Phenotypic and Genetic Characterization of Temperature-Induced Mutagenesis and Mortality in Cupriavidus metallidurans

Cupriavidus metallidurans strains display a decreased viability when incubated in rich medium at a temperature of 37°C compared to their normal growth temperature of 30°C, a phenomenon coined “temperature-induced mortality and mutagenesis” (TIMM). To scrutinize this aberrant phenotype further, the contributions of specific inducers and protective agents were determined. Different growth media, including lysogeny broth (LB) and Schatz, and components, including casamino acids, in particular amino acids (proline, cysteine, glycine, glutamine, leucine, histidine and phenylalanine) and ammonium, were found to induce TIMM at 37°C. Sorbitol was found to counteract TIMM. Furthermore, although TIMM is well conserved within the C. metallidurans species, multiple and strain-specific TIMM inducers exist. Twenty-nine percent of the TIMM survivors inherited resistance to TIMM. Whole-genome sequencing of two resistant derivatives revealed an important role of an uncharacterized oxidoreductase, indicating putative metabolic poisoning when grown in high-concentration nitrogen-containing media at 37°C.

Overexpression of the Aspergillus fumigatus Small GTPase, RsrA, Promotes Polarity Establishment during Germination

Cell polarization comprises highly controlled processes and occurs in most eukaryotic organisms. In yeast, the processes of budding, mating and filamentation require coordinated mechanisms leading to polarized growth. Filamentous fungi, such as Aspergillus fumigatus, are an extreme example of cell polarization, essential for both vegetative and pathogenic growth. A major regulator of polarized growth in yeast is the small GTPase Rsr1, which is essential for bud-site selection. Here, we show that deletion of the putative A. fumigatus ortholog, rsrA, causes only a modest reduction of growth rate and delay in germ tube emergence. In contrast, overexpression of rsrA results in a morphogenesis defect, characterized by a significant delay in polarity establishment followed by the establishment of multiple growth axes. This aberrant phenotype is reversed when rsrA expression levels are decreased, suggesting that correct regulation of RsrA activity is crucial for accurate patterning of polarity establishment. Despite this finding, deletion or overexpression of rsrA resulted in no changes of A. fumigatus virulence attributes in a mouse model of invasive aspergillosis. Additional mutational analyses revealed that RsrA cooperates genetically with the small GTPase, RasA, to support A. fumigatus viability.

Identification of Prognostic Immunophenotypes at First Diagnosis in Patients with Acute Myeloid Leukemia (AML) By a Standardized Multicolor Flow Cytometry (MFC) Panel Originally Designed to Detect Measurable Residual Disease (MRD) at Follow-up

