Project description:The cyclin-dependent kinases (CDK) CDK6 and CDK4 have redundant functions in regulating cell-cycle progression. We describe a novel role for CDK6 in hematopoietic and leukemic stem cells (HSCs and LSCs) that exceeds its function as cell-cycle regulator. Although hematopoiesis appears regular under steady state conditions Cdk6-/- HSCs do not efficiently repopulate upon competitive transplantation and Cdk6-deficient mice are significantly more susceptible to 5-fluorouracil (5-FU) treatment. We find that activation of HSCs requires CDK6, which interferes with transcription of key regulators including Egr1. The central role of Egr1 is supported by transcriptional profiling of HSCs. The impaired repopulation capacity extends to BCR-ABLp210+ leukemic stem cells. Transplantation with BCR-ABLp210+-infected bone marrow (BM) from Cdk6-/- mice fails to induce disease although recipient mice do harbor LSCs. Egr1 knock-down in cdk6-/- BCR-ABLp210+ LSKs significantly enhances colony formation underlining the importance of the Cdk6-Egr1 axis. Our findings define CDK6 as an important regulator of stem cell activation and as essential component of a transcriptional complex that suppresses Egr1 in HSCs and LSCs. Four-condition experiment, Untreated or polyI:C-treated CDK6-/- cells versus untreated or polyI:C-treated wild-type cells. Biological replicates: 3 untreated replicates, 3 polyI:C-treated replicates.
Project description:The cyclin-dependent kinases (CDK) CDK6 and CDK4 have redundant functions in regulating cell-cycle progression. We describe a novel role for CDK6 in hematopoietic and leukemic stem cells (HSCs and LSCs) that exceeds its function as cell-cycle regulator. Although hematopoiesis appears regular under steady state conditions Cdk6-/- HSCs do not efficiently repopulate upon competitive transplantation and Cdk6-deficient mice are significantly more susceptible to 5-fluorouracil (5-FU) treatment. We find that activation of HSCs requires CDK6, which interferes with transcription of key regulators including Egr1. The central role of Egr1 is supported by transcriptional profiling of HSCs. The impaired repopulation capacity extends to BCR-ABLp210+ leukemic stem cells. Transplantation with BCR-ABLp210+-infected bone marrow (BM) from Cdk6-/- mice fails to induce disease although recipient mice do harbor LSCs. Egr1 knock-down in cdk6-/- BCR-ABLp210+ LSKs significantly enhances colony formation underlining the importance of the Cdk6-Egr1 axis. Our findings define CDK6 as an important regulator of stem cell activation and as essential component of a transcriptional complex that suppresses Egr1 in HSCs and LSCs.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes. Mouse hematopoietic stem cells were purified from bone marrow cells using negative and positive selection with a Magnetic-Activated Cell Sorter (MACS). total RNA and mRNA were purified from the purified cells using Trizol reagent and magnetic oligo dT beads. Double strand cDNAs were synthesized using a cDNA synthesis kit and anchored oligo dT primers. After NlaIII digestion, 3’ cDNAs were isolated and amplified through 16-cycle PCR. SAGE tags were released from the 3’ cDNA after linker ligation. Ditags were formed, concatemerized and cloned into a pZERO vector. Sequencing reactions were performed with the ET sequencing terminator kit. Sequences were collected using a Megabase 1000 sequencer. SAGE tag sequences were extracted using SAGE 2000 software.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:The mechanisms underlying operational tolerance after hematopoietic stem cell transplantation in humans are poorly understood. We studied two independent cohorts of patients who underwent allogeneic hematopoietic stem cell transplantation from human leukocyte antigen-identical siblings. Primary tolerance was associated with long-lasting reshaping of the recipients' immune system compared to their healthy donors with an increased proportion of regulatory T cell subsets and decreased T cell activation, proliferation, and migration. Transcriptomics profiles also identified a role for nicotinamide adenine dinucleotide biosynthesis in the regulation of immune cell functions. We then compared individuals with operational tolerance and nontolerant recipients at the phenotypic, transcriptomic, and metabolomic level. We observed alterations centered on CD38<sup>+</sup>-activated T and B cells in nontolerant patients. In tolerant patients, cell subsets with regulatory functions were prominent. RNA sequencing analyses highlighted modifications in the tolerant patients' transcriptomic profiles, particularly with overexpression of the ectoenzyme <i>NT5E</i> (encoding CD73), which could counterbalance CD38 enzymatic functions by producing adenosine. Further, metabolomic analyses suggested a central role of androgens in establishing operational tolerance. These data were confirmed using an integrative approach to evaluating the immune landscape associated with operational tolerance. Thus, balance between a CD38-activated immune state and CD73-related production of adenosine may be a key regulator of operational tolerance.
Project description:The mechanisms underlying operational tolerance after hematopoietic stem cell transplantation in humans are poorly understood. We studied two independent cohorts of patients who underwent allogeneic hematopoietic stem cell transplantation from human leukocyte antigen-identical siblings. Primary tolerance was associated with long-lasting reshaping of the recipients' immune system compared to their healthy donors with an increased proportion of regulatory T cell subsets and decreased T cell activation, proliferation, and migration. Transcriptomics profiles also identified a role for nicotinamide adenine dinucleotide biosynthesis in the regulation of immune cell functions. We then compared individuals with operational tolerance and nontolerant recipients at the phenotypic, transcriptomic, and metabolomic level. We observed alterations centered on CD38<sup>+</sup>-activated T and B cells in nontolerant patients. In tolerant patients, cell subsets with regulatory functions were prominent. RNA sequencing analyses highlighted modifications in the tolerant patients' transcriptomic profiles, particularly with overexpression of the ectoenzyme <i>NT5E</i> (encoding CD73), which could counterbalance CD38 enzymatic functions by producing adenosine. Further, metabolomic analyses suggested a central role of androgens in establishing operational tolerance. These data were confirmed using an integrative approach to evaluating the immune landscape associated with operational tolerance. Thus, balance between a CD38-activated immune state and CD73-related production of adenosine may be a key regulator of operational tolerance.