Project description:We aimed at investigating the function of TIP60 in the in the mammalian hippocampus. For this, we used mice with a forebrain-specific deletion of Tip60 upon tamoxifen injection (Tip60 cKO). RNA-sequencing was applied to examine the transcriptome changes in the CA1 region upon Tip60 deletion. We observed massive transcriptional changes and identified a neurodegeneration-related signature at a time when there are no obvious morphological changes in Tip60 cKO mice. Later on these mice develop extensive neurodegeneration in hippocampal CA1.
Project description:Hematopoietic stem cells (HSC) have the potential to replenish the blood system for the lifetime of the organism. Their two defining properties, self-renewal and differentiation, are tightly regulated by the epigenetic machineries. Here, using conditional gene knockout models, we demonstrate a critical requirement of lysine acetyltransferase 5 (also known as Tip60) for murine HSC maintenance both in the embryonic and adult stages, which depends on its acetyltransferase activity. Genome-wide chromatin and transcriptome profiling revealed that Tip60 co-localizes with c-Myc and that Tip60 deletion suppress the expression of Myc target genes, which are associated with critical biological processes for HSC maintenance, cell-cycle and DNA repair. Notably, acetylated H2A.Z (acH2A.Z) was enriched at the Tip60-bound active chromatin and Tip60 deletion induced a robust reduction in the acH2A.Z / H2A.Z ratio. These results uncover a critical epigenetic regulatory layer for HSC maintenance through Tip60 dependent H2A.Z acetylation to activate Myc target genes.
Project description:The Tip60 (also known as Kat5) lysine acetyltransferase functions broadly as a transcriptional co-activator that acetylates histones. In contrast, Tip60 functions in embryonic stem cells (ESCs) both to silence genes that promote differentiation and to activate genes required for proliferation. The mechanism by which Tip60 functions as a repressor is unknown. Here we show that the class II histone deacetylase Hdac6 co-purifies with Tip60-p400 complex from ESCs and is necessary for complete silencing of most differentiation genes targeted by Tip60. In contrast to differentiated cells, where Hdac6 is mainly cytoplasmic and does not interact with Tip60, Hdac6 is largely nuclear in ESCs and neural stem cells (NSCs) and interacts with Tip60-p400 in both cell types. Hdac6 is enriched at promoters bound by Tip60-p400 in ESCs, but while Tip60 binds on both sides of transcription start sites (TSSs), Hdac6 binding overlaps with only the downstream Tip60 peak. Surprisingly, Hdac6 does not deacetylate histones at these sites, but rather is required for Tip60 binding. These data suggest that nuclear exclusion of Hdac6 during differentiation plays a major role in modulation of Tip60-p400 function. We determined the genome-wide localization of Tip60 and Hdac6 in mouse ES cells, and examined genomic binding profiles of Tip60 and Hdac6 upon indicated knockdown by ChIP-seq. We examined genomic binding profiles of p400 upon indicated knockdown by ChIP-seq.
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:Mechanistic study on the differential responses of the two hippocampal adjoining regions, i.e., CA1 and CA3, to elevated oxidative stress. Keywords: Time course stress response study
Project description:Although histone-modifying enzymes are assumed to function in a manner dependent on their enzymatic activities, this assumption remains untested for many factors. Here we show the Tip60 (Kat5) lysine acetyltransferase (KAT), which is essential for embryonic stem cell (ESC) self-renewal and pre-implantation development, performs these functions independently of its KAT activity. Unlike ESCs depleted of Tip60, KAT–deficient ESCs exhibited minimal alterations in gene expression, chromatin accessibility at Tip60 binding sites, and self-renewal, thus demonstrating a critical KAT–independent role of Tip60 in ESC maintenance. In contrast, KAT–deficient ESCs exhibited impaired differentiation into mesoderm and endoderm, demonstrating a second, KAT–dependent function in differentiation. Consistent with this phenotype, KAT–deficient mouse embryos exhibited post-implantation developmental defects. These findings establish separable KAT–dependent and KAT–independent functions of Tip60 in ESCs and during embryonic development, raising the possibility of undiscovered catalysis-independent functions of additional KATs.
Project description:Aging is associated with a decline in hippocampal mediated learning and memory, a process which can be ameliorated by dietary (caloric) restriction. We used Affymetrix gene expression analysis to monitor changes in three regions of the hippocampus (CA1, CA3, DG) of middle aged (18 months) and old (28 month) rats that were exposed to dietary restriction. Old rats were determined to be good performers (GP) or poor performers (PP) in behavioural tests to assess their hippocampal function. We used Affymetrix gene expression analysis to monitor changes in three regions of the hippocampus (CA1, CA3, DG) of middle aged (18 months) and old (28 month) rats that were exposed to dietary restriction.