Aims In AML, several risk factors obtained at first diagnosis (FD) have been reported to be associated with shorter RFS and OS. The primary prognostic relevance of multicolour flow cytometry (MFC) has been a matter of debate for years. During follow-up (FU), the prognostic relevance of MRD as detected by MFC is less controversial and MFC is recommended in particular (but not exclusive) for those patients (pts) with no reliable genetic marker. We thought to evaluate the prognostic value at FD of a recently established antigen panel and a corresponding analysis strategy, which had been originally developed for MRD-detection. Methods Based on an 8-colour antibody panel (CD45, CD34, CD117, HLA-DR, CD13, CD33, CD7, CD56), we have developed a hierarchical gating strategy with mainly fixed gates. That allows to detect MRD with a high level of standardization and inter-observer reliability (Röhnert M., et al. 25th EHA 2020). Four distinct categories of aberrations (deficiency of CD13 or CD33, cross-lineage expression of CD7 or CD56) detectable on at least 10% of the myeloid blast population were used to define aberrant phenotypes termed leukemia associated immunophenotypes (LAIP) at FD. These categories were also chosen to define MRD during FU. MRDpos by LAIP was defined as the (re-)occurrence of an aberrant category already detectable at FD, while MRDpos by DfN (different from normal) was defined by the de-novo detection of an aberrant category at FU. The prognostic value of the aberrant phenotypes at FD was examined in a cohort of 528 pts. In 122 pts, we further analysed MRD (LAIP/DfN) after completion of intensive induction chemotherapy (IT). Consolidation therapy consisted of allogeneic hematopoietic stem cell transplantation (n=77) or chemotherapy (n=45). The bone marrow samples were measured centrally and analysed independently by three different investigators. Results The probability to achieve a complete remission (CR) varied between the different aberrant phenotypes (LAIP) at FD. Compared to pts without aberrant phenotype (CR rate=68%, n/N=100/148), pts with CD56only (the sole aberrant category was a cross-lineage expression of CD56=only) had a significantly lower CR rate (46%, n/N=15/33, p=0.019). The other exclusive aberrant categories did not significantly influence CR rates compared to pts without LAIP: CD13only (75%, n/N=53/71, p=0.286), CD33only (64%, n/N=59/97, p=0.28) and CD7only (62%, n/N=31/50, p=0.472). In pts with possibly co-occurring aberrant categories (compound aberrant phenotype=comp), the CR rate was significantly higher in CD13comp compared to all other patients (75% vs. 64%, 107/143 vs. 246/385, p=0.018). The other compound aberrancies did not significantly influence CR rates: CD33comp (63% vs. 68%, 90/143 vs. 263/385, p=0.244), CD7comp (66% vs. 67%, 72/109 vs. 281/419, p=0.842) and CD56comp (68% vs. 66%, 84/123 vs. 269/405, p=0.699). Regarding overall survival (OS), just CD56only retained its statistical significance (HR 2.5, CI 1.4-4.7, p=0.004). CD13comp was associated with favourable outcome but without reaching statistical significance (HR 0.7, CI 0.4-1.0, p=0.059). In the cohort of pts with MRD assessment at the end of IT, 67% were classified as responders (CR n=62, CRi n=19) and 33% as non-responders (PR n=14, refractory n=26) by cytomorphology. By MFC, 71% of these pts were classified as MRDpos (n=51/36 responders/non-responders) and 29% as MRDneg (n=30/4). MRDpos was defined by LAIP only (23%), DfN only (44%) or concordantly by LAIP+DfN (33%). OS of MRDneg pts was significantly longer compared to MRDpos patients (HR 4.3, CI 1.0-18.1, p=0.033). Conclusions Using our analysis approach originally developed for MRD monitoring, MFC could provide additional information for initial risk stratification. The presence of an isolated cross-lineage expression of CD56 (CD56only) was associated with a lower CR rate and significant shorter OS. In contrast, CD13comp (CD13 deficiency ± other aberrant categories) was associated with a higher CR rate and prolonged OS. Furthermore, MRDpos as defined by the combined LAIP/DfN strategy provided significant prognostic information. The presented results are currently refined and validated using genetically defined subcategories. The approach has to be confirmed in an independent cohort of pts. Disclosures Rollig: Amgen, Astellas, BMS, Daiichi Sankyo, Janssen, Roche: Consultancy; Abbvie, Novartis, Pfizer: Consultancy, Research Funding. Buecklein:Pfizer: Consultancy; Novartis: Research Funding; Celgene: Research Funding; Amgen: Consultancy; Gilead: Consultancy, Research Funding. Subklewe:Novartis: Consultancy, Research Funding; Janssen: Consultancy; Roche AG: Consultancy, Research Funding; AMGEN: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Morphosys: Research Funding; Seattle Genetics: Research Funding; Pfizer: Consultancy, Honoraria; Gilead Sciences: Consultancy, Honoraria, Research Funding. Krause:Pfizer: Honoraria; MSD: Honoraria; Takeda: Honoraria; Gilead: Other: Travel Support; Celgene: Other: Travel Support; Siemens: Research Funding. Schlenk:Roche: Research Funding; AstraZeneca: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; PharmaMar: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accomodations, Expenses, Research Funding, Speakers Bureau; Novartis: Speakers Bureau.

Aberrant Phenotypes in Acute Myeloid Leukemia and Its Relationship with Prognosis and Survival: A Systematic Review and Meta-Analysis

Background: The aim of this review was to evaluate the influence of aberrant phenotypes in prognosis and survival in acute myeloid leukemia (AML) patients by multiparametric flow cytometry. Materials and Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a review of PubMed, Scopus, Science Direct and Web of Science was carried out through 1998 to 2016, conducted by two reviewers independently, evaluating titles, abstracts and full-texts of the selected studies. Results: Ten studies were included on this review, in which the aberrant phenotype expression of 17 markers were detected in AML patients. From these, 11 aberrant phenotypes were associated with prognosis, which eight had shown negative impact on prognosis: CD7, CD56, CD15, CD2, CD3, CD90low, CD123high, CD117high, and three others were associated with good prognosis: CD19, CD98high and CD117+/CD15+. Meta-analysis showed that aberrant expression of CD56 as a poor prognostic marker with unfavorable outcomes is implicated in decreased overall survival in AML patients in 28 months (95% CI: 0.62 to 0.92). Conclusion: This was observed when there was association between CD56 expression and other prognostic factors, influencing on patients’ management care and treatment.

