Chordin Like-1 Regulates Osteoblast and Adipocyte Differentiation Through Stabilizing Insulin-Like Growth Factor Binding Protein 3.

Chordin like-1 (CHRDL1) is an antagonist of bone morphogenetic proteins (BMPs) that acts through binding BMPs and blocking their interaction with BMP receptors. CHRDL1 plays a role in osteoblast differentiation but controversial effects were reported. On the other hand, the role of CHRDL1 in adipogenesis is unknown. In the present study, we investigated the function of CHRDL1 in regulating differentiation of osteoblasts and adipocytes and elucidated the underlying mechanism. CHRDL1 expression was downregulated during osteogenesis while it was upregulated during adipogenesis in primary cultured and established mesenchymal progenitor cell lines. Functional experiments revealed that CHRDL1 suppressed osteoblast differentiation and promoted adipocyte differentiation. Mechanistic explorations revealed that CHRDL1 is directly bound to insulin-like growth factor binding protein 3 (IGFBP3) and attenuated the degradation of the latter. Furthermore, CHRDL1 and IGFBP3 suppressed the activity of insulin receptor substrate 1 (IRS1)/AKT serine/threonine kinase (AKT)/mechanistic target of rapamycin kinase complex 1 (mTORC1) signaling in progenitor cells undergoing osteogenic differentiation. By contrast, they activated AKT/mTORC1 signaling independently of IRS1 during adipogenic differentiation. CHRDL1 enhanced the interaction of nuclear IGFBP3 and retinoid X receptor α (RXRα) during adipogenesis, and inhibition of RXR inactivated AKT and attenuated the stimulation of adipogenic differentiation by CHRDL1. Overexpression of IGFBP3 relieved the perturbation of osteogenic and adipogenic differentiation of progenitor cells induced by CHRDL1 silencing. Finally, CHRDL1 and IGFBP3 were upregulated in the trabecular bone of aged mice. Our study provides evidence that CHRDL1 reciprocally regulates osteoblast and adipocyte differentiation through stabilizing IGFBP3 and differentially modulating AKT/mTORC1 signaling.

Autopodial development is selectively impaired by misexpression of chordin-like 1 in the chick limb.

Chordin-like 1 (CHRDL1) is a secreted bone morphogenetic protein (BMP) antagonist expressed in mesenchymal tissues whose function in development of the skeleton has not been examined in detail. Here we show Chrdl1 is dynamically expressed in the early distal limb bud mesenchyme, with expression becoming downregulated as development proceeds. Chrdl1 expression is largely excluded from the critical signaling center of the posterior limb bud, the Zone of Polarizing Activity (ZPA), as has been described for the BMP antagonist Gremlin (GREM1) (Scherz et al., 2004, Science, 305, 396-399). Unlike Grem1, Chrdl1 is expressed in the hindlimb by a small subset of ZPA cells and their descendants suggesting divergent regulation and function between the various BMP antagonists. Ectopic expression of Chrdl1 throughout the avian limb bud using viral misexpression resulted in an oligodactyly phenotype with loss of digits from the anterior limb, although the development of more proximal elements of the zeugopod and stylopod were unaffected. Overgrowths of soft tissue and syndactyly were also observed, resulting from impaired apoptosis and failure of the anterior mesenchyme to undergo SOX9-dependent chondrogenesis, instead persisting as an interdigital-like soft tissue phenotype. Sonic hedgehog (SHH) and fibroblast growth factor (FGF) signaling were upregulated and persisted later in development, however these changes were only detected late in limb development at timepoints when endogenous Grem1 would normally be downregulated and increasing BMP signaling would cause termination of Shh and Fgf expression. Our results suggest that the early stages of the GREM1-SHH-FGF signaling network are resistant to Chrdl1-overexpression, leading to normal formation of proximal limb structures, but that later Bmp expression, impaired by ectopic CHRDL1, is essential for formation of the correct complement of digits.

Chordin-like 1, a Novel Adipokine, Markedly Promotes Adipogenesis and Lipid Accumulation.

White adipose tissue serves as a metabolically dynamic organ that can synthesize and secrete biologically active compounds such as adipokines as well as a caloric reservoir for maintaining energy homeostasis. Adipokines are involved in diverse biological and physiological processes and there have been extensive attempts to characterize the effects of over two dozen adipokines. However, many of these adipokines are produced by not only adipose tissue, but also other tissues. Therefore, investigations into the effects of adipokines on physiological functions have been challenged. In this regard, we aimed to identify a new secreted protein that is encoded by genes specifically expressed in white adipose tissue through analysis of multi-tissue transcriptome and protein expression. As a result, we report a novel adipokine that is encoded by the adipose-specific gene, chordin-like 1 (Chrdl1), which is specifically expressed in white adipose tissue in mice; this expression pattern was conserved in the human orthologous CHRDL1 gene. The expression of Chrdl1 was enriched in fat cells and developmentally regulated in vitro and in vivo, and moreover, its retrovirus-mediated overexpression and recombinant protein treatment led to markedly increased adipogenesis. Further pathway enrichment analysis revealed enriched pathways related to lipogenesis and adipogenic signaling. Our findings support a pro-adipogenic role of CHRDL1 as a new adipokine and pave the way toward animal studies and future research on its clinical implications and development of anti-obesity therapy.

Absence of chordin-like 1 aids motor recovery in a mouse model of stroke.

