Dysregulation of STAT3 signaling is associated with endplate-oriented herniations of the intervertebral disc in Adgrg6 mutant mice

Abstract

Degenerative changes of the intervertebral disc (IVD) are a leading cause of disability affecting humans worldwide and has been attributed primarily to trauma and the accumulation of pathology during aging. While genetic defects have also been associated with disc degeneration, the precise mechanisms driving the initiation and progression of disease have remained elusive due to a paucity of genetic animal models. Here, we discuss a novel conditional mouse genetic model of endplate-oriented disc herniations in adult mice. Using conditional mouse genetics, we show increased mechanical stiffness and reveal dysregulation of typical gene expression profiles of the IVD in adhesion G-protein coupled receptor G6 (Adgrg6) mutant mice prior to the onset of endplate-oriented disc herniations in adult mice. We observed increased STAT3 activation prior to IVD defects and go on to demonstrate that treatment of Adgrg6 conditional mutant mice with a small molecule inhibitor of STAT3 activation ameliorates endplate-oriented herniations. These findings establish ADGRG6 and STAT3 as novel regulators of IVD endplate and growth plate integrity in the mouse, and implicate ADGRG6/STAT3 signaling as promising therapeutic targets for endplate-oriented disc degeneration.

Genomic characterization of the adolescent idiopathic scoliosis associated transcriptome and regulome

“…For example, the genetic network surrounding ADGRG6, an important AIS susceptibility gene (4,5,13), showed interactions with several other genes that have been implicated in AIS, with one of these genes being SOX9, a master regulator of chondrogenesis (24). This interaction is supported by direct observation that loss of Adgrg6 in the IVD is associated with reduced SOX9 expression in cartilaginous endplate and annulus fibrosus regions of the IVD in mouse (21). Thus our analyses allowed us to identify genetic networks and predict interactions between several AIS genes, which will assist future studies on the intricate interplay of these loci in driving susceptibly to this complex disease.…”

“…As chondrocytes were shown to be an important cell type underlying AIS susceptibility (13,21,23), we functionally tested putative chondrocyte enhancers that overlap AIS-associated SNPs using enhancer assays. We identified three novel functional enhancer sequences that encompass SNPs in LD with AIS GWAS SNPs.…”

“…Further analysis of our tissue-specific datasets using Ingenuity Pathway Analysis (IPA) (19) revealed novel genetic networks up-and down-stream of AIS-associated genes as well as interactions between multiple AIS genes in specific tissues ( Fig 2C). For example, tumor necrosis factor-alpha (TNF-alpha) was shown to be a potent inhibitor of SOX9 in cartilage (20) and ADGRG6 expression was reported to be decreased when SOX9 is deleted (21). These analyses highlight genetic networks and putative molecular pathways involved in AIS pathogenesis.…”

“…To functionally validate some of these sequences, we focused our analysis on H3K27ac peaks identified in mouse chondrocytes, as chondrocytes were implicated as a major cell type underlying AIS susceptibility (13,21,23) and existing cell lines can be easily transfected for in vitro validation experiments. We identified chondrocyte-specific H3K27ac peaks overlapping AIS-associated SNPs at the ADGRG6 ( Fig 4A) and BNC2 loci.…”

Protocol for parallel proteomic and metabolomic analysis of mouse intervertebral disc tissues

“…We have explored the effect of mechanical loading on the IVD in mice [42][43][44] and used transgenic mice to study IVD development, 45 disc degeneration, 16,46 and diffuse idiopathic skeletal hyperostosis (DISH). [47][48][49][50] Important insights have likewise been provided by others using mouse models to study disc development, [51][52][53] inflammation, 54 IVD degeneration, 10,13,[55][56][57][58] calcification, 59,60 and scoliosis. [61][62][63] The multitude of available mouse models of spine pathologies allows for global molecular comparisons to uncover novel biological insights.…”