De novo mutations in FBRSL1 cause a novel recognizable malformation and intellectual disability syndrome

We report truncating de novo variants in specific exons of FBRSL1 in three unrelated children with an overlapping syndromic phenotype with respiratory insufficiency, postnatal growth restriction, microcephaly, global developmental delay and other malformations. The function of FBRSL1 is largely unknown. Interestingly, mutations in the FBRSL1 paralogue AUTS2 lead to an intellectual disability syndrome (AUTS2 syndrome). We determined human FBRSL1 transcripts and describe protein-coding forms by Western blot analysis as well as the cellular localization by immunocytochemistry stainings. All detected mutations affect the two short N-terminal isoforms, which show a ubiquitous expression in fetal tissues. Next, we performed a Fbrsl1 knockdown in Xenopus laevis embryos to explore the role of Fbrsl1 during development and detected craniofacial abnormalities and a disturbance in neurite outgrowth. The aberrant phenotype in Xenopus laevis embryos could be rescued with a human N-terminal isoform, while the long isoform and the N-terminal isoform containing the mutation p.Gln163* isolated from a patient could not rescue the craniofacial defects caused by Fbrsl1 depletion. Based on these data, we propose that the disruption of the validated N-terminal isoforms of FBRSL1 at critical timepoints during embryogenesis leads to a hitherto undescribed complex neurodevelopmental syndrome.

NCAM2 Regulates Dendritic and Axonal Differentiation through the Cytoskeletal Proteins MAP2 and 14-3-3

Neural cell adhesion molecule 2 (NCAM2) is involved in the development and plasticity of the olfactory system. Genetic data have implicated the NCAM2 gene in neurodevelopmental disorders including Down syndrome and autism, although its role in cortical development is unknown. Here, we show that while overexpression of NCAM2 in hippocampal neurons leads to minor alterations, its downregulation severely compromises dendritic architecture, leading to an aberrant phenotype including shorter dendritic trees, retraction of dendrites, and emergence of numerous somatic neurites. Further, our data reveal alterations in the axonal tree and deficits in neuronal polarization. In vivo studies confirm the phenotype and reveal an unexpected role for NCAM2 in cortical migration. Proteomic and cell biology experiments show that NCAM2 molecules exert their functions through a protein complex with the cytoskeletal-associated proteins MAP2 and 14-3-3γ and ζ. We provide evidence that NCAM2 depletion results in destabilization of the microtubular network and reduced MAP2 signal. Our results demonstrate a role for NCAM2 in dendritic formation and maintenance, and in neural polarization and migration, through interaction of NCAM2 with microtubule-associated proteins.

VE-PTP participates in vasculogenic mimicry by preventing autophagic degradation of VE-cadherin

Aberrant extra-vascular expression of VE-cadherin has been observed in metastasis associated with Vasculogenic Mimicry (VM); we have recently shown that in VM prone (VM+) tumor cells VE-cadherin is mainly in the form of pVE-cadherin in Y658 allowing an increased plasticity that potentiates VM development. As excessive VE-cadherin phosphorylation is regulated by the phosphatase VEPTP in endothelial cells in the current study we analysed its role in this aberrant phenotype in malignant tumor cells. We show that human malignant melanoma cells VM+, also express VE-PTP although at lower levels than endothelial cells. The complex VE-PTP/VE-Cadherin/p120-catenin act as a safeguard to prevent VE-cadherin degradation by autophagy. Indeed, silencing of VE-PTP results in complete degradation of VE-cadherin with the features of autophagy and increases the global p120 tyrosine phosphorylation status. In summary, we show that VE-PTP is involved in VM formation and disruption of VE-PTP/VE-Cadherin/p120 complex results in enhanced autophagy in aggressive VM+ cells.