E3 ubiquitin ligase BCA2 promotes breast cancer stemness by up-regulation of SOX9 by LPS.

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. Breast cancer stem cells (BCSCs) are believed to play a crucial role in the carcinogenesis, therapy resistance, and metastasis of TNBC. It is well known that inflammation promotes stemness. Several studies have identified breast cancer-associated gene 2 (BCA2) as a potential risk factor for breast cancer incidence and prognosis. However, whether and how BCA2 promotes BCSCs has not been elucidated. Here, we demonstrated that BCA2 specifically promotes lipopolysaccharide (LPS)-induced BCSCs through LPS induced SOX9 expression. BCA2 enhances the interaction between myeloid differentiation primary response protein 88 (MyD88) and Toll-like receptor 4 (TLR4) and inhibits the interaction of MyD88 with deubiquitinase OTUD4 in the LPS-mediated NF-κB signaling pathway. And SOX9, an NF-κB target gene, mediates BCA2's pro-stemness function in TNBC. Our findings provide new insights into the molecular mechanisms by which BCA2 promotes breast cancer and potential therapeutic targets for the treatment of breast cancer.

Osteophyte Cartilage as a Potential Source for Minced Cartilage Implantation: A Novel Approach for Articular Cartilage Repair in Osteoarthritis.

Osteoarthritis (OA) is a common joint disorder characterized by cartilage degeneration, often leading to pain and functional impairment. Minced cartilage implantation (MCI) has emerged as a promising one-step alternative for large cartilage defects. However, the source of chondrocytes for MCI remains a challenge, particularly in advanced OA, as normal cartilage is scarce. We performed in vitro studies to evaluate the feasibility of MCI using osteophyte cartilage, which is present in patients with advanced OA. Osteophyte and articular cartilage samples were obtained from 22 patients who underwent total knee arthroplasty. Chondrocyte migration and proliferation were assessed using cartilage fragment/atelocollagen composites to compare the characteristics and regenerative potential of osteophytes and articular cartilage. Histological analysis revealed differences in cartilage composition between osteophytes and articular cartilage, with higher expression of type X collagen and increased chondrocyte proliferation in the osteophyte cartilage. Gene expression analysis identified distinct gene expression profiles between osteophytes and articular cartilage; the expression levels of COL2A1, ACAN, and SOX9 were not significantly different. Chondrocytes derived from osteophyte cartilage exhibit enhanced proliferation, and glycosaminoglycan production is increased in both osteophytes and articular cartilage. Osteophyte cartilage may serve as a viable alternative source of MCI for treating large cartilage defects in OA.

The single-cell chromatin landscape in gonadal cell lineage specification.

Gonad development includes sex determination and divergent maturation of the testes and ovaries. Recent advances in measuring gene expression in single cells are providing new insights into this complex process. However, the underlying epigenetic regulatory mechanisms remain unclear. Here, we profiled chromatin accessibility in mouse gonadal cells of both sexes from embryonic day 11.5 to 14.5 using single-cell assay for transposase accessible chromatin by sequencing (scATAC-seq). Our results showed that individual cell types can be inferred by the chromatin landscape, and that cells can be temporally ordered along developmental trajectories. Integrative analysis of transcriptomic and chromatin-accessibility maps identified multiple putative regulatory elements proximal to key gonadal genes Nr5a1, Sox9 and Wt1. We also uncover cell type-specific regulatory factors underlying cell type specification. Overall, our results provide a better understanding of the epigenetic landscape associated with the progressive restriction of cell fates in the gonad.

Increased water temperature contributes to a chondrogenesis response in the eyes of spotted wolffish.

