Analysis of hematopoietic LSK(Lin-Sca1+c-Kit+) cells lacking the Serum response factor (SRF) gene. Results provide insight into the role of SRF in regulating genetic programs important for hematopoietic stem cell development
The transcription factor Srf regulates hematopoietic stem cell adhesion.
Specimen part
View SamplesKnockdown of the transcription factor PU.1 (Spi1) leads to acute myeloid leukemia (AML) in mice. We examined the transcriptome of PU.1 knockdown hematopoietic stem cells (HSC) in the preleukemic phase by linear amplification and genome-wide array analysis to identify transcriptional changes preceding malignant transformation. Hierarchical cluster analysis and principal component analysis clearly distinguished PU.1 knockdown from wildtype HSC. Jun family transcription factors c-Jun and JunB were among the top downregulated targets. Retroviral restoration of c-Jun expression in bone marrow cells of preleukemic mice partially rescued the PU.1-initiated myelomonocytic differentiation block. Lentiviral restoration of JunB at the leukemic stage led to reduced clonogenic growth, loss of leukemic self-renewal capacity, and prevented leukemia in transplanted NOD-SCID mice. Examination of 305 AML patients confirmed the correlation between PU.1 and JunB downregulation and suggests its relevance in human disease. These results delineate a transcriptional pattern that precedes the leukemic transformation in PU.1 knockdown HSC and demonstrate that decreased levels of c-Jun and JunB contribute to the development of PU.1-induced AML by blocking differentiation (c-Jun) and increasing self-renewal (JunB). Therefore, examination of disturbed gene expression in HSC can identify genes whose dysregulation is essential for leukemic stem cell function and are targets for therapeutic interventions.
Essential role of Jun family transcription factors in PU.1 knockdown-induced leukemic stem cells.
No sample metadata fields
View SamplesDuring development, a polarized sheet of epidermal cells undergoes stratification and differentiation to produce the skin barrier. Through mechanisms poorly understood, the process involves adhesion and Notch signaling. To elucidate how epidermal embryogenesis is governed, we conditionally targeted transcription factor serum response factor (SRF), which has been shown to be essential for proper epidermal differentiation in vitro and in vivo. Seeking mechanism, we identified actomyosin-related genes as well-known SRF targets downregulated shortly after ablation. We show that this results in a diminished cortical actomyosin network which fails to regulate the transition of cells from the basal proliferative layer to the suprabasal differentiating layer resulting in an inability of cells to properly execute stratification and differentiation.
Developmental roles for Srf, cortical cytoskeleton and cell shape in epidermal spindle orientation.
No sample metadata fields
View SamplesPolycomb protein group (PcG)-dependent trimethylation on H3-K27(H3K27me3) regulates identity of embryonic stem cells (SCs). How H3K27me3 governs adult SCs and tissue development is unclear. Here, we conditionally target H3-K27-methyltransferases Ezh2 and Ezh1 to address their roles in mouse skin homeostasis. Postnatal phenotypes appear only in doubly-targeted skin, where H3K27me3 is abolished, revealing functional redundancy in EZH1/2 proteins. Surprisingly, while Ezh1/2-null hair follicles (HFs) arrest morphogenesis and degenerate due to defective proliferation and increased apoptosis, epidermis hyperproliferates and survives engraftment. mRNA-microarray studies reveal that despite these striking phenotypic differences, similar genes are upregulated in HF and epidermal Ezh1/2-null progenitors. Featured prominently are a) PcG-controlled non-skin lineage genes, whose expression is still significantly lower than in native tissues, and b) the PcG-regulated Ink4a/Inkb/Arf locus. Interestingly, even though Ink4a/Arf/Ink4b genes are fully activated in HF cells, they only partially so in epidermal-progenitors. Importantly, transduction of Ink4b/Ink4a/Arf shRNAs restores proliferation/survival of Ezh1/2-null HF progenitors in vitro, pointing towards the relevance of this locus to the observed HF phenotypes. Our findings reveal new insights into Polycomb-dependent tissue control and provide a new twist to how different progenitors within one tissue respond to loss of H3K27me3.
EZH1 and EZH2 cogovern histone H3K27 trimethylation and are essential for hair follicle homeostasis and wound repair.
