Lysine specific demethylase 1 conditional myeloid cell knockout mice have decreased osteoclast differentiation due to increased IFN- gene expression.

Osteoclasts are large multinucleated cells that degrade bone mineral and extracellular matrix. Investigating the epigenetic mechanisms orchestrating osteoclast differentiation is key to our understanding of the pathogenesis of skeletal related diseases such as periodontitis and osteoporosis. Lysine specific demethylase 1 (LSD1/KDM1A) is a member of the histone demethylase family that mediates the removal of mono- and dimethyl groups from H3K4 and H3K9 to elicit dichotomous effects on gene expression. Prior to our study, little was known about the contributions of LSD1 to skeletal development and osteoclast differentiation. Here we show that conditional deletion of within the myeloid lineage or macrophage/osteoclast precursors results in enhanced bone mass of male and female mice accompanied by diminished osteoclast size in vivo. Furthermore, deletion decreased osteoclast differentiation and activity within in vitro assays. Our bulk RNA-SEQ data suggest ablation in male and female mice inhibits osteoclast differentiation due to enhanced expression of interferon-β target genes. Lastly, we demonstrate that LSD1 forms an immune complex with HDAC1 and HDAC2. These data suggest that the combination of methylation and acetylation of histone residues, facilitated by LSD1, mechanistically promotes osteoclast gene expression.