Genome-wide association study identifies novel susceptible loci and highlights Wnt/beta-catenin pathway in the development of adolescent idiopathic scoliosis

Association between the GLP1R A316T Mutation and Adolescent Idiopathic Scoliosis in French Canadian and Italian Cohorts

Studies have revealed anthropometric discrepancies in girls with adolescent idiopathic scoliosis (AIS) compared to non-scoliotic subjects, such as a higher stature, lower weight, and lower body mass index. While the causes are still unknown, it was proposed that metabolic hormones could play a role in AIS pathophysiology. Our objectives were to evaluate the association of GLP1R A316T polymorphism in AIS susceptibility and to study its relationship with disease severity and progression. We performed a retrospective case-control association study with controls and AIS patients from an Italian and French Canadian cohort. The GLP1R rs10305492 polymorphism was genotyped in 1025 subjects (313 non-scoliotic controls and 712 AIS patients) using a validated TaqMan allelic discrimination assay. Associations were evaluated by odds ratio and 95% confidence intervals. In the AIS group, there was a higher frequency of the variant genotype A/G (4.2% vs. 1.3%, OR = 3.40, p = 0.016) and allele A (2.1% vs. 0.6%, OR = 3.35, p = 0.017) than controls. When the AIS group was stratified for severity (≤40° vs. >40°), progression of the disease (progressor vs. non-progressor), curve type, or body mass index, there was no statistically significant difference in the distribution of the polymorphism. Our results support that the GLP1R A316T polymorphism is associated with a higher risk of developing AIS, but without being associated with disease severity and progression.

A transcriptomics-based investigation of the mechanism of pulmonary fibrosis induced by nickel oxide nanoparticles

Nickel oxide nanoparticles (NiONPs) are an emerging nanomaterial, which poses a huge threat to the health of workplace population. Nanoparticles induce pulmonary fibrosis, and its mechanisms are associated with noncoding RNAs (ncRNAs). However, ncRNAs and competing endogenous RNA (ceRNA) networks which involved in NiONP-induced pulmonary fibrosis are still unclear. This study aimed to identify ncRNA-related ceRNA networks and investigate the role of the Wnt/β-catenin pathway in pulmonary fibrosis. Male Wistar rats were intratracheally instilled with 0.015, 0.06, and 0.24 mg/kg NiONPs twice a week for 9 weeks. First, we found there were 93 circularRNAs (circRNAs), 74 microRNAs (miRNAs), 124 long non-coding RNAs (lncRNAs), and 1675 messenger RNAs (mRNAs) differentially expressed through microarray analysis. Second, we constructed ceRNA networks among lncRNAs/circRNAs, miRNAs and mRNAs and identified two ceRNA networks (lncMelttl16/miR-382-5p/Hsd17b7 and circIqch/miR-181d-5p/Stat1) after real time-quantitative polymerase chain reaction (RT-qPCR) validation. Furthermore, based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, ncRNAs were found to be involved in biological processes and signaling pathways related to pulmonary fibrosis. KEGG analysis showed that NiONPs activated the Wnt/β-catenin pathway in rats. In vitro, HFL1 cells were treated with 0, 50, 100, and 200 μg/mL NiONPs for 24 h. We found that NiONPs induced collagen deposition and Wnt/β-catenin pathway activation. Moreover, a blockade of Wnt/β-catenin pathway alleviated NiONP-induced collagen deposition. In conclusion, these observations suggested that ncRNAs were crucial in pulmonary fibrosis development and that the Wnt/β-catenin pathway mediated the deposition of collagen.

Comparative analysis of paraspinal muscle imbalance between idiopathic scoliosis and congenital scoliosis from the transcriptome aspect

Background

Previous studies have analyzed paraspinal muscle imbalance in idiopathic scoliosis (IS) with methods including imaging, histology and electromyography. However, whether paraspinal muscle imbalance is the cause or the consequence of spinal deformities in IS remains unclear. Comparison of paraspinal muscle imbalance between IS and congenital scoliosis (CS) may shed some light on the causality of paraspinal muscle imbalance and IS. This study aimed to elucidate the generality and individuality of paraspinal muscle imbalance between IS and CS from gene expression.

Methods

Five pairs of surgical-treated IS and CS patients were matched. Bilateral paraspinal muscles at the apex were collected for transcriptome sequencing. Differentially expressed genes (DEGs) between the convexity and concavity in both IS and CS were identified. Comparison of DEGs between IS and CS was conducted to discriminate IS-specific DEGs from DEGs shared by both IS and CS. Bioinformatics analysis was performed. The top 10 hub genes in the protein-protein interaction (PPI) network of IS-specific DEGs were validated by quantitative PCR (qPCR) in 10 pairs of IS and CS patients.

Results

A total of 370 DEGs were identified in IS, whereas 380 DEGs were identified in CS. Comparison of DEGs between IS and CS identified 59 DEGs shared by IS and CS, along with 311 DEGs specific for IS. These IS-specific DEGs were enriched in response to external stimulus and signaling receptor binding in GO terms and calcium signaling pathway in KEGG pathways. The top 10 hub genes in the PPI network of IS-specific DEGs include BDKRB1, PRH1-TAS2R14, CNR2, NPY4R, HTR1E, CXCL3, ICAM1, ALB, ADIPOQ, and GCGR. Among these hub genes, the asymmetrical expression of PRH1-TAS2R14 and ADIPOQ in IS but not CS were validated by qPCR.

Conclusions

Transcriptomic differences in bilateral paraspinal muscles between the convexity and concavity in IS share few similarities with those in CS.

Association between genetic polymorphisms and risk of adolescent idiopathic scoliosis in case-control studies: a systematic review

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a structural lateral spinal curvature of ≥10° with rotation. Approximately 2%-3% of children across populations are affected with AIS, and this condition is responsible for ~$3 billion in costs within the USA. Although AIS is believed to have a strong genetic contribution, clinical translation of identified genetic variants has stalled.

METHODS

The databases MEDLINE (via PubMed), Embase, Google Scholar and Ovid MEDLINE were searched and limited to articles in English. Title and abstract, full-text and data extraction screening was conducted through Covidence, followed by data transfer to a custom REDCap database. Studies containing variant-level data using genome-wide methodology as well as validation studies of genome-wide methods were considered. Quality assessment was conducted using Q-Genie.

RESULTS

33 studies were included, including 9 genome-wide association studies, 4 whole exome sequencing and 20 validation studies. Combined, these studies included data from >35,000 cases and >67,000 controls, not including validation cohorts. Additionally, results from six meta-analyses containing novel cohorts were also reported. All included study cohorts were from populations of primarily East Asian or Caucasian descent. Quality assessment found that overall study quality was high and control group selection was moderate. The highest number of reported associations were in single nucleotide polymorphisms (SNPs) in or near LBX1, LBX1-AS1, GPR126/ADGRG6 or BNC2.

CONCLUSION

AIS risk may be influenced by specific SNPs, particularly those in/near LBX1 and GPR126. Translatability of study findings is unknown due to an underrepresentation of most ethnic groups as well as few identified genome-wide studies. Further studies may benefit from increased cohort diversity and thorough evaluation of control cohort groups.

Advances in genetic factors of adolescent idiopathic scoliosis: a bibliometric analysis

Objective

This study offers a bibliometric analysis of the current situation, hotspots, and cutting-edge domains of genetic factors of adolescent idiopathic scoliosis (AIS).

Methods

All publications related to genetic factors of AIS from January 1, 1992, to February 28, 2023, were searched from the Web of Science. CiteSpace software was employed for bibliometric analysis, collecting information about countries, institutions, authors, journals, and keywords of each article.

Results

A cumulative number of 308 articles have been ascertained. Since 2006, publications relating to genetic factors of AIS have significantly increased. China leads in both productivity and influence in this area, with the Chinese Academy of Medical Sciences being the most productive institution. The most prolific scholars in this field are Y. Qiu and Z. Z. Zhu. The publications that contributed the most were from Spine and European Spine Journal. The most prominent keywords in the genetic factors of AIS were "fibrillin gene", "menarche", "calmodulin", "estrogen receptor gene", "linkage analysis", "disc degeneration", "bone mineral density", "melatonin signaling dysfunction", "collagen gene", "mesenchymal stem cell", "LBX1", "promoter polymorphism", "Bone formation", "cerebrospinal fluid flow" and "extracellular matrix".

Conclusion

This analysis provides the frontiers and trends of genetic factors in AIS, including relevant research, partners, institutions and countries.

Asymmetric expression of PIEZO2 in paraspinal muscles of adolescent idiopathic scoliosis

BACKGROUND

Muscle imbalance has long been recognized as one of the possible pathogeneses for adolescent idiopathic scoliosis (AIS). PIEZO2, the susceptibility gene of AIS, has been identified to play an important role in neuromuscular activities.

OBJECTIVE

This study aims to compare the mRNA expression of PIEZO2 between concave and convex paraspinal muscles of AIS patients and to identify the relationship between the ratio of PIEZO2 expression and curve magnitude.

