Zhibin Huang

Acute monocytic leukemia (AML-M5) is a type of acute myeloid leukemia, characterized by a dominance of monocytes in the bone marrow and peripheral blood. AML-M5 exhibits a poor prognosis compared to other AML subtypes. Despite clinical recognition, current research on AML-M5 remains relatively limited, and its underlying pathogenic mechanisms are not yet fully understood. In this study, we uncover a distinct and heightened expression of CBX4, a core component of PRC1, in the peripheral blood of individuals diagnosed with AML-M5. By generating cbx4 overexpression transgenic and deleted mutant zebrafish lines, we observe elevated cbx4 expression in monocyte/macrophage, selectively modulating their production during zebrafish hematopoiesis. Notably, aging zebrafish with cbx4 overexpression exhibit a progression to AML-M5-like hematopoiesis. Further mechanistic analyses reveal that Cbx4 regulates the fate of monocyte/macrophage lineage by suppressing runx1 expression. This suppression is achieved through the recruitment of HDAC to the runx1 promoter via cbx4, resulting in the down-regulation of the H3K27 acetylation level of runx1. These findings offer novel insights, providing potential avenues for risk assessment and molecular diagnosis of AML-M5 leukemia. Moreover, CBX4 emerges as a promising target for the diagnosis and treatment of AML-M5 leukemia.

Aplastic anemia (AA) is a rare hematological disorder characterized by the failure of bone marrow hematopoiesis. Although somatic mutations are known to play pivotal roles in the pathogenesis and clinical progression of AA, their molecular characteristics in Chinese AA patients remain poorly characterized. In this study, we perform whole-exome sequencing on 126 Chinese AA patients to delineate the somatic mutation landscape. Our analysis reveal recurrently mutated genes enriched in immune regulatory pathways. Notably, we identify eight AA cases harboring mutations in the tyrosine kinase motif of C-terminal Src kinase (CSK), a critical regulator of T-cell receptor (TCR) signaling. Functional validation and RNA sequencing in Jurkat T cells demonstrate that these mutations induce aberrant T-cell activation in vitro, suggesting a potential mechanistic link to AA pathogenesis. Furthermore, we detect copy number variations in multiple loci containing immune-related genes, which may additionally contribute to disease development. Collectively, our study provides a comprehensive characterization of somatic mutations in a large Chinese AA cohort and elucidates the functional impact of CSK mutations on AA pathogenesis. These findings deepen our understanding of the disease mechanisms underlying AA and identify potential molecular targets for future therapeutic strategies.

Hematopoietic stem and progenitor cells (HSPCs) sustain blood cell production by balancing self-renewal and differentiation. While regulatory networks of transcription factors are well established during development of these cells, intrinsic cytoskeletal elements remain unclear. Here we show that the gamma-tubulin ring complex (γ-TuRC), a key regulator of microtubule nucleation, is essential for HSPC expansion in zebrafish. Forward genetic screening identifies the zebrafish smu1347 mutant, which exhibits HSPC exhaustion during definitive hematopoiesis. Positional cloning reveals a nonsense mutation in the tubgcp6 gene, encoding a core component of γ-TuRC, as responsible for the smu1347 phenotype. Mutation of Tubgcp6 causes mitotic arrest, disorganized spindle formation, and increased p53-dependent apoptosis. Time-lapse imaging and lineage tracing further demonstrate that Tubgcp6-deficient HSPCs preferentially undergo symmetric differentiation rather than self-renewal. Disrupting other γ-TuRC subunits (Tubgcp3, Tubgcp4, Tubgcp5) produces similar hematopoietic defects, underscoring the importance of intact microtubule nucleation for stem cell maintenance. These findings identify γ-TuRC-mediated microtubule organization as a critical regulator of HSPC fate and suggest that Tubgcp6 may represent a potential therapeutic target for bone marrow failure syndromes and stem cell exhaustion disorders.

