Translation of cytoplasmic UBA1 contributes to VEXAS syndrome pathogenesis.

Somatic mutations in UBA1 cause vacuoles, E1 ubiquitin-activating enzyme, X-linked, autoinflammatory somatic (VEXAS) syndrome, an adult-onset inflammatory disease with an overlap of hematologic manifestations. VEXAS syndrome is characterized by a high mortality rate and significant clinical heterogeneity. We sought to determine independent predictors of survival in VEXAS and to understand the mechanistic basis for these factors. We analyzed 83 patients with somatic pathogenic variants in UBA1 at p.Met41 (p.Met41Leu/Thr/Val), the start codon for translation of the cytoplasmic isoform of UBA1 (UBA1b). Patients with the p.Met41Val genotype were most likely to have an undifferentiated inflammatory syndrome. Multivariate analysis showed ear chondritis was associated with increased survival, whereas transfusion dependence and the p.Met41Val variant were independently associated with decreased survival. Using in vitro models and patient-derived cells, we demonstrate that p.Met41Val variant supports less UBA1b translation than either p.Met41Leu or p.Met41Thr, providing a molecular rationale for decreased survival. In addition, we show that these 3 canonical VEXAS variants produce more UBA1b than any of the 6 other possible single-nucleotide variants within this codon. Finally, we report a patient, clinically diagnosed with VEXAS syndrome, with 2 novel mutations in UBA1 occurring in cis on the same allele. One mutation (c.121 A>T; p.Met41Leu) caused severely reduced translation of UBA1b in a reporter assay, but coexpression with the second mutation (c.119 G>C; p.Gly40Ala) rescued UBA1b levels to those of canonical mutations. We conclude that regulation of residual UBA1b translation is fundamental to the pathogenesis of VEXAS syndrome and contributes to disease prognosis.

The Core Competencies for Public Health in Canada: Opportunities and Recommendations for Modernization.

CONTEXT: The 2008 Public Health Agency of Canada's (PHAC's) "Core Competencies for Public Health in Canada" (the "Canadian core competencies") outline the skills, attitudes, and knowledge essential for the practice of public health. The core competencies represent an important part of public health practice, workforce development, and education in Canada and internationally. However, the core competencies are considered outdated and are facing calls for review, expansion, and revision. OBJECTIVE: To examine the literature on public health competencies to identify opportunities and recommendations for consideration when reviewing and updating the Canadian core competencies. METHODS: This narrative literature review included 4 components: 3 literature searches conducted between 2021 and 2022 using similar search strategies, as well as an analysis of competency frameworks from comparable jurisdictions. The 3 searches were conducted in collaboration with the Health Library to identify core competency-relevant scholarly and gray literature published in English since 2007. Reference lists of sources identified were also reviewed. During the data extraction process, one researcher screened each source, extracted competency-relevant information, and categorized these data into key findings. RESULTS: After identifying 2392 scholarly and gray literature sources, 166 competency-relevant sources were included in the review. Findings from these sources were synthesized into 3 main areas: (1) competency framework methodology and structure; (2) competencies to add; and (3) competencies to modify. DISCUSSION: These findings demonstrate that updates to Canada's core competencies are needed and overdue. Recommendations to support this process include establishing a formal governance structure for the competencies' regular review, revision, and implementation, as well as ensuring that priority topics applicable across all competency categories are integrated as overarching themes. Limitations of the evidence include the potential lack of applicability and generalizability to the Canadian context, as well as biases associated with the narrative literature review methodology.

DNAJC21 Mutations Link a Cancer-Prone Bone Marrow Failure Syndrome to Corruption in 60S Ribosome Subunit Maturation.

A substantial number of individuals with bone marrow failure (BMF) present with one or more extra-hematopoietic abnormality. This suggests a constitutional or inherited basis, and yet many of them do not fit the diagnostic criteria of the known BMF syndromes. Through exome sequencing, we have now identified a subgroup of these individuals, defined by germline biallelic mutations in DNAJC21 (DNAJ homolog subfamily C member 21). They present with global BMF, and one individual developed a hematological cancer (acute myeloid leukemia) in childhood. We show that the encoded protein associates with rRNA and plays a highly conserved role in the maturation of the 60S ribosomal subunit. Lymphoblastoid cells obtained from an affected individual exhibit increased sensitivity to the transcriptional inhibitor actinomycin D and reduced amounts of rRNA. Characterization of mutations revealed impairment in interactions with cofactors (PA2G4, HSPA8, and ZNF622) involved in 60S maturation. DNAJC21 deficiency resulted in cytoplasmic accumulation of the 60S nuclear export factor PA2G4, aberrant ribosome profiles, and increased cell death. Collectively, these findings demonstrate that mutations in DNAJC21 cause a cancer-prone BMF syndrome due to corruption of early nuclear rRNA biogenesis and late cytoplasmic maturation of the 60S subunit.

L-Leucine improves the anaemia in models of Diamond Blackfan anaemia and the 5q- syndrome in a TP53-independent way.