METHODS

Twenty female AIS patients (right thoracic curve) who underwent spinal correction surgery were divided into moderate (n= 12) and severe (⩾ 70 degrees) curve groups (n= 8). The morphology of the paraspinal muscles was assessed with spinal MRI. Multifidus specimens were collected during surgical operations from the concave and convex sides of the apical region, and mRNA expression of the PIEZO2 gene was compared between sides. The localization of PIEZO2 protein expression was confirmed with the markers PAX7 and PAX3, and the percentage of PIEZO2+ cells was also investigated.

RESULTS

In the moderate curve group, fatty infiltration in the deep paraspinal muscle was significantly higher on the concave side than on the convex side. There were no differences in deep muscle area, superficial muscle area, or fatty infiltration of superficial paraspinal muscle. The mRNA expression of PIEZO2 was significantly increased on the concave side, and the asymmetric expression predominantly occurred in moderate curves rather than severe ones. PIEZO2 was expressed on satellite cells instead of fibers of the muscle spindle. The percent of PIEZO2+PAX7+ cells in myofibers was significantly higher on the concave side in the moderate curve group, but not in the severe curve group.

CONCLUSIONS

Asymmetric morphological changes occur in the deep paraspinal muscles of AIS. The PIEZO2 is asymmetrically expressed in the multifidus muscle and is preferentially expressed in satellite cells.

A historical perspective of macroautophagy regulation by biochemical and biomechanical stimuli

Macroautophagy is a lysosomal degradative pathway for intracellular macromolecules, protein aggregates, and organelles. The formation of the autophagosome, a double membrane-bound structure that sequesters cargoes before their delivery to the lysosome, is regulated by several stimuli in multicellular organisms. Pioneering studies in rat liver showed the importance of amino acids, insulin, and glucagon in controlling macroautophagy. Thereafter, many studies have deciphered the signaling pathways downstream of these biochemical stimuli to control autophagosome formation. Two signaling hubs have emerged: the kinase mTOR, in a complex at the surface of lysosomes which is sensitive to nutrients and hormones; and AMPK, which is sensitive to the cellular energetic status. Besides nutritional, hormonal, and energetic fluctuations, many organs have to respond to mechanical forces (compression, stretching, and shear stress). Recent studies have shown the importance of mechanotransduction in controlling macroautophagy. This regulation engages cell surface sensors, such as the primary cilium, in order to translate mechanical stimuli into biological responses.

The Role of Muscle Biomarkers in Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is the predominant orthopedic disorder in children, affecting 1-3% of the global population. Research in this field has tried to delineate the genetic factors behind scoliosis and its association with heredity since AIS is considered a polygenic disease and has different genetic and epigenetic factors. The current study conducted a narrative review of the literature, focusing on biomarkers in the pathophysiology of muscle in AIS patients. Articles were collected from Scopus, Pubmed, and Web of Science. The key screening parameters were scoliosis classification, sampling, and the biomarkers evaluated. This review emphasizes potential key mechanisms and molecular regulators in muscle tissue. While there has been limited focus on the proteins contributing to muscle changes in AIS, significant attention has been given to genomic studies of single-nucleotide polymorphisms, particularly in LBX1. Despite these efforts, the exact causes of AIS remain elusive, with several theories suggesting genetic and hormonal factors. This review identified critical protein biomarkers such as Gi-protein alpha subunits, fibrillin-1 and -2, and various differentially expressed proteins, which may be linked to muscle alterations in AIS. This field of research is still limited due to a lack of homogeneity in the distinction of patients by groups and curve severity. Although the pathophysiology of AIS is still unclear, molecular research is important to guide the treatment of AIS before achieving skeletal maturity, thus avoiding serious problems associated with posture changes and low quality of life. In the future, a more comprehensive synergy between orthopedic and molecular research might ameliorate the diagnosis and treatment of AIS patients.

Research progress on the regulation of bone marrow stem cells by noncoding RNAs in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a common spinal deformity in young women, but its pathogenesis remains unclear. The primary pathogenic factors contributing to its development include genetics, abnormal bone metabolism, and endocrine factors. Bone marrow stem cells (BMSCs) play a crucial role in the pathogenesis of AIS by regulating its occurrence and progression. Noncoding RNAs (ncRNAs) are also involved in the pathogenesis of AIS, and their role in regulating BMSCs in patients with AIS requires further evaluation. In this review, we discuss the relevant literature regarding the osteogenic, chondrogenic, and lipogenic differentiation of BMSCs. The corresponding mechanisms of ncRNA-mediated BMSC regulation in patients with AIS, recent advancements in AIS and ncRNA research, and the importance of ncRNA translation profiling and multiomics are highlighted.

Proteomic Comparison of Paraspinal Muscle Imbalance Between Idiopathic Scoliosis and Congenital Scoliosis

OBJECTIVE

This study aims to compare the proteomic profiles of paraspinal muscle imbalance between idiopathic scoliosis (IS) and congenital scoliosis (CS).

METHODS

Bilateral paraspinal muscles of 5 pairs of matched IS and CS patients were collected. Proteome patterns of paraspinal muscles were established. Differentially expressed proteins (DEPs) in paraspinal muscles between the convexity and the concavity were screened out. DEPs shared by both IS and CS and IS-specific DEPs were identified. Bioinformatic analyses of DEPs were performed.

RESULTS

Among 105 DEPs identified in IS, 30 displayed predominant expression on the convexity, whereas other 75 exhibited predominant expression on the concavity. DEPs in IS were mainly enriched in calcium ion binding and DNA binding in gene ontology (GO) term and glycolysis/gluconeogenesis and purine metabolism in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. Among 48 DEPs identified in CS, 25 were predominantly expressed on the convexity and 23 on the concavity. DEPs in CS were mainly enriched in receptor activity and immune response in GO term and glycolysis/gluconeogenesis and cellular senescence in KEGG pathway. Comparison of DEPs between IS and CS identified only 8 proteins shared by both types of scoliosis. Among the 97 IS-specific DEPs, 28 were predominantly expressed on the convexity and 69 on the concavity. IS-specific genes were enriched in calcium ion binding and protein glycosylation in GO term and glycolysis/gluconeogenesis and hypertrophic cardiomyopathy in KEGG pathway.

CONCLUSION

IS and CS exhibit proteomic imbalance in bilateral paraspinal muscles but share few similarities. Paraspinal muscle imbalance in IS might not be the consequence of spinal deformities.

A mutational hotspot in AMOTL1 defines a new syndrome of orofacial clefting, cardiac anomalies, and tall stature

AMOTL1 encodes angiomotin-like protein 1, an actin-binding protein that regulates cell polarity, adhesion, and migration. The role of AMOTL1 in human disease is equivocal. We report a large cohort of individuals harboring heterozygous AMOTL1 variants and define a core phenotype of orofacial clefting, congenital heart disease, tall stature, auricular anomalies, and gastrointestinal manifestations in individuals with variants in AMOTL1 affecting amino acids 157-161, a functionally undefined but highly conserved region. Three individuals with AMOTL1 variants outside this region are also described who had variable presentations with orofacial clefting and multi-organ disease. Our case cohort suggests that heterozygous missense variants in AMOTL1, most commonly affecting amino acid residues 157-161, define a new orofacial clefting syndrome, and indicates an important functional role for this undefined region.

The asymmetrical ESR1 signaling in muscle progenitor cells determines the progression of adolescent idiopathic scoliosis

Adolescent Idiopathic Scoliosis (AIS) is a common pediatric skeletal disease highly occurred in females. The pathogenesis of AIS has not been fully elucidated. Here, we reveal that ESR1 (Estrogen Receptor 1) expression declines in muscle stem/progenitor cells at the concave side of AIS patients. Furthermore, ESR1 is required for muscle stem/progenitor cell differentiation and disrupted ESR1 signaling leads to differentiation defects. The imbalance of ESR1 signaling in the para-spinal muscles induces scoliosis in mice, while reactivation of ESR1 signaling at the concave side by an FDA approved drug Raloxifene alleviates the curve progression. This work reveals that the asymmetric inactivation of ESR1 signaling is one of the causes of AIS. Reactivation of ESR1 signaling in para-spinal muscle by Raloxifene at the concave side could be a new strategy to treat AIS.

Genetic animal modeling for idiopathic scoliosis research: history and considerations

PURPOSE

Idiopathic scoliosis (IS) is defined as a structural lateral spinal curvature ≥ 10° in otherwise healthy children and is the most common pediatric spinal deformity. IS is known to have a strong genetic component; however, the underlying etiology is still largely unknown. Animal models have been used historically to both understand and develop treatments for human disease, including within the context of IS. This intended audience for this review is clinicians in the fields of musculoskeletal surgery and research.

METHODS

In this review article, we synthesize current literature of genetic animal models of IS and introduce considerations for researchers.

RESULTS

Due to complex genetic and unique biomechanical factors (i.e., bipedalism) hypothesized to contribute to IS in humans, scoliosis is a difficult condition to replicate in model organisms.

