Association between common variants near LBX1 and adolescent idiopathic scoliosis replicated in the Chinese Han population

Deletion of a conserved genomic region associated with adolescent idiopathic scoliosis leads to vertebral rotation in mice

Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis, in which spinal curvature develops in adolescence, and 90% of patients are female. Scoliosis is a debilitating disease that often requires bracing or surgery in severe cases. AIS affects 2%-5.2% of the population; however, the biological origin of the disease remains poorly understood. In this study, we aimed to determine the function of a highly conserved genomic region previously linked to AIS using a mouse model generated by CRISPR-CAS9 gene editing to knockout this area of the genome to understand better its contribution to AIS, which we named AIS_CRMΔ. We also investigated the upstream factors that regulate the activity of this enhancer in vivo, whether the spatial expression of the LBX1 protein would change with the loss of AIS-CRM function, and whether any phenotype would arise after deletion of this region. We found a significant increase in mRNA expression in the developing neural tube at E10.5, and E12.5, for not only Lbx1 but also other neighboring genes. Adult knockout mice showed vertebral rotation and proprioceptive deficits, also observed in human AIS patients. In conclusion, our study sheds light on the elusive biological origins of AIS, by targeting and investigating a highly conserved genomic region linked to AIS in humans. These findings provide valuable insights into the function of the investigated region and contribute to our understanding of the underlying causes of this debilitating disease.

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.

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.

Etiopathogenesis of adolescent idiopathic scoliosis (AIS): Role of genetic and environmental factors

Adolescent idiopathic scoliosis (AIS) has been known to be related closely to genetic factors. Higher prevalence of AIS among individuals with family history of scoliosis suggesting critical roles of genetic in the pathogenesis of AIS. However, evidence also suggested that environmental factors such as latitude and sun exposure also play a critical role in the pathogenesis of the disease. While genetic factors played an important role in the occurrence of AIS, environmental factors are more likely to affect the progression of the disease. Although the pathogenesis of AIS remains elusive, current knowledge suggests that genetic factors and its interaction with environmental factors are crucial in the development of the disease, explaining differences in clinical characteristics of AIS across the globe. The aim of this review is to summarize the current knowledge of genetic and environmental factors contributing to AIS and their interactions.

Proprioception-related gene mutations in relation to the aetiopathogenesis of idiopathic scoliosis: A scoping review

Since idiopathic scoliosis is a multifactorial disorder, the proprioceptive defect is considered one of its etiological factors. Genetic studies have separately revealed this relationship, yet it remains indeterminate which specific genes that related to proprioception contributed to the initiation, progression, pathology, and treatment outcomes of the curvature. A systematic search was conducted on four online databases, including PubMed, Web of Science, Embase, and Academic search complete. Studies were included if they involved human or animal subjects with idiopathic scoliosis and evaluated with proprioceptive genes. The search period was the inception of the database to February 21, 2023. Four genes (i.e., Ladybird homeobox 1 [LBX1], Piezo type mechanosensitive ion channel component 2 [PIEZO2], Runx family transcription factor 3 [RUNX3], and neurotrophin 3 [NTF3]) investigated in 19 studies were included. LBX1 has confirmed the correlation with the development of idiopathic scoliosis in 10 ethnicities, whereas PIEZO2 has shown a connection with clinical proprioceptive tests in subjects with idiopathic scoliosis. However, curve severity was less likely to be related to the proprioceptive genes. The potential pathology took place at the proprioceptive neurons. Evidence of proprioception-related gene mutations in association with idiopathic scoliosis was established. Nevertheless, the causation between the initiation, progression, and treatment outcomes with proprioceptive defect requires further investigation.

Single Nucleotide Polymorphisms and Adolescent Idiopathic Scoliosis: A Systematic Review and Meta-Analysis of the Literature

STUDY DESIGN

Meta-analysis.

OBJECTIVE

To determine the single nucleotide polymorphisms (SNPs) that are related to adult idiopathic scoliosis.

SUMMARY AND BACKGROUND DATA

Adolescent idiopathic scoliosis (AIS) is considered one of the most prevalent spinal diseases. Even though the cause of AIS is yet to be determined, family history and sex have shown conclusive associations. Multiple studies have indicated that AIS is more prevalent in families where at least one other first-degree relative is similarly affected, indicating a possible genetic etiology to AIS.

