Role for notch/RBPj in preserving hematopoietic stem cell activity

Abstract

Notch and Wnt signals are required for Hematopoietic Stem Cells (HSCs) generation, however, their putative role for maintenance of HSC in physiological conditions remains unclear. For example specific deletion of RBPj or β-catenin in the hematopoietic system does not compromise the viability of the mice and HSC maintain some repopulation capacity. However, limiting dilution demonstrated that β-catenin-deficient HSCs have decreased self-renewal capacity. In contrast, no evidence for Notch signalling on HSC function has been described. We here analyzed the reconstitution capacity of vav-cre;RBPjlox bone marrow cells by competitive transplant assays into irradiated syngenic mice. We found a significant decrease in the capacity of RBP mutant cells to engraft in primary recipients when compared to wildtype cells, similar to the β-catenin-deficient phenotype. Since both pathways function in an intimate collaboration in other tissues, we generated double RBPj and β-catenin deletion mutants of the hematopoietic system (by using vav1-cre). Interestingly, double knockout animals were viable and born at Mendelian ratios. We will here describe and discuss the phenotype of these double mutants including a detailed analysis of HSC potential and differentiation of the different hematopoietic lineages. Our preliminary data reveals a new role for Notch in maintaining the functionality of adult HSCs, which may involve Wnt/β-catenin. This research is funded by by Ministerio Ciencia e Innovación (PLE2009-0111, SAF2010-15450, RD12/0036/0054), AGAUR (2009SGR-23 and CONES2010-0006). Notch and Wnt signals are required for Hematopoietic Stem Cells (HSCs) generation, however, their putative role for maintenance of HSC in physiological conditions remains unclear. For example specific deletion of RBPj or β-catenin in the hematopoietic system does not compromise the viability of the mice and HSC maintain some repopulation capacity. However, limiting dilution demonstrated that β-catenin-deficient HSCs have decreased self-renewal capacity. In contrast, no evidence for Notch signalling on HSC function has been described. We here analyzed the reconstitution capacity of vav-cre;RBPjlox bone marrow cells by competitive transplant assays into irradiated syngenic mice. We found a significant decrease in the capacity of RBP mutant cells to engraft in primary recipients when compared to wildtype cells, similar to the β-catenin-deficient phenotype. Since both pathways function in an intimate collaboration in other tissues, we generated double RBPj and β-catenin deletion mutants of the hematopoietic system (by using vav1-cre). Interestingly, double knockout animals were viable and born at Mendelian ratios. We will here describe and discuss the phenotype of these double mutants including a detailed analysis of HSC potential and differentiation of the different hematopoietic lineages. Our preliminary data reveals a new role for Notch in maintaining the functionality of adult HSCs, which may involve Wnt/β-catenin. This research is funded by by Ministerio Ciencia e Innovación (PLE2009-0111, SAF2010-15450, RD12/0036/0054), AGAUR (2009SGR-23 and CONES2010-0006).