CONCLUSION

We advocate careful selection of animal models based on the scientific question and introduce gaps and limitations in the current literature. We advocate future research efforts to include animal models with multiple characterized genetic or environmental perturbations to reflect current understanding of the human condition.

Association of FBN1 polymorphism with susceptibility of adolescent idiopathic scoliosis: a case-control study

BACKGROUND

Fibrillin-1 (FBN1) is an extracellular matrix glycoprotein essential to the structural component of microfibrils and FBN1 gene polymorphisms can be associated with adolescent idiopathic scoliosis (AIS) susceptibility. This study aimed to evaluate the potential role of the FBN1 rs12916536 polymorphism in AIS development or severity and the variation in Cobb angle in relation to patient's characteristics.

METHODS

DNA from 563 subjects (185 AIS patients and 378 controls) were genotyped using a validated TaqMan allelic discrimination assay. A multivariate logistic regression model evaluated the association between polymorphism and AIS, using the adjusted odds ratios (OR) with their respective 95% confidence intervals (95% CI). A linear regression analysis evaluated the variation in Cobb angle according to the patient's age and body mass index (BMI).

RESULTS

Among the AIS group there was a predominance of females (12:1), low or normal BMI (90%), 58% had a Cobb angle greater than 45° and 74% were skeletally mature. Age was a risk factor (4-fold) for curve progression higher than BMI (P < 0.001). The allelic frequency of the rs12916536 G > A polymorphism was 40% in controls and 31% in AIS cases; and this difference was statistically significant (P = 0.004). FBN1 rs12916536 GA + AA genotypes were associated with a lower risk of AIS susceptibility (OR = 0.58 and 95% CI = 0.35-0.98), after adjustment for age, sex and BMI. However, no significant differences were detected in polymorphism distribution with the severity of the disease (Cobb < 45° or ≥ 45°).

CONCLUSION

Age was a risk factor for progression of the scoliotic curve and FBN1 rs12916536 polymorphism a protective factor for AIS susceptibility.

Tent5a modulates muscle fiber formation in adolescent idiopathic scoliosis via maintenance of myogenin expression

OBJECTIVE

Paravertebral muscle asymmetry may be involved in the pathogenesis of adolescent idiopathic scoliosis (AIS), and the Tent5a protein was recently identified as a novel active noncanonical poly(A) polymerase. We, therefore, explored the function of the AIS susceptibility gene Tent5a in myoblasts.

MATERIALS AND METHODS

RNA-seq of AIS paravertebral muscle was performed, and the molecular differences in paravertebral muscle were investigated. Twenty-four AIS susceptibility genes were screened, and differential expression of Tent5a in paravertebral muscles was confirmed with qPCR and Western blot. After the knockdown of Tent5a, the functional effects of Tent5a on C2C12 cell proliferation, migration, and apoptosis were detected by Cell Counting Kit-8 assay, wound-healing assay, and TUNEL assay, respectively. Myogenic differentiation markers were tested with immunofluorescence and qPCR in vitro, and muscle fiber formation was compared in vivo.

RESULTS

The AIS susceptibility gene Tent5a was differentially expressed in AIS paravertebral muscles. Tent5a knockdown inhibited the proliferation and migration of C2C12 cells and inhibited the maturation of type I muscle fibers in vitro and in vivo. Mechanistically, the expression of myogenin was decreased along with the suppression of Tent5a.

CONCLUSIONS

Tent5a plays an important role in the proliferation and migration of myoblasts, and it regulates muscle fiber maturation by maintaining the stability of myogenin. Tent5a may be involved in the pathogenesis of AIS by regulating the formation of muscle fiber type I.

The axonemal dynein heavy chain 10 gene is essential for monocilia motility and spine alignment in zebrafish

Adolescent idiopathic scoliosis (AIS) is a common pediatric musculoskeletal disorder worldwide, characterized by atypical spine curvatures in otherwise healthy children. Human genetic studies have identified candidate genes associated with AIS, however, only a few of these have been shown to recapitulate adult-viable scoliosis in animal models. Using an F0 CRISPR screening approach in zebrafish, we demonstrate that disruption of the dynein axonemal heavy chain 10 (dnah10) gene results in recessive adult-viable scoliosis in zebrafish. Using a stably segregating dnah10 mutant zebrafish, we showed that the ependymal monocilia lining the hindbrain and spinal canal displayed reduced beat frequency, which was correlated with the disassembly of the Reissner fiber and the onset of body curvatures. Taken together, these results suggest that monocilia function in larval zebrafish contributes to the polymerization of the Reissner fiber and straightening of the body axis.

Turning the Curve Into Straight: Phenogenetics of the Spine Morphology and Coordinate Maintenance in the Zebrafish

The vertebral column, or spine, provides mechanical support and determines body axis posture and motion. The most common malformation altering spine morphology and function is adolescent idiopathic scoliosis (AIS), a three-dimensional spinal deformity that affects approximately 4% of the population worldwide. Due to AIS genetic heterogenicity and the lack of suitable animal models for its study, the etiology of this condition remains unclear, thus limiting treatment options. We here review current advances in zebrafish phenogenetics concerning AIS-like models and highlight the recently discovered biological processes leading to spine malformations. First, we focus on gene functions and phenotypes controlling critical aspects of postembryonic aspects that prime in spine architecture development and straightening. Second, we summarize how primary cilia assembly and biomechanical stimulus transduction, cerebrospinal fluid components and flow driven by motile cilia have been implicated in the pathogenesis of AIS-like phenotypes. Third, we highlight the inflammatory responses associated with scoliosis. We finally discuss recent innovations and methodologies for morphometrically characterize and analyze the zebrafish spine. Ongoing phenotyping projects are expected to identify novel and unprecedented postembryonic gene functions controlling spine morphology and mutant models of AIS. Importantly, imaging and gene editing technologies are allowing deep phenotyping studies in the zebrafish, opening new experimental paradigms in the morphometric and three-dimensional assessment of spinal malformations. In the future, fully elucidating the phenogenetic underpinnings of AIS etiology in zebrafish and humans will undoubtedly lead to innovative pharmacological treatments against spinal deformities.

A Functional SNP in the Promoter of LBX1 Is Associated With the Development of Adolescent Idiopathic Scoliosis Through Involvement in the Myogenesis of Paraspinal Muscles

Previous studies have shown that LBX1 is associated with adolescent idiopathic scoliosis (AIS) in multiple populations. For the first time, rs1322330 located in the putative promoter region of LBX1 was found significantly associated with AIS in the Chinese population [p = 6.08 × 10^–14, odds ratio (OR) = 1.42, 95% confidence interval of 1.03–1.55]. Moreover, the luciferase assay and electrophoretic mobility shift assay supported that the allele A of rs1322330 could down-regulate the expression of LBX1 in the paraspinal muscles of AIS. In addition, silencing LBX1 in the myosatellite cells resulted in significantly inhibited cell viability and myotube formation, which supported an essential role of LBX1 in muscle development of AIS. To summarize, rs1322330 may be a novel functional SNP regulating the expression of LBX1, which was involved in the etiology of AIS possibly via regulation of myogenesis in the paraspinal muscles.

A Decade in Review after Idiopathic Scoliosis Was First Called a Complex Trait-A Tribute to the Late Dr. Yves Cotrel for His Support in Studies of Etiology of Scoliosis

Adolescent Idiopathic Scoliosis (AIS) is a prevalent and important spine disorder in the pediatric age group. An increased family tendency was observed for a long time, but the underlying genetic mechanism was uncertain. In 1999, Dr. Yves Cotrel founded the Cotrel Foundation in the Institut de France, which supported collaboration of international researchers to work together to better understand the etiology of AIS. This new concept of AIS as a complex trait evolved in this setting among researchers who joined the annual Cotrel meetings. It is now over a decade since the first proposal of the complex trait genetic model for AIS. Here, we review in detail the vast information about the genetic and environmental factors in AIS pathogenesis gathered to date. More importantly, new insights into AIS etiology were brought to us through new research data under the perspective of a complex trait. Hopefully, future research directions may lead to better management of AIS, which has a tremendous impact on affected adolescents in terms of both physical growth and psychological development.

Altered Circulating Cell-free Mitochondrial DNA of Patients with Congenital Scoliosis

STUDY DESIGN

Case-control study.

OBJECTIVE

The aim of this study was to estimate the relationship between circulating cell-free DNA (ccf DNA) and clinical parameters of patients with congenital scoliosis (CS).

SUMMARY OF BACKGROUND DATA

CS is a complex spinal deformity characteristic of congenital vertebral malformations. Although numerous studies have centered on the etiology of CS, the cause of CS remains unclear. Previously, we reported that circulating cell-free DNA (ccf DNA) is altered in adolescent idiopathic scoliosis (AIS). However, the relationship between ccf DNA and the clinical parameters of patients with CS remains unclear.