Adult vertebrate cartilage is usually quiescent. Some vertebrates possess ocular scleral skeletons composed of cartilage or bone. The morphological characteristics of the spotted wolffish (Anarhichas minor) scleral skeleton have not been described. Here we assessed the scleral skeletons of cultured spotted wolffish, a globally threatened marine species. The healthy spotted wolffish we assessed had scleral skeletons with a low percentage of cells staining for the chondrogenesis marker sex-determining region Y-box (Sox) 9, but harboured a population of intraocular cells that co-express immunoglobulin M (IgM) and Sox9. Scleral skeletons of spotted wolffish with grossly observable eye abnormalities displayed a high degree of perochondrial activation as evidenced by cellular morphology and expression of proliferating cell nuclear antigen (PCNA) and phosphotyrosine. Cells staining for cluster of differentiation (CD) 45 and IgM accumulated around sites of active chondrogenesis, which contained cells that strongly expressed Sox9. The level of scleral chondrogenesis and the numbers of scleral cartilage PCNA positive cells increased with the temperature of the water in which spotted wolffish were cultured. Our results provide new knowledge of differing Sox9 spatial tissue expression patterns during chondrogenesis in normal control and ocular insult paradigms. Our work also provides evidence that spotted wolffish possess an inherent scleral chondrogenesis response that may be sensitive to temperature. This work also advances the fundamental knowledge of teleost ocular skeletal systems.

CEBPA restricts alveolar type 2 cell plasticity during development and injury-repair.

Cell plasticity theoretically extends to all possible cell types, but naturally decreases as cells differentiate, whereas injury-repair re-engages the developmental plasticity. Here we show that the lung alveolar type 2 (AT2)-specific transcription factor (TF), CEBPA, restricts AT2 cell plasticity in the mouse lung. AT2 cells undergo transcriptional and epigenetic maturation postnatally. Without CEBPA, both neonatal and mature AT2 cells reduce the AT2 program, but only the former reactivate the SOX9 progenitor program. Sendai virus infection bestows mature AT2 cells with neonatal plasticity where Cebpa mutant, but not wild type, AT2 cells express SOX9, as well as more readily proliferate and form KRT8/CLDN4+ transitional cells. CEBPA promotes the AT2 program by recruiting the lung lineage TF NKX2-1. The temporal change in CEBPA-dependent plasticity reflects AT2 cell developmental history. The ontogeny of AT2 cell plasticity and its transcriptional and epigenetic mechanisms have implications in lung regeneration and cancer.

Circ-0075305 hinders gastric cancer stem cells by indirectly disrupting TCF4-ß-catenin complex and downregulation of SOX9.

CircRNAs are covalently closed, single-stranded RNA that form continuous loops and play a crucial role in the initiation and progression of tumors. Cancer stem cells (CSCs) are indispensable for cancer development; however, the regulation of cancer stem cell-like properties in gastric cancer (GC) and its specific mechanism remain poorly understood. We elucidate the specific role of Circ-0075305 in GC stem cell properties. Circ-0075305 associated with chemotherapy resistance was identified by sequencing GC cells. Subsequent confirmation in both GC tissues and cell lines revealed that patients with high expression of Circ-0075305 had significantly better overall survival (OS) rates than those with low expression, particularly when treated with postoperative adjuvant chemotherapy for GC. In vitro and in vivo experiments confirmed that overexpression of Circ-0075305 can effectively reduce stem cell-like properties and enhance the sensitivity of GC cells to Oxaliplatin compared with the control group. Circ-0075305 promotes RPRD1A expression by acting as a sponge for corresponding miRNAs. The addition of LF3 (a ß-catenin/TCF4 interaction antagonist) confirmed that RPRD1A inhibited the formation of the TCF4-ß-catenin transcription complex through competitive to ß-catenin and suppressed the transcriptional activity of stem cell markers such as SOX9 via the Wnt/ß-catenin signaling pathway. This leads to the downregulation of stem cell-like property-related markers in GC. This study revealed the underlying mechanisms that regulate Circ-0075305 in GCSCs and suggests that its role in reducing ß-catenin signaling may serve as a potential therapeutic candidate.

Sox9-coordinated cellular neighborhoods generate fibrosis.

Poorly regenerative organs deposit scar tissue to mend damage. Aggarwal et al. establish that transient Sox9 activity is necessary for early proximal tubule epithelial regeneration, while Trogisch et al. and Aggarwal et al. show that persistent Sox9 activity in epithelial and endothelial cells activates fibroblasts creating fibrotic microdomains in multiple organs.

Downregulation of SOX9 expression in developing entheses adjacent to intramembranous bone.

