Greenberg, P. L. | bioRxiv Science

bioRxiv2023

Shared and Distinct Mechanisms of UBA1 Inactivation Across Different Diseases

Most cellular ubiquitin signaling is initiated by UBA1, which activates and transfers ubiquitin to tens of E2 enzymes. Clonally acquired UBA1 missense mutations cause an inflammatory-hematologic overlap disease called VEXAS (vacuoles, E1, X-linked, autoinflammatory, somatic) syndrome. Despite extensive clinical investigation into this lethal disease, little is known about the underlying molecular mechanisms. Here, by dissecting VEXAS-causing UBA1 mutations, we discovered that p.Met41 mutations alter cytoplasmic isoform expression, whereas other mutations reduce catalytic activity of nuclear and cytoplasmic isoforms by diverse mechanisms, including aberrant oxyester formation. Strikingly, non-p.Met41 mutations most prominently affect transthioesterification, revealing ubiquitin transfer to cytoplasmic E2 enzymes as a shared property of pathogenesis amongst different VEXAS syndrome genotypes. A similar E2 charging bottleneck exists in some lung cancer-associated UBA1 mutations, but not in spinal muscular atrophy-causing UBA1 mutations, which instead, render UBA1 thermolabile. Collectively, our results highlight the precision of conformational changes required for faithful ubiquitin transfer, define distinct and shared mechanisms of UBA1 inactivation in diverse diseases, and suggest that specific E1-E2 modules control different aspects of tissue differentiation and maintenance.

biochemistry↗

bioRxiv2019

Profiling Myelodysplastic Syndromes by Mass Cytometry Demonstrates Abnormal Progenitor Cell Phenotype and Differentiation

PurposeWe sought to enhance the cytometric analysis of MDS by performing a pilot study of a single cell mass cytometry (MCM) assay to more comprehensively analyze patterns of surface marker expression in patients with MDS.\n\nExperimental DesignTwenty-three MDS and five healthy donor bone marrow samples were studied using a 34-parameter mass cytometry panel utilizing barcoding and internal reference standards. The resulting data were analyzed by both traditional gating and high-dimensional clustering.\n\nResultsThis high-dimensional assay provided three major benefits relative to traditional cytometry approaches: First, MCM enabled detection of aberrant surface maker at high resolution, detecting aberrancies in 27/31 surface markers, encompassing almost every previously reported MDS surface marker aberrancy. Additionally, three previously unrecognized aberrancies in MDS were detected in multiple samples at least one developmental stage: increased CD321 and CD99; and decreased CD47. Second, analysis of the stem and progenitor cell compartment (HSPCs), demonstrated aberrant expression in 21 of the 23 MDS samples, which were not detected in three samples from patients with idiopathic cytopenia of undetermined significance (ICUS). These immunophenotypically abnormal HSPCs were also the single most significant distinguishing feature between clinical risk groups. Third, unsupervised clustering of high-parameter MCM data allowed identification of abnormal differentiation patterns associated with immunophenotypically aberrant myeloid cells similar to myeloid derived suppressor cells.\n\nConclusionsThese results demonstrate that high-parameter cytometry methods that enable simultaneous analysis of all bone marrow cell types could enhance the diagnostic utility of immunophenotypic analysis in MDS.\n\nStatement of SignificanceO_LIHigh-dimensional mass cytometry enables high-resolution characterization of abnormal maker expression and myeloid development in MDS.\nC_LIO_LIThis technology could enhance MDS diagnosis and therapeutic monitoring and merits further research.\nC_LI\n\nStatement Translational RelevanceIn spite of several studies suggesting the utility of flow cytometry in the diagnosis of myelodysoplastic syndrome (MDS), this technique has not been widely adopted. We sought to enhance the utility of cytometry in MDS by performing the first high-dimensional mass cytometry characterization of a cohort of MDS patients. High-dimensional mass cytometry allowed all bone marrow cell populations to be simultaneously analyzed enabling high-resolution characterization of abnormal maker expression and myeloid development in MDS. This approach could identify almost all previously identified aberrant surface marker expression patterns in MDS while simultaneously enabling analysis by unsupervised clustering. Additionally, this mass cytometry analysis approach enabled the modeling of abnormal differentiation in MDS. This technology could enhance MDS diagnosis and therapeutic monitoring and merits further research.

cancer biology↗