Approximately 30% of patients with myelodysplastic syndrome (MDS) progress to secondary acute myeloid leukemia (sAML) via accumulating gene mutations. Genomic analyses reveal a complex interplay among mutant genes, with co-occurring and mutually exclusive patterns. Hyperactivation of c-MYB and deficiency of PU.1 have been linked to myeloid disorders. We report a case of AML with concurrent PU.1 and c-MYB mutations, exhibiting early onset, high blast count, chemo-resistance, indicating high-risk features, along with elevated Pelger–Huët anomaly (PHA). However, the synergistic mechanism of c-MYB and PU.1 in sAML remains unclear. Using c-Myb-hyperactivation and Pu.1-deficient double-strain ( c-myb ^hyper ;pu.1 ^G242D/G242D ) zebrafish, we investigated MDS/sAML progression. Surprisingly, the double mutant exhibited a distinct type of neutrophil resembling clinical PHA cells and demonstrated a higher rate of MDS/sAML transformation. Further expression analysis revealed reduced lmnb1 expression in double-mutant zebrafish. Knockdown of lmnb1 resulted in PHA and increased blast cells, while overexpression of lmnb1 in c-myb ^hyper ;pu.1 ^G242D/G242D reduced PHA cell level. This suggests that c-Myb hyperactivation and Pu.1 deficiency synergistically reduce lmnb1 expression, inducing the development of PHA-like neutrophils and promoting MDS/sAML progression in zebrafish. Moreover, coadministration of cell cycle inhibitor cytarabine (Ara-C) and the differential inducer all-trans retinoic acid (ATRA) could effectively relieve the neutrophil expansion and PHA symptoms in c-myb ^hyper ;pu.1 ^G242D/G242D zebrafish. Our findings revealed that c-Myb hyperactivation and Pu.1 deficiency played a synergistic role in sAML development and suggests a phenotypic association between the emergence of PH-like cells and the transformation to sAML. Furthermore, c-myb ^hyper ;pu.1 ^G242D/G242D zebrafish might serve as a suitable sAML model for drug screening.

Acute promyelocytic leukemia (APL) is driven by the specific fusion gene PML-RARA produced by chromosomal translocation. Three classic isoforms, L, V, and S, are found in more than 95% of APL patients. However, atypical PML-RARA isoforms are usually associated with uncertain disease progression and treatment prognosis. Recently, we found a novel PML-RARA isoform (named PA) in a patient with atypical clinical characteristics of APL. In order to provide valuable insights for clinical treatment, we constructed the novel PML-RARA isoform zebrafish model for all-trans retinoic acid (ATRA) treatment experiments and comparison with classical isoforms. We found that the effect of PA PML-RARA on the expression of neutrophil-related genes was comparable with classical isoforms and ATRA treatment worked successfully in the zebrafish model. Sequence and structure analysis of the PA protein confirmed its similarity to classical isoforms and the fusion site of PA PML-RARA did not affect the ATRA binding site. As expected, the patient achieved complete remission within two months of treatment with ATRA in combination with arsenic trioxide (ATO) and had a favorable prognosis during the three-year follow-up. Our study highlights the accuracy and efficacy of the PML-RARA zebrafish model in combination with protein structure prediction in support of clinical treatment strategies.

The CCAAT enhancer binding protein alpha (CEBPA) is crucial for myeloid differentiation and the balance of haematopoietic stem and progenitor cell (HSPC) quiescence and self-renewal, and its dysfunction can drive leukemogenesis. However, its role in HSPC generation has not been fully elucidated. Here, we utilized various zebrafish cebpa mutants to investigate the function of Cebpa in the HSPC compartment. Co-localization analysis showed that cebpa expression is enriched in nascent HSPCs. Complete loss of Cebpa function resulted in a significant reduction in early HSPC generation and the overall HSPC pool during embryonic haematopoiesis. Interestingly, while myeloid differentiation was impaired in cebpa N-terminal mutants expressing the truncated zP30 protein, the number of HSPCs was not affected, indicating a redundant role of Cebpa P42 and P30 isoforms in HSPC development. Additionally, epistasis experiments confirmed that Cebpa functions downstream of Runx1 to regulate HSPC emergence. Our findings uncover a novel role of Cebpa isoforms in HSPC generation and maintenance, and provide new insights into HSPC development.