Snai2 maintains bone marrow niche cells by repressing osteopontin expression

Bone marrow (BM) mesenchymal stem and progenitor cells (MSPCs) are a critical constituent of the hematopoietic stem cell (HSC) niche. Previous studies have suggested that the zinc-finger epithelial-mesenchymal transition transcription factor Snai2 (also known as Slug) regulated HSCs autonomously. Here, we show that Snai2 expression in the BM is restricted to the BM stromal compartment where it regulates the HSC niche. Germline or MSPC-selective Snai2 deletion reduces the functional MSPC pool, their mesenchymal lineage output, and impairs HSC niche function during homeostasis and after stress. RNA-sequencing analysis revealed that Spp1 (osteopontin) expression is markedly upregulated in Snai2-deficient MSPCs.  Genetic deletion of Spp1 in Snai2-deficient mice, rescues MSPCs’ functions.  Thus, SNAI2 is a critical regulator of the transcriptional network maintaining MSPCs by the suppression of osteopontin expression. mRNA profiles were generated from FACS sorted bone marrow mesenchymal stem and progenitor cells of 8wk old control and Snai2-/- littermates in triplicates by Illumina HiSeq 2500 sequencing