Potential role of WISP3 (CCN6) in regulating the accumulation of reactive oxygen species

A spectral framework to map QTLs affecting joint differential networks of gene co-expression

Studying the mechanisms underlying the genotype-phenotype association is crucial in genetics. Gene expression studies have deepened our understanding of the genotype → expression → phenotype mechanisms. However, traditional expression quantitative trait loci (eQTL) methods often overlook the critical role of gene co-expression networks in translating genotype into phenotype. This gap highlights the need for more powerful statistical methods to analyze genotype → network → phenotype mechanism. Here, we develop a network-based method, called snQTL, to map quantitative trait loci affecting gene co-expression networks. Our approach tests the association between genotypes and joint differential networks of gene co-expression via a tensor-based spectral statistics, thereby overcoming the ubiquitous multiple testing challenges in existing methods. We demonstrate the effectiveness of snQTL in the analysis of three-spined stickleback (Gasterosteus aculeatus) data. Compared to conventional methods, our method snQTL uncovers chromosomal regions affecting gene co-expression networks, including one strong candidate gene that would have been missed by traditional eQTL analyses. Our framework suggests the limitation of current approaches and offers a powerful network-based tool for functional loci discoveries.

CCN6 influences transcription and controls mitochondrial mass and muscle organization

Mutations in Cellular Communication Network Factor 6 (CCN6) are linked to the debilitating musculoskeletal disease Progressive Pseudo Rheumatoid Dysplasia (PPRD), which disrupts mobility. Yet, much remains unknown about CCN6 function at the molecular level. In this study, we revealed a new function of CCN6 in transcriptional regulation. We demonstrated that CCN6 localizes to chromatin and associates with RNA Polymerase II in human chondrocyte lines. Using zebrafish as a model organism we validated the nuclear presence of CCN6 and its association with RNA Polymerase II in different developmental stages from 10 hpf embryo to adult fish muscle. In concurrence with these findings, we confirmed the requirement of CCN6 in the transcription of several genes encoding mitochondrial electron transport complex proteins in the zebrafish, both in the embryonic stages and in the adult muscle. Reduction in the expression of these genes upon morpholino-mediated knockdown of CCN6 protein expression led to reduced mitochondrial mass, which correlated with defective myotome organization during zebrafish muscle development. Overall, this study suggests that the developmental musculoskeletal abnormalities linked with PPRD could be contributed at least partly by impaired expression of genes encoding mitochondrial electron transport complexes due to defects in CCN6 associated transcriptional regulation.

Progressive pseudorheumatoid dysplasia: a case series report

rogressive pseudorheumatoid dysplasia (PPRD) is a rare autosomal-recessive, noninflammatory arthropathy. Several cases have been reported worldwide; however, diagnosis remains challenging. Three unrelated children with PPRD were retrospectively studied. All three patients in this study were initially misdiagnosed. The misdiagnoses included juvenile rheumatoid arthritis, myodystrophy and idiopathic short stature. The time from the onset of symptoms to a definitive diagnosis was 3 to 8 years. Clinical signs and radiological phenotypes were analyzed carefully, and they were all consistent with the characteristics of PPRD and noninflammatory polyarticular enlargement. The small joints of both the hands and lower limbs are the most affected. The imaging findings of the patients were flat vertebrae with beak- or bullet-like changes in front of the cone and peripheral metaphysis widening. DNA samples obtained from the family were sequenced to identify the causal gene using whole-exome sequencing (WES). Four Wnt1-inducible signaling pathway protein 3 (WISP3) mutations were verified. c.271delC was not reported previously. The other three mutations, namely, c.136C>T (p. Gln46*), c.667T>G (p. Cys223Gly) and c.589+2T>C, were previously identified. All three patients had a long journey to diagnosis. Early genetic diagnosis can help prevent unnecessary treatments and procedures in patients. Growth hormone is not a good choice for treatment.

Ccn6 Is Required for Mitochondrial Integrity and Skeletal Muscle Function in Zebrafish

Mutations in the CCN6 (WISP3) gene are linked with a debilitating musculoskeletal disorder, termed progressive pseudorheumatoid dysplasia (PPRD). Yet, the functional significance of CCN6 in the musculoskeletal system remains unclear. Using zebrafish as a model organism, we demonstrated that zebrafish Ccn6 is present partly as a component of mitochondrial respiratory complexes in the skeletal muscle of zebrafish. Morpholino-mediated depletion of Ccn6 in the skeletal muscle leads to a significant reduction in mitochondrial respiratory complex assembly and activity, which correlates with loss of muscle mitochondrial abundance. These mitochondrial deficiencies are associated with notable architectural and functional anomalies in the zebrafish muscle. Taken together, our results indicate that Ccn6-mediated regulation of mitochondrial respiratory complex assembly/activity and mitochondrial integrity is important for the maintenance of skeletal muscle structure and function in zebrafish. Furthermore, this study suggests that defects related to mitochondrial respiratory complex assembly/activity and integrity could be an underlying cause of muscle weakness and a failed musculoskeletal system in PPRD.

