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:COP1 and DET1 are components of an E3 ubiquitin ligase that is conserved from plants to humans. Mammalian COP1 binds to DET1 and is a substrate adaptor for the CUL4A-DDB1-RBX1 RING E3 ligase. Its transcription factor substrates, including c-Jun, ETV4, and ETV5, are targeted for proteasomal degradation to effect rapid transcriptional changes in response to cues such as growth factor deprivation. Here we show that a homozygous DET1R26W mutation that is linked to lethal developmental abnormalities in humans disrupts DET1 binding to DDB1 and compromises E3 ligase function. Human-induced pluripotent stem cells bearing the homozygous DET1R26W mutation expressed ETV4 and ETV5 highly, had alterations in mitochondrial protein expression, and exhibited impaired neuronal differentiation. Mice lacking Det1 died during embryogenesis, while Det1 deletion just in neural stem cells elicited hydrocephalus, cerebellar dysplasia, and neonatal lethality. Our findings highlight an important role for DET1 in the neurological development of mice and humans.
Project description:COP1 and DET1 are components of an E3 ubiquitin ligase that is conserved from plants to humans. Mammalian COP1 binds to DET1 and is a substrate adaptor for the CUL4A-DDB1-RBX1 RING E3 ligase. Its transcription factor substrates, including c-Jun, ETV4, and ETV5, are targeted for proteasomal degradation to effect rapid transcriptional changes in response to cues such as growth factor deprivation. Here we show that a homozygous DET1R26W mutation that is linked to lethal developmental abnormalities in humans disrupts DET1 binding to DDB1 and compromises E3 ligase function. Human-induced pluripotent stem cells bearing the homozygous DET1R26W mutation expressed ETV4 and ETV5 highly, had alterations in mitochondrial protein expression, and exhibited impaired neuronal differentiation. Mice lacking Det1 died during embryogenesis, while Det1 deletion just in neural stem cells elicited hydrocephalus, cerebellar dysplasia, and neonatal lethality. Our findings highlight an important role for DET1 in the neurological development of mice and humans.
Project description:Cullin proteins are scaffolds that coordinate assembly of cullin-RING E3 ubiquitin (Ub) ligases (CRL), complexes that control post-translational ubiquitin modification and degradation of cellular proteins. Cullin-5 (Cul5) coordinates assembly of CRL complexes containing the RING E3 ligase Rbx1/2, the adapter proteins Elongins B and C, and a Suppressor of Cytokine Signalling (SOCS) box-containing substrate recognition protein. To explore potential roles for Cul5, we generated mice lacking Cul5 in the in hematopoietic system. Analyses included biological and molecular studies including proteomic analysis of differential expression of proteins in primary purified hematopoietic stem/progenitor (LSK) cells lacking Cul5.
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.