Project description:Hematopoietic stem cells (HSC) are regulated to keep the balance between self-renewal and differentiation. However, little is known about post-translational regulations in HSCs. In this study, we characterize the role of DDB1, a component of the Cul4A-DDB1 E3 ubiquitin ligase complex, in HSCs and progenitors by using conditional DDB1 knockout models. We show that the maintenance and differentiation of both adult and fetal HSCs and progenitor cells is dependent on DDB1 function. Deletion of DDB1 alters cell cycle progression and induces apoptosis. Furthermore, deletion of DDB1 in developing thymocytes had no effects on T cell differentiation, whereas DDB1-deficient peripheral T cells were not able to enter cell cycle when stimulated in vitro. In addition, DDB1 is essential for T cell leukemia initiation. Our results reveal that DDB1 is required for adult and fetal hematopoiesis as it controls progenitor and stem cell homeostasis. Transcriptional consequences of inactivating DDB1 in fetal LSK cells. Four samples were analyzed: wild-type (WT) control and DDB1-deficient (DDB1) Lin-ckit+Sca1+ (LSK) cells sorted from fetal livers E16.5 of DDB1 flox/flox, VavCre+ and control mice.
Project description:Hematopoietic stem cells (HSC) are regulated to keep the balance between self-renewal and differentiation. However, little is known about post-translational regulations in HSCs. In this study, we characterize the role of DDB1, a component of the Cul4A-DDB1 E3 ubiquitin ligase complex, in HSCs and progenitors by using conditional DDB1 knockout models. We show that the maintenance and differentiation of both adult and fetal HSCs and progenitor cells is dependent on DDB1 function. Deletion of DDB1 alters cell cycle progression and induces apoptosis. Furthermore, deletion of DDB1 in developing thymocytes had no effects on T cell differentiation, whereas DDB1-deficient peripheral T cells were not able to enter cell cycle when stimulated in vitro. In addition, DDB1 is essential for T cell leukemia initiation. Our results reveal that DDB1 is required for adult and fetal hematopoiesis as it controls progenitor and stem cell homeostasis. Transcriptional consequences of inactivating DDB1 in fetal LSK cells.
Project description:Quiescent hepatic stem cells (HSCs) can be activated when hepatocyte proliferation is compromised. Chemical injury rodent models have been widely used to study the locazation, biomarkers, and signaling pathways in HSCs, but these models usually exhibit severe promiscuous toxicity and fail to distinguish damaged and non-damaged cells. Our goal is to establish new animal models to overcome these limitations, thereby providing new insights into HSC biology and application. We generated mutant mice with constitutive or inducible deletion of Damaged DNA Binding protein 1 (DDB1), an E3 ubiquitin ligase, in hepatocytes. We show that deletion of DDB1 abolishes self-renewal capacity of mouse hepatocytes in vivo, leading to compensatory activation and proliferation of DDB1-expressing OCs. Importantly, the DDB1 mutant mice exhibit very minor liver damage, compared to a chemical injury model. Microarray analysis reveals several previously unrecognized markers, enriched in oval cells. This genetic model in which irreversible inhibition of hepatocyte duplication results in HSC-driven liver regeneration. The DDB1 mutant mice can be broadly applied to studies of HSC differentiation, HSC niche and HSCs as origin of liver cancer. Total RNA obtained from isolated EpCAM+ cells from DDB1 mutant mice compared to wild type hepatocytes
Project description:We identified the ubiquitin ligase Huwe1 as a crucial regulator of hematopoietic stem cell (HSC) functions. We generated Huwe1 conditional knock-out mice and discovered that the loss of this ligase causes an increased proliferation and stem cell exhaustion, together with a decreased lymphoid specification in vivo. We observed that the ubiquitin ligase Huwe1 is controlling the expression of N-myc at the level of the most immature stem and progenitor hematopoietic populations, mediating the described effects. Hematopoietic stem cells (HSC) from the bone marrow of transgenic animals carrying a N-myc/mCherry fusion gene were sorted according to N-myc expression (defined by mCherry) into N-myc high and low subpopulations. Each of these 2 populations was subjected to microarray gene expression profiling.