METHODS

The plasma of peripheral blood from 35 patients with CS and 32 age-matched controls was collected for ccf DNA analysis. Quantitative PCR was used to detect ccf n-DNA and ccf mt-DNA levels, and correlation analyses between ccf n-DNA and ccf mt-DNA levels were conducted. Receiver-operating characteristic (ROC) curves were used to analyze the sensitivity and specificity of ccf n-DNA and ccf mt-DNA levels to different characteristics.

RESULTS

The plasma ccf mt-DNA levels of both ND1 and CYTC were significantly decreased in patients with CS compared with levels in controls both in total and by sex, whereas the plasma ccf n-DNA levels showed no significant difference. There is no difference in both ccf mt-DNA and ccf n-DNA between S-SDV and M-SDV according to The International Consortium for Vertebral Anomalies and Scoliosis (ICVAS) classification. The ROC curve analyses showed a reliable sensitivity and specificity of CS predicted by ccf mt-DNA levels in total but failed to distinguish different ICVAS types.

CONCLUSION

Significantly decreased plasma ccf mt-DNA levels were observed in patients with CS compared with those in controls. Although this finding has limited significance for clinical practice, it indicates that ccf mt-DNA may predict the onset or development of CS. Further studies should focus on the role of ccf mt-DNA in embryo development and whether ccf mt-DNAs could be considered as a marker for prenatal screening in development disorder like CS.Level of Evidence: 4.

Shear wave elastography of the lateral abdominal muscles in C-shaped idiopathic scoliosis: a case-control study

Considering that knowledge about lateral abdominal muscles (LAM) in idiopathic scoliosis (IS) is still very limited, the aims of this study were: (a) to compare LAM thickness and elasticity between C-shaped IS and non-scoliotic population; and (b) to compare LAM thickness and elasticity between C-shaped thoracic, thoracolumbar, and lumbar IS. A total of 259 adolescents were included in the final analysis; among these, 108 were IS and 151 were non-IS. LAM thickness and elasticity were measured at rest and during isometric contraction by an Aixplorer ultrasound scanner. Out of all LAM, only OE thickness was higher on the convex body side compared to the concave side in lumbar and thoracolumbar scoliosis. It may be related with muscle’s atrophy/hypertrophy or other tissues displacement rather than different force generated by the muscle on both body sides, because an asymmetry in the elasticity of the LAM between the convex and concave side was not presented. The only TrA was stiffer in lumbar scoliosis compared to thoracolumbar and thoracic scoliosis. LAM elasticity was similar in IS and non-IS adolescents.

Novel Mutations in UTS2R are Associated with Adolescent Idiopathic Scoliosis in the Chinese Population

STUDY DESIGN

A case-control study.

OBJECTIVES

To investigate the association of urotensin II (UTS2) signals with the susceptibility of adolescent idiopathic scoliosis (AIS) in the Chinese Han population.

SUMMARY OF BACKGROUND DATA

Dysregulated UTS2 signals induced by impaired cerebrospinal fluid flow have been implicated in the development of idiopathic scoliosis through studies on zebrafish. Furthermore, mutations in urotensin II receptor (UTS2R) were reported to cause severe scoliosis in zebrafish. In spite of the evidence presented in animal models, there is still a lack of knowledge concerning the role of UTS2 signaling related genes in AIS.

METHODS

In the discovery stage, exons of UTS2, UTS2R, and UTS2D were sequenced for 200 AIS patients and 200 healthy controls. Newly identified mutations were further genotyped in another independent cohort of 1000 AIS patients and 1000 controls by allelic-specific multiple ligase detection reactions. Gene expression analysis was performed in 36 AIS patients and 36 age-matched congenital scoliosis patients. The Chi-square test was used to compare the genotyping data between the groups. Gene expression analysis was compared with the Student t test.

RESULTS

Association between two novel mutations (rs11654140, c.51T > C; rs568196624, c.1146C > G) and the development of AIS was identified. Allele C of rs11654140 and allele G of rs568196624 were significantly associated with the risk of AIS (1.5% vs. 0.5%, odds ratio = 3.02, P = 0.01 for rs11654140; 1.41% vs. 0.58%, odds ratio = 2.29, P = 0.04 for rs568196624). The mRNA expression of UTS2R in the AIS group was significantly higher as compared with that in the control group (0.059 ± 0.015 vs. 0.035 ± 0.013, P < 0.01).

CONCLUSIONS

Rare mutations in UTS2R were significantly associated with AIS. Expression of UTS2R was significantly increased in AIS patients. The role of UTS2 signaling in the development of AIS is worthy of further investigation.Level of Evidence: N/A.

The Susceptibility and Potential Functions of the LBX1 Gene in Adolescent Idiopathic Scoliosis

Genome-wide association studies have identified many susceptibility genes for adolescent idiopathic scoliosis (AIS). However, most of the results are hard to be replicated in multi-ethnic populations. LBX1 is the most promising candidate gene in the etiology of AIS. We aimed to appraise the literature for the association of LBX1 gene polymorphisms with susceptibility and curve progression in AIS. We also reviewed the function of the LBX1 gene in muscle progenitor cell migration and neuronal determination processes. Three susceptibility loci (rs11190870, rs625039, and rs11598564) near the LBX1 gene, as well as another susceptibility locus (rs678741), related to LBX1 regulation, have been successfully verified to have robust associations with AIS in multi-ethnic populations. The LBX1 gene plays an essential role in regulating the migration and proliferation of muscle precursor cells, and it is known to play a role in neuronal determination processes, especially for the fate of somatosensory relay neurons. The LBX1 gene is the most promising candidate gene in AIS susceptibility due to its position and possible functions in muscle progenitor cell migration and neuronal determination processes. The causality between susceptibility loci related to the LBX1 gene and the pathogenesis of AIS deserves to be explored with further integrated genome-wide and epigenome-wide association studies.

Genetic Variant of TBX1 Gene Is Functionally Associated With Adolescent Idiopathic Scoliosis in the Chinese Population

STUDY DESIGN

A genetic association study.

OBJECTIVE

The aim of this study was to investigate whether rs1978060 of TBX1 gene was a susceptible locus of adolescent idiopathic scoliosis (AIS) in the Chinese Han population and to better define the functional role of TBX1 in the development and progression of AIS.

SUMMARY OF BACKGROUND DATA

A recent genome-wide association study reported a novel susceptible locus in TBX1 gene, which was associated with the development of AIS in the Japanese population. However, there is a paucity of knowledge concerning the functional role of TBX1 in the Chinese AIS population.

METHODS

The SNP rs1978060 was genotyped in 1725 female AIS patients and 2600 healthy controls. Paraspinal muscle samples were collected from 30 AIS patients and 26 age-matched congenital scoliosis (CS) patients for the analysis of tissue expression. The differences of genotype and allele distributions between the patients and the controls were calculated using the χ test. The Pearson correlation analysis was carried out to investigate the relation between the expression of the PAX1 gene and the curve severity.

RESULTS

SNP rs1978060 was significantly associated with the susceptibility of AIS. Allele G of rs1978060 could significantly add to the risk of AIS with an odds ratio of 1.12. The tissue expression of TBX1 was obviously decreased in AIS patients. There was a remarkable correlation between the curve magnitude and the TBX1 expression (r = -0.519, P = 0.003).

CONCLUSION

The association between TBX1 and the susceptibility of AIS was successfully replicated in the Chinese population. Moreover, rs1978060 may be a functional variant regulating the expression of TBX1. More studies were warranted to explore the functional role of TBX1 in the onset and progression of AIS.

LEVEL OF EVIDENCE

3.

Coding Variants Coupled With Rapid Modeling in Zebrafish Implicate Dynein Genes, dnaaf1 and zmynd10, as Adolescent Idiopathic Scoliosis Candidate Genes

Adolescent idiopathic scoliosis (AIS) is the most common pediatric spine disorder affecting ∼3% of children worldwide. Human genetic studies suggest a complex polygenic disease model for AIS with large genetic and phenotypic heterogeneity. However, the overall genetic etiology of AIS remains poorly understood. To identify additional AIS susceptibility loci, we performed whole-exome sequencing (WES) on a cohort of 195 Southern Chinese AIS patients. Bioinformatics analysis identified 237 novel rare variants associated with AIS, located in 232 new susceptibility loci. Enrichment analysis of these variants revealed 10 gene families associated with our AIS cohort. We screened these gene families by comparing our candidate gene list with IS candidate genes in the Human Phenotype Ontology (HPO) database and previous reported studies. Two candidate gene families, axonemal dynein and axonemal dynein assembly factors, were retained for their associations with ciliary architecture and function. The damaging effects of candidate variants in dynein genes dnali1, dnah1, dnaaf, and zmynd10, as well as in one fibrillin-related gene tns1, were functionally analyzed in zebrafish using targeted CRISPR/Cas9 screening. Knockout of two candidate genes, dnaaf1 or zmynd10, recapitulated scoliosis in viable adult zebrafish. Altogether, our results suggest that the disruption of one or more dynein-associated factors may correlate with AIS susceptibility in the Southern Chinese population.

