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Glycolipids can be synthetized in deep eutectic solvents (DESs) as they possess low water content allowing a reversed lipase activity and thus enables ester formation. Based on this principle, honey can also serve as a media for glycolipid synthesis. Indeed, this supersaturated sugar solution is comparable in terms of physicochemical properties to the sugar-based DESs. Honey-based products being commercially available for therapeutic applications, it appears interesting to enhance its bioactivity. In the current work, we investigate if enriching medical grade honey with in situ enzymatically-synthetized glycolipids can improve the antimicrobial property of the mixture. The tested mixtures are composed of Manuka honey that is enriched with octanoate, decanoate, laurate, and myristate sugar esters, respectively dubbed GOH, GDH, GLH, and GMH. To characterize the bioactivity of those mixtures, first a qualitative screening using an agar well diffusion assay has been performed with methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Candida bombicola, Escherichia coli, and Pseudomonas putida which confirmed considerably enhanced susceptibility of these micro-organisms to the different glycolipid enriched honey mixtures. Then, a designed biosensor E. coli strain that displays a stress reporter system consisting of three stress-specific inducible, red, green, and blue fluorescent proteins which respectively translate to physiological stress, genotoxicity, and cytotoxicity was used. Bioactivity was, therefore, characterized, and a six-fold enhancement of the physiological stress that was caused by GOH compared to regular Manuka honey at a 1.6% (v/v) concentration was observed. An antibacterial agar well diffusion assay with E. coli was performed as well and demonstrated an improved inhibitory potential with GOH upon 20% (v/v) concentration.

Sustained ANKRD26 expression associated with germline ANKRD26 mutations causes Thrombocytopenia 2 (THC2), an inherited platelet disorder associated with leukemia predisposition. Some of those patients present also erythrocytosis and/or leukocytosis. Using multiple human-relevant in vitro models (cell lines, primary patient cells and patient-derived iPSCs) we demonstrate for the first time that ANKRD26 is expressed during the early steps of erythroid, megakaryocyte and granulocyte differentiation, and is necessary for progenitor proliferation. As differentiation progresses, ANKRD26 expression is progressively silenced, to complete the cellular maturation of the three myeloid lineages. In primary cells, abnormal ANKRD26 expression in committed progenitors directly impacts the proliferation/differentiation balance for these three cell types. We show that ANKRD26 interacts with and crucially modulates the activity of MPL, EPOR and G-CSFR, three homodimeric type I cytokine receptors that regulate blood cell production. Higher than normal levels of ANKRD26 prevent the receptor internalization, which leads to increased signaling and cytokine hypersensitivity. Altogether these findings show that ANKRD26 overexpression or the absence of its silencing during differentiation are responsible for myeloid blood cell abnormalities in THC2 patients.

Somatic mutations in the calreticulin (CALR) gene are associated with approximately 30% of essential thrombocythemia (ET) and primary myelofibrosis (PMF). CALR mutations, including the two most frequent 52 bp deletion (del52) and 5 bp insertion (ins5), induce a frameshift to the same alternative reading frame generating new C-terminal tails. In patients, del52 and ins5 induce two phenotypically distinct myeloproliferative neoplasms (MPNs). They are equally found in ET, but del52 is more frequent in PMF. We generated heterozygous and homozygous conditional inducible knock-in (KI) mice expressing a chimeric murine CALR del52 or ins5 with the human mutated C-terminal tail to investigate their pathogenic effects on hematopoiesis. Del52 induces greater phenotypic changes than ins5 including thrombocytosis, leukocytosis, splenomegaly, bone marrow hypocellularity, megakaryocytic lineage amplification, expansion and competitive advantage of the hematopoietic stem cell compartment. Homozygosity amplifies these features, suggesting a distinct contribution of homozygous clones to human MPNs. Moreover, homozygous del52 KI mice display features of a penetrant myelofibrosis-like disorder with extramedullary hematopoiesis linked to splenomegaly, megakaryocyte hyperplasia and the presence of reticulin fibers. Overall, modeling del52 and ins5 mutations in mice successfully recapitulates the differences in phenotypes observed in patients., Calreticulin del52 and ins5 mutations induce two phenotypically distinct myeloproliferative neoplasms in patients. Here the authors show that modeling these mutations in knock-in mice recapitulate the two diseases and highlight how they impact the different hematopoietic compartments.

