Project description:ZBTB24, encoding a protein of the ZBTB family of transcriptional regulators, is one of four known genes – the other three being DNMT3B, CDCA7 and HELLS – that are mutated in immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome, a genetic disorder characterized by DNA hypomethylation and antibody deficiency. The molecular mechanisms by which ZBTB24 regulates gene expression and the biological functions of ZBTB24 are poorly understood. Here we identified a 12-bp consensus sequence [CT(G/T)CCAGGACCT] occupied by ZBTB24 in the mouse genome. The sequence is present at multiple loci, including the Cdca7 promoter region, and ZBTB24 binding is mostly associated with gene activation. Crystallography and DNA-binding data revealed that the last four of the eight zinc fingers (ZFs) (i.e. ZF5-8) in ZBTB24 confer specificity of DNA binding. Two ICF missense mutations have been identified in the ZBTB24 ZF domain that alter zinc-binding cysteine residues. We demonstrated that the corresponding C382Y and C407G mutations in mouse ZBTB24 abolish specific DNA binding and fail to induce Cdca7 expression. Our analyses indicate, and suggest a structural basis for, the sequence specific recognition by a transcription factor centrally important for the pathogenesis of ICF syndrome.
Project description:The autosomal recessive immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome is a genetically heterogeneous disorder. Despite recent successes in the identification of the underlying gene defects, it is currently unclear how mutations in any of the four known ICF genes cause a primary immunodeficiency. Here we demonstrate that loss of ZBTB24 in B cells from ICF2 patients impairs non-homologous end-joining (NHEJ) during immunoglobulin class-switch recombination and consequently impairs immunoglobulin production and subtype balance. Mechanistically, we found that ZBTB24 associates with poly(ADP-ribose) polymerase 1 (PARP1) and stimulates auto-poly(ADP-ribosyl)ation of this enzyme. The zinc finger in ZBTB24 binds PARP1-associated poly(ADP-ribose) chains and mediates the PARP1-dependent recruitment of ZBTB24 to DNA breaks. Moreover, by binding to poly(ADP-ribose) chains ZBTB24 protects these moieties from degradation by poly(ADP-ribose) glycohydrolase (PARG). This enhances the poly(ADP-ribose)-dependent interaction between PARP1 and the LIG4/XRCC4 NHEJ complex and promotes NHEJ by facilitating the assembly of this repair complex at DNA breaks. Thus, we uncover ZBTB24 as a regulator of PARP1-dependent NHEJ and class-switch recombination, providing a molecular basis for the immunodeficiency in ICF syndrome.
Project description:ICF syndrome, a rare autosomal recessive disorder characterized by immunodeficiency, centromeric instability and facial anomalies, is caused by mutations in DNMT3B, ZBTB24, CDCA7 or HELLS. In this study we show that mice deficient for Zbtb24 in the hematopoietic lineage exhibit a phenotype that recapitulates major clinical features of ICF patients, including hypogammaglobulinemia. RNA-Seq analysis of splenic follicular B cells and marginal zone B cells identifies dozens of genes that show differential expression in the absence of Zbtb24. These include Cdca7, Taf6, Cdc40, Ostc, Crisp3 and Il5ra.
Project description:The interplay between transcription factors and epigenetic writers like the DNA methyltransferases (DNMTs), and the role of this interplay in modulating gene expression, is being increasingly appreciated. We investigated the interplay between ZBTB24, a zinc-finger protein belonging to the BTB-POZ family of transcription factors, and the de novo DNA methyltransferase DNMT3B. Both factors, when mutated, cause Immunodeficiency, Centromere Instability, and Facial anomalies (ICF) syndrome, suggesting they are mechanistically linked in some way, but almost nothing is known about ZBTB24. In this study, we identified genomic targets regulated by ZBTB24, and identified its recognition motif, binding to which leads to activation. Chromatin immunoprecipitation in model cell line systems revealed common genes bound by ZBTB24 and DNMT3B, where they function to regulate gene body methylation. Genes coordinately regulated by ZBTB24 and DNMT3B are enriched for molecular mechanisms essential for cellular homeostasis, highlighting the importance of the ZBTB24-DNMT3B interplay in maintaining epigenetic patterns required for normal cellular function.
