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Transcriptional deregulation during osteoclastic differentiation due to diuron exposure affects preferentially super-enhancers regulated genes

ABSTRACT: Osteoclasts are major actors in the maintenance of bone homeostasis. The full functional maturation of osteoclasts from monocyte lineage cells is essential for the degradation of old/damaged bone matrix. To better characterize the differentiation and maturation of CD14+ monocytes into functionally mature osteoclasts, we performed Chromatin Immunoprecipitation against H3K27ac followed by Sequencing (ChIP-Seq) and RNA-Sequencing at different stages of an in vitro differentiation model. The combinatorial study of the epigenetic and transcriptional dynamics taking place during the course of differentiation has allowed us to reveal a very dynamic epigenetic profile that supports the expression of genes vital for osteoclasts differentiation and function. In total, we identified 122 genes induced by dynamic super-enhancers at late days. Since diuron, a commonly detected herbicide in our environment, is suspected to affect bone development, we then sought to evaluate the potential impact of diuron exposure on bone homeostasis. We performed RNA-Seq and functional test during in vitro osteoblastic and osteoclastic differentiation. First of all, our data suggest that high-dose of diuron (50 µM) affects viability of mesenchymal stem cells and thus inhibits bone mineralization. We observed at lower dose (1 µM) an inhibitory effect of this herbicide on number of osteoclasts derived from CD14+ monocytes without affecting cell viability. RNA-Seq data analysis revealed that diuron is specifically affecting the transcriptional network dedicated to osteoclasts differentiation and activity. Among the diuron affected genes, our analysis suggests a significant enrichment of genes targeted by gained super-enhancers along the differentiation process, with an odds ratio of 5.12 (ρ = 2.59 x 10-5). Taken together our results suggest that diuron exposure disrupts osteoclasts maturation by impairing the expression of cell-identity determining genes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE178196 | GEO | 2023/06/21

REPOSITORIES: GEO

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Project description:Enhanced osteoclastogenesis and osteoclast activity contribute to the development of osteoporosis, which is characterized by increased bone resorption and inadequate bone formation. As novel anti-osteoporotic therapeutics are needed, understanding the genetic regulation of human osteoclastogenesis could help identify potential treatment targets. This study aimed to provide an overview of the transcriptional reprogramming during human osteoclast differentiation. Osteoclasts were differentiated from CD14+-monocytes from eight female donors. RNA-sequencing during differentiation demonstrated 8980 differentially expressed genes grouped into eight temporal patterns conserved across donors. These patterns showed distinct molecular functions, associated with postmenopausal osteoporosis susceptibility genes based on RNA from iliac crest biopsies, and bone mineral density SNPs. Network analyses showed mutual dependencies between the temporal expression patterns and provides insight into subtype-specific transcriptional networks. Donor specific expression patterns identified genes at monocyte stage, such as filamin B (FLNB) and oxidized low density lipoprotein receptor 1 (OLR1, encoding LOX-1), that are predictive for the resorptive activity of mature osteoclasts. Differentially expressed G-protein coupled receptors showed strong expression during osteoclast differentiation and associated with bone mineral density SNPs, implying a pivotal role in osteoclast differentiation and activity. The regulatory effects of three differentially expressed G-protein coupled receptors were exemplified by in vitro pharmacological modulation of complement 5A receptor 1 (C5AR1), somatostatin receptor 2 (SSTR2), and free fatty acid receptor 4 (FFAR4/GPR120). Activating C5AR1 enhanced osteoclast formation, while activating SSTR2 decreased resorptive activity of mature osteoclasts, and activating FFAR4 decreased both number and resorptive activity of mature osteoclasts. In conclusion, we report the transcriptional reprogramming during human osteoclast differentiation and identified SSTR2 and FFAR4 as anti-resorptive G-protein coupled receptors as well as FLNB and LOX-1 as potential molecular markers of osteoclast activity. These data can help future investigations to identify molecular regulators of osteoclast differentiation and activity and provide the basis for novel anti-osteoporotic targets.