CCN6 regulates mitochondrial respiratory complex assembly and activity

Cellular communication network factor 6 (CCN6) mutations are linked with Progressive Pseudo Rheumatoid Dysplasia (PPRD) a debilitating musculoskeletal disorder. The function of CCN6 and the mechanism of PPRD pathogenesis remain unclear. Accordingly, we focused on the functional characterization of CCN6 and CCN6 mutants. Using size exclusion chromatography and native polyacrylamide gel electrophoresis we demonstrated that CCN6 is present as a component of the mitochondrial respiratory complex in human chondrocyte lines. By means of siRNA-mediated transfection and electron microscopy we showed that moderate reduction in CCN6 expression decreases the RER- mitochondria inter-membrane distance. Parallel native PAGE, immunoblotting and Complex I activity assays furthermore revealed increase in both mitochondrial distribution of CCN6 and mitochondrial respiratory complex assembly/activity in CCN6 depleted cells. CCN6 mutants resembling those linked with PPRD, which were generated by CRISPR-Cas9 technology displayed low level of expression of mutant CCN6 protein and inhibited respiratory complex assembly/activity. Electron microscopy and MTT assay of the mutants revealed abnormal mitochondria and poor cell viability. Taken together, our results indicate that CCN6 regulates mitochondrial respiratory complex assembly/activity as part of the mitochondrial respiratory complex by controlling the proximity of RER with the mitochondria, and CCN6 mutations disrupt mitochondrial respiratory complex assembly/activity resulting in mitochondrial defects and poor cell viability.

CCN6 mutation detection in Chinese patients with progressive pseudo-rheumatoid dysplasia and identification of four novel mutations

Background

No formal diagnostic criteria for progressive pseudo‐rheumatoid dysplasia (PPD) are available because of insufficient clinical data, which results in that PPD is often misdiagnosed with other diseases. Whole exome sequencing (WES) and Sanger sequencing were employed to reveal the novel mutations on CCN6 of five patients with PPD from China in order to increase the clinical data of PPD.

Methods

Four suspected PPD pedigrees containing five patients in total were collected from 1998 to 2018 in our medical center. The phenotypes of each suspected PPD case were recorded in detail, and peripheral blood samples were collected for subsequent sequencing. Genomic DNA was extracted from peripheral blood samples, and Agilent liquid phase chip capture system was utilized for efficient enrichment of whole exome region DNA. After acquiring raw sequenced reads of whole exome region, bioinformatics analysis was completed in conjunction with reference or genome sequence (GRCh37/hg19). Sanger sequencing was performed to identify the results of WES.

Results

In total, four novel PPD‐related mutation sites in CCN6 gene were identified including (CCN6):c.643 + 2T>C, (CCN6):c.1064_1065dupGT(p.Gln356ValfsTer33), (CCN6):c.1064G > A), and exon4:c.670dupA:p.W223fs.

Conclusion

Our findings increase the clinical data of PPD including the CCN6 mutation spectrum, the clinical symptoms and signs. Moreover, the study highlights the utility of WES in reaching definitive diagnoses for PPD.

Exploring the cytotoxic activity of new phenanthroline salicylaldimine Zn(II) complexes

