Single cell index sorting reveals mutated hematopoietic progenitors in systemic mastocytosis
Jennine Grootens1, Johanna S. Ungerstedt2, Gunnar Nilsson1, Joakim S. Dahlin1
1Department of Medicine, Karolinska Institutet, and Karolinska University Hospital, Stockholm, Sweden. 2Department of Medicine Huddinge, Karolinska Institutet and Hematology Center, Karolinska University Hospital, Stockholm, Sweden.
Systemic mastocytosis is a myeloid neoplasm that is characterized by accumulation of mast cells in several tissues. A mutation in the KIT receptor has been found in multiple mature blood cells, mainly affecting the mast cell lineage. In this project we utilize the KIT mutation in systemic mastocytosis to study the hematopoiesis on single cell level, thereby gaining more insight in the disease ontology. Hematopoietic progenitors were isolated from a bone marrow sample of patients with systemic mastocytosis and stained with an antibody panel that distinguishes eight different progenitor populations, forming erythroid, myeloid and lymphoid cells. Single CD34+ progenitors were sorted and screened for the KIT mutation using a highly specific multiplexed qPCR method. Index sorting data allows assigning mutation-positive cells to a progenitor population in retrospect. We sorted and analysed 684 to 1605 single CD34+ progenitor cells in seven patients, five with indolent SM and two with aggressive SM. Mutated KIT was found in all patients and in all eight progenitors, ranging from 0.12-3.07% of total single sorted CD34+ progenitors. Along with CD34+ progenitors, we analysed single mature mast cells and found that 66.7-99.0% of the cells carried the KIT mutation. This data provides insight in the hematopoiesis of systemic mastocytosis and can be used to study mast cell development.