological and immunophenotypic features

The diagnosis of infectious mononucleosis (acute Epstein–Barr virus (EBV) infection) is usually made on the basis of clinical and laboratory findings. However, an atypical clinical presentation occasionally results in a lymph node or tonsillar biopsy. The morphological features of EBV-infected lymphoid tissue can easily mimic lymphoma. Furthermore, the immunophenotype of the immunoblasts has not been well characterized. To assess the morphological spectrum of acute EBV infection and the utility of immunohistochemistry in diagnosing difficult cases that resemble lymphoma, we reviewed 18 cases of acute EBV infection submitted in consultation to our institution with an initial diagnosis of/or suspicion for lymphoma. Patients included nine male and nine female individuals with a median age of 18 years (range 9–69). Biopsies were obtained from lymph nodes (3/18) or Waldeyers ring (15/18). Infectious mononucleosis was confirmed by monospot or serological assays in 72% of cases (13/18). All cases featured architectural distortion by a polymorphous infiltrate with an immunoblastic proliferation, sometimes forming sheets. Reed–Sternberg-like cells were present in 8/18 (44%) of the cases. Infiltrates were often accompanied by necrosis (10/18) and mucosal ulceration (6/15). The majority of immunoblasts in all cases were CD20+ B cells with a post-germinal center immunophenotype (strongly positive for MUM1/IRF4 (18/18), CD10− (18/18 negative) and BCL-6− (16/18 negative; 2/18 faint BCL-6 expression in <10% of immunoblasts)). Immunoblasts showed variable weak expression of BCL-2 and polyclonal expression of κ and λ immunoglobulin light chains in 81% cases. Reed–Sternberg-like cells in 8/8 cases were CD30+, CD15−, BOB.1+ and OCT-2+. In conclusion, an atypical lymphoid infiltrate with numerous MUM1+, CD10−, BCL-6− immunoblasts should raise the suspicion of a reactive process, such as infectious mononucleosis, and warrants additional consideration before a diagnosis of lymphoma is made.

High rate of unnecessary thymectomy and its cause. Can computed tomography distinguish thymoma, lymphoma, thymic hyperplasia, and thymic cysts?

PURPOSE To determine the non-therapeutic thymectomy rate in a recent six-year consecutive thymectomy cohort, the etiology of these unnecessary thymectomies, and the differentiating CT features of thymoma, lymphoma, thymic hyperplasia, and thymic cysts. MATERIALS AND METHODS Electronic data base query of all thymectomies performed at the Massachusetts General Hospital from 2006 to 2012 yielded 160 thymectomy cases, 124 of which had available imaging. The non-therapeutic thymectomy rate (includes thymectomy for lymphoma and benign disease) was calculated. Preoperative clinical and CT imaging features were assessed by review of the in-house electronic medical record by 2 thoracic surgeons and 2 pathology-blinded radiologists, respectively. RESULTS The non-therapeutic thymectomy rate of 43.8% (70/160) was largely secondary to concern for thymoma and was comprised of lymphoma (54.3%, 38/70), thymic bed cysts (24.3%, 17/70), thymic hyperplasia (17.1%, 12/70), and reactive or atrophic tissue (4.3%, 3/70). Among these four lesions, there were significant differences in location with respect to midline, morphology, circumscription, homogeneity of attenuation, fatty intercalation, coexistent lymphadenopathy, overt pericardial invasion, and mass effect (p<0.001). True thymic cysts ranged in attenuation from -20 to 58Hounsfield units (HU), with a mean attenuation of 23HU. CONCLUSION The high rate of unnecessary thymectomy was due to misinterpretation of thymic cysts, thymic hyperplasia, and lymphoma as thymoma on chest CT. This study demonstrates differentiating features between thymoma, lymphoma, thymic hyperplasia, and thymic cysts on chest CT which may help triage more patients away from thymectomy toward less invasive and non-invasive means of diagnosis and thereby lower the non-therapeutic thymectomy rate.

Myeloid neoplasms secondary to plasma cell myeloma: an intrinsic predisposition or therapy-related phenomenon? A clinicopathologic study of 41 cases and correlation of cytogenetic features with treatment regimens.

