Identification of CREBBP bound genes in germinal center B cells

Inactivating mutations of the gene encoding for the CREBBP acetyltransferase are highly frequent in diffuse large B cell lymphoma (DLBCL, 30% of cases) and follicular lymphoma (FL, 60% of cases), the two most common cancers derived from the germinal-center (GC). However, the role of CREBBP inactivation in lymphomagenesis remains unclear. Using functional epigenomics and mouse genetics, here we define the program modulated by CREBBP in primary human GC B cells and show that CREBBP regulates enhancer/super-enhancer networks, with specific roles in GC/post-GC cell fate decisions. Conditional GC-specific deletion of Crebbp in the mouse perturbs the expression of a limited set of genes involved in the regulation of signal transduction (BCR, TLR and CD40), lineage specification (NF-κB and BCL6) and terminal B cell differentiation (PRDM1, IRF4). Consistently, Crebbp-deficient B cells exhibit proliferative advantage and show impaired plasma cell differentiation. While GC-specific loss of Crebbp was not sufficient to initiate malignant transformation, compound Crebbp-haploinsufficient/BCL2-transgenic mice, mimicking the genetics ofFL and DLBCL, display an increased incidence of clonal lymphoid malignancies recapitulating the features of the human diseases. These findings establish CREBBPas a haploinsufficient tumor suppressor gene in GC B cells and provide insights into the mechanisms and targets by which loss of CREBBP contributes to lymphomagenesis. ChIP-seq analysis of CREBBP bound regions and H3K27Ac in purified human germinal center B cells.