National audience; Face au constat d’une hétérogénéité grandissante des savoir-faire et connaissances en informatique des étudiants à l’arrivée en première année, et le risque de son exacerbation dans le contexte du « nouveau bac », nous avons voulu expérimenter une approche pédagogique, qui permette une gestion de cette hétérogénéité tout en respectant les contraintes d’un emploi du temps homogène et un coût constant. Les actions menées s’articulent autour de 4 pôles : la constitution de groupes de niveau, avec une attention particulière portée sur les 2 niveaux extrêmes (renforcement et avancé/en autonomie), la mise en place de QCMs réguliers, l’utilisation ponctuelle de l’Apprentissage Par Problème (APP), et un auto-positionnement. L’expérimentation est encore en cours, mais déjà de premiers éléments permettent d’ouvrir les échanges.

Thrombocytopenia is a major side effect of a new class of anticancer agents that target histone deacetylase (HDAC). Their mechanism is poorly understood. Here, we show that HDAC6 inhibition and genetic knockdown lead to a strong decrease in human proplatelet formation (PPF). Unexpectedly, HDAC6 inhibition-induced tubulin hyperacetylation has no effect on PPF. The PPF decrease induced by HDAC6 inhibition is related to cortactin (CTTN) hyperacetylation associated with actin disorganization inducing important changes in the distribution of megakaryocyte (MK) organelles. CTTN silencing in human MKs phenocopies HDAC6 inactivation and knockdown leads to a strong PPF defect. This is rescued by forced expression of a deacetylated CTTN mimetic. Unexpectedly, unlike human-derived MKs, HDAC6 and CTTN are shown to be dispensable for mouse PPF in vitro and platelet production in vivo. Our results highlight an unexpected function of HDAC6–CTTN axis as a positive regulator of human but not mouse MK maturation., Histone deacetylase (HDAC) inhibitors, a class of cancer therapeutics, cause thrombocytopenia via an unknown mechanism. Here, the authors show that HDAC6 inhibition impairs proplatelet formation in human megakaryocytes, and show that this is linked to hyperacetylation of the actin-binding protein cortactin.

Frameshift mutations in the calreticulin (CALR) gene are present in 30% of essential thrombocythemia and myelofibrosis patients. The two most frequent mutations are CALR del52 (type 1, approximately 60%) and CALR ins5 (type 2, around 30%), but many other rarer mutations exist accounting each for less than 2% of all CALR mutations. Most of them are structurally classified as type 1-like and type 2-like CALR mutations according to the absence or presence of a residual wild-type calcium-binding motif and the modification of the alpha-helix structure. Yet, several key questions remain unanswered, especially the reason of such low frequencies of these other mutations. In an attempt to investigate specific pathogenic differences between type 1-like and type 2-like CALR mutations and del52 and ins5, we modeled two type 1-like (del34 and del46) and one type 2-like (del19) mutations in cell lines and in mice. All CALR mutants constitutively activate JAK2 and STAT5/3/1 in a similar way in the presence of the thrombopoietin receptor (MPL) and induced cytokine-independent cell growth but to a lesser extent with rare mutants over time. This correlates with reduced expression levels of rare CALR mutants compared to del52 and ins5. Lethally irradiated mice that were engrafted with bone marrow transduced with the different CALR mutations developed thrombocytosis, but to a much lesser extent with ins5 and the type 2-like CALR mutation. In contrast to type 2-like mice, type 1-like mice developed marked myelofibrosis and splenomegaly 10 months after engraftment. Similar to del52, type 1-like CALR mutations induced an expansion at an early stage of hematopoiesis compared to ins5 and type 2-like mutation. Thus, type 1-like and type 2-like CALR mutants structurally and functionally resemble del52 and ins5 mutants, respectively.