Entheses are classified into three types: fibrocartilaginous, fibrous, and periosteal insertions. However, the mechanism behind the development of fibrous entheses and periosteal insertions remains unclear. Since both entheses are part of the temporomandibular joint (TMJ), this study analyzes the TMJ entheses. Here, we show that SOX9 expression is negatively regulated during TMJ enthesis development, unlike fibrocartilage entheses which are modularly formed by SCX and SOX9 positive progenitors. The TMJ entheses was adjacent to the intramembranous bone rather than cartilage. SOX9 expression was diminished during TMJ enthesis development. To clarify the functional role of Sox9 in the development of TMJ entheses, we examined these structures in TMJ using Wnt1Cre;Sox9flox/+ reporter mice. Wnt1Cre;Sox9flox/+ mice showed enthesial deformation at the TMJ. Next, we also observed a diminished SOX9 expression area at the enthesis in contact with the clavicle's membranous bone portion, similar to the TMJ entheses. Together, these findings reveal that the timing of SOX9 expression varies with the ossification development mode.

Conditional disruption of Nr5a1 directed by Sox9-Cre impairs adrenal development.

The current study aimed to investigate the effect of Sox9-Cre-directed Nr5a1-conditional knockout (Sox9-Cre;Nr5a1flox/flox) on adrenal development. We showed that SOX9 is expressed by adrenocortical cells at E10.5-E11.5 but is extinguished no later than E12.5. The number of adrenocortical cells significantly reduced in Sox9-Cre;Nr5a1flox/flox mice while the number of cleaved caspase 3-positive cells increased compared to that in the controls at E11.5-E12.5, when the adrenal primordium (AP) is about to expand. This indicated that fetal adrenocortical cells are lost via apoptosis due to Nr5a1 ablation by E12.5. Both medulla formation and encapsulation were perturbed, accompanied by a smaller AP size, in Sox9-Cre;Nr5a1flox/flox mice during embryonic development. Adult Sox9-Cre;Nr5a1flox/flox adrenals were hypoplastic and exhibited irregular organization of the medulla with aberrant sex differentiation in the X zone. Additionally, there were histologically eosin-negative vacuolated cells, which were negative for both the X-zone marker 20αHSD and the steroidogenesis marker 3ßHSD at the innermost cortex of Sox9-Cre;Nr5a1flox/flox adrenals. Although Nr5a1+/- adrenals were hypoplastic, a small number of chromaffin cells were properly located in the center, having normal sex differences in the X-zone. The results collectively provided in-vivo evidence that Nr5a1 plays a critical role in AP expansion and subsequent adrenal development.

SOX9 promotes stemness in the CAL27 cell line of tongue squamous cell carcinoma.

Tongue squamous cell carcinoma (TSCC) is a prevalent form of oral malignancy, with increasing incidence. Unfortunately, the 5-year survival rate for patients has not exceeded 50%. Studies have shown that sex-determining region Y box 9 (SOX9) correlates with malignancy and tumor stemness in a variety of tumors. To investigate the role of SOX9 in TSCC stemness, we analyzed its influence on various aspects of tumor biology, including cell proliferation, migration, invasion, sphere and clone formation, and drug resistance in TSCC. Our data suggest a close association between SOX9 expression and both the stemness phenotype and drug resistance in TSCC. Immunohistochemical experiments revealed a progressive increase of SOX9 expression in normal oral mucosa, paracancerous tissues, and tongue squamous carcinoma tissues. Furthermore, the expression of SOX9 was closely linked to the TNM stage, but not to lymph node metastasis or tumor diameter. SOX9 is a crucial gene in TSCC responsible for promoting the stemness function of cancer stem cells. Developing drugs that target SOX9 is extremely important in clinical settings.

Androgen receptor splice variants drive castration-resistant prostate cancer metastasis by activating distinct transcriptional programs.

