This week we will explore the impact of calreticulin (or CALR) haploinsufficiency on hematopoietic stem cell activity in the context of myeloproliferative neoplasms, explore mechanisms of leukemogenesis related to the E2A-PBX1 fusion protein in childhood B-cell acute lymphoblastic leukemia, and learn about the connection between intestinal microbiota, their metabolite short chain fatty acids and chronic graft versus host disease after allogeneic stem cell transplantation.