Project description:In solid tumors, quiescent/G0 cell populations likely play important roles in maintaining cellular heterogeneity and promoting recurrence after stand of care. However, little is known about the mechanisms of tumor cell G0 ingress and egress. To discover regulators of G0-like states for glioblastoma (GBM), we performed a genome-wide CRISPR-Cas9 screen in patient-derived GBM stem-like cells (GSCs) for genes that when inhibited trap cells in G0-like states. We identify the protein acetyltransferase KAT5 as a key regulator of G0 and cell cycle dynamics in GSCs and GSC-derived tumors. In primary gliomas, KAT5low cells display quiescent properties, while overall KAT5 activity increases as tumors become more aggressive. Further, we find that KAT5 activity suppresses the emergence of non-dividing subpopulations with oligodendrocyte progenitor and radial glial cell characteristics both in vitro and in a GSC tumor model. These results reveal that KAT5 activity regulates transitions between non-dividing, neurodevelopmental, and proliferative states in GBM tumors.
Project description:In solid tumors, quiescent/G0 cell populations likely play important roles in maintaining cellular heterogeneity and promoting recurrence after stand of care. However, little is known about the mechanisms of tumor cell G0 ingress and egress. To discover regulators of G0-like states for glioblastoma (GBM), we performed a genome-wide CRISPR-Cas9 screen in patient-derived GBM stem-like cells (GSCs) for genes that when inhibited trap cells in G0-like states. We identify the protein acetyltransferase KAT5 as a key regulator of G0 and cell cycle dynamics in GSCs and GSC-derived tumors. In primary gliomas, KAT5low cells display quiescent properties, while overall KAT5 activity increases as tumors become more aggressive. Further, we find that KAT5 activity suppresses the emergence of non-dividing subpopulations with oligodendrocyte progenitor and radial glial cell characteristics both in vitro and in a GSC tumor model. These results reveal that KAT5 activity regulates transitions between non-dividing, neurodevelopmental, and proliferative states in GBM tumors.
Project description:Many cells in mammals exist in the state of quiescence, which is characterized by reversible exit from the cell cycle. Quiescent cells are widely reported to exhibit reduced size, nucleotide synthesis, and metabolic activity. Much lower glycolytic rates have been reported in quiescent compared with proliferating lymphocytes. In contrast, we show here that primary human fibroblasts continue to exhibit high metabolic rates when induced into quiescence via contact inhibition. By monitoring isotope labeling through metabolic pathways and quantitatively identifying fluxes from the data, we show that contact-inhibited fibroblasts utilize glucose in all branches of central carbon metabolism at rates similar to those of proliferating cells, with greater overflow flux from the pentose phosphate pathway back to glycolysis. Inhibition of the pentose phosphate pathway resulted in apoptosis preferentially in quiescent fibroblasts. By feeding the cells labeled glutamine, we also detected a “backwards” flux in the tricarboxylic acid cycle from α-ketoglutarate to citrate that was enhanced in contact-inhibited fibroblasts; this flux likely contributes to shuttling of NADPH from the mitochondrion to cytosol for redox defense or fatty acid synthesis. The high metabolic activity of the fibroblasts was directed in part toward breakdown and resynthesis of protein and lipid, and in part toward excretion of extracellular matrix proteins. Thus, reduced metabolic activity is not a hallmark of the quiescent state. Quiescent fibroblasts, relieved of the biosynthetic requirements associated with generating progeny, direct their metabolic activity to preservation of self integrity and alternative functions beneficial to the organism as a whole. mRNAs were analyzed by two color microarray from two separate human neonatal dermal fibroblasts cell lines in proliferating, 7 days contact inhibition, or 14 days contact inhibition. Contact inhibited samples were co-hybridized to proliferating samples as a control, while an additional array co-hybridized the two proliferating samples to analyze reproducibility.