Chordin-like 1 (Chrdl1) is an astrocyte-secreted protein that regulates synaptic maturation, and limits plasticity via GluA2-containing AMPA receptors (AMPARs). It was demonstrated that Chrdl1 expression is very heterogeneous throughout the brain, and it is enriched in astrocytes in cortical layers 2/3, with peak expression in the visual cortex at postnatal day 14. In response to ischemic stroke, Chrdl1 is upregulated during the acute and sub-acute phases in the peri-infarct region, potentially hindering recovery after stroke. Here, we used photothrombosis to model ischemic stroke in the motor cortex of adult male and female mice. In this study, we demonstrate that elimination of Chrdl1 in a global knock-out mouse reduces apoptotic cell death at early post-stroke stages and prevents ischemia-driven synaptic loss of AMPA receptors at later time points, all contributing to faster motor recovery. This suggests that synapse-regulating astrocyte-secreted proteins such as Chrdl1 have therapeutic potential to aid functional recovery after an ischemic injury.

Chordin-like 1 is a novel prognostic biomarker and correlative with immune cell infiltration in lung adenocarcinoma.

Chordin-like 1 (CHRDL1), an inhibitor of bone morphogenetic proteins(BMPs), has been recently reported to participate in the progression of numerous tumors, however, its role in lung adenocarcinoma (LUAD) remains unclear. Our study aimed to demonstrate relationship between CHRDL1 and LUAD based on data from The Cancer Genome Atlas (TCGA). Among them, CHRDL1 expression revealed promising power for distinguishing LUAD tissues form normal sample. Low CHRDL1 was correlated with poor clinicopathologic features, including high T stage (OR=0.45, P<0.001), high N stage (OR=0.57, P<0.003), bad treatment effect (OR=0.64, P=0.047), positive tumor status (OR=0.63, P=0.018), and TP53 mutation (OR=0.49, P<0.001). The survival curve illustrated that low CHRDL1 was significantly correlative with a poor overall survival (HR=0.60, P<0.001). At multivariate Cox regression analysis, CHRDL1 remained independently correlative with overall survival. GSEA identified that the CHRDL1 expression was related to cell cycle and immunoregulation. Immune infiltration analysis suggested that CHRDL1 was significantly correlative with 7 kinds of immune cells. Immunohistochemical validation showed that CHRDL1 was abnormally elevated and negatively correlated with Th2 cells in LUAD tissues. In conclusion, CHRDL1 might become a novel prognostic biomarker and therapy target in LUAD. Moreover, CHRDL1 may improve the effectiveness of immunotherapy by regulating immune infiltration.

Chordin-Like 1 Regulates Epithelial-to-Mesenchymal Transition and Metastasis via the MAPK Signaling Pathway in Oral Squamous Cell Carcinoma.

Background: Accumulating evidence suggests that dysregulation of Chordin-like 1 (CHRDL1) is associated with malignant biological behaviors in multiple cancers. However, the exact function and molecular mechanism of CHRDL1 in oral squamous cell carcinoma (OSCC) remain unclear. Methods: The expression levels of CHRDL1 in OSCC tissues and CAL27 cells were determined by RT-qPCR. Immunohistochemical staining was applied to detect CHRDL1 protein expression in sample tissues from OSCC patients. Gain of function and knockdown by lentivirus were further used to examine the effects of CHRDL1 on cell proliferation, migration, invasion, and adhesion in OSCC. Tail vein injection of CAL27 cells with dysregulated CHRDL1 expression was further used to examine the effect of CHRDL1 on lung colonization. RNA sequencing was performed to explore the molecular mechanisms of CHRDL1 that underlie the progression of OSCC. Results: CHRDL1 was significantly downregulated in OSCC tissues and CAL27 cells compared to controls. CHRDL1 knockdown enhanced migration, invasion, adhesion, and EMT, but not proliferation, in CAL27 cells. Overexpression of CHRDL1 had the opposite effects. Moreover, CHRDL1 was proven to inhibit tumor metastasis in vivo. Mechanistically, MAPK signaling pathway components, including ERK1/2, p38, and JNK, were found to regulate the malignant biological behaviors of CAL27 cells. Conclusions: Our results suggest that CHRDL1 has an inhibitory effect on OSCC metastasis via the MAPK signaling pathway, which provides a new possible potential therapeutic target against OSCC.

X-linked Megalocornea Associated with the Novel CHRDL1 Gene Mutation p.(Pro56Leu*8).

BACKGROUND: The genetic basis of X-linked megalocornea (MGC1) was reported in 2012 to be caused by mutations in the CHRDL1 gene. We sought to confirm that mutations in CHRDL1 are associated with MGC1 in a previously unreported pedigree. MATERIALS AND METHODS: Slit lamp examination, corneal pachymetry, corneal topography and DNA collection for screening of the CHRDL1 gene were performed for members of an affected family. RESULTS: Examination of a woman and her four sons, ranging in age between 3 and 15 years, demonstrated horizontal corneal diameters of 14 mm in three of the four sons and a normal corneal diameter of 12 mm in the mother and other son. Central corneal thickness in the individuals with enlarged corneal diameters averaged 474 microns, compared to 604 microns in their unaffected brother. Corneal topographic imaging demonstrated an average K value of 44.4 D in the affected individuals compared with 41.6 D in their unaffected sibling. Screening of the CHRDL1 gene demonstrated the novel hemizygous frameshift mutation c.167delC (p.(Pro56Leu*8)) in exon 3 in the affected individuals and in the heterozygous state in their mother. This mutation was not present in the unaffected brother or in unrelated controls. CONCLUSION: We provide the initial confirmation that X-linked megalocornea is associated with mutations in the CHRDL1 gene.