One critical mechanism through which prostate cancer (PCa) adapts to treatments targeting androgen receptor (AR) signaling is the emergence of ligand-binding domain-truncated and constitutively active AR splice variants, particularly AR-V7. While AR-V7 has been intensively studied, its ability to activate distinct biological functions compared with the full-length AR (AR-FL), and its role in regulating the metastatic progression of castration-resistant PCa (CRPC), remain unclear. Our study found that, under castrated conditions, AR-V7 strongly induced osteoblastic bone lesions, a response not observed with AR-FL overexpression. Through combined ChIP-seq, ATAC-seq, and RNA-seq analyses, we demonstrated that AR-V7 uniquely accesses the androgen-responsive elements in compact chromatin regions, activating a distinct transcription program. This program was highly enriched for genes involved in epithelial-mesenchymal transition and metastasis. Notably, we discovered that SOX9, a critical metastasis driver gene, was a direct target and downstream effector of AR-V7. Its protein expression was dramatically upregulated in AR-V7-induced bone lesions. Moreover, we found that Ser81 phosphorylation enhanced AR-V7's pro-metastasis function by selectively altering its specific transcription program. Blocking this phosphorylation with CDK9 inhibitors impaired the AR-V7-mediated metastasis program. Overall, our study has provided molecular insights into the role of AR splice variants in driving the metastatic progression of CRPC.

SRY-Box transcription factor 9 triggers YAP nuclear entry via direct interaction in tumors.

The translocation of YAP from the cytoplasm to the nucleus is critical for its activation and plays a key role in tumor progression. However, the precise molecular mechanisms governing the nuclear import of YAP are not fully understood. In this study, we have uncovered a crucial role of SOX9 in the activation of YAP. SOX9 promotes the nuclear translocation of YAP by direct interaction. Importantly, we have identified that the binding between Asp-125 of SOX9 and Arg-124 of YAP is essential for SOX9-YAP interaction and subsequent nuclear entry of YAP. Additionally, we have discovered a novel asymmetrical dimethylation of YAP at Arg-124 (YAP-R124me2a) catalyzed by PRMT1. YAP-R124me2a enhances the interaction between YAP and SOX9 and is associated with poor prognosis in multiple cancers. Furthermore, we disrupted the interaction between SOX9 and YAP using a competitive peptide, S-A1, which mimics an α-helix of SOX9 containing Asp-125. S-A1 significantly inhibits YAP nuclear translocation and effectively suppresses tumor growth. This study provides the first evidence of SOX9 as a pivotal regulator driving YAP nuclear translocation and presents a potential therapeutic strategy for YAP-driven human cancers by targeting SOX9-YAP interaction.

Transcriptional variations at perilesional site in vitiligo patients: probably a fight for cell-survival.

Exploration of gene expression variations is a potential source to unravel biological pathways involved in pathological changes in body and understand the mechanism underneath. Vitiligo patients were explored for gene expression changes transcriptionally at perilesional site in comparison to normal site of same patients for melanogenesis pathway (TYR, DCT & TYRP1) cell adhesion (MMPs & TIMP1), cell survival (BCL2 & BAX1) as well as proliferation, migration & development (SOX9, SOX10 & MITF) regulatory system, using skin biopsy samples. Results were also compared with changes in gene expression for melanocytes under stress after hydrogen peroxide treatment in-vitro. Gene amplification was carried out via real time PCR. We found increased expression of proliferation, migration & development regulatory genes as well as melanogenesis pathway genes at perilesional site of patients. In-vitro study also supports induced MITF expression and disturbed melanogenesis in melanocytes under stress. Expression level ratio of cell survival regulatory genes' (BCL2/BAX1) as well as cell adhesion regulatory genes (MMPs/TIMP1) was observed upregulated at patient's perilesional site however downregulated in hydrogen peroxide treated melanocytes in-vitro. Observed upregulated gene expression at perilesional site of patients may be via positive feedback loop in response to stress to increase cell tolerance power to survive against adverse conditions. Gene expression analysis suggests better cell survival and proliferation potential at perilesional site in vitiligo patients. It seems in-vivo conditions/growth factors supports cells to fight for survival to accommodate stressed conditions.