Zinc(II) complexes bearing N-salicylideneglycinate (Sal-Gly) and 1,10-phenanthroline (phen) or phenanthroline derivatives [NN = 5-chloro-1,10-phenanthroline, 5-amine-1,10-phenanthroline (amphen), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline] are synthesized. Complexes formulated as [Zn(NN)₂(H₂O)₂]²⁺(NN = phen and amphen), are also prepared. The cytotoxicity of the compounds is evaluated towards a panel of human cancer cells: ovarian (A2780), breast (MCF7) and cervical (HeLa), as well as non-tumoral V79 fibroblasts. All compounds display higher cytotoxicity than cisplatin (IC₅₀ = 22.5 ± 5.0 μM) towards ovarian cells, showing IC₅₀values in the low micromolar range. Overall, all compounds show higher selectivity for the A2780 cells than for the non-tumoral cells and higher selectivity indexes (IC₅₀(V79)/IC₅₀(A2780) than cisplatin. [Zn(Sal-Gly)(NN)(H₂O)] complexes induce caspase-dependent apoptosis in A2780 cells, except [Zn(Sal-Gly)(Bphen)(H₂O)], one of the most cytotoxic of the series. The cellular uptake in the ovarian cells analyzed by Inductively Coupled Plasma mass spectrometry indicates different Zn distribution profiles. Transmission electronic microscopy shows mitochondria alterations and apoptotic features consistent with caspase activation; cells incubated with [Zn(Sal-Gly)(amphen)(H₂O)] present additional nuclear membrane alterations in agreement with significant association with the nucleus. The increase of reactive oxygen species and lipid peroxidation forms could be related to apoptosis induction. [Zn(NN)₂(H₂O)₂]²⁺complexes have high ability to bind DNA through intercalation/groove binding, and circular dichroism data suggests that the main type of species that interact with DNA is [Zn(NN)]²⁺. Studies varying the % of fetal bovine serum (1-15%) in cell media show that albumin binding decreases the complex activity, indicating that distinct speciation of Zn- and phen-containing species in cell media may affect the cytotoxicity.

A Novel Homozygous Frameshift Mutation in CCN6 Causing Progressive Pseudorheumatoid Dysplasia (PPRD) in a Consanguineous Yemeni Family

Background: Progressive pseudorheumatoid dysplasia (PPRD) inherited in an autosomal recessive fashion, is a disabling disease, characterized by platyspondyly, irregularities of the vertebral bodies, narrowing of the intervertebral discs and intraarticular spaces, widening of the epiphysis-metaphysis, polyarthralgia, multiple joint contractures, and disproportionate short stature. A number of studies have been performed on this deformity in various populations around the globe, including the Arab population. Mutations in CCN6, located on 6q22, are reported to cause this anomaly. Case Presentation: The present study describes the investigation of a consanguineous family of Yemeni origin. Clinical examination of the patient revealed short stature with progressive skeletal abnormalities, stiffness and enlargement of small joints of the hands along with restriction of movements of proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with weakness and gait disturbance. Sanger sequencing revealed a novel homozygous frameshift deletion mutation (c.746delT; p.Val249Glyfs^*10) in CCN6 which may lead to NMD (Nonsense mediated decay). This mutation expands the spectrum of pathogenic variants in CCN6 causing PPRD.

Progressive pseudorheumatoid dysplasia: a rare childhood disease

Progressive pseudorheumatoid dysplasia (PPRD) is a genetic bone disorder characterised by the progressive degeneration of articular cartilage that leads to pain, stiffness and joint enlargement. As PPRD is a rare disease, available literature is mainly represented by single case reports and only a few larger case series. Our aim is to review the literature concerning clinical, laboratory and radiological features of PPRD. PPRD is due to a mutation in Wnt1-inducible signalling protein 3 (WISP3) gene, which encodes a signalling factor involved in cartilage homeostasis. The disease onset in childhood and skeletal changes progresses over time leading to significant disability. PPRD is a rare condition that should be suspected if a child develops symmetrical polyarticular involvement without systemic inflammation, knobbly interphalangeal joints of the hands, and gait abnormalities. A full skeletal survey, or at least a lateral radiograph of the spine, can direct towards a correct diagnosis that can be confirmed molecularly. More than 70 WISP3 mutations have so far been reported. Genetic testing should start with the study of genomic DNA extracted from blood leucocytes, but intronic mutations in WISP3 causing splicing aberrations can only be detected by analysing WISP3 mRNA, which can be extracted from cultured skin fibroblasts. A skin biopsy is, therefore, indicated in patients with typical PPRD findings and negative mutation screening of genomic DNA.

