The establishment of long-lasting immunity against pathogens is facilitated by the germinal center (GC) reaction, during which B cells increase their antibody affinity and differentiate into antibody-secreting cells (ASC) and memory cells. These events involve modifications in chromatin packaging that orchestrate the profound restructuring of gene expression networks that determine cell fate. While several chromatin remodelers were implicated in lymphocyte functions, less is known about SMARCA5. Here, using ribosomal pull-down for analyzing translated genes in GC B cells, coupled with functional experiments in mice, we identified SMARCA5 as a key chromatin remodeler in B cells. While the naive B cell compartment remained unaffected following conditional depletion of Smarca5, effective proliferation during B cell activation, immunoglobulin class switching, and as a result GC formation and ASC differentiation were impaired. Single-cell multiomic sequencing analyses revealed that SMARCA5 is crucial for facilitating the transcriptional modifications and genomic accessibility of genes that support B cell activation and differentiation. These findings offer novel insights into the functions of SMARCA5, which can be targeted in various human pathologies.

• MeSH
• Adenosine Triphosphatases MeSH
• Lymphocyte Activation immunology   MeSH
• B-Lymphocytes * metabolism   immunology   MeSH
• Cell Differentiation * MeSH
• Chromosomal Proteins, Non-Histone * metabolism   genetics   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Immunoglobulin Class Switching genetics   MeSH
• Chromatin Assembly and Disassembly * MeSH
• Germinal Center * immunology   metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adenosine Triphosphatases MeSH
• Chromosomal Proteins, Non-Histone * MeSH
• Smarca5 protein, mouse MeSH Browser

The formation of hematopoietic cells relies on the chromatin remodeling activities of ISWI ATPase SMARCA5 (SNF2H) and its complexes. The Smarca5 null and conditional alleles have been used to study its functions in embryonic and organ development in mice. These mouse model phenotypes vary from embryonic lethality of constitutive knockout to less severe phenotypes observed in tissue-specific Smarca5 deletions, e.g., in the hematopoietic system. Here we show that, in a gene dosage-dependent manner, the hypomorphic allele of SMARCA5 (S5tg) can rescue not only the developmental arrest in hematopoiesis in the hCD2iCre model but also the lethal phenotypes associated with constitutive Smarca5 deletion or Vav1iCre-driven conditional knockout in hematopoietic progenitor cells. Interestingly, the latter model also provided evidence for the role of SMARCA5 expression level in hematopoietic stem cells, as the Vav1iCre S5tg animals accumulate stem and progenitor cells. Furthermore, their hematopoietic stem cells exhibited impaired lymphoid lineage entry and differentiation. This observation contrasts with the myeloid lineage which is developing without significant disturbances. Our findings indicate that animals with low expression of SMARCA5 exhibit normal embryonic development with altered lymphoid entry within the hematopoietic stem cell compartment.

• MeSH
• Adenosine Triphosphatases metabolism   MeSH
• Cell Differentiation genetics   MeSH
• Hematopoietic Stem Cells * metabolism   MeSH
• Hematopoiesis * genetics   MeSH
• Mice MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphatases MeSH

ISWI chromatin remodeling ATPase SMARCA5 (SNF2H) is a well-known factor for its role in regulation of DNA access via nucleosome sliding and assembly. SMARCA5 transcriptionally inhibits the myeloid master regulator PU.1. Upregulation of SMARCA5 was previously observed in CD34+ hematopoietic progenitors of acute myeloid leukemia (AML) patients. Since high levels of SMARCA5 are necessary for intensive cell proliferation and cell cycle progression of developing hematopoietic stem and progenitor cells in mice, we reasoned that removal of SMARCA5 enzymatic activity could affect the cycling or undifferentiated state of leukemic progenitor-like clones. Indeed, we observed that CRISPR/cas9-mediated SMARCA5 knockout in AML cell lines (S5KO) inhibited the cell cycle progression. We also observed that the SMARCA5 deletion induced karyorrhexis and nuclear budding as well as increased the ploidy, indicating its role in mitotic division of AML cells. The cytogenetic analysis of S5KO cells revealed the premature chromatid separation. We conclude that deleting SMARCA5 in AML blocks leukemic proliferation and chromatid cohesion.

• Keywords
• AML, CRISPR, SMARCA5, SNF2H, leukemia, therapeutic target,
• MeSH
• Adenosine Triphosphatases deficiency   metabolism   MeSH
• Leukemia, Myeloid, Acute * enzymology   genetics   pathology   MeSH
• K562 Cells MeSH
• Chromatids * genetics   metabolism   MeSH
• Chromosomal Proteins, Non-Histone deficiency   metabolism   MeSH
• Gene Knockout Techniques * MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Neoplasm Proteins * deficiency   metabolism   MeSH
• Cell Proliferation * MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adenosine Triphosphatases MeSH
• Chromosomal Proteins, Non-Histone MeSH
• Neoplasm Proteins * MeSH
• SMARCA5 protein, human MeSH Browser