SBDS and Decreased total neutrophil count: To interrogate HSC responses to neutropenia, we exploited our previously reported mouse model of neutropenia, through targeted downregulation of Sbds (loss-of-function, the causative event in SDS) in hematopoietic progenitor cells (HPCs) expressing the myeloid transcription factor CCAAT/enhancer binding protein α (C/EBPα, encoded by the Cebpa gene)23.