Fibroblast-like synoviocytes-derived exosomal circFTO deteriorates rheumatoid arthritis by enhancing N6-methyladenosine modification of SOX9 in chondrocytes.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic inflammatory disease that causes disability worldwide. Exosomes released by fibroblast-like synoviocytes in RA (RA-FLSs-Exos) play a role in the development of RA, and circular RNAs (circRNAs) are important for RA progression. This study aimed to investigate the molecular mechanisms underlying the effects of RA-FLSs-Exos in RA and identify the potential pathway responsible for these effects. METHODS: We initially conducted microarray analysis to identify dysregulated circRNAs in exosomes associated with RA. We then co-cultured isolated RA-FLSs-Exos with chondrocytes to examine their role in RA. In vivo experiments were performed using collagen-induced arthritis mouse models, and circFTO knockdown was achieved through intra-articular injection of AAV5 vectors. RESULTS: Our findings revealed increased expression of circFTO in both RA-FLSs-Exos and synovial tissues from patients with RA. Exosomal circFTO hindered chondrocyte proliferation, migration, and anabolism while promoting apoptosis and catabolism. Mechanistically, we discovered that circFTO facilitates the formation of methyltransferases complex to suppress SRY-related high-mobility group box 9 (SOX9) expression with assistance from YTH domain family 2 (YTHDF2) through an m6A-dependent mechanism. Furthermore, inhibition of circFTO improved symptoms of RA in vivo. CONCLUSION: Taken together, our study demonstrates that exosomal circFTO derived from FLSs contributes to the progression of RA by targeting SOX9. These findings highlight a promising target for treating RA.

High glucose promotes osteogenic differentiation of human lens epithelial cells through hypoxia-inducible factor (HIF) activation.

Cataract, a leading cause of blindness, is characterised by lens opacification. Type 2 diabetes is associated with a two- to fivefold higher prevalence of cataracts. The risk of cataract formation increases with the duration of diabetes and the severity of hyperglycaemia. Hydroxyapatite deposition is present in cataractous lenses that could be the consequence of osteogenic differentiation and calcification of lens epithelial cells (LECs). We hypothesised that hyperglycaemia might promote the osteogenic differentiation of human LECs (HuLECs). Osteogenic medium (OM) containing excess phosphate and calcium with normal (1 g/L) or high (4.5 g/L) glucose was used to induce HuLEC calcification. High glucose accelerated and intensified OM-induced calcification of HuLECs, which was accompanied by hyperglycaemia-induced upregulation of the osteogenic markers Runx2, Sox9, alkaline phosphatase and osteocalcin, as well as nuclear translocation of Runx2. High glucose-induced calcification was abolished in Runx2-deficient HuLECs. Additionally, high glucose stabilised the regulatory alpha subunits of hypoxia-inducible factor 1 (HIF-1), triggered nuclear translocation of HIF-1α and increased the expression of HIF-1 target genes. Gene silencing of HIF-1α or HIF-2α attenuated hyperglycaemia-induced calcification of HuLECs, while hypoxia mimetics (desferrioxamine, CoCl2) enhanced calcification of HuLECs under normal glucose conditions. Overall, this study suggests that high glucose promotes HuLEC calcification via Runx2 and the activation of the HIF-1 signalling pathway. These findings may provide new insights into the pathogenesis of diabetic cataracts, shedding light on potential factors for intervention to treat this sight-threatening condition.

Inefficient Sox9 upregulation and absence of Rspo1 repression lead to sex reversal in the B6.XYTIR mouse gonad†.

Sry on the Y-chromosome upregulates Sox9, which in turn upregulates a set of genes such as Fgf9 to initiate testicular differentiation in the XY gonad. In the absence of Sry expression, genes such as Rspo1, Foxl2, and Runx1 support ovarian differentiation in the XX gonad. These two pathways antagonize each other to ensure the development of only one gonadal sex in normal development. In the B6.YTIR mouse, carrying the YTIR-chromosome on the B6 genetic background, Sry is expressed in a comparable manner with that in the B6.XY mouse, yet, only ovaries or ovotestes develop. We asked how testicular and ovarian differentiation pathways interact to determine the gonadal sex in the B6.YTIR mouse. Our results showed that (1) transcript levels of Sox9 were much lower than in B6.XY gonads while those of Rspo1 and Runx1 were as high as B6.XX gonads at 11.5 and 12.5 days postcoitum. (2) FOXL2-positive cells appeared in mosaic with SOX9-positive cells at 12.5 days postcoitum. (3) SOX9-positive cells formed testis cords in the central area while those disappeared to leave only FOXL2-positive cells in the poles or the entire area at 13.5 days postcoitum. (4) No difference was found at transcript levels of all genes between the left and right gonads up to 12.5 days postcoitum, although ovotestes developed much more frequently on the left than the right at 13.5 days postcoitum. These results suggest that inefficient Sox9 upregulation and the absence of Rspo1 repression prevent testicular differentiation in the B6.YTIR gonad.