WISP-3/CCN6 inhibits apoptosis by regulating caspase pathway after hyperoxia in lung epithelial cells

Cell death is a normal phenomenon in the course of biological development, moreover, which is also a prominent feature in lung exposed to hyperoxia. Severe hypoxia occurs in ALI/ARDS patients, who generally require high concentration oxygen therapy assisted by mechanical ventilation. Nevertheless, high oxygen can cause excessive reactive oxygen species (ROS), leading to apoptosis in lung epithelial cells, which has been reported in our previous study. Herein, the correlation between increments of ROS and CCN6 expression was negative in CCN6-mediated the mitochondria dependent, intrinsic apoptotic pathway. Our latest research explained that CCN6 can inhibit caspase-8 mediated extrinsic apoptotic pathway to protect cells from hyperoxia-induced apoptosis. As demonstrated by Western Blot Analysis, Caspase 8 cleavage and Caspase 3 cleavage in CCN6-depleted cells exceeded the control group treated with high oxygen (48 h). And deletion of CCN6 enhanced caspase-8 activation after hyperoxia shown by Flow Cytometry. Although, it is unclear how CCN6 participated in the regulation of apoptotic pathways, the future targeted therapy drugs inhibiting CCN6 may be useful in the treatment of ALI/ARDS.

CCN6 regulates mitochondrial function

Despite established links of CCN6, or Wnt induced signaling protein-3 (WISP3), with progressive pseudo rheumatoid dysplasia, functional characterization of CCN6 remains incomplete. In light of the documented negative correlation between accumulation of reactive oxygen species (ROS) and CCN6 expression, we investigated whether CCN6 regulates ROS accumulation through its influence on mitochondrial function. We found that CCN6 localizes to mitochondria, and depletion of CCN6 in the chondrocyte cell line C-28/I2 by using siRNA results in altered mitochondrial electron transport and respiration. Enhanced electron transport chain (ETC) activity of CCN6-depleted cells was reflected by increased mitochondrial ROS levels in association with augmented mitochondrial ATP synthesis, mitochondrial membrane potential and Ca(2+) Additionally, CCN6-depleted cells display ROS-dependent PGC1α (also known as PPARGC1A) induction, which correlates with increased mitochondrial mass and volume density, together with altered mitochondrial morphology. Interestingly, transcription factor Nrf2 (also known as NFE2L2) repressed CCN6 expression. Taken together, our results suggest that CCN6 acts as a molecular brake, which is appropriately balanced by Nrf2, in regulating mitochondrial function.

Genetic Evaluation of Schizophrenia Using the Illumina HumanExome Chip

INTRODUCTION

Schizophrenia is a genetically heterogeneous disorder that is associated with several common and rare genetic variants. As technology involved, cost advantages of chip based genotyping was combined with information about rare variants, resulting in the Infinium HumanExome Beadchip. Using this chip, a sample of 493 patients with schizophrenia or schizoaffective disorder and 484 healthy controls was genotyped.

RESULTS

From the initial 242901 SNVs, 88306 had at least one minor allele and passed quality control. No variant reached genomewide-significant results (p<10(-8)). The SNP with the lowest p-value was rs1230345 in WISP3 (p = 3.05*10(-6)), followed by rs9311525 in CACNA2D3 (p = 1.03*10(-5)) and rs1558557 (p = 3.85*10(-05)) on chromosome 7. At the gene level, 3 genes were of interest: WISP3, on chromosome 6q21, a signally protein from the extracellular matrix. A second candidate gene is CACNA2D3, a regulator of the intracerebral calcium pathway. A third gene is TNFSF10, associated with p53 mediated apoptosis.

WISP3-IGF1 interaction regulates chondrocyte hypertrophy

WISP3 (Wnt induced secreted protein 3) is a multi-domain protein of mesenchymal origin. Mutations in several domains of WISP3 cause PPRD (progressive pseudo rheumatoid dysplasia), which is associated with cartilage loss and restricted skeletal development. Despite several studies focusing on the functional characterization of WISP3, the molecular details underlying the course of PPRD remain unresolved. We are interested in analyzing the function of WISP3 in the context of cartilage integrity. The current study demonstrates that WISP3 binds to insulin-like growth factor 1 (IGF1) and inhibits IGF1 secretion. Additionally, WISP3 curbs IGF1-mediated collagen X expression, accumulation of reactive oxygen species (ROS) and alkaline phosphatase activity, all of which are associated with the induction of chondrocyte hypertrophy. Interestingly, both IGF1 and ROS in turn trigger an increase in WISP3 expression. Together, our results are indicative of an operational WISP3-IGF1 regulatory loop whereby WISP3 preserves cartilage integrity by restricting IGF1-mediated hypertrophic changes in chondrocytes, at least partly, upon interaction with IGF1.