From genetics to epigenetics to unravel the etiology of adolescent idiopathic scoliosis

Scoliosis is defined as the three-dimensional (3D) structural deformity of the spine with a radiological lateral Cobb angle (a measure of spinal curvature) of ≥10° that can be caused by congenital, developmental or degenerative problems. However, those cases whose etiology is still unknown, and affect healthy children and adolescents during growth, are the commonest form of spinal deformity, known as adolescent idiopathic scoliosis (AIS). In AIS management, early diagnosis and the accurate prediction of curve progression are most important because they can decrease negative long-term effects of AIS treatment, such as unnecessary bracing, frequent exposure to radiation, as well as saving the high costs of AIS treatment. Despite efforts made to identify a method or technique capable of predicting AIS progression, this challenge still remains unresolved. Genetics and epigenetics, and the application of machine learning and artificial intelligence technologies, open up new avenues to not only clarify AIS etiology, but to also identify potential biomarkers that can substantially improve the clinical management of these patients. This review presents the most relevant biomarkers to help explain the etiopathogenesis of AIS and provide new potential biomarkers to be validated in large clinical trials so they can be finally implemented into clinical settings.

IS (Idiopathic Scoliosis) etiology: Multifactorial genetic research continues. A systematic review 1950 to 2017

Objective

IS (idiopathic scoliosis) is a common spinal condition occurring in otherwise completely healthy adolescents. The root cause of IS remains unclear. This systematic review will focus on an update of genetic factors and IS etiology. Though it is generally accepted that the condition is not due to a single gene effect, etiology studies continue looking for a root cause including genetic variants. Though susceptibility from multiple genetic components is plausible based on known family history data, the literature remains unclear regarding multifactorial genetic influences. The objective of this study was to critically evaluate the evidence behind genetic causes (not single gene) of IS through a systematic review and strength-of-study analysis of existing genetic and genome-wide association studies (GWAS). We used the protocol of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Methods

PubMed was searched for the terms IS, scoliotic, spinal curve, genetic, gene, etiology, polymorphisms. Articles were assessed for risk-of-bias. Level-of-evidence grading was completed via Oxford Centre for Evidence-Based Medicine criteria. The assessment scores factor strength of a study in determining a positive or negative association to a gene etiology.

Results

After screening of 36 eligible papers, 8 relevant studies met inclusion criteria at this time, 3 were in favor of a genetic factor for IS, whereas 5 studies were against it.

Conclusion

Based on the literature analyzed, there is moderate evidence with a low risk-of-bias that does not clarify a genetic cause of IS. The 2 studies in favor of a genetic etiology were completed in homogeneous populations, limiting their generalizability. Relying on a genetic etiology alone for IS may over simplify its multifactorial nature and limit appreciation of other influences.

Autophagy in kidney homeostasis and disease

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic components. Basal autophagy in kidney cells is essential for the maintenance of kidney homeostasis, structure and function. Under stress conditions, autophagy is altered as part of the adaptive response of kidney cells, in a process that is tightly regulated by signalling pathways that can modulate the cellular autophagic flux - mammalian target of rapamycin, AMP-activated protein kinase and sirtuins are key regulators of autophagy. Dysregulated autophagy contributes to the pathogenesis of acute kidney injury, to incomplete kidney repair after acute kidney injury and to chronic kidney disease of varied aetiologies, including diabetic kidney disease, focal segmental glomerulosclerosis and polycystic kidney disease. Autophagy also has a role in kidney ageing. However, questions remain about whether autophagy has a protective or a pathological role in kidney fibrosis, and about the precise mechanisms and signalling pathways underlying the autophagy response in different types of kidney cells and across the spectrum of kidney diseases. Further research is needed to gain insights into the regulation of autophagy in the kidneys and to enable the discovery of pathway-specific and kidney-selective therapies for kidney diseases and anti-ageing strategies.

Muscular Contribution to Adolescent Idiopathic Scoliosis from the Perspective of Stem Cell-Based Regenerative Medicine

Adolescent idiopathic scoliosis (AIS) is a relatively frequent disease within a range 0.5%-5.0% of population, with higher frequency in females. While a resultant spinal deformity is usually medically benign condition, it produces far going psychosocial consequences, which warrant attention. The etiology of AIS is unknown and current therapeutic approaches are symptomatic only, and frequently inconvenient or invasive. Muscular contribution to AIS is widely recognized, although it did not translate to clinical routine as yet. Muscle asymmetry has been documented by pathological examinations as well as systemic muscle disorders frequently leading to scoliosis. It has been also reported numerous genetic, metabolic and radiological alterations in patients with AIS, which are linked to muscular and neuromuscular aspects. Therefore, muscles might be considered an attractive and still insufficiently exploited therapeutic target for AIS. Stem cell-based regenerative medicine is rapidly gaining momentum based on the tremendous progress in understanding of developmental biology. It comes also with a toolbox of various stem cells such as satellite cells or mesenchymal stem cells, which could be transplanted; also, the knowledge acquired in research on regenerative medicine can be applied to manipulation of endogenous stem cells to obtain desired therapeutic goals. Importantly, paravertebral muscles are located relatively superficially; therefore, they can be an easy target for minimally invasive approaches to treatment of AIS. It comes in pair with a fast progress in image guidance, which allows for precise delivery of therapeutic agents, including stem cells to various organs such as brain, muscles, and others. Summing up, it seems that there is a link between AIS, muscles, and stem cells, which might be worth of further investigations with a long-term goal of setting foundations for eventual bench-to-bedside translation.

Asymmetric Expression of Wnt/B-catenin Pathway in AIS: Primary or Secondary to the Curve?

STUDY DESIGN

A prospective case-control study.

OBJECTIVES

To investigate whether the asymmetric changes are primary or secondary to spinal deformity.

SUMMARY OF BACKGROUND DATA

Previous study reported significantly decreased expression of Wnt/B-catenin pathway in adolescent idiopathic scoliosis (AIS) patients. To date, there is a lack of study investigating the relationship between differentially expressed Wnt/B-catenin pathway and the onset of the curve.

METHODS

Paraspinal muscles were collected from 40 female AIS patients and 20 age-matched congenital scoliosis (CS) patients. For CS patients, the samples were collected from the concave side and the convex side at the apical region. For AIS patients, the samples were collected from the proximal bilateral sides of the spine in addition to the apical region. qPCR and western blot were used to determine the expression of LBX1, B-catenin, and PAX3, all of which are regulated by the Wnt/B-catenin pathway. The relative mRNA expression level between the concave and the convex side was performed with the Student t test. Pearson correlation analysis was used to determine the relationship between gene expression and the curve magnitude.

RESULTS

AIS patients were found to have remarkably lower mRNA and protein expression of B-catenin, LBX1, and PAX3 in the concave side than in the convex side at the apical region. By contrast, at the proximal region, the mRNA expression of these three genes was comparable. Moreover, no significant difference regarding mRNA expression was found between the concave side and the convex side of CS patients. There was no remarkable correlation between the mRNA expression of the three genes and Cobb angle.

CONCLUSION

There exists remar kably asymmetric expression of Wnt/B-catenin pathway at the apical region of AIS, which however was comparable at the apical region of CS patients. Further investigation of Wnt/B-catenin signaling pathway may help reveal the etiology of AIS in future study.

LEVEL OF EVIDENCE

4.

Inhibition of soluble epoxide hydrolase attenuates renal tubular mitochondrial dysfunction and ER stress by restoring autophagic flux in diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD), and renal tubular cell dysfunction contributes to the pathogenesis of DN. Soluble epoxide hydrolase (sEH) is an enzyme that can hydrolyze epoxyeicosatrienoic acids (EETs) and other epoxy fatty acids (EpFAs) into the less biologically active metabolites. Inhibition of sEH has multiple beneficial effects on renal function, however, the exact role of sEH in hyperglycemia-induced dysfunction of tubular cells is still not fully elucidated. In the present study, we showed that human proximal tubular epithelial (HK-2) cells revealed an upregulation of sEH expression accompanied by the impairment of autophagic flux, mitochondrial dysfunction, ubiquitinated protein accumulation and enhanced endoplasmic reticulum (ER) stress after high glucose (HG) treatment. Furthermore, dysfunctional mitochondria accumulated in the cytoplasm, which resulted in excessive reactive oxygen species (ROS) generation, Bax translocation, cytochrome c release, and apoptosis. However, t-AUCB, an inhibitor of sEH, partially reversed these negative outcomes. Moreover, we also observed increased sEH expression, impaired autophagy flux, mitochondrial dysfunction and enhanced ER stress in the renal proximal tubular cells of db/db diabetic mice. Notably, inhibition of sEH by treatment with t-AUCB attenuated renal injury and partially restored autophagic flux, improved mitochondrial function, and reduced ROS generation and ER stress in the kidneys of db/db mice. Taken together, these results suggest that inhibition of sEH by t-AUCB plays a protective role in hyperglycemia-induced proximal tubular injury and that the potential mechanism of t-AUCB-mediated protective autophagy is involved in modulating mitochondrial function and ER stress. Thus, we provide new evidence linking sEH to the autophagic response during proximal tubular injury in the pathogenesis of DN and suggest that inhibition of sEH can be considered a potential therapeutic strategy for the amelioration of DN.