MATERIALS AND METHODS

Articles were collected from 3 different search engines and then processed in 2 stages for final article selection for quantitative analysis. Five different genetic models were represented to show the association between the different SNPs and AIS. The Hardy-Weinberg equilibrium was examined using Fisher exact test, with significance set at P <0.05. The final analysis paper's quality was evaluated using the Newcastle Ottawa Scale. Kappa interrater agreement was calculated to evaluate the agreement between authors.

RESULTS

The final analysis comprised 43 publications, 19412 cases, 22005 controls, and 25 distinct genes. LBX1 rs11190870 T>C and MATN-1 SNPs were associated with an increased risk of AIS in one or all of the 5 genetic models. IGF-1 , estrogen receptor alfa, and MTNR1B , SNPs were not associated with AIS in all 5 genetic models. Newcastle Ottawa Scale showed good quality for the selected articles. Cohen k = 0.741 and Kappa interrater agreement of 84% showed that the writers were in strong agreement.

CONCLUSIONS

There seem to be associations between AIS and genetic SNP. Further larger studies should be conducted to validate the results.

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.

Genetic variants associated with the occurrence and progression of adolescent idiopathic scoliosis: a systematic review protocol

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a structural lateral spinal curvature of ≥ 10° with rotation. Approximately 2-3% of children in most populations are affected with AIS, and this condition is responsible for approximately $1.1 billion in surgical costs to the US healthcare system. Although a genetic factor for AIS has been demonstrated for decades, with multiple potentially contributory loci identified across populations, treatment options have remained limited to bracing and surgery.

METHODS

The databases MEDLINE (via PubMed), Embase, Google Scholar, and Ovid MEDLINE will be searched and limited to articles in English. We will conduct title and abstract, full-text, and data extraction screening through Covidence, followed by data transfer to a custom REDCap database. Quality assessment will be confirmed by multiple reviewers. Studies containing variant-level data (i.e., GWAS, exome sequencing) for AIS subjects and controls will be considered. Outcomes of interest will include presence/absence of AIS, scoliosis curve severity, scoliosis curve progression, and presence/absence of nucleotide-level variants. Analyses will include odds ratios and relative risk assessments, and subgroup analysis (i.e., males vs. females, age groups) may be applied. Quality assessment tools will include GRADE and Q-Genie for genetic studies.

DISCUSSION

In this systematic review, we seek to evaluate the quality of genetic evidence for AIS to better inform research efforts, to ultimately improve the quality of patient care and diagnosis.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration #CRD42021243253.

Predictive value of single-nucleotide polymorphisms in curve progression of adolescent idiopathic scoliosis

PURPOSE

Genetic diagnosis is a promising approach because several single-nucleotide polymorphisms (SNPs) associated with adolescent idiopathic scoliosis (AIS) progression have been reported. We review the predictive value of SNPs in curve progression of adolescent idiopathic scoliosis.

METHODS

We reviewed DNA-based prognostic testing to predict curve progression. Then, the multiple polymorphisms in loci related to AIS progression were also reviewed, and we elucidated the predictive value of SNPs from four functional perspectives, including endocrine metabolism, neuromuscular system, cartilage and extracellular matrix, enzymes, and cytokines.

RESULTS

The ScoliScores were less successful predictors than expected, and the weak power of predictive SNPs might account for its failure. Susceptibility loci in ESR1, ESR2, GPER, and IGF1, which related to endocrine metabolism, have been reported to predict AIS progression. Neuromuscular imbalance might be a potential mechanism of scoliosis, and SNPs in LBX1, NTF3, and SOCS3 have been reported to predict the curve progression of AIS. Susceptibility loci in SOX9, MATN1, AJAP1, MMP9, and TIMP2, which are related to cartilage and extracellular matrix, are also potentially related to AIS progression. Enzymes and cytokines play essential roles in regulating bone metabolism and embryonic development. SNPs in BNC2, SLC39A8, TGFB1, IL-6, IL-17RC, and CHD7 were suggested as predictive loci for AIS curve progression.

CONCLUSIONS

Many promising SNPs have been identified to predict the curve progression of AIS. However, conflicting results from replication studies and different ethnic groups hamper their reliability. Convincing SNPs from multiethnic populations and functional verification are needed.

