A splicing factor switch controls hematopoietic lineage specification of pluripotent stem cells.

Alternative splicing (AS) leads to transcriptome diversity in eukaryotic cells and is one of the key regulators driving cellular differentiation. Although AS is of crucial importance for normal hematopoiesis and hematopoietic malignancies, its role in early hematopoietic development is still largely unknown. Here, by using high-throughput transcriptomic analyses, we show that pervasive and dynamic AS takes place during hematopoietic development of human pluripotent stem cells (hPSCs). We identify a splicing factor switch that occurs during the differentiation of mesodermal cells to endothelial progenitor cells (EPCs). Perturbation of this switch selectively impairs the emergence of EPCs and hemogenic endothelial progenitor cells (HEPs). Mechanistically, an EPC-induced alternative spliced isoform of NUMB dictates EPC specification by controlling NOTCH signaling. Furthermore, we demonstrate that the splicing factor SRSF2 regulates splicing of the EPC-induced NUMB isoform, and the SRSF2-NUMB-NOTCH splicing axis regulates EPC generation. The identification of this splicing factor switch provides a new molecular mechanism to control cell fate and lineage specification.

Transgenerational toxicity induced by maternal AFB1 exposure in Caenorhabditis elegans associated with underlying epigenetic regulations.

Aflatoxin B1 (AFB1), usually seriously contaminates in grain and oil foods or feed, displayed significant acute and chronic toxic effects in human and animal populations. However, little is known about the transgenerational toxic effects induced by a maternal AFB1 intake at a lower dose on offspring. In our study, only parental wild-type Caenorhabditis elegans was exposed to AFB1 (0-8 µg/ml) and the following three filial generations were grown on AFB1-free NGM. Results showed that the toxic effects of AFB1 on the growth (body length) and reproduction (brood size, generation time and morphology of gonad arm) can be transmitted through generations. Moreover, the levels of MMP and ATP were irreversibly inhibited in the filial generations. By using RNomics and molecular biology techniques, we found that steroid biosynthesis, phagosome, valine/leucine/isoleucine biosynthesis and oxidative phosphorylation (p < 0.05) were the core signaling pathways to exert the transgenerational toxic effects on nematodes. Also, notably increased histone methylation level at H3K36me3 was observed in the first generation. Taken together, our study demonstrated that AFB1 has notable transgenerational toxic effects, which were resulted from the complex regulatory network of various miRNAs, mRNAs and epigenetic modification in C. elegans.

SETD7 promotes lateral plate mesoderm formation by modulating the Wnt/ß-catenin signaling pathway.

The role of SET domain containing 7 (SETD7) during human hematopoietic development remains elusive. Here, we found that deletion of SETD7 attenuated the generation of hematopoietic progenitor cells (HPCs) during the induction of hematopoietic differentiation from human embryonic stem cells (hESCs). Further analysis specified that SETD7 was required for lateral plate mesoderm (LPM) specification but dispensable for the generation of endothelial progenitor cells (EPCs) and HPCs. Mechanistically, rather than depending on its histone methyltransferase activity, SETD7 interacted with ß-catenin at lysine residue 180 facilitated its degradation. Diminished SETD7 expression led to the accumulation of ß-catenin and the consequent activation of the Wnt signaling pathway, which altered LPM patterning and facilitated the production of paraxial mesoderm (PM). Taken together, the findings indicate that SETD7 is related to LPM and PM patterning via posttranslational regulation of the Wnt/ß-catenin signaling pathway, providing novel insights into mesoderm specification during hematopoietic differentiation from hESCs.

Clinico-Laboratory Features and Associated Factors of Lupus Mesenteric Vasculitis.

INTRODUCTION: Lupus mesenteric vasculitis (LMV) is a rare but potentially life-threatening clinical entity in systemic lupus erythematosus (SLE) patients. OBJECTIVE: The present study was initiated to explore the clinical features and associated factors of LMV in SLE patients. METHODS: We conducted a retrospective study on 50 cases of SLE patients with lupus mesenteric vasculitis (LMV) from January 2010 to December 2019 and 89 cases of non-LMV-SLE patients with similar demographic and comorbidities were included as control. All the data regarding clinical features, laboratory findings, and treatment were reviewed independently by two experts in the field. Both univariate and multivariate logistic regression analyses were employed to identify the associated factors of LMV. RESULTS: The incidence of LMV was 2.9% among hospitalized SLE patients in the current study. The most frequent symptom and physical sign of LMV were respectively abdominal pain (48, 96%) and abdominal tenderness (45, 90%). Through univariate and subsequent multivariate analysis, oral ulcer (OR, 4.25; P = 0.024), urinary tract involvement (OR, 5.23; P = 0.021), and elevated D-dimer (OR, 1.121; P = 0.008) were demonstrated to be positively associated with LMV, while percentage of lymphocytes (OR, 0.928; P = 0.004) and complement 3 (OR, 0.048; P = 0.008) were negatively correlated with LMV. CONCLUSIONS: Oral ulcer, urinary tract involvement, reduced percentage of lymphocytes and complement 3, elevated D-dimer could be associated factors for LMV in SLE patients.

Severe ineffective erythropoiesis discriminates prognosis in myelodysplastic syndromes: analysis based on 776 patients from a single centre.

The underlying mechanisms and clinical significance of ineffective erythropoiesis in myelodysplastic syndromes (MDS) remain to be fully defined. We conducted the ex vivo erythroid differentiation of megakaryocytic-erythroid progenitors (MEPs) from MDS patients and discovered that patient-derived erythroblasts exhibit precocity and premature aging phenotypes, partially by inducing the pro-aging genes, like ERCC1. Absolute reticulocyte count (ARC) was chosen as a biomarker to evaluate the severity of ineffective erythropoiesis in 776 MDS patients. We found that patients with severe ineffective erythropoiesis displaying lower ARC (<20 × 109/L), were more likely to harbor complex karyotypes and high-risk somatic mutations (p < 0.05). Lower ARCs are associated with shorter overall survival (OS) in univariate analysis (p < 0.001) and remain significant in multivariable analysis. Regardless of patients of lower-risk who received immunosuppressive therapy or higher-risk who received decitabine treatment, patients with lower ARC had shorter OS (p < 0.001). Whereas no difference in OS was found between patients receiving allo-hematopoietic stem cell transplantations (Allo-HSCT) (p = 0.525). Our study revealed that ineffective erythropoiesis in MDS may be partially caused by premature aging and apoptosis during erythroid differentiation. MDS patients with severe ineffective erythropoiesis have significant shorter OS treated with immunosuppressive or hypo-methylating agents, but may benefit from Allo-HSCT.

[Knockout of LSD1 Gene by CRISPR/Cas9 System Significantly Inhibited Proliferation and Expression of CD235a in K562 Cells].

OBJECTIVE: To study the effect of LSD1 knock-out on human chronic myeloid leukemia cells(K562 cells). METHODS: The LSD1 gene in K562 cells was knocked-out specifically by using CRISPR/Cas9 system, the single cells were gained by flow cytometric sorting technique, the LSD1+/- and LSD1-/- cell lines were gained after amplificantion and culture, identification of Western blot and sequencing. The MTS assay was used to detect the effect of LSD1 knockout on the proliferation of K562 cells, the flow cytometry was used to examine the expression of K562 cell surface marker after LSD1 knockout. RESULTS: The LSD1 stable knockout cell line of K562 (LSD1+/- and LSD1-/-)were successfully costructed. It was found that knockout of LSD1 significantly inhibited the proliferation of K562 and the expression of CD235a. CONCLUSION: LSD1 plays a key role in the regulation of K562 cell proliferation and CD235a expression.