@article{Lijian Shao_Kilian Sottoriva_Karol Palasiewicz_Jizhou Zhang_James Hyun_Sweta S. Soni_Na Yoon Paik_Xiaopei Gao_Henar Cuervo_Asrar B. Malik_Jalees Rehman_Daniel Lucas_Kostandin V. Pajcini_2019, place={Pavia, Italy}, title={A Tie2-Notch1 signaling axis regulates regeneration of the endothelial bone marrow niche}, volume={104}, url={https://haematologica.org/article/view/9119}, DOI={10.3324/haematol.2018.208660}, abstractNote={Loss-of-function studies have determined that Notch signaling is essential for hematopoietic and endothelial development. By deleting a single allele of the Notch1 transcriptional activation domain we generated viable, post-natal mice exhibiting hypomorphic Notch signaling. These heterozygous mice, which lack only one copy of the transcriptional activation domain, appear normal and have no endothelial or hematopoietic phenotype, apart from an inherent, cell-autonomous defect in T-cell lineage development. Following chemotherapy, these hypomorphs exhibited severe pancytopenia, weight loss and morbidity. This phenotype was confirmed in an endothelial-specific, loss-of-function Notch1 model system. Ang1, secreted by hematopoietic progenitors after damage, activated endothelial Tie2 signaling, which in turn enhanced expression of Notch ligands and potentiated Notch1 receptor activation. In our heterozygous, hypomorphic model system, the mutant protein that lacks the Notch1 transcriptional activation domain accumulated in endothelial cells and interfered with optimal activity of the wildtype Notch1 transcriptional complex. Failure of the hypomorphic mutant to efficiently drive transcription of key gene targets such as <em>Hes1</em> and <em>Myc</em&gt; prolonged apoptosis and limited regeneration of the bone marrow niche. Thus, basal Notch1 signaling is sufficient for niche development, but robust Notch activity is required for regeneration of the bone marrow endothelial niche and hematopoietic recovery.}, number={11}, journal={Haematologica}, author={Lijian Shao and Kilian Sottoriva and Karol Palasiewicz and Jizhou Zhang and James Hyun and Sweta S. Soni and Na Yoon Paik and Xiaopei Gao and Henar Cuervo and Asrar B. Malik and Jalees Rehman and Daniel Lucas and Kostandin V. Pajcini}, year={2019}, month={Oct.}, pages={2164-2177} }