Sex, Age, Specimen part
View SamplesImmune privileged Sertoli cells (SC) survive when transplanted across immunological barriers and prolong the survival of co-transplanted allogeneic and xenogeneic cells in rodent models. However, the mechanism for this survival and protection remains unresolved. We have recently identified a mouse Sertoli cell line (MSC-1) that lacks some of the immunoprotective abilities associated with primary SC. The objective of this study was to compare the survival and gene expression profiles of primary SC and MSC-1 cells to identify factors or immune-related pathways potentially important for SC immune privilege. Primary SC or MSC-1 cells were transplanted as allografts to the renal subcapsular area of nave BALB/c mice and cell survival was analyzed by immunohistochemistry. Additionally, transcriptome differences were investigated by microarray and pathway analyses. While primary SC were detected within the grafts with 100% graft survival throughout the 20-day study, MSC-1 cells w ere rejected between 11 and 14 days with 0% graft survival at 20 days post-transplantation. Microarray analysis identified 3198 genes that were differentially expressed with a 4-fold or higher level in primary SC. Cluster and pathway analyses indicate that the mechanism of SC immune privilege is likely complex with multiple immune modulators being involved such as immunosuppressive cytokines and complement inhibitors, lipid mediators for controlling inflammation, and junctional molecules that control leukocyte movement in and out of the immune privileged space. Further study of these immune modulators will increase our understanding of SC immune privilege and in the long-term lead to improvements in transplantation success.
Immunoprotective properties of primary Sertoli cells in mice: potential functional pathways that confer immune privilege.
Specimen part, Cell line
View SamplesMost human B cell lymphomas (B-NHL) are derived from germinal centers (GCs), the structure where B-cells undergo class switch recombination (CSR) and somatic hypermutation (SHM) and are selected for high-affinity antibody production. The pathogenesis of B-NHL is associated with distinct genetic lesions, including chromosomal translocations and aberrant somatic hypermutation, which appear to arise from mistakes occurring during CSR and SHM. To ascertain the role of CSR and SHM in lymphomagenesis, we crossed three oncogene-driven (MYC, BCL6, MYC/BCL6) mouse models of B cell lymphoma with mice lacking activation-induced cytidine deaminase (AID), the enzyme required for both processes.
AID is required for germinal center-derived lymphomagenesis.
Specimen part
View SamplesGroup-2 innate lymphoid cells (ILC2) serve crucial function in allergy and asthma. Activated ILC2 rapidly proliferate and secret large amounts of type-2 cytokines, such as IL-5 and IL-13. Mechanisms underlying still remain ambiguous. Here we report that Myc is required for ILC2 proliferation and activation in allergic airway inflammation. Inhibition of Myc impair the ILC2 proliferation in vivo and prevented ILC2-mediated airway hyperresponsiveness in vivo.
A critical role for c-Myc in group 2 innate lymphoid cell activation.
Genotype, Cell line
View SamplesLong non-coding RNAs (lncRNAs) regulate diverse biological pathways. Unlike protein coding genes, where methods to comprehensibly study their functional roles in cellular systems are available, techniques to systematically investigate lncRNAs have largely remained unexplored. Here, we report a technology for combined Knockdown and Localization Analysis of Non-coding RNAs (c-KLAN) that merges phenotypic characterization and localization approaches to study lncRNAs. Using a library of endoribonuclease prepared short interfering RNAs (esiRNAs) coupled with a pipeline for synthesizing labeled riboprobes for RNA fluorescence in situ hybridization (FISH), we demonstrate the utility of c-KLAN by identifying a novel transcript Panct1 (Pluripotency associated non-coding transcript 1) that regulates embryonic stem cell identity. We postulate that c-KLAN should be generally useful in the discovery of lncRNAs implicated in various biological processes.
Combined RNAi and localization for functionally dissecting long noncoding RNAs.
Specimen part
View SamplesNarcolepsy is a sleep disorder characterized by excessive daytime sleepiness and attacks of muscle atonia triggered by strong emotions (cataplexy). The best biological marker of narcolepsy is orexin deficiency with dramatic loss in hypothalamic orexin-producing neurons. Together with a tight HLA and T-cell receptor alpha(5) association, narcolepsy is believed to be autoimmune although all attempts to prove it have failed.To characterize orexin specific peptides we produced a transgenic mouse model to access to the orexin neurons transcription profile. We generated BAC-based transgenic mice by replacing the orexin coding sequence by a flag-tagged poly(A) binding protein (Pabp1) cDNA sequence. The basis of this construct is to take advantage of the ability of Pabp1 to bind to the poly(A) tails of mRNAs in vivo. Thus mRNAs from orexin cells are expected to be enriched by cross-linking them to the flag-tagged PABP and then co-immunoprecipitating this complex with a specific anti-flag monoclonal antibody.
Elevated Tribbles homolog 2-specific antibody levels in narcolepsy patients.
Age
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