Project description:Dominant mutations in cardiac transcription factor genes cause human inherited congenital heart defects (CHDs), but their molecular basis is not understood. Transcription factors and Brg1/Brm-associated factor (BAF) chromatin remodeling complex interactions suggest potential mechanisms, but the role of BAF complexes in cardiogenesis is not known. Here we show that dosage of Brg1 is critical for mouse and zebrafish cardiogenesis. Disrupting the balance between Brg1 and disease-causing cardiac transcription factors, including Tbx5, Tbx20, and Nkx2-5, causes severe cardiac anomalies, revealing an essential allelic balance between Brg1 and these cardiac transcription factor genes. This suggests that relative levels of transcription factors and BAF complexes are important for heart development, which is supported by reduced occupancy of Brg1 at cardiac genes in Tbx5 haploinsufficient hearts. Our results reveal complex dosage-sensitive interdependence between transcription factors and BAF complexes, providing a potential mechanism underlying transcription factor haploinsufficiency, with implications for multigenic inheritance of CHDs. We performed transcriptional profiling of E11.5 hearts from mice heterozygous for deletions of Brg1, Tbx5, or Nkx2-5, and mice that were compound heterozygotes for Brg1 and each transcription factor gene (Tbx5 and Nkx2-5).
Project description:Dominant mutations in cardiac transcription factor genes cause human inherited congenital heart defects (CHDs), but their molecular basis is not understood. Transcription factors and Brg1/Brm-associated factor (BAF) chromatin remodeling complex interactions suggest potential mechanisms, but the role of BAF complexes in cardiogenesis is not known. Here we show that dosage of Brg1 is critical for mouse and zebrafish cardiogenesis. Disrupting the balance between Brg1 and disease-causing cardiac transcription factors, including Tbx5, Tbx20, and Nkx2-5, causes severe cardiac anomalies, revealing an essential allelic balance between Brg1 and these cardiac transcription factor genes. This suggests that relative levels of transcription factors and BAF complexes are important for heart development, which is supported by reduced occupancy of Brg1 at cardiac genes in Tbx5 haploinsufficient hearts. Our results reveal complex dosage-sensitive interdependence between transcription factors and BAF complexes, providing a potential mechanism underlying transcription factor haploinsufficiency, with implications for multigenic inheritance of CHDs.
Project description:Chromatin plays a crucial role in the intermediation between cell signaling and gene expression. The nucleolus is sensitive to stress and can orchestrate a chain of cellular events in response to stress signals. Despite being a growth factor, FGF2 has anti-proliferative and tumor-suppressive functions in some cellular contexts. In this work, we investigated how the antiproliferative effect of FGF2 modulates chromatin, nucleolus, and rDNA-associated proteins. The chromatin and nucleolar proteome indicated that FGF2 stimulation modulates proteins related to transcription regulation, particularly rRNA expression, and chromatin remodeling proteins. Upon 24 hrs of FGF2 stimulation, the global transcriptional rate and nucleolus area increased in associationalong with intense nucleolar disorganization detected by fibrillarin dispersion and electron microscopy analyses. We confirmed that FGF2 stimulation induced immature rRNA accumulation by increasing rRNA transcription regardless of changes in ribosome profiling. The rDNA-associated protein analysis reinforced that FGF2 stimulus interferes with transcription and rRNA processing/modification, since the proteins Nolc1 and Tcof1 are were upregulated after FGF2 stimulation. Changes in rRNA expression may be crucial for triggering the antiproliferative effect induced by FGF2 since inhibiting RNA Pol I, responsible for rRNA expression, partially reversed the growth arrest induced by FGF2. Taken together, we demonstrate that the antiproliferative FGF2 stimulus triggers significant transcriptional changes, and modulation modulates of the main cell transcription site, the nucleolus, directly modulating the proteome of the rDNA loci.
Project description:Chromatin plays a crucial role in the intermediation between cell signaling and gene expression. The nucleolus is sensitive to stress and can orchestrate a chain of cellular events in response to stress signals. Despite being a growth factor, FGF2 has anti-proliferative and tumor-suppressive functions in some cellular contexts. In this work, we investigated how the antiproliferative effect of FGF2 modulates chromatin, nucleolus, and rDNA-associated proteins. The chromatin and nucleolar proteome indicated that FGF2 stimulation modulates proteins related to transcription regulation, particularly rRNA expression, and chromatin remodeling proteins. Upon 24 hrs of FGF2 stimulation, the global transcriptional rate and nucleolus area increased in associationalong with intense nucleolar disorganization detected by fibrillarin dispersion and electron microscopy analyses. We confirmed that FGF2 stimulation induced immature rRNA accumulation by increasing rRNA transcription regardless of changes in ribosome profiling. The rDNA-associated protein analysis reinforced that FGF2 stimulus interferes with transcription and rRNA processing/modification, since the proteins Nolc1 and Tcof1 are were upregulated after FGF2 stimulation. Changes in rRNA expression may be crucial for triggering the antiproliferative effect induced by FGF2 since inhibiting RNA Pol I, responsible for rRNA expression, partially reversed the growth arrest induced by FGF2. Taken together, we demonstrate that the antiproliferative FGF2 stimulus triggers significant transcriptional changes, and modulation modulates of the main cell transcription site, the nucleolus, directly modulating the proteome of the rDNA loci.