Project description:We identified the ubiquitin ligase Huwe1 as a crucial regulator of hematopoietic stem cell (HSC) functions. We generated Huwe1 conditional knock-out mice and discovered that the loss of this ligase causes an increased proliferation and stem cell exhaustion, together with a decreased lymphoid specification in vivo. We observed that the ubiquitin ligase Huwe1 is controlling the expression of N-myc at the level of the most immature stem and progenitor hematopoietic populations, mediating the described effects.
Project description:We identified the ubiquitin ligase Huwe1 as a crucial regulator of hematopoietic stem cell (HSC) functions. We generated Huwe1 conditional knock-out mice and discovered that the loss of this ligase causes an increased proliferation and stem cell exhaustion, together with a decreased lymphoid specification in vivo. We observed that the ubiquitin ligase Huwe1 is controlling the expression of N-myc at the level of the most immature stem and progenitor hematopoietic populations, mediating the described effects.
Project description:Aged hematopoietic stem cells (HSCs) exhibit compromised reconstitution capacity and differentiation-bias towards myeloid lineage. While, the molecular mechanism behind it remains not fully understood. In this study, we observed that the expression of pseudouridine (Ψ) synthase 10 is increased in aged hematopoietic stem and progenitor cells (HSPCs) and enforced PUS10 recapitulates the phenotype of aged HSCs, which is not achieved by its Ψ synthase activity. Consistently, we observed no difference of tRNA pseudouridylation profile between young and aged HSPCs. No significant alteration of hematopoietic homeostasis and HSC function is observed in young Pus10-/- mice, while aged Pus10-/-mice exhibit mild alteration of hematopoietic homeostasis and HSC function. Moreover, we observed that PUS10 is ubiquitinated by E3 ubiquitin ligase CRL4DCAF1 complex and the increase of PUS10 in aged HSPCs is due to aging-declined CRL4DCAF1-mediated ubiquitination degradation signaling. Taken together, this study for the first time evaluated the role of PUS10 in HSC aging and function, and provided novel insight for HSC rejuvenation and clinical application.
Project description:Hematopoietic cell fate decisions such as self-renewal and differentiation are highly regulated through multiple molecular pathways. One pathway, the ubiquitin proteasome system (UPS), controls protein levels by tagging them with polyubiquitin chains and promoting their degradation through the proteasome. Ubiquitin E3 ligases serve as the substrate-recognition component of the UPS. Through investigating the FBOX family of E3 ligases, we discovered that Fbxo21 was highly expressed in the hematopoietic stem and progenitor cell (HSPC) population, and showed low to no expression in mature myeloid populations. To determine the role of FBXO21 on HSPC maintenance, self-renewal, and differentiation, we generated shRNAs against FBXO21 and a hematopoietic specific Fbxo21 conditional knockout (cKO) mouse model. We found that silencing FBXO21 in HSPCs led to a loss in colony formation and an increase in cell differentiation in vitro. Additionally, stressing the HSPC populations in our Fbxo21 cKO mouse with 5-FU injections resulted in a decrease in survival, despite these populations showing minimal alterations during steady-state hematopoiesis. Although FBXO21 has previously been proposed to regulate cytokine signaling via ASK and p38, our results show that depletion of FBXO21 led to altered ERK signaling in vitro. Together, these findings suggest ubiquitin E3 ligase FBXO21 regulates HSPCs through cytokine mediated pathways.
Project description:DDB1 is typically recognized as a component of the Cullin4 (CUL4)-RING E3 ubiquitin ligase complex. Here, we show that DDB1 functions independently of CUL4 to promote adipogenesis and diet-induced obesity. In contrast to depletion of CUL4A or CUL4B that stimulates adipogenesis, lack of DDB1 dramatically suppresses the process. Re-introduction of a DDB1 mutant that lacks the binding ability to CUL4A or CUL4B fully restores adipogenesis in DDB1-deficient preadipocytes. Furthermore, while inducibly knocking out Cul4a or Cul4b in mice aggravates diet-induced obesity, Ddb1+/- mice are lean on high-fat diet. Mechanistically, by binding the bromodomain-containing histone reader BRWD3, DDB1 is recruited to acetylated histones in the proximal promoters of immediate-early response genes, where it facilitates the release of paused RNA polymerase II (Pol II) and activates the transcription of these genes. Our findings have thus uncovered a mechanism of activating the transcriptional cascade in adipogenesis by DDB1-mediated release of paused Pol II.