We describe 41 cases of myeloid neoplasms (MNs) secondary to plasma cell myeloma (PCM). The types of MN included myelodysplastic syndrome (MDS) in 34 (82.9%), acute myeloid leukemia (AML) in 4 (9.8%), and myeloproliferative neoplasm (MPN) or MDS/MPN in 3 (7.3%) cases. The latency from treatment to diagnosis of MN ranged from 9 to 384 months, with a median of 60 months. Of 37 cases with cytogenetic studies, complex abnormalities were detected in 22 (59.5%), -5(q)/-7(q) in 4 (10.8%), other abnormalities in 8 (21.6%), and normal karyotype in 3 (8.1%) cases. Complex abnormalities and -5(q)/-7(q) correlated directly with multiple chemotherapeutic regimens, particularly with combined melphalan/cyclophosphamide. Moreover, the features of cytogenetic abnormalities in our series were significantly different from those with concomitant PCM/MN who had significantly lower complex abnormalities. The latency, skewed proportion of MDS, and bias toward complex cytogenetic abnormalities/unbalanced aberrations of chromosomes 5/7 suggested an alkylating mutagenic effect on pathogenesis of secondary MN. Kaplan-Meier survival analysis demonstrated a median survival of 19 months, which was better than that for therapy-related (t)-MDS/AML. In contrast to t-MDS, the survival in our patients appeared to depend on subtypes of MDS as seen in de novo diseases.

IκB Kinase β (IKBKB) Mutations in Lymphomas That Constitutively Activate Canonical Nuclear Factor κB (NFκB) Signaling

Background: How IκB kinaseβ K171E and K171T mutations mediate lymphomagenesis is not known. Results: We performed biochemical, molecular modeling and TALEN-based knockin studies on wild-type and mutant IKKβ. Conclusion: Mutant IKKβ molecules are constitutively active in an activation-loop phosphorylation-independent manner. Significance: These results have broad implications for the function of positively charged residues in all activation loop-dependent kinases. Somatic mutations altering lysine 171 of the IKBKB gene that encodes (IKKβ), the critical activating kinase in canonical (NFκB) signaling, have been described in splenic marginal zone lymphomas and multiple myeloma. Lysine 171 forms part of a cationic pocket that interacts with the activation loop phosphate in the activated wild type kinase. We show here that K171E IKKβ and K171T IKKβ represent kinases that are constitutively active even in the absence of activation loop phosphorylation. Predictive modeling and biochemical studies establish why mutations in a positively charged residue in the cationic pocket of an activation loop phosphorylation-dependent kinase result in constitutive activation. Transcription activator-like effector nuclease-based knock-in mutagenesis provides evidence from a B lymphoid context that K171E IKKβ contributes to lymphomagenesis.

Crystal analyser-based X-ray phase contrast imaging in the dark field: implementation and evaluation using excised tissue specimens.

AbstractObjectivesWe demonstrate the soft tissue discrimination capability of X-ray dark-field imaging (XDFI) using a variety of human tissue specimens.MethodsThe experimental setup for XDFI comprises an X-ray source, an asymmetrically cut Bragg-type monochromator-collimator (MC), a Laue-case angle analyser (LAA) and a CCD camera. The specimen is placed between the MC and the LAA. For the light source, we used the beamline BL14C on a 2.5-GeV storage ring in the KEK Photon Factory, Tsukuba, Japan.ResultsIn the eye specimen, phase contrast images from XDFI were able to discriminate soft-tissue structures, such as the iris, separated by aqueous humour on both sides, which have nearly equal absorption. Superiority of XDFI in imaging soft tissue was further demonstrated with a diseased iliac artery containing atherosclerotic plaque and breast samples with benign and malignant tumours. XDFI on breast tumours discriminated between the normal and diseased terminal duct lobular unit and between invasive and in-situ cancer.ConclusionsX-ray phase, as detected by XDFI, has superior contrast over absorption for soft tissue processes such as atherosclerotic plaque and breast cancer.Key points• X-ray dark field imaging (XDFI) can dramatically increase sensitivity of phase detection. • XDFI can provide enhanced soft tissue discrimination. • With XDFI, abnormal anatomy can be visualised with high spatial/contrast resolution.

Aleukemic cutaneous myeloid sarcoma.

Aleukemic cutaneous myeloid sarcoma (CMS) represents an important yet rare entity denoting the presence of a cutaneous myeloid leukemic infiltrate without concurrent peripheral blood or bone marrow disease. The clinicopathologic diagnosis remains elusive due to isolated skin findings and variable immunostaining. Cytogenetic and molecular findings have infrequently been reported.