Introduction Primary and secondary myelofibrosis (MF) present the worst prognosis in the group of BCR-ABL-negative myeloproliferative neoplasms. Presently there is no really efficient therapy of myelofibrosis, except allogenic bone marrow transplantation. In PMF patients, the JAK inhibitors ruxolitinib and fedratinib do not significantly reduce the MF itself or the natural progression of the disease. This could be due to the absence of direct link between JAK2 signaling level and the development of MF. However, ruxolitinib only partially inhibits JAK2 signaling and a reactivation of JAK/STAT signaling through heterodimerization of JAK2 with other JAK may occur (Koppikar et al, Nature, 2012). Complete inhibition of JAK2 signaling would likely induce a profound anemia and thrombocytopenia and at long-term an aplastic anemia. It therefore remains of great interest to identify and inhibit specific downstream targets dysregulated by JAK2 activation that may be responsible of the MF to circumvent the absence of a specific JAK2V617F inhibitor. JAK2V617F mutation leads to the autonomous activation of homodimeric type 1 cytokine receptors and their downstream signaling that induces G1/S cell cycle transition by activating the cyclin-dependent kinases CDK4/6. Cdk6 loss in Jak2V617F KI mice delays the development of the MPN and increases mouse survival (Uras et al, Blood, 2019). We hypothesized that intensifying the JAK2V617F-mediated CDK4/6 increased activity could potentially accelerate the MF development, which is a late event in the Jak2V617F KI model. Our study aims to explore the role of CDK4/6 overactivation or inhibition in the disease and MF development. Methods Since p19INK4D is a cyclin dependent kinase inhibitor, which inhibits CDK4 and to a lesser extent CDK6 and which specifically regulate megakaryocyte (MK) cell cycle and the arrest of endomitosis, we established a pre-clinical MF model by crossing p19Ink4d knock-out (KO) mice with heterozygous inducible Jak2V617F KI mice to obtain p19Ink4d-/-/Jak2FLEXV617F/+SCL-Cre+/-mice called here KOKI mice. With this model, we studied the development of the myeloproliferative disorder. To prevent a MF development in this model, a CDK4/6 inhibitor Palbociclib was administered from 2 to 4 weeks post-Jak2V617F induction. Results In contrast to Jak2V617F (KI) mice that developed a severe MF, in both bone marrow and spleen, at 24 weeks post-Jak2V617F induction, all KOKI mice developed a grade I MF as early as 3 weeks after Jak2V617F induction that progressed to severe fibrosis at 8 weeks (grade III). KOKI mice were characterized by the rapid onset of an extramedullary hematopoiesis (EMH) and megakaryocytic hyperplasia in bone marrow and spleen. As MK are known to be a major source of TGF-β1 in the development of MF, we further focused on the MK lineage. At 1 week post-Jak2V617F induction, prior to MF development, the numbers of MK progenitors (MK-P) were markedly increased in the spleen of KOKI mice (11-fold) while only 3.9-fold increase was observed for KI mice as compared to WT littermates. A significant 2.6-fold increase in the number of MK in the spleen was only visible in KOKI mice, in accordance with splenomegaly and EMH. The analysis of mean ploidy level (>4N) revealed that it increased to 34.8N in KI, 43.7N in KO p19 and 59.4N in KOKI mice as compared to 19N in WT mice. Total TGF-β1 bone marrow levels were moderately elevated in KOKI mice, with a higher proportion of activated TGF-β1. Treatment of KOKI mice with a CDK4/6 inhibitor, Palbociclib, prevented the development of MF and markedly decreased the EMH, the abnormalities of the megakaryocyte differentiation including the ploidy level and the total and activated TGF-β1 levels. Conclusions Altogether, using a KOKI mouse model we show that the deregulation of CDK4/6 mainly in megakaryocytes is sufficient to induce a severe MF strongly suggesting that CDK4/6 inhibitors could be a very promising therapeutic issue for MF patients (Figure). Disclosure of Prior Presentation/Publication : The abstract will not have been presented and published between January 1, 2020 and December 5, 2020. Figure 1 Disclosures No relevant conflicts of interest to declare.

ω-Transaminases (ω-TAs) are important biocatalysts for the synthesis of active, chiral pharmaceutical ingredients containing amino groups, such as β-amino acids which are important in peptidomimetics and as building blocks for drugs. However, the application of ω-TAs is limited by the availability and stability of enzymes with high conversion rates. One strategy for the synthesis and optical resolution of β-phenylalanine and other important aromatic β-amino acids, is the biotransformation utilizing an ω-transaminase from Variovorax paradoxus. We designed variants of this ω-TA to gain higher process stability, based on predictions calculated using the FoldX software. We here report the first thermostabilization of a non-thermostable (S)-selective ω-TA via FoldX guided site directed mutagenesis. The melting point (Tm) of our best performing mutant was increased to 59.3°C, an increase of 4.0°C in comparison with the wild type enzyme, while the mutant fully retained its specific activity.