Haploinsufficiency of ribosomal proteins (RPs) and upregulation of the tumour suppressor TP53 have been shown to be the common basis for the anaemia observed in Diamond Blackfan anaemia and 5q- myelodysplastic syndrome. We previously demonstrated that treatment with L-Leucine resulted in a marked improvement in anaemia in disease models. To determine if the L-Leucine effect was Tp53-dependent, we used antisense MOs to rps19 and rps14 in zebrafish; expression of tp53 and its downstream target cdkn1a remained elevated following L-leucine treatment. We confirmed this observation in human CD34+ cells. L-Leucine thus alleviates anaemia in RP-deficient cells in a TP53-independent manner.

L-Leucine improves the anemia and developmental defects associated with Diamond-Blackfan anemia and del(5q) MDS by activating the mTOR pathway.

Haploinsufficiency of ribosomal proteins (RPs) has been proposed to be the common basis for the anemia observed in Diamond-Blackfan anemia (DBA) and myelodysplastic syndrome with loss of chromosome 5q [del(5q) MDS]. We have modeled DBA and del(5q) MDS in zebrafish using antisense morpholinos to rps19 and rps14, respectively, and have demonstrated that, as in humans, haploinsufficient levels of these proteins lead to a profound anemia. To address the hypothesis that RP loss results in impaired mRNA translation, we treated Rps19 and Rps14-deficient embryos with the amino acid L-leucine, a known activator of mRNA translation. This resulted in a striking improvement of the anemia associated with RP loss. We confirmed our findings in primary human CD34⁺ cells, after shRNA knockdown of RPS19 and RPS14. Furthermore, we showed that loss of Rps19 or Rps14 activates the mTOR pathway, and this is accentuated by L-leucine in both Rps19 and Rps14 morphants. This effect could be abrogated by rapamycin suggesting that mTOR signaling may be responsible for the improvement in anemia associated with L-leucine. Our studies support the rationale for ongoing clinical trials of L-leucine as a therapeutic agent for DBA, and potentially for patients with del(5q) MDS.

Endothelial von Willebrand factor regulates angiogenesis.

The regulation of blood vessel formation is of fundamental importance to many physiological processes, and angiogenesis is a major area for novel therapeutic approaches to diseases from ischemia to cancer. A poorly understood clinical manifestation of pathological angiogenesis is angiodysplasia, vascular malformations that cause severe gastrointestinal bleeding. Angiodysplasia can be associated with von Willebrand disease (VWD), the most common bleeding disorder in man. VWD is caused by a defect or deficiency in von Willebrand factor (VWF), a glycoprotein essential for normal hemostasis that is involved in inflammation. We hypothesized that VWF regulates angiogenesis. Inhibition of VWF expression by short interfering RNA (siRNA) in endothelial cells (ECs) caused increased in vitro angiogenesis and increased vascular endothelial growth factor (VEGF) receptor-2 (VEGFR-2)-dependent proliferation and migration, coupled to decreased integrin αvß3 levels and increased angiopoietin (Ang)-2 release. ECs expanded from blood-derived endothelial progenitor cells of VWD patients confirmed these results. Finally, 2 different approaches, in situ and in vivo, showed increased vascularization in VWF-deficient mice. We therefore identify a new function of VWF in ECs, which confirms VWF as a protein with multiple vascular roles and defines a novel link between hemostasis and angiogenesis. These results may have important consequences for the management of VWD, with potential therapeutic implications for vascular diseases.

Ddx18 is essential for cell-cycle progression in zebrafish hematopoietic cells and is mutated in human AML.

In a zebrafish mutagenesis screen to identify genes essential for myelopoiesis, we identified an insertional allele hi1727, which disrupts the gene encoding RNA helicase dead-box 18 (Ddx18). Homozygous Ddx18 mutant embryos exhibit a profound loss of myeloid and erythroid cells along with cardiovascular abnormalities and reduced size. These mutants also display prominent apoptosis and a G1 cell-cycle arrest. Loss of p53, but not Bcl-xl overexpression, rescues myeloid cells to normal levels, suggesting that the hematopoietic defect is because of p53-dependent G1 cell-cycle arrest. We then sequenced primary samples from 262 patients with myeloid malignancies because genes essential for myelopoiesis are often mutated in human leukemias. We identified 4 nonsynonymous sequence variants (NSVs) of DDX18 in acute myeloid leukemia (AML) patient samples. RNA encoding wild-type DDX18 and 3 NSVs rescued the hematopoietic defect, indicating normal DDX18 activity. RNA encoding one mutation, DDX18-E76del, was unable to rescue hematopoiesis, and resulted in reduced myeloid cell numbers in ddx18(hi1727/+) embryos, indicating this NSV likely functions as a dominant-negative allele. These studies demonstrate the use of the zebrafish as a robust in vivo system for assessing the function of genes mutated in AML, which will become increasingly important as more sequence variants are identified by next-generation resequencing technologies.

cpsf1 is required for definitive HSC survival in zebrafish.

