Project description:The cytoplasmic functions of Wiskott-Aldrich Syndrome family (WASP) proteins are well known and include roles in cytoskeleton reorganization and membrane-cytoskeletal interactions important for membrane/vesicle trafficking, morphogenesis, immune response and signal transduction. Mis-regulation of these proteins is associated with immune deficiency and metastasis. Cytoplasmic WASP proteins act as effectors of Rho family GTPases and polymerize branched actin through the Arp2/3 complex. However, recent evidence has revealed that this classically cytoplasmic protein family also functions in the nucleus. Previously, we identified Drosophila washout (wash) as a new member of the WASP family with essential cytoplasmic roles in early development. Here we show that Wash is also present in the nucleus and plays a key role in nuclear organization via its interaction with Lamin Dm0 at the nuclear envelope. Wash and Lamin Dm0 occupy similar genomic regions that overlap with transcriptionally silent chromatin including constitutive heterochromatin. Strikingly, wash mutant and knockdown nuclei exhibit the same abnormal wrinkled morphology observed in diverse laminopathies, including the Hutchinson-Gilford progeria syndrome, and consistent with disruption of the nuclear organization of several sub-nuclear structures including cajal bodies and the chromocenter in salivary glands. We also found that Wash and Lamin knockdown disrupt chromatin accessibility of repressive compartments in agreement with an observed global redistribution of repressive histone modifications. Functional genetic approaches show wash mutants exhibit similar phenotypes to lamin Dm0 mutants, suggesting they participate in similar regulatory networks. Our results reveal a novel role for Wash in modulating nuclear organization via its interaction with the nuclear envelope protein Lamin Dm0. These findings highlight the functional complexity of WASP family proteins and provide new venues to understand their molecular roles in cell biology and disease. DamID chromatin profiling demostrate that Wash binds similar regions to those bound by Lamin Dm0, in particular transcriptional silent chromatin
Project description:Drosophila Haspin kinase phosphorylates Histone H3 at threonine 3 at centromeric heterochromatin and either lamin- or polycomb-enriched euchromatic regions, being required for nuclear organization of interphase cells and polycomb-dependent gene silencing.
Project description:The cytoplasmic functions of Wiskott-Aldrich Syndrome family (WASP) proteins are well known and include roles in cytoskeleton reorganization and membrane-cytoskeletal interactions important for membrane/vesicle trafficking, morphogenesis, immune response and signal transduction. Mis-regulation of these proteins is associated with immune deficiency and metastasis. Cytoplasmic WASP proteins act as effectors of Rho family GTPases and polymerize branched actin through the Arp2/3 complex. However, recent evidence has revealed that this classically cytoplasmic protein family also functions in the nucleus. Previously, we identified Drosophila washout (wash) as a new member of the WASP family with essential cytoplasmic roles in early development. Here we show that Wash is also present in the nucleus and plays a key role in nuclear organization via its interaction with Lamin Dm0 at the nuclear envelope. Wash and Lamin Dm0 occupy similar genomic regions that overlap with transcriptionally silent chromatin including constitutive heterochromatin. Strikingly, wash mutant and knockdown nuclei exhibit the same abnormal wrinkled morphology observed in diverse laminopathies, including the Hutchinson-Gilford progeria syndrome, and consistent with disruption of the nuclear organization of several sub-nuclear structures including cajal bodies and the chromocenter in salivary glands. We also found that Wash and Lamin knockdown disrupt chromatin accessibility of repressive compartments in agreement with an observed global redistribution of repressive histone modifications. Functional genetic approaches show wash mutants exhibit similar phenotypes to lamin Dm0 mutants, suggesting they participate in similar regulatory networks. Our results reveal a novel role for Wash in modulating nuclear organization via its interaction with the nuclear envelope protein Lamin Dm0. These findings highlight the functional complexity of WASP family proteins and provide new venues to understand their molecular roles in cell biology and disease. We evaluated the effect of Wash knockdown in S2R+ cells on chromatin accessibility using an M.SssI-based approach.
Project description:The nuclear lamina (NL) is a filamentous layer lining the inner-nuclear-membrane (INM) that aids in the organization of the genome in large domains of low transcriptional activity. Recently, it was shown that the single-cell genome-NL interactions are much more dynamic than previously anticipated, which challenges the concept of the NL as a safe guard for transcriptional repressed genes. Here we discuss the role of the NL in light of these new findings and introduce Lamin A and BAF as potential modulators of LAD positioning BAF-chromatin and Lamin B2-chromatin interactions were assayed in human HT1080 by DamID on Nimblegen microarrays, with two biological replicates each, that were hybridized in a dye-swap design.
Project description:Specific interactions of the genome with the nuclear lamina (NL) are thought to assist chromosome folding inside the nucleus and to contribute to the regulation of gene expression. High-resolution mapping has recently identified hundreds of large, sharply defined lamina-associated domains (LADs) in the human genome, and suggested that the insulator protein CTCF may help to demarcate these domains. Here, we report the detailed structure of LADs in Drosophila cells, and investigate the putative roles of five insulator proteins in LAD organization. We found that of these five proteins, only SU(HW) binds preferentially at LAD borders and at specific positions inside LADs, while GAF, CTCF, BEAF-32 and DWG are mostly absent from these regions. By knockdown and overexpression studies we demonstrate that SU(HW) weakens LAD – NL interactions by a local antagonistic effect. Our results provide insights into the evolution of LAD organization and reveal a role for SU(HW) in the regulation of genome – NL interactions. DamID experiments for Lamin, CTCF, SU(HW), GAF, DWG, and BEAF-32, and for Lamin after overexpression and after knockdown of SU(HW), were performed in Drosophila cell cultures. Samples were hybridized to 380k NimbleGen arrays with 300 bp probe spacing. Every experiment was done in duplicate in the reverse dye orientation. The supplementary file 'GSE20311_DamID_norm_mean.txt' contains the mean log2(Dam-fusion/Dam-only) values of two replicates.
Project description:The nuclear lamina (NL) binds chromatin in vitro and is thought to function in its organisation, but genes that interact with the NL are unknown. Using an in vivo approach we identified 474 Drosophila genes that interact with B–type lamin, Lam. These genes are transcriptionally silent, late replicating, lack active histone marks, and are widely spaced. These factors collectively predict Lamin binding behavior, indicating the NL integrates variant and invariant chromatin features. Consistently, NE proximity is partly conserved between cell types and induction of gene expression or active histone marks reduces Lam binding. Lam target genes cluster in the genome, and these clusters are coordinately expressed during development. This genome-wide analysis gives clear insight into the nature and dynamic behavior of the genome at the NL. Keywords: DamID and expression profiling
Project description:In this study, we showed that reduced nuclear lamin-B marks the onset of physiological decline in young adult Drosophila and its ectopic expression in dopaminergic neurons is sufficient to improve their locomotor activity during aging. Furthermore, the decline in lamin-B protein appeared to be unrelated to its mRNA level. Instead, we found drastic changes to its protein solubility during aging. Given the importance of nuclear lamin-B in genome organization and the advancement of single-cell epigenome profiling technology, our findings provide the community the basis to further study how altered level of lamin-B protein may elicit changes in gene expression that can contribute to the onset of physiological decline in animals.