Project description:Many cells in mammals exist in the state of quiescence, which is characterized by reversible exit from the cell cycle. Quiescent cells are widely reported to exhibit reduced size, nucleotide synthesis, and metabolic activity. Much lower glycolytic rates have been reported in quiescent compared with proliferating lymphocytes. In contrast, we show here that primary human fibroblasts continue to exhibit high metabolic rates when induced into quiescence via contact inhibition. By monitoring isotope labeling through metabolic pathways and quantitatively identifying fluxes from the data, we show that contact-inhibited fibroblasts utilize glucose in all branches of central carbon metabolism at rates similar to those of proliferating cells, with greater overflow flux from the pentose phosphate pathway back to glycolysis. Inhibition of the pentose phosphate pathway resulted in apoptosis preferentially in quiescent fibroblasts. By feeding the cells labeled glutamine, we also detected a “backwards” flux in the tricarboxylic acid cycle from α-ketoglutarate to citrate that was enhanced in contact-inhibited fibroblasts; this flux likely contributes to shuttling of NADPH from the mitochondrion to cytosol for redox defense or fatty acid synthesis. The high metabolic activity of the fibroblasts was directed in part toward breakdown and resynthesis of protein and lipid, and in part toward excretion of extracellular matrix proteins. Thus, reduced metabolic activity is not a hallmark of the quiescent state. Quiescent fibroblasts, relieved of the biosynthetic requirements associated with generating progeny, direct their metabolic activity to preservation of self integrity and alternative functions beneficial to the organism as a whole.
Project description:Isolated proximal tubular cells from proximal tubular cell-specific KAT5 knockout mice for RNA extraction and hybridization on Affymetrix microarrays. We sought to obtain the physiological significance of KAT5 in proximal tubular cells.
Project description:KAT5 encodes an essential lysine acetyltransferase previously called TIP60 involved in gene expression, DNA repair, chromatin remodeling, apoptosis and cell proliferation; but it remains unclear whether variants in this gene causes a genetic disease. Here, we study three individuals with heterozygous de novo missense variants in KAT5 that affect normally invariant residues, with one at the chromodomain (p.Arg53His) and two at or near the acetyl-CoA binding site (p.Cys369Ser and p.Ser413Ala). All three individuals have cerebral malformations, seizures, global developmental delay or intellectual disability, and severe sleep disturbance. Progressive cerebellar atrophy was also noted. Histone acetylation assays with purified mutant KAT5 demonstrated that the variants decrease or abolish the ability of the resulting NuA4/TIP60 multi-subunit complexes to acetylate the histone H4 tail in chromatin. Transcriptomic analysis in patient-derived fibroblasts showed deregulation of multiple genes controlling development. Moreover, there was also upregulated expression of PER1 (a key gene involved in circadian control), in agreement with sleep anomalies in all the patients. In conclusion, dominant missense KAT5 variants cause histone acetylation deficiency with transcriptional dysregulation of multiples genes, thereby leading to a neurodevelopmental syndrome with sleep disturbance, cerebellar atrophy and facial dysmorphisms suggesting a recognizable syndrome.
Project description:The cranial neural crest plays a fundamental role in orofacial development and morphogenesis. As a pluripotent and dynamic cell population, the cranial neural crest is undergoing vast transcriptional alterations throughout embryogenesis and the formation of facial structures. These transcriptional changes are regulated by several transcription factors and remodeling complexes. Previously, we revealed the relevance of the Ep400/Kat5 histone acetyltransferase complex in the cranial neural crest and showed that the knockout of Ep400 causes neural crest-related malformations such as orofacial clefting. Furthermore, a case study identified three patients carrying missense mutations in Kat5 who showed severe mental impairments as well as orofacial clefts.2 The exact molecular causes and mechanisms, however, are still unknown. In this study we selectively knocked out Ep400 or Kat5 in the murine cranial neural crest cell line O9-1 to examine its roles in neural crest biology. To understand the regulatory effects of Ep400 and Kat5, knockout neural crest cells were investigated via bulk RNA sequencing to unravel transcriptomic changes in the affected cells. Bioinformatic analyses hinted at the regulation of major cellular functions such as proliferation, ATP generation and protein synthesis by the Ep400/Kat5 complex. Reduced proliferation was confirmed by crystal violet staining, phospho-histone H3 staining and the determination of mitotic cells with condensed chromatin in vitro. We did not detect increased apoptosis in the knockout cell lines. The energetic profile of the cells was investigated by Seahorse technology. The ATP-rate assay showed a decreased glycolytic activity in Ep400- or Kat5-deficient cells. An O-propargyl-puromycin (OPP) Click-iT assay revealed a significant reduction in protein synthesis. To verify in vivo the discovered in vitro effects, Ep400 and Kat5 were selectively ablated in cranial neural crest using Wnt1-Cre in transgenic mice. The knockout of each of the subunits resulted in severe craniofacial malformations from E12.5 onwards. At E10.5 a significant reduction in neural crest-derived tissue and proliferation rate was evident. The strong defect in orofacial structures of mice lacking Kat5 or Ep400 completely correspond to the milder orofacial malformations in patients carrying heterozygous missense mutations. Our results furthermore argue that changes of metabolism, protein synthesis and proliferation in cranial neural crest cells are responsible for the orofacial defects observed in patients.