A Novel Coding Variant in SLC39A8 Is Associated With Adolescent Idiopathic Scoliosis in Chinese Han Population

STUDY DESIGN

A genetic case-control association study.

OBJECTIVE

The aim of this study was to investigate the association of SLC39A8 with the susceptibility of adolescent idiopathic scoliosis (AIS) in Chinese Han population.

SUMMARY OF BACKGROUND DATA

A recent exome-wide association study identified a missense variant rs13107325 in SLC39A8 that was associated with AIS. However, there was a lack of study validating the association of this novel mutation with AIS in other populations.

METHODS

The variant rs13107325 was genotyped in 965 AIS patients and 976 healthy controls by allelic specific multiple ligase detection reactions. Variants located in the coding region of SLC39A8 were identified by exon sequencing for 192 AIS patients and 192 controls. Paraspinal muscles from 36 AIS patients and 36 age-matched congenital scoliosis patients were collected for the gene expression analysis. Comparison between the cases and controls was performed with the χ test for genotyping data or with Student t test for gene expression analysis.

RESULTS

For the missense variant rs13107325, there was no case of mutation detected in the patients or the controls. All the subjects had homozygous genotype CC. Exon sequencing revealed that a coding variant rs11097773 of SLC39A8 had a significantly different distribution of minor allele frequency between patients and controls (7.81% vs. 14.8%, P = 0.002). The mRNA expression of SLC39A8 in the patients was remarkably lower than that in the controls (0.0015 ± 0.00026 vs. 0.0021 ± 0.00033, P < 0.001).

CONCLUSION

The association of previously reported novel mutation (rs13107325 in SLC39A8) with AIS was not replicated in the Chinese population. Interestingly, a novel coding variant rs11097773 of SLC39A8 is found significantly associated with AIS. Moreover, the expression of SLC39A8 was obviously decreased in AIS patients. Further study is warranted to clarify the functional role of rs11097773 in the development of AIS.

LEVEL OF EVIDENCE

3.

A Genetic Predictive Model Estimating the Risk of Developing Adolescent Idiopathic Scoliosis

Background:

Previous GWASs have revealed several susceptible variants associated with adolescent idiopathic scoliosis (AIS). Risk prediction based on these variants can potentially improve disease prognosis. We aimed to evaluate the combined effects of genetic factors on the development of AIS and to further develop a genetic predictive model.

Methods:

A total of 914 AIS patients and 1441 normal controls were included in the discovery stage, which was followed by the replication stage composed of 871 patients and 1239 controls. Genotyping assay was performed to analyze 10 previously reported susceptible variants, including rs678741 of LBX1, rs241215 of AJAP1, rs13398147 of PAX3, rs16934784 of BNC2, rs2050157 of GPR126, rs2180439 of PAX1, rs4940576 of BCL2, rs7593846 of MEIS1, rs7633294 of MAGI1 and rs9810566 of TNIK. Logistic regression analysis was performed to generate a risk predictive model. The predicted risk score was calculated for each participant in the replication stage.

Results:

The association of the 10 variants with AIS was successfully validated. The established model could explain approximately 7.9% of the overall variance. In the replication stage, patients were found to have a remarkably higher risk score as compared to the controls (44.2 ± 14.4 vs. 33.9 ± 12.5, p <0.001). There was a remarkably higher proportion of the risk score i.e. >40 in the patients than in the controls (59% vs. 28.9%, p <0.001).

Conclusion:

Risk predictive model based on the previously reported genetic variants has a remarkable discriminative power. More clinical and genetic factors need to be studied, to further improve the proba-bility to predict the onset of AIS.

Genetic Variants of ABO and SOX6 are Associated With Adolescent Idiopathic Scoliosis in Chinese Han Population

STUDY DESIGN

A genetic association study.

OBJECTIVE

The aim of this study was to determine whether variants of ABO, SOX6, and CDH13 are associated with the susceptibility of AIS in Chinese Han population.

SUMMARY OF BACKGROUND DATA

A recent large-scale genome-wide association study reported three novel loci in CDH13, ABO, and SOX6 genes associated with adolescent idiopathic scoliosis (AIS) in Japanese population. However, the association of these three genes with AIS in other populations remains obscure.

METHODS

The SNPs rs4513093, rs687621, and rs1455114 were genotyped in 1208 female patients and 2498 healthy controls. Samples for the expression analysis in paraspinal muscles were collected from 49 AIS and 33 congenital scoliosis (CS) patients during surgical interventions. Chi-square analysis was used to assess the difference regarding genotype and allele frequency between cases and controls. Tissue expressions of ABO, CDH13, and SOX6 were compared between AIS and CS patients by the Student t test.

RESULTS

SNPs rs4513093 of CDH13 and rs687621 of ABO were found to be significantly associated with AIS with an odds ratio of 0.8691 and 1.203, respectively. There was no significant association of rs1455114 with AIS. Moreover, AIS patients were found to have significantly increased expression of ABO. As for expression of CDH13 and SOX6, no remarkable difference was found between the two groups.

CONCLUSION

The association of CDH13 and ABO variants with AIS was successfully replicated in the Chinese Han population. More studies are warranted to explore the functional role of ABO in the development of AIS.

LEVEL OF EVIDENCE

N/A.

Genome-wide association study identifies 14 previously unreported susceptibility loci for adolescent idiopathic scoliosis in Japanese

Adolescent idiopathic scoliosis (AIS) is the most common pediatric spinal deformity. Several AIS susceptibility loci have been identified; however, they could explain only a small proportion of AIS heritability. To identify additional AIS susceptibility loci, we conduct a meta-analysis of the three genome-wide association studies consisting of 79,211 Japanese individuals. We identify 20 loci significantly associated with AIS, including 14 previously not reported loci. These loci explain 4.6% of the phenotypic variance of AIS. We find 21 cis-expression quantitative trait loci-associated genes in seven of the fourteen loci. By a female meta-analysis, we identify additional three significant loci. We also find significant genetic correlations of AIS with body mass index and uric acid. The cell-type specificity analyses show the significant heritability enrichment for AIS in multiple cell-type groups, suggesting the heterogeneity of etiology and pathogenesis of AIS. Our findings provide insights into etiology and pathogenesis of AIS.

Adolescent idiopathic scoliosis (AIS) is a common pediatric disease leading to spinal deformities. Here, the authors report GWAS followed by genome-wide meta-analysis in up to 79,211 Japanese individuals, identifying 20 genetic loci for AIS, 14 of which were previously unreported, and perform in vitro validation for rs1978060.

Functional variants of hepatocyte growth factor identified in patients with adolescent idiopathic scoliosis

The genetic etiology of adolescent idiopathic scoliosis (AIS) remains obscure. Whole-genome sequencing was performed in four members of one family. Then, we performed a rigorous computational analysis to determine the deleterious effects of the identified variants. Furthermore, the structural differences between the native hepatocyte growth factor (HGF) protein and a protein encoded by an HGF variant containing one mutation (p.T596M) were analyzed using molecular dynamic stimulation. A novel heterozygous mutation (p.T596M) within the HGF gene was identified and found to cosegregate with scoliosis phenotypes in three affected family members. Subsequent modeling and structure-based analyses supported the theory that this mutation is functionally deleterious. Functional analyses demonstrated that the HGF p.T596 M mutation changed the ability of the HGF protein to be secreted and impaired migration and invasion in HEK293T cells. Furthermore, an HGF knockdown zebrafish model exhibited a curly tailed phenotype. Mutation in HGF is associated with an autosomal dominant pattern of inheritance of AIS. This finding increases our understanding of the genetic heterogeneity of AIS.

New Evidence Supporting the Role of FBN1 in the Development of Adolescent Idiopathic Scoliosis

STUDY DESIGN

A genetic association study.

OBJECTIVE

To determine whether common variants of fibrillin-1 (FBN1) and fibrillin-2 (FBN2) are associated with adolescent idiopathic scoliosis (AIS), and to further investigate to further investigate the functional role of FBN1 in the onset and progression of AIS.

SUMMARY OF BACKGROUND DATA

Previous studies have identified several rare variants in FBN1 and FBN2 that were associated with AIS. There is, however, a lack of knowledge concerning the association between common variants of FBN1 and FBN2 and AIS.

METHODS

Common variants covering FBN1 and FBN2 were genotyped in 952 patients with AIS and 1499 controls. Paraspinal muscles were collected from 66 patients with AIS and 18 patients with lumbar disc herniation (LDH) during surgical interventions. The differences of genotype and allele distributions between patients and controls were calculated using Chi-square test. The Student t test was used to compare the expression of FBN1 and FBN2 between patients with AIS and LDH. One-way analysis of variance test was used to compare the gene expression among different genotypes of the significantly associated variant. The Pearson correlation analysis was used to determine the relationship between FBN1 expression and the curve severity.