Severity of Idiopathic Scoliosis Is Associated with Differential Methylation: An Epigenome-Wide Association Study of Monozygotic Twins with Idiopathic Scoliosis

Epigenetic mechanisms may contribute to idiopathic scoliosis (IS). We identified 8 monozygotic twin pairs with IS, 6 discordant (Cobb angle difference > 10°) and 2 concordant (Cobb angle difference ≤ 2°). Genome-wide methylation in blood was measured with the Infinium HumanMethylation EPIC Beadchip. We tested for differences in methylation and methylation variability between discordant twins and tested the association between methylation and curve severity in all twins. Differentially methylated region (DMR) analyses identified gene promoter regions. Methylation at cg12959265 (chr. 7 DPY19L1) was less variable in cases (false discovery rate (FDR) = 0.0791). We identified four probes (false discovery rate, FDR < 0.10); cg02477677 (chr. 17, RARA gene), cg12922161 (chr. 2 LOC150622 gene), cg08826461 (chr. 2), and cg16382077 (chr. 7) associated with curve severity. We identified 57 DMRs where hyper- or hypo-methylation was consistent across the region and 28 DMRs with a consistent association with curve severity. Among DMRs, 21 were correlated with bone methylation. Prioritization of regions based on methylation concordance in bone identified promoter regions for WNT10A (WNT signaling), NPY (regulator of bone and energy homeostasis), and others predicted to be relevant for bone formation/remodeling. These regions may aid in understanding the complex interplay between genetics, environment, and IS.

Whole Exome Sequencing of 23 Multigeneration Idiopathic Scoliosis Families Reveals Enrichments in Cytoskeletal Variants, Suggests Highly Polygenic Disease

Adolescent idiopathic scoliosis (AIS) is a lateral spinal curvature >10° with rotation that affects 2–3% of healthy children across populations. AIS is known to have a significant genetic component, and despite a handful of risk loci identified in unrelated individuals by GWAS and next-generation sequencing methods, the underlying etiology of the condition remains largely unknown. In this study, we performed exome sequencing of affected individuals within 23 multigenerational families, with the hypothesis that the occurrence of rare, low frequency, disease-causing variants will co-occur in distantly related, affected individuals. Bioinformatic filtering of uncommon, potentially damaging variants shared by all sequenced family members revealed 1448 variants in 1160 genes across the 23 families, with 132 genes shared by two or more families. Ten genes were shared by >4 families, and no genes were shared by all. Gene enrichment analysis showed an enrichment of variants in cytoskeletal and extracellular matrix related processes. These data support a model that AIS is a highly polygenic disease, with few variant-containing genes shared between affected individuals across different family lineages. This work presents a novel resource for further exploration in familial AIS genetic research.

Mutations in KIF7 implicated in idiopathic scoliosis in humans and axial curvatures in zebrafish

Idiopathic scoliosis (IS) is a spinal disorder affecting up to 3% of otherwise healthy children. IS has a strong familial genetic component and is believed to be genetically complex due to significant variability in phenotype and heritability. Previous studies identified putative loci and variants possibly contributing to IS susceptibility, including within extracellular matrix, cilia, and actin networks, but the genetic architecture and underlying mechanisms remain unresolved. Here, we used whole-exome sequencing from three affected individuals in a multigenerational family with IS and identified 19 uncommon variants (minor allele frequency < 0.05). Genotyping of additional family members identified a candidate heterozygous variant (H1115Q, G>C, rs142032413) within the ciliary gene KIF7, a regulator within the hedgehog (Hh) signaling pathway. Resequencing of the second cohort of unrelated IS individuals and controls identified several severe mutations in KIF7 in affected individuals only. Subsequently, we generated a mutant zebrafish model of kif7 using CRISPR-Cas9. kif7^co63/co63 zebrafish displayed severe scoliosis, presenting in juveniles and progressing through adulthood. We observed no deformities in the brain, Reissner fiber, or central canal cilia in kif7^co63/co63 embryos, although alterations were seen in Hh pathway gene expression. This study suggests defects in KIF7-dependent Hh signaling, which may drive pathogenesis in a subset of individuals with IS.

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.

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.