SOX9 depletion attenuates retinal ganglion cell ferroptosis through blocking ERK/p38 signaling.

BACKGROUND: Retinal ischemia-refusion (I/R) is a leading cause of irreversible blindness worldwide. This study aims to explore the regulatory role of SOX9 in retinal I/R injury, and attempts to elucidate its potential regulatory mechanism. METHODS: Retinal I/R injury model was established in vivo, and the histological changes was examined by hematoxylin and eosin (H&E) staining and immunofluorescent assay was performed to examine SOX9 expression. Oxygenation-glucose deprivation/reoxygenation (OGD/R)-induced retinal ischemia/reperfusion (I/R) injury in 661 W cells was constructed as an in vitro cellular model of glaucoma. The production of cytokines, lactate dehydrogenase (LDH) and the antioxidant enzymes were assessed by their commercial kits. Cellular reactive oxygen species (ROS) and lipid ROS was detected using DCFH-DA and C11-BODIPY 581/591 staining, respectively. Lipid peroxidation and Fe2+ level were detected to assess the ferroptosis level. Protein expression was examined by western blot. LM22B-10, the agonist of ERK signaling, was used to pretreat 661 W cells for mechanism investigation. RESULTS: SOX9 was aberrantly upregulated following retinal I/R injury both in vivo and in vitro. SOX9 knockdown exerted a protective role against OGD/R-triggered oxidative stress, inflammatory response and ferroptosis in 661 W cells. Further, ERK/p38 signaling was activated in 661 W cells following OGD/R induction, which was repressed by SOX9 knockdown, and the ERK signaling agonist partially counteracted the protective role of SOX9 knockdown against oxidative stress, inflammatory response and ferroptosis in OGD/R-induced 661 W cells. CONCLUSION: Collectively, inhibiting SOX9 to block oxidative stress, inflammation and ferroptosis by inactivating ERK/p38 signaling might be effective to prevent retinal I/R injury, thereby alleviating glaucoma.

SOX9 Induces Orbital Fibroblast Activation in Thyroid Eye Disease Via MAPK/ERK1/2 Pathway.

Purpose: To evaluate the expression of sry-box transcription factor 9 (SOX9) in orbital fibroblasts (OFs) of thyroid eye disease (TED) and to find its potential role and underlying mechanism in orbital fibrosis. Methods: OFs were cultured from orbital connective tissues obtained from patients with TED (n = 10) and healthy controls (n = 6). SOX9 was depleted by small interfering RNA or overexpressed through lentivirus transduction in OFs. Fibroblast contractile activity was measured by collagen gel contraction assay and proliferation was examined by EdU assay. Transcriptomic changes were assessed by RNA sequencing. Results: The mRNA and protein levels of SOX9 were significantly higher in OFs cultured from patients with TED than those from healthy controls. Extracellular matrix-related genes were down-regulated by SOX9 knockdown and up-regulated by SOX9 overexpression in TED-OFs. SOX9 knockdown significantly decrease the contraction and the antiapoptotic ability of OFs, whereas the overexpression of SOX9 increased the ability of transformation, migration, and proliferation of OFs. SOX9 knockdown suppressed the expression of phosphorylated ERK1/2, whereas its overexpression showed the opposite effect. Epidermal growth factor receptor (EGFR) is one of the notably down-regulated genes screened out by RNA sequencing. Chromatin immunoprecipitation-qPCR demonstrated SOX9 binding to the EGFR promoter. Conclusions: A high expression of SOX9 was found in TED-OFs. SOX9 can activate OFs via MAPK/ERK1/2 signaling pathway, which in turn promotes proliferation and differentiation of OFs. EGFR was a downstream target gene of SOX9. SOX9/EGFR can be considered as therapeutic targets for the treatment of orbital fibrosis in TED.