Project description:Chromatin plays a crucial role in the intermediation between cell signaling and gene expression. The nucleolus is sensitive to stress and can orchestrate a chain of cellular events in response to stress signals. Despite being a growth factor, FGF2 has anti-proliferative and tumor-suppressive functions in some cellular contexts. In this work, we investigated how the antiproliferative effect of FGF2 modulates chromatin, nucleolus, and rDNA-associated proteins. The chromatin and nucleolar proteome indicated that FGF2 stimulation modulates proteins related to transcription regulation, particularly rRNA expression, and chromatin remodeling proteins. Upon 24 hrs of FGF2 stimulation, the global transcriptional rate and nucleolus area increased in associationalong with intense nucleolar disorganization detected by fibrillarin dispersion and electron microscopy analyses. We confirmed that FGF2 stimulation induced immature rRNA accumulation by increasing rRNA transcription regardless of changes in ribosome profiling. The rDNA-associated protein analysis reinforced that FGF2 stimulus interferes with transcription and rRNA processing/modification, since the proteins Nolc1 and Tcof1 are were upregulated after FGF2 stimulation. Changes in rRNA expression may be crucial for triggering the antiproliferative effect induced by FGF2 since inhibiting RNA Pol I, responsible for rRNA expression, partially reversed the growth arrest induced by FGF2. Taken together, we demonstrate that the antiproliferative FGF2 stimulus triggers significant transcriptional changes, and modulation modulates of the main cell transcription site, the nucleolus, directly modulating the proteome of the rDNA loci.
Project description:The SWI/SNF (or BAF) complex is an essential chromatin remodeler that regulates DNA accessibility at developmental genes and enhancers. SWI/SNF subunits are among the most frequently mutated genes in cancer and neurodevelopmental disorders. These mutations are often heterozygous loss-of-function alleles, indicating a dosage-sensitive role for SWI/SNF subunits in chromatin regulation. However, the molecular mechanisms that regulate SWI/SNF subunit dosage to ensure proper complex assembly remain largely unexplored. We performed a genome-wide CRISPR KO screen, using epigenome editing in mouse embryonic stem cells, and identified Mlf2 and Rbm15 as regulators of SWI/SNF complex activity. First, we show that MLF2, a poorly characterized chaperone protein, regulates a subset of SWI/SNF target genes by promoting its chromatin remodeling activity. Rapid degradation of MLF2 reduces chromatin accessibility at sites that depend on high levels of SWI/SNF binding to maintain open chromatin. Next, we find that RBM15, part of the m6A RNA methylation writer complex, controls m6A modifications on specific SWI/SNF mRNAs to regulate protein levels of these subunits. Misregulation of m6A methylation causes overexpression of core SWI/SNF subunits leading to the assembly of incomplete complexes lacking the catalytic ATPase/ARP subunits. These data indicate that targeting modulators of SWI/SNF complex assembly may offer a potent therapeutic strategy for diseases associated with impaired chromatin remodeling.
Project description:The SWI/SNF (or BAF) complex is an essential chromatin remodeler that regulates DNA accessibility at developmental genes and enhancers. SWI/SNF subunits are among the most frequently mutated genes in cancer and neurodevelopmental disorders. These mutations are often heterozygous loss-of-function alleles, indicating a dosage-sensitive role for SWI/SNF subunits in chromatin regulation. However, the molecular mechanisms that regulate SWI/SNF subunit dosage to ensure proper complex assembly remain largely unexplored. We performed a genome-wide CRISPR KO screen, using epigenome editing in mouse embryonic stem cells, and identified Mlf2 and Rbm15 as regulators of SWI/SNF complex activity. First, we show that MLF2, a poorly characterized chaperone protein, regulates a subset of SWI/SNF target genes by promoting its chromatin remodeling activity. Rapid degradation of MLF2 reduces chromatin accessibility at sites that depend on high levels of SWI/SNF binding to maintain open chromatin. Next, we find that RBM15, part of the m6A RNA methylation writer complex, controls m6A modifications on specific SWI/SNF mRNAs to regulate protein levels of these subunits. Misregulation of m6A methylation causes overexpression of core SWI/SNF subunits leading to the assembly of incomplete complexes lacking the catalytic ATPase/ARP subunits. These data indicate that targeting modulators of SWI/SNF complex assembly may offer a potent therapeutic strategy for diseases associated with impaired chromatin remodeling.