A comprehensive understanding of the genes and pathways regulating hematopoiesis is needed to identify genes causally related to bone marrow failure syndromes, myelodysplastic syndromes, and hematopoietic neoplasms. To identify novel genes involved in hematopoiesis, we performed an ethyl-nitrosourea mutagenesis screen in zebrafish (Danio rerio) to search for mutants with defective definitive hematopoiesis. We report the recovery and analysis of the grechetto mutant, which harbors an inactivating mutation in cleavage and polyadenylation specificity factor 1 (cpsf1), a gene ubiquitously expressed and required for 3' untranslated region processing of a subset of pre-mRNAs. grechetto mutants undergo normal primitive hematopoiesis and specify appropriate numbers of definitive HSCs at 36 hours postfertilization. However, when HSCs migrate to the caudal hematopoietic tissue at 3 days postfertilization, their numbers start decreasing as a result of apoptotic cell death. Consistent with Cpsf1 function, c-myb:EGFP(+) cells in grechetto mutants also show defective polyadenylation of snrnp70, a gene required for HSC development. By 5 days postfertilization, definitive hematopoiesis is compromised and severely decreased blood cell numbers are observed across the myeloid, erythroid, and lymphoid cell lineages. These studies show that cpsf1 is essential for HSC survival and differentiation in caudal hematopoietic tissue.

Diamond-Blackfan anemia in adults: In pursuit of a common approach for a rare disease.

Diamond-Blackfan anemia (DBA) is a rare bone marrow failure syndrome, usually caused by loss-of function variants in genes encoding ribosomal proteins. The hallmarks of DBA are anemia, congenital anomalies and cancer predisposition. Although DBA usually presents in childhood, the prevalence in later life is increasing due to an expanding repertoire of implicated genes, improvements in genetic diagnosis and increasing life expectancy. Adult patients uniquely suffer the manifestations of end-organ damage caused by the disease and its treatment, and transition to adulthood poses specific issues in disease management. To standardize and optimize care for this rare disease, in this review we provide updated guidance on the diagnosis and management of DBA, with a specific focus on older adolescents and adults. Recommendations are based upon published literature and our pooled clinical experience from three centres in the United Kingdom (U·K.). Uniquely we have also solicited and incorporated the views of affected families, represented by the independent patient organization, DBA U.K.

Expression of the cytoplasmic NPM1 mutant (NPMc+) causes the expansion of hematopoietic cells in zebrafish.

Mutations in the human nucleophosmin (NPM1) gene are the most frequent genetic alteration in adult acute myeloid leukemias (AMLs) and result in aberrant cytoplasmic translocation of this nucleolar phosphoprotein (NPMc+). However, underlying mechanisms leading to leukemogenesis remain unknown. To address this issue, we took advantage of the zebrafish model organism, which expresses 2 genes orthologous to human NPM1, referred to as npm1a and npm1b. Both genes are ubiquitously expressed, and their knockdown produces a reduction in myeloid cell numbers that is specifically rescued by NPM1 expression. In zebrafish, wild-type human NPM1 is nucleolar while NPMc+ is cytoplasmic, as in human AML, and both interact with endogenous zebrafish Npm1a and Npm1b. Forced NPMc+ expression in zebrafish causes an increase in pu.1(+) primitive early myeloid cells. A more marked perturbation of myelopoiesis occurs in p53(m/m) embryos expressing NPMc+, where mpx(+) and csf1r(+) cell numbers are also expanded. Importantly, NPMc+ expression results in increased numbers of definitive hematopoietic cells, including erythromyeloid progenitors in the posterior blood island and c-myb/cd41(+) cells in the ventral wall of the aorta. These results are likely to be relevant to human NPMc+ AML, where the observed NPMc+ multilineage expression pattern implies transformation of a multipotent stem or progenitor cell.

Technologies bringing young Zebrafish from a niche field to the limelight.

Fundamental life science and pharmaceutical research are continually striving to provide physiologically relevant context for their biological studies. Zebrafish present an opportunity for high-content screening (HCS) to bring a true in vivo model system to screening studies. Zebrafish embryos and young larvae are an economical, human-relevant model organism that are amenable to both genetic engineering and modification, and direct inspection via microscopy. The use of these organisms entails unique challenges that new technologies are overcoming, including artificial intelligence (AI). In this perspective article, we describe the state-of-the-art in terms of automated sample handling, imaging, and data analysis with zebrafish during early developmental stages. We highlight advances in orienting the embryos, including the use of robots, microfluidics, and creative multi-well plate solutions. Analyzing the micrographs in a fast, reliable fashion that maintains the anatomical context of the fluorescently labeled cells is a crucial step. Existing software solutions range from AI-driven commercial solutions to bespoke analysis algorithms. Deep learning appears to be a critical tool that researchers are only beginning to apply, but already facilitates many automated steps in the experimental workflow. Currently, such work has permitted the cellular quantification of multiple cell types in vivo, including stem cell responses to stress and drugs, neuronal myelination and macrophage behavior during inflammation and infection. We evaluate pro and cons of proprietary versus open-source methodologies for combining technologies into fully automated workflows of zebrafish studies. Zebrafish are poised to charge into HCS with ever-greater presence, bringing a new level of physiological context.