Introduction BCR-ABL-negative myeloproliferative neoplasms (MPNs) result from the transformation of a hematopoietic stem cell (HSC). Somatic mutations in the calreticulin (CALR) gene are associated with approximately 30% of essential thrombocythemia (ET) and primary myelofibrosis (PMF). All CALR mutations induce a frameshift to the same alternative reading frame generating a new C-terminal tail. The two most frequent CALR mutations are a 52 bp deletion (del52) or type 1 and a 5 bp insertion (ins5) or type 2. In patients, del52 and ins5 are equally found in ET but del52 is more frequent in PMF. In mouse retroviral model, del52 mice progress from ET to myelofibrosis (MF) while ins5 mice remain mostly with an ET. Methods In order to study the effect of endogenous levels of del52 and ins5 in hematopoiesis, we generated conditional knock-in (KI) mice expressing the murine CALR del52 or ins5 with the human mutated C-terminal tail under the control of a Scl-driven tamoxifen-inducible Cre recombinase (Scl-CreERT). We have also used Ubi-GFP transgenic mice to perform competitive engraftments. Results After tamoxifen-induction, both del52 and ins5 KI mice developed a rapid thrombocytosis, more severe in the homozygous than the heterozygous setting. In contrast, leukocytosis was observed only in homozygous setting. At similar zygosity, del52 induced a higher thrombocytosis compared to ins5. After 10 months of induction, both the bone marrow (BM) and the spleen of homozygous del52 KI mice and, to a much lower extent of homozygous ins5 KI mice, presented a significant increase in megakaryocytes (MKs) and in MK progenitors by flow cytometry. Von Willebrand factor staining showed that both del52 and ins5 homozygous mice displayed giant polylobulated MKs, associated with a similar increase in ploidy (mean ploidy 32N-33N). Heterozygous del52 presented also an increase ploidy of MK (mean of 25N) compared to controls (mean of 17N), whereas the MK ploidy of heterozygous ins5 mice was similar to control mice. The increase in number and size of MKs in homozygous del52 mice partially explained the significant decrease in BM cellularity and the splenomegaly. Moreover, we observed a decrease in BM erythroblasts and, in spleen, an increase in both erythroblast and granulocytic precursors together with a decrease in lymphocytes associated with a major disorganization of white pulp territories. Thus, the del52 homozygous KI mice developed features of a MF-like disease further illustrated by the presence of reticulin fibers stained with silver, mainly in spleen. Presence of fibrosis was not as pronounced in heterozygous del52 mice and more rarely observed in spleen of homozygous ins5 KI mice. In homozygous del52 KI mice, there was a significant amplification of the HSC compartment in both BM and spleen that was stronger than in homozygous ins5 mice. To study whether del52 and ins5 could provide a competitive advantage to HSCs, we performed BM transplantation with increasing percentages of non-induced homozygous del52 or ins5 cells with wild-type GFP+ cells into lethally-irradiated recipient mice. The homozygous del52 BM cells strongly competed wild-type hematopoiesis from an initial engraftment as low as 10% of mutated clones, reaching 100% in both blood myeloid cells and BM HSC compartments at 4 months. In contrast, out-competition of wild-type hematopoiesis by homozygous ins5 cells was slower, especially when less than 50% of mutated cells were initially engrafted suggesting that del52 provides a stronger advantage to the HSCs than ins5. Conclusion In conclusion, these results demonstrate that modeling CALRdel52 and ins5 mutations in mice can successfully recapitulate the differences in phenotype observed in patients, i.e del52 KI mice recapitulate an ET progressing to MF while ins5 KI mice only mimic an ET. This might be explained by a more profound effect of del52 than ins5 at the level of HSC. These KI mice offer solid in vivo models to investigate the mechanism of action of both types of mutations on HSCs and MKs and will be used to test new therapeutic approaches. Disclosures: No relevant conflicts of interest to declare. Disclosures Constantinescu: AlsaTech: Other: Co-Founde; Wiley & Sons: Other: Editor in Chief, Journal of Cellular and Molecular Medicine; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AgenDix GmbH: Other: Co-Founder, MyeloPro Research and Diagnostics.

The immune response in the fox (Vulpes vulpes), despite the success of the oral rabies vaccine is not well characterized, and specific immunological tools are needed. To investigate both the humoral and cellular immune response, we used ovalbumin (OVA) and cholera toxin B (CTB) as an antigenic model to set-up ELISA and ELISPOT antibodies secreting cells (ASC) assays in the fox model. Identification of antibodies that cross-react with fox immunoglobulin was performed by Western blot, and their use was adapted for both the ELISA and ELISPOT ASC assay. The humoral and cellular specific immune responses were assessed after intra-muscular or intra-nasal immunization. Intra-muscular immunization resulted in the development of both cellular and humoral anti-OVA and anti-CTB responses in peripheral blood mononuclear cells (PBMCs). Immunization via the intra-nasal route resulted in the development of a cellular and humoral response against CTB in PBMCs. This immune response was confirmed using splenocytes from immunized animals by ELISPOT assay at euthanasia. Females immunized via the intra-nasal route developed specific anti-CTB IgM, IgA and IgG in vaginal fluids after the initial boost (day 26) showing that mucosal immunization produces a vaginal immune response in foxes. These immunological tools developed here are now available to be adapted to other antigenic models to facilitate further immune studies in foxes.