Project description:The interplay between transcription factors and epigenetic writers like the DNA methyltransferases (DNMTs), and the role of this interplay in modulating gene expression, is being increasingly appreciated. We investigated the interplay between ZBTB24, a zinc-finger protein belonging to the BTB-POZ family of transcription factors, and the de novo DNA methyltransferase DNMT3B. Both factors, when mutated, cause Immunodeficiency, Centromere Instability, and Facial anomalies (ICF) syndrome, suggesting they are mechanistically linked in some way, but almost nothing is known about ZBTB24. In this study, we identified genomic targets regulated by ZBTB24, and identified its recognition motif, binding to which leads to activation. Chromatin immunoprecipitation in model cell line systems revealed common genes bound by ZBTB24 and DNMT3B, where they function to regulate gene body methylation. Genes coordinately regulated by ZBTB24 and DNMT3B are enriched for molecular mechanisms essential for cellular homeostasis, highlighting the importance of the ZBTB24-DNMT3B interplay in maintaining epigenetic patterns required for normal cellular function.
Project description:The goal of this study was to investigate DNA methylation and gene expression changes in a zebrafish model of ICF Syndrome which were generated by mutation of ICF-gene zbtb24. Comparison of gene expression changes between wildtype and zbtb24 homozygous mutants revealed upregulation of interferon response genes following zbtb24 deletion. Upregulation of interferon response genes was blocked by mutation of the dsRNA helicase Mda5.
Project description:The goal of this study was to investigate DNA methylation and gene expression changes in a zebrafish model of ICF Syndrome which were generated by mutation of ICF-gene zbtb24. Comparison of gene expression changes between wildtype and zbtb24 homozygous mutants revealed upregulation of interferon response genes following zbtb24 deletion. Upregulation of interferon response genes was blocked by mutation of the dsRNA helicase Mda5.
Project description:The goal of this study was to investigate DNA methylation and gene expression changes in a zebrafish model of ICF Syndrome which were generated by mutation of ICF-gene zbtb24. Comparison of gene expression changes between wildtype and zbtb24 homozygous mutants revealed upregulation of interferon response genes following zbtb24 deletion. Upregulation of interferon response genes was blocked by mutation of the dsRNA helicase Mda5.
Project description:Immunodeficiency, Centromeric Instability, and Facial Anomalies Type I (ICF1) Syndrome is a rare genetic disease caused by mutations in DNMT3B, a de novo DNA methyltransferase. However, the molecular basis of how DNMT3B-deficiency leads to ICF1 pathogenesis is unclear. Induced pluripotent stem cell (iPSC) technology facilitates the study of early human developmental diseases via facile in vitro paradigms. Here, we generate iPSCs from ICF Type 1 Syndrome patient fibroblasts followed by directed differentiation of ICF1-iPSCs to mesenchymal stem cells (MSCs). By performing genome-scale bisulfite sequencing, we find that DNMT3B-deficient iPSCs exhibit global loss of non-CG methylation and select CG hypomethylation at gene promoters and enhancers. Further unbiased scanning of ICF1 iPSC methylomes also identifies large megabase regions of CG hypomethylation typically localized in centromeric and subtelomeric regions. RNA sequencing of ICF1 and control iPSCs reveals abnormal gene expression in ICF1 iPSCs relevant to ICF Syndrome phenotypes, some directly associated with promoter or enhancer hypomethylation. Upon differentiation of ICF1 iPSCs to mesenchymal stem cells (MSCs), we find virtually all CG hypomethylated regions remained hypomethylated when compared to either wild-type iPSC-derived MSCs or primary bone-marrow MSCs. Collectively, our results show specific methylome and transcriptome defects in both ICF1-iPSCs and differentiated somatic cell lineages, providing a valuable stem cell system for further in vitro study of the molecular pathogenesis of ICF1 Syndrome. MethylC-seq and RNA-Seq in ICF Syndrome patient fibroblast derived induced pluripotent stem cells.