https://orcid.org/0000-0002-9424-043X
Key Points
SAMD1 promotes GATA2 expression and suppresses the megakaryopoietic and erythropoietic differentiation programs.
SAMD1 facilitates H3K4me2/3 methylation status at a subset of erythroid gene promoters/enhancers.
Cell progenitor to progeny transitions depend on precise transcriptional mechanisms to adjust gene expression. The sterile alpha motif-containing 1 protein (SAMD1) regulates a shift in transcriptional activity during embryonic stem cell exit from pluripotency. SAMD1 interacts with and facilitates the activity of the histone H3 lysine demethylating enzyme LSD1. SAMD1 is expressed throughout many biological systems, but its role in hematopoiesis is unknown. In human and mouse hematopoietic stem/progenitor cells, we tested the role of SAMD1 in hematopoiesis and erythropoiesis using loss-of-function approaches. SAMD1 promoted expression of critical drivers of hematopoiesis, including the GATA2 transcription factor, while opposing erythroid programs. Loss of SAMD1 in ex vivo differentiating cells increased erythroid and megakaryocyte differentiation and altered the landscape of histone H3K4 methylation genome-wide. Cohorts of SAMD1-repressed genes are linked to erythropoietic activities. SAMD1 expression promoted ERK signaling via SCF/Kit stimulation in progenitor populations. In erythroid precursor cells, SAMD1 co-occupies chromatin with LSD1 and GATA factors. Whereas SAMD1 downregulates H3K4me2 levels genome-wide, contributing to gene repression, SAMD1 also elevates transcription at select sites. To test Samd1 function in hematopoiesis, we performed competitive transplant experiments in mice. Samd1 knockdown hematopoietic stem cells (HSCs) contributed more to peripheral blood mononuclear cells versus control HSCs. Our results establish SAMD1 as a coordinator of H3K4 methylation and stem/progenitor activity in hematopoiesis and erythropoiesis.