RESULTS

The common variant rs12916536 of FBN1 was significantly associated with AIS. Patients were found to have significantly lower frequency of allele A than the controls (0.397 vs. 0.450, P = 1.10 × 10) with an odds ratio of 0.81. Moreover, patients with AIS were found to have significantly lower FBN1 expression than patients with LDH (0.00033 ± 0.00015 vs. 0.00054 ± 0.00031, P = 1.70 × 10). The expression level of FBN1 was remarkably correlated with the curve severity (r = -0.352, P = 0.02). There was no significant difference of FBN1 expression among different genotypes of rs12916536.

CONCLUSION

Common variant of FBN1 is significantly associated with the susceptibility of AIS. Moreover, the decreased expression of FBN1 is significantly correlated with the curve severity of AIS. The functional role of FBN in AIS is worthy of further investigation.

LEVEL OF EVIDENCE

3.

Anti-microRNA screen uncovers miR-17 family within miR-17~92 cluster as the primary driver of kidney cyst growth

Autosomal dominant polycystic kidney disease (ADPKD) is the leading genetic cause of renal failure. We have recently shown that inhibiting miR-17~92 is a potential novel therapeutic approach for ADPKD. However, miR-17~92 is a polycistronic cluster that encodes microRNAs (miRNAs) belonging to the miR-17, miR-18, miR-19 and miR-25 families, and the relative pathogenic contribution of these miRNA families to ADPKD progression is unknown. Here we performed an in vivo anti-miR screen to identify the miRNA drug targets within the miR-17~92 miRNA cluster. We designed anti-miRs to individually inhibit miR-17, miR-18, miR-19 or miR-25 families in an orthologous ADPKD model. Treatment with anti-miRs against the miR-17 family reduced cyst proliferation, kidney-weight-to-body-weight ratio and cyst index. In contrast, treatment with anti-miRs against the miR-18, 19, or 25 families did not affect cyst growth. Anti-miR-17 treatment recapitulated the gene expression pattern observed after miR-17~92 genetic deletion and was associated with upregulation of mitochondrial metabolism, suppression of the mTOR pathway, and inhibition of cyst-associated inflammation. Our results argue against functional cooperation between the various miR-17~92 cluster families in promoting cyst growth, and instead point to miR-17 family as the primary therapeutic target for ADPKD.

Etiology of Adolescent Idiopathic Scoliosis: A Literature Review

Adolescent idiopathic scoliosis (AIS) is the peripubertal development of spinal curvature of a minimum of 10°. AIS is thought to be attributable to genetic factors, nutrition, early exposure to toxins, and hormonal dysregulation. Recent literature suggests these factors may compound to determine both disease onset and severity. Currently, treatment is limited to observation, bracing, and surgical intervention. Intervention is presently determined by severity and risk of curve progression. As they emerge, new therapies may target specific etiologies of AIS.

Rare variant of HSPG2 is not involved in the development of adolescent idiopathic scoliosis: evidence from a large-scale replication study

BACKGROUND

Rare variants of HSPG2 have recently been reported to function as a potential contributor to the susceptibility of adolescent idiopathic scoliosis (AIS) in the Caucasians. A replication study in the different population is warranted to validate the role of HSPG2 in AIS. The aim of this study was to determine the association between HSPG2 and AIS in the Chinese patients and to further investigate its influence on the phenotype of the patients.

METHODS

SNVs p.Asn786Ser of HSPG2 was genotyped in 1752 patients and 1584 normal controls using multiple ligase detection reactions. The mRNA expression of HSPG2 in the paraspinal muscles was quantified for 90 patients and 26 controls. The The Student's t test was used to analyze the inter-group comparison of the HSPG2 expression. The relationship between the HSPG2 expression and the curve magnitude of the patients was analyzed by the Pearson correlation analysis.

RESULTS

No case of mutation in the reported SNV p.Asn786Ser of HSPG2 was found in our cohort. The mRNA expression of HSPG2 in patients was comparable with that in the controls (0.0016 ± 0.0013 vs. 0.0019 ± 0.0012, p = 0.29). 42 patients with curve magnitude > 60 degrees were assigned to the severe curve group. The other 58 patients were assigned to the moderate curve group. These two groups were found to have comparable HSPG2 expression (0.0015 ± 0.0011 vs. 0.0017 ± 0.0014, p = 0.57). And there was no remarkable correlation between the expression level of HSPG2 and the curve severity (r = 0.131, p = 0.71).

CONCLUSIONS

HSPG2 gene was not associated with the susceptibility or the phenotypes of AIS in the Chinese population. The whole HSPG2 gene can be sequenced in more AIS patients to identify potentially causative mutations.

Idiopathic Scoliosis Families Highlight Actin-Based and Microtubule-Based Cellular Projections and Extracellular Matrix in Disease Etiology

Idiopathic scoliosis (IS) is a structural lateral spinal curvature of ≥10° that affects up to 3% of otherwise healthy children and can lead to life-long problems in severe cases. It is well-established that IS is a genetic disorder. Previous studies have identified genes that may contribute to the IS phenotype, but the overall genetic etiology of IS is not well understood. We used exome sequencing to study five multigenerational families with IS. Bioinformatic analyses identified unique and low frequency variants (minor allele frequency ≤5%) that were present in all sequenced members of the family. Across the five families, we identified a total of 270 variants with predicted functional consequences in 246 genes, and found that eight genes were shared by two families. We performed GO term enrichment analyses, with the hypothesis that certain functional annotations or pathways would be enriched in the 246 genes identified in our IS families. Using three complementary programs to complete these analyses, we identified enriched categories that include stereocilia and other actin-based cellular projections, cilia and other microtubule-based cellular projections, and the extracellular matrix (ECM). Our results suggest that there are multiple paths to IS and provide a foundation for future studies of IS pathogenesis.

Common Variant of POC5 Is Associated With the Susceptibility of Adolescent Idiopathic Scoliosis

STUDY DESIGN

A case-control study.

OBJECTIVE

To validate the relationship between POC5 and adolescent idiopathic scoliosis (AIS) in the Chinese patients and to further investigate the functional role of POC5.

SUMMARY OF BACKGROUND DATA

Three rare functional variants in the POC5 were recently reported to be strongly associated with the disease in a large family with multiple members affected with idiopathic scoliosis. To our knowledge, the association between the mutations of POC5 and AIS remains undetermined in the Chinese population.

METHODS

Single nucleotide variants c.1336G>A, c.1286C>T, and c.1363G>C of POC5 were genotyped in 2432 patients with AIS and 2292 healthy controls using multiple ligase detection reactions. Common variants covering POC5 gene were genotyped in 1446 patients and 2080 controls. The mRNA expression of POC5 was determined in the paraspinal muscles collected from 98 patients and 28 controls. The Student t test was used to compare mRNA expression level between the patients and the controls. In addition, the POC5 expression was compared among different genotypes of the remarkably associated single nucleotide polymorphism (SNP) with analysis of variance test.

RESULTS

There was no case of mutation for the three reported variants of POC5. SNP rs6892146 was observed to have significantly different distribution of minor allele frequency in the two group (0.485 vs. 0.446, P = 0.004). The mRNA expression of POC5 was 1.5-fold higher in patients than in the controls (0.00012 ± 0.00009 vs. 0.00008 ± 0.00006, P = 0.02). Patients with genotype GG have a significantly increased expression of POC5 than those with CC (0.00014 ± 0.00007 vs. 0.00009 ± 0.00007, P = 0.03).

CONCLUSION

Common variant rs6892146 of POC5 is associated with the development of AIS in the Chinese population. Targeted regional sequencing of POC5 may help identify novel mutations associated with AIS.

LEVEL OF EVIDENCE

4.

Aberrant miR-145-5p/β-catenin signal impairs osteocyte function in adolescent idiopathic scoliosis

Recently, noncoding RNAs have been thought to play important roles in the sporadic occurrence of spinal deformity of adolescent idiopathic scoliosis (AIS). As a prognostic factor for curve progression, low bone mass has been hypothesized to crosstalk with AIS pathogenesis. Abnormal osteoblasts activities are reported in AIS without a clear mechanism. In this study, bone biopsies from patients with AIS and control subjects and the primary osteoblasts derived from those samples were used to identify the potential microRNA (miRNA) candidates that interfere with osteoblasts and osteocytes function. Microarray analysis identified miRNA-145-5p (miR-145) as a potential upstream regulator. miR-145 and β-catenin mRNA ( CTNNB1) were overexpressed in AIS bone tissues and primary osteoblasts, and their expression correlated positively in AIS. Knockdown of miR-145 restored impaired osteocyte activity through the down-regulation of active β-catenin expression and its transcriptional activity. Significant negative correlations between circulating miR-145 and serum sclerostin, osteopontin, and osteoprotegerin were noted in patients with AIS, which was in line with our cellular findings. This is the first study to demonstrate the effect of aberrant miRNA expression and its effect on osteocyte function in AIS, which may contribute to the low bone mass. Our findings also provide insight into the development of circulating microRNAs as a bone quality biomarker or even a prognostic biomarker for AIS.-Zhang, J., Chen, H., Leung, R. K. K., Choy, K. W., Lam, T. P., Ng, B. K. W., Qiu,Y., Feng, J. Q., Cheng, J. C. Y., Lee, W. Y. W. Aberrant miR-145-5p/β-catenin signal impairs osteocyte function in adolescent idiopathic scoliosis.

