2024-03-28T16:52:22Zhttps://www.tdx.cat/oai/requestoai:www.tdx.cat:10803/6682792020-05-27T01:00:26Zcom_10803_1col_10803_35851
nam a 5i 4500
Factors de transcripció
Factores de transcripción
Transcription factors
Limfòcits
Linfocitos
Lymphocytes
Cèl·lules B
Células B
B cells
Unveiling novel functions of the trascriptional repressor HDAC7 in B lymphocyte development
[Barcelona] :
Universitat de Barcelona,
2020
Accés lliure
http://hdl.handle.net/10803/668279
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Azagra Rodríguez, Alba,
autor
1 recurs en línia (237 pàgines)
Tesis realitzada a l’Institut d’Investigació Biomèdica de Bellvitge (IDIBELL)
Tesi
Doctorat
Universitat de Barcelona. Facultat de Biologia
2019
Universitat de Barcelona. Facultat de Biologia
Tesis i dissertacions electròniques
Parra, Maribel,
supervisor acadèmic
Tauler Girona, Albert,
supervisor acadèmic
TDX
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 is still not totally understood. The Cellular Differentiaion group had previously reported that the transcriptional repressor HDAC7 is highly expressed in B cell progenitors (pro-B cells) and B cell precursors (pre-B cells) but not in myeloid cells such as macrophages.
Here, we have demonstrated that HDAC7 is essential for early B cell development and the acquisition of proper B cell identity. There is a block of pro-B to pre-B cell stages transition and a significant increase of cell death rate upon HDAC7 deletion in these populations. We found that HDAC7 represses myeloid and T lymphocyte genes in pro-B cells through specific interaction with the TF MEF2C. Chromatin immunoprecipitation (ChIP) experiments revealed that HDAC7 is recruited to the promoters and enhancers of lineage inappropriate genes in normal pro-B, leading to their transcriptional silencing.
Notably, by using in vivo and in vitro experimental approaches, we found that HDAC7 represses Tet2 in pro-B. On one hand, microarray and RT-qPCR analysis showed that Tet2 expression is up-regulated in pro-B cells from HDAC7-deficient mice. On the other hand, we found that HDAC7 is down-regulated during the conversion of pre-B cells into macrophages and its exogenous expression blocks the up-regulation of Tet2. Similarly to the case of other lineage inappropriate lineage genes, HDAC7 is recruited to the promoter and enhancer of the Tet2 gene in pro-B cells and its absence leads to an increase and a decrease in active and repressive histone marks, respectively. Additionally, we observed that the absence of HDAC7 from pro-B cells results in a significant increase in the percentage of global 5-hydroxymethylation (5-hmC). To definitively prove the role of HDAC7 in 5-hmC, we performed a genome-wide experimental approach. hMeDIP- sequencing experiments revealed an increase in the enrichment of this epigenetic modification at many loci related to lineage inappropriate genes in the absence of HDAC7. Interestingly, we observed 5-hmC enrichment at retrotransposon elements (LINE-1) in HDAC7 deficient pro-B cells, suggesting a potential protector function of HDAC7 against chromatin instability and DNA damage. Additonal results revealed that 5-hmC enrichment at microRNAs and their expression was also regulated by HDAC7. Several miRNAs
involved in normal and aberrant hematopoiesis changed their expression levels depending on the presence of HDAC7 in pro-B cells.
Finally, we found that HDAC7 is expressed at very low levels in certain hematological malignancies, such as Burkitt lymphoma and B cell acute lymphoblastic leukemia (B-ALL) cell lines. In fact, induction of HDAC7 expression in these tumoral cells led to the activation of apoptotic processes, reducing significantly their viability, and to the reduction of oncogene c-MYC expression. Importantly, those effects were observed by interaction with the TF MEF2C and independently of the class I HDAC3 function. These results suggest an anti-oncogenic role for HDAC7 in some types of B cell malignancies.
Altogether, our results demonstrate that HDAC7 is an essential transcriptional repressor during early B cell development that silences lineage or functionally inappropriate genes at multiple levels. It exerts its function by direct recruitment to target genes through specific TF, by regulating LINE-1 and miRNA expression and by controlling the expression levels of a critical epigenetic regulator such as TET2 demethylase enzyme.
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