Project description:Correct B cell identity at each stage of cellular differentiation during B lymphocyte development is critically dependent on a tightly controlled epigenomic landscape. We previously identified HDAC7 as an essential regulator of early B cell development and its absence leads to a drastic block at the pro-B to pre-B cell transition. More recently, we demonstrated that HDAC7 loss in pro-B-ALL in infants associates with a worse prognosis. Here we delineate the molecular mechanisms by which HDAC7 modulates early B cell development. We find that HDAC7 deficiency drives global chromatin de-condensation, histone marks deposition and deregulates other epigenetic regulators and mobile elements. Specifically, the absence of HDAC7 induces TET2 expression, which promotes DNA 5-hydroxymethylation and chromatin de-condensation. HDAC7 deficiency also results in the aberrant expression of microRNAs and LINE-1 transposable elements. These findings shed light on the mechanisms by which HDAC7 loss or misregulation may lead to B cell–based hematological malignancies.
Project description:The establishment of proper epigenomic landscape is essential during B lymphocyte development in order to acquire a correct B cell identity at each cellular differentiation stage. We previously identified HDAC7 as a critical regulator of early B cell development. Its absence indeed led to the aberrant activation of inappropriate lineage genes, a reduction of proliferation and an increase in cell apoptosis. More recently, we have demonstrated that HDAC7 loss in infant pro-B-ALL associates with poor prognosis. Here we shed light into the HDAC7-mediated molecular mechanisms during early B cell development. HDAC7 deficiency drives not only the expression of inappropriate lineage genes, but also global chromatin de-condensation and deregulation of epigenetic regulators of DNA methylation and potential damaging elements. Specifically, HDAC7 absence induces the expression of TET2, which promotes DNA 5-hydroxymethylation and aberrant gene activation. HDAC7 deficiency also results in the uncontrolled expression of microRNAs and non-coding elements such as LINE-1 transposable elements. These findings are relevant for the mechanistic explanation of why HDAC7 is affected in multiple B-related hematological malignancies. Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) for histone modifications H3K27ac and H3K27me3 in murine pro-B lymphocytes.
Project description:The establishment of proper epigenomic landscape is essential during B lymphocyte development in order to acquire a correct B cell identity at each cellular differentiation stage. We previously identified HDAC7 as a critical regulator of early B cell development. Its absence indeed led to the aberrant activation of inappropriate lineage genes, a reduction of proliferation and an increase in cell apoptosis. More recently, we have demonstrated that HDAC7 loss in infant pro-B-ALL associates with poor prognosis. Here we shed light into the HDAC7-mediated molecular mechanisms during early B cell development. HDAC7 deficiency drives not only the expression of inappropriate lineage genes, but also global chromatin de-condensation and deregulation of epigenetic regulators of DNA methylation and potential damaging elements. Specifically, HDAC7 absence induces the expression of TET2, which promotes DNA 5-hydroxymethylation and aberrant gene activation. HDAC7 deficiency also results in the uncontrolled expression of microRNAs and non-coding elements such as LINE-1 transposable elements. These findings are relevant for the mechanistic explanation of why HDAC7 is affected in multiple B-related hematological malignancies. Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq) was performed in murine pro-B and pre-B lymphocytes.
Project description:B lymphopoiesis is the result of several cell lineage choices and differentiation steps whose perturbation leads to B cell malignancies. Cellular transitions for B cell generation have been associated with gene activation and silencing by networks of B cell specific transcription factors (TFs) and dynamic changes in DNA methylation. How gene repression is established and which lineage-specific transcriptional repressors are involved during B cell lymphopoiesis are still not totally understood. Here, by using our in vivo experimental approach, we have found that HDAC7 represses Tet2 enzyme in pro-B cells. In fact, HDAC7 deficient pro-B cells show a significant increase in the percentage of global 5-hydroxymethylation. To prove the role of HDAC7 in 5-hydroxymethylation, we have performed a genome-wide experimental approach. hMeDIP-sequencing experiments reveal an increase in the enrichment of this epigenetic modification at many loci related to lineage inappropriate genes. Our results corroborate that HDAC7 is an essential transcriptional regulator during early B cell development that silences lineage or functionally inappropriate genes and unveil an unexpected role of a class IIa HDAC in controlling DNA methylation
Project description:B lymphocyte development is a complex process tightly controlled at the transcriptional level by the action of networks of transcription factors. The repression of genes from alternative lineages is necessary to ensure the acquisition of the correct B cell identity. However, the mechanisms of transcriptional repression during B cell generation are largely unknown. Here, using a conditional knockout mouse model, we show that the histone deacetylase HDAC7 is essential for B cell development. Early deletion of HDAC7 dramatically blocked B cell development at the pro-B cell stage and gave rise to a severe lymphopenia in peripheral organs. HDAC7-deficient pro-B cells exhibit cell lineage promiscuity, expressing myeloid and T lymphocyte genes. In wild-type B cells HDAC7 is recruited to myocyte enhancer factor 2C (MEFC2) binding sites located at the promoters of macrophage and T lymphocyte genes. Our results demonstrate that HDAC7 is a bona fide transcriptional repressor essential for B cell development.