The matri-cellular proteins 'cysteine-rich, angiogenic-inducer, 61' and 'connective tissue growth factor' are regulated in experimentally-induced sepsis with multiple organ dysfunction

Organ failure is a severe complication in sepsis for which the pathophysiology remains incompletely understood. Recently, the matri-cellular cysteine-rich, angiogenic induced, 61 (Cyr61/CCN1); connective tissue growth factor (Ctgf/CCN2); and nephroblastoma overexpressed gene (Nov/CCN3) (CCN)-protein family have been attributed organ-protective properties. Their expression is sensitive to mediators of sepsis pathophysiology but a potential role in sepsis remains elusive. To provide an initial assessment, 50 rats were subjected to 18 h of cecal-ligation and puncture or sham operation. Hepatic and pulmonary CCN1 mRNA displayed an average 7.4- and 3.3-fold induction, while its cardiac expression was unchanged. The changes coincided with excessive hepatic and pulmonary inflammatory gene activation and a restricted cardiac inflammation. Furthermore, hepatocytes displayed a dosage-dependent CCN1 mRNA response in vitro, supporting a cytokine-mediated CCN1 regulation in sepsis. CCN2 mRNA was 2.2-fold induced in the liver, while 2.0-fold and 1.4-fold repressed in the heart and lung. Meanwhile, it did not respond to TNF-α exposure in vitro, which indicates different means of regulation than for CCN1. Taken together, this study provides the first evidence for multi-organ regulation of CCN1 and CCN2 in early stages of sepsis, and implies the eruption of inflammatory mediators as a potential mechanism behind the observed CCN1 regulation.

The CCN proteins: important signaling mediators in stem cell differentiation and tumorigenesis

The CCN proteins contain six members, namely CCN1 to CCN6, which are small secreted cysteine-rich proteins. The CCN proteins are modular proteins, containing up to four functional domains. Many of the CCN members are induced by growth factors, cytokines, or cellular stress. The CCNs show a wide and highly variable expression pattern in adult and in embryonic tissues. The CCN proteins can integrate and modulate the signals of integrins, BMPs, VEGF, Wnts, and Notch. The involvement of integrins in mediating CCN signaling may provide diverse context-dependent responses in distinct cell types. CCN1 and CCN2 play an important role in development, angiogenesis and cell adhesion, whereas CCN3 is critical to skeletal and cardiac development. CCN4, CCN5 and CCN6 usually inhibit cell growth. Mutations of Ccn6 are associated with the progressive pseudorheumatoid dysplasia and spondyloepiphyseal dysplasia tarda. In stem cell differentiation, CCN1, CCN2, and CCN3 play a principal role in osteogenesis, chondrogenesis, and angiogenesis. Elevated expression of CCN1 is associated with more aggressive phenotypes of human cancer, while the roles of CCN2 and CCN3 in tumorigenesis are tumor type-dependent. CCN4, CCN5 and CCN6 function as tumor suppressors. Although CCN proteins may play important roles in fine-tuning other major signaling pathways, the precise function and mechanism of action of these proteins remain undefined. Understanding of the biological functions of the CCN proteins would not only provide insight into their roles in numerous cellular processes but also offer opportunities for developing therapeutics by targeting CCN functions.

The CCN family member Wisp3, mutant in progressive pseudorheumatoid dysplasia, modulates BMP and Wnt signaling

In humans, loss-of-function mutations in the gene encoding Wnt1 inducible signaling pathway protein 3 (WISP3) cause the autosomal-recessive skeletal disorder progressive pseudorheumatoid dysplasia (PPD). However, in mice there is no apparent phenotype caused by Wisp3 deficiency or overexpression. Consequently, the in vivo activities of Wisp3 have remained elusive. We cloned the zebrafish ortholog of Wisp3 and investigated its biologic activity in vivo using gain-of-function and loss-of-function approaches. Overexpression of zebrafish Wisp3 protein inhibited bone morphogenetic protein (BMP) and Wnt signaling in developing zebrafish. Conditioned medium-containing zebrafish and human Wisp3 also inhibited BMP and Wnt signaling in mammalian cells by binding to BMP ligand and to the Wnt coreceptors low-density lipoprotein receptor-related protein 6 (LRP6) and Frizzled, respectively. Wisp3 proteins containing disease-causing amino acid substitutions found in patients with PPD had reduced activity in these assays. Morpholino-mediated inhibition of zebrafish Wisp3 protein expression in developing zebrafish affected pharyngeal cartilage size and shape. These data provide a biologic assay for Wisp3, reveal a role for Wisp3 during zebrafish cartilage development, and suggest that dysregulation of BMP and/or Wnt signaling contributes to cartilage failure in humans with PPD.