Genetic Variant of SOCS3 Gene is Functionally Associated With Lumbar Adolescent Idiopathic Scoliosis

STUDY DESIGN

This is a genetic association study.

OBJECTIVE

To investigate association between suppressor of cytokine signaling-3 (SOCS3) gene polymorphisms and the onset and progression of lumbar adolescent idiopathic scoliosis (AIS) and to further clarify its role in the regulation of SOCS3 expression in AIS patients.

SUMMARY OF BACKGROUND DATA

Some studies showed that muscle development imbalance may be responsible for onset and progression of lumbar AIS. SOCS3 is one of the significant regulators of skeletal muscle development, and in vitro study showed that SOCS3 influences myoblast differentiation.

MATERIALS AND METHODS

Rs4969198 was genotyped in 476 lumbar AIS patients and 672 controls. The differences of genotype and allele distributions between patients and controls were calculated using the χ test. Paravertebral muscles were collected from 53 AIS, 23 congenital scoliosis, and 18 lumbar disk herniation patients. AIS patients were classified into 3 groups according to the genotypes of each single nucleotide polymorphisms, and 1-way analysis of variance test was used to compare SOCS3 expression among different groups and genotypes.

RESULTS

Patients were found to have a significantly higher frequency of GG than the controls (40.8% vs. 29.9%, odds ratio=1.36; P=0.000), and the frequency of allele G was found to be remarkably higher in the patients than the controls (65.3% vs. 56.7%, odds ratio=1.15; P=0.000). AIS patients had significantly less muscle expression of the SOCS3 than the congenital scoliosis patients (2.73±2.17 vs. 4.62±2.41; P=0.006) and the lumbar disk herniation patients (2.73±2.17 vs. 4.12±2.93; P=0.009). The SOCS3 expression was significantly correlated with the curve severity (r=0.472; P=0.014).

CONCLUSIONS

The SOCS3 gene is significantly associated with the development of lumbar AIS in Chinese population. Decreased expression of SOCS3 is associated with larger severity of lumbar AIS.

LEVEL OF EVIDENCE

Level III.

Circulating miRNAs as diagnostic biomarkers for adolescent idiopathic scoliosis

The aetiology of adolescent idiopathic scoliosis (AIS) has been linked to many factors, such as asymmetric growth, neuromuscular condition, bone strength and genetic background. Recently, epigenetic factors have been proposed as contributors of AIS physiopathology, but information about the molecular mechanisms and pathways involved is scarce. Regarding epigenetic factors, microRNAs (miRNAs) are molecules that contribute to gene expression modulation by regulating important cellular pathways. We herein used Next-Generation Sequencing to discover a series of circulating miRNAs detected in the blood samples of AIS patients, which yielded a unique miRNA biomarker signature that diagnoses AIS with high sensitivity and specificity. We propose that these miRNAs participate in the epigenetic control of signalling pathways by regulating osteoblast and osteoclast differentiation, thus modulating the genetic background of AIS patients. Our study yielded two relevant results: 1) evidence for the deregulated miRNAs that participate in osteoblast/osteoclast differentiation mechanisms in AIS; 2) this miRNA-signature can be potentially used as a clinical tool for molecular AIS diagnosis. Using miRNAs as biomarkers for AIS diagnostics is especially relevant since miRNAs can serve for early diagnoses and for evaluating the positive effects of applied therapies to therefore reduce the need of high-risk surgical interventions.

A Replication Study for Association of LBX1 Locus With Adolescent Idiopathic Scoliosis in French-Canadian Population

STUDY DESIGN

A case-control association study.

OBJECTIVES

To investigate the relationship between LBX1 (lady bird homeobox1) polymorphisms and adolescent idiopathic scoliosis (AIS) in French-Canadian population.

SUMMARY OF BACKGROUND DATA

It is widely accepted that genetic factors contribute to AIS. Although the LBX1 locus is so far the most successfully replicated locus in different AIS cohorts, these associations were replicated mainly in Asian populations, with few studies in Caucasian populations of European descent.

METHODS

We recruited 1568 participants (667 AIS patients and 901 healthy controls) in the French-Canadian population. Genomic data were generated using the Illumina Human Omni 2.5M BeadChip. An additional 121 AIS cases and 51 controls were genotyped for specific single-nucleotide polymorphisms (SNPs) by multiplex polymerase chain reaction using standard procedures. BEAGLE 3 was used to impute the following markers: rs7893223, rs11190878, and rs678741 against the 1000-genomes European cohort phased genotypes given that they were absent in our genome wide association studies (GWAS) panel. Resulting genotypes were combined then used for single marker and haplotyped-based association.

RESULTS

Four markers showed association with AIS in our cohort at this locus; rs11190870 the most studied marker, rs7893223, rs594791, and rs11190878. When we restricted the analysis to severe cases only, four additional SNPs showed associations: rs11598177, rs1322331, rs670206, and rs678741. In addition, we analyzed the associations of the observed haplotypes and dihaplotypes formed by these SNPs. The haplotype TTAAGAAA and its homozygous dihaplotype showed the highest association with our severe group and was the highest risk haplotype. The haplotype CCGCAGGG was significantly more associated with the control group, and its homozygous or heterozygous dihaplotype was less frequent in the severe group compared with the control group, suggesting that CCGCAGGG may represent a protective haplotype.

CONCLUSION

We have replicated the association of the LBX1 locus with AIS in French-Canadian population, a novel European descent cohort, which is known for its unique genetic architecture.

LEVEL OF EVIDENCE

3.

Differences in vertebral morphology around the apical vertebrae between neuromuscular scoliosis and idiopathic scoliosis in skeletally immature patients: a three-dimensional morphometric analysis

Background

Recent morphological analyses of vertebrae in patients with scoliosis have revealed three-dimensional (3D) deformities in the vertebral bodies. However, it remains controversial whether these deformities are secondary changes caused by asymmetrical vertebral loading or primary changes caused by aberrant asymmetrical vertebral growth. Furthermore, the difference in vertebral morphology between scoliosis with different pathogeneses remains unclear. This study was aimed to investigate the difference in the coronal asymmetry of vertebral bodies between neuromuscular scoliosis (NS) in Duchenne muscular dystrophy (DMD) and idiopathic scoliosis (IS) using in vivo 3D analysis.

Methods

Twelve male skeletally immature patients with NS in DMD and 13 female skeletally immature patients with IS who underwent corrective fusion at our institution were included retrospectively. 3D bone models of the apical and adjacent upper and lower vertebrae in the major curve in the NS patients and in the main and compensatory curves in the IS patients were constructed using an image processing workstation. The heights of the concave and convex sides of the vertebral bodies were measured at the anterior, middle, and posterior and the concave-to-convex vertebral height ratios (VHR) were calculated.

Results

The mean VHRs (anterior/middle/posterior) for the main curve for IS (0.897 ± 0.072/0.832 ± 0.086/0.883 ± 0.059) were significantly smaller than those for NS (0.970 ± 0.048/0.934 ± 0.081/0.958 ± 0.043) in all three parts (p < 0.001). Those of the compensatory curve in IS (0.968 ± 0.045/0.942 ± 0.067/0.967 ± 0.046) did not differ significantly from the NS values in any part.

Conclusions

When compared to the wedging of the vertebral bodies around apical vertebrae in the major curve in NS, which was caused by asymmetric loading, the wedge deformities in both the main and compensatory curves in IS were more severe than would be expected. Our results indicated that morphometric characteristics of vertebral bodies differed according to the pathogenesis of scoliosis and that the pathology of the wedging of vertebral bodies in IS could not be a result only of asymmetric loading to the vertebral bodies.

Postural Screening for Adolescent Idiopathic Scoliosis with Infrared Thermography

Adolescent idiopathic scoliosis (AIS) is a multifactorial, three-dimensional deformity of the spine and trunk. School scoliosis screening (SSS) is recommended by researchers as a means of early detection of AIS to prevent its progression in school-aged children. The traditional screening technique for AIS is the forward bending test because it is simple, non-invasive and inexpensive. Other tests, such as the use of Moiré topography, have reduced the high false referral rates. The use of infrared (IR) thermography for screening purposes based on the findings of previous studies on the asymmetrical paraspinal muscle activity of scoliotic patients compared with non-scoliotic subjects was explored in this study. IR thermography is performed with an IR camera to determine the temperature differences in paraspinal muscle activity. A statistical analysis showed that scoliotic subjects demonstrate a statistically significant difference between the left and right sides of the regions of interest. This difference could be due to the higher IR emission of the convex side of the observed area, thereby creating a higher temperature distribution. The findings of this study suggest the feasibility of incorporating IR thermography as part of SSS. However, future studies could also consider a larger sample of both non-scoliotic and scoliotic subjects to further validate the findings.