Skeletal growth is enhanced by a shared role for SOX8 and SOX9 in promoting reserve chondrocyte commitment to columnar proliferation.

SOX8 was linked in a genome-wide association study to human height heritability, but roles in chondrocytes for this close relative of the master chondrogenic transcription factor SOX9 remain unknown. We undertook here to fill this knowledge gap. High-throughput assays demonstrate expression of human SOX8 and mouse Sox8 in growth plate cartilage. In situ assays show that Sox8 is expressed at a similar level as Sox9 in reserve and early columnar chondrocytes and turned off when Sox9 expression peaks in late columnar and prehypertrophic chondrocytes. Sox8-/- mice and Sox8fl/flPrx1Cre and Sox9fl/+Prx1Cre mice (inactivation in limb skeletal cells) have a normal or near normal skeletal size. In contrast, juvenile and adult Sox8fl/flSox9fl/+Prx1Cre compound mutants exhibit a 15 to 20% shortening of long bones. Their growth plate reserve chondrocytes progress slowly toward the columnar stage, as witnessed by a delay in down-regulating Pthlh expression, in packing in columns and in elevating their proliferation rate. SOX8 or SOX9 overexpression in chondrocytes reveals not only that SOX8 can promote growth plate cell proliferation and differentiation, even upon inactivation of endogenous Sox9, but also that it is more efficient than SOX9, possibly due to greater protein stability. Altogether, these findings uncover a major role for SOX8 and SOX9 in promoting skeletal growth by stimulating commitment of growth plate reserve chondrocytes to actively proliferating columnar cells. Further, by showing that SOX8 is more chondrogenic than SOX9, they suggest that SOX8 could be preferred over SOX9 in therapies to promote cartilage formation or regeneration in developmental and degenerative cartilage diseases.

LncRNA SOX9-AS1 triggers a transcriptional program involved in lipid metabolic reprogramming, cell migration and invasion in triple-negative breast cancer.

At the molecular level, triple-negative breast cancer (TNBC) is frequently categorized as PAM50 basal-like subtype, but despite the advances in molecular analyses, the clinical outcome for these subtypes is uncertain. Long non-coding RNAs (lncRNAs) are master regulators of genes involved in hallmarks of cancer, which makes them suitable biomarkers for breast cancer (BRCA) diagnosis and prognosis. Here, we evaluated the regulatory role of lncRNA SOX9-AS1 in these subtypes. Using the BRCA-TCGA cohort, we observed that SOX9-AS1 was significantly overexpressed in basal-like and TNBC in comparison with other BRCA subtypes. Survival analyzes showed that SOX9-AS1 overexpression was associated with a favorable prognosis in TNBC and basal-like patients. To study the functions of SOX9-AS1, we determined the expression levels in a panel of nine BRCA cell lines finding increased levels in MDA-MB-468 and HCC1187 TNBC. Using subcellular fractionation in these cell lines, we ascertained that SOX9-AS1 was located in the cytoplasmic compartment. In addition, we performed SOX9-AS1 gene silencing using two short-harping constructs, which were transfected in both cell models and performed a genome-wide RNA-seq analysis. Data showed that 351 lncRNAs and 740 mRNAs were differentially expressed in MDA-MB-468 while 56 lncRNAs and 100 mRNAs were modulated in HCC1187 cells (Log2FC < - 1.5 and > 1.5, p.adj value < 0.05). Pathway analysis revealed that the protein-encoding genes potentially regulate lipid metabolic reprogramming, and epithelial-mesenchymal transition (EMT). Expression of lipid metabolic-related genes LIPE, REEP6, GABRE, FBP1, SCD1, UGT2B11, APOC1 was confirmed by RT-qPCR. Functional analysis demonstrated that the knockdown of SOX9-AS1 increases the triglyceride synthesis, cell migration and invasion in both two TNBC cell lines. In conclusion, high SOX9-AS1 expression predicts an improved clinical course in patients, while the loss of SOX9-AS1 expression enhances the aggressiveness of TNBC cells.