Genetic Variations of Ultraconserved Elements in the Human Genome

Ultraconserved elements (UCEs) are among the most popular DNA markers for phylogenomic analysis. In at least three of five placental mammalian genomes (human, dog, cow, mouse, and rat), 2189 UCEs of at least 200 bp in length that are identical have been identified. Most of these regions have not yet been functionally annotated, and their associations with diseases remain largely unknown. This is an important knowledge gap in human genomics with regard to UCE roles in physiologically critical functions, and by extension, their relevance for shared susceptibilities to common complex diseases across several mammalian organisms in the event of their polymorphic variations. In the present study, we remapped the genomic locations of these UCEs to the latest human genome assembly, and examined them for documented polymorphisms in sequenced human genomes. We identified 29,983 polymorphisms within analyzed UCEs, but revealed that a vast majority exhibits very low minor allele frequencies. Notably, only 112 of the identified polymorphisms are associated with a phenotype in the Ensembl genome browser. Through literature analyses, we confirmed associations of 37 (i.e., out of the 112) polymorphisms within 23 UCEs with 25 diseases and phenotypic traits, including, muscular dystrophies, eye diseases, and cancers (e.g., familial adenomatous polyposis). Most reports of UCE polymorphism-disease associations appeared to be not cognizant that their candidate polymorphisms were actually within UCEs. The present study offers strategic directions and knowledge gaps for future computational and experimental work so as to better understand the thus far intriguing and puzzling role(s) of UCEs in mammalian genomes.

Paraspinal muscle ladybird homeobox 1 (LBX1) in adolescent idiopathic scoliosis: a cross-sectional study

BACKGROUND CONTEXT

Adolescent idiopathic scoliosis (AIS) is the leading cause of spinal deformity in adolescents globally. Recent evidence from genome-wide association studies has implicated variants in or near the ladybird homeobox 1 (LBX1) gene, encoding the ladybird homeobox 1 transcription factor, in AIS development. This gene plays a critical role in guiding embryonic neurogenesis and myogenesis and is vital in muscle mass determination. Despite the confirmation of the role for LBX1 gene variants in the development of AIS, the biological basis of LBX1 contribution to AIS remains mostly unknown.

PURPOSE

To investigate the potential role of LBX1 in driving spinal curving, curve laterality, and progression through muscle-based mechanisms in AIS patients by analyzing its gene and protein expression.

STUDY DESIGN

This is a cross-sectional study using clinical data and biological samples from the Immunometabolic CONnections to Scoliosis study (ICONS study).

PATIENT SAMPLE

Twenty-five patients with AIS provided informed consent. Paraspinal muscle biopsies from the maximal points of concavity and convexity for gene expression and protein analysis were obtained at the start of corrective spinal surgery.

OUTCOME MEASURES

The outcome measures included the detection of paraspinal muscle LBX1 mRNA abundance and LBX1 protein expression and the correlation of the latter with age, sex, and curve severity.

METHODS

The measurement of mRNA abundance was done using quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, protein lysates from the biopsied muscle samples were probed with a monoclonal LBX1 antibody to compare the muscle protein levels on either side of the scoliotic curve by western blot. This study received funding from the Division of Orthopedics, Department of Surgery, McMaster University, Hamilton, Ontario, Canada ($39,900 CAN for 2 years). The authors have no conflicts of interest to disclose.

RESULTS

LBX1 mRNA abundance (concave 2.98±0.87, convex 3.40±1.10, p value 0.73) and protein expression (concave 1.20±0.13, convex 1.21±0.10, p value 0.43) were detected on both sides of the scoliotic curve at equivalent levels. The expression of LBX1 protein did not correlate with age (concave: correlation coefficient 0.32, p value 0.12; convex: correlation coefficient 0.08, p value 0.69), sex (concave: correlation coefficient -0.03, p value 0.08; convex: correlation coefficient 0.07, p value 0.72), or the severity of spinal curving measured using the Cobb angle (concave: correlation coefficient -0.16, p value 0.45; convex: correlation coefficient -0.08, p value 0.69).

CONCLUSIONS

LBX1 is expressed in erector spinae muscles, and its levels are equal in muscles on both sides of the scoliotic curve in AIS. The expression of LBX1 on the convex and concave sides of the scoliotic curve did not correlate with age, sex, or the severity of spinal curving. The molecular mechanisms by which LBX1contributes to the development and propagation of AIS need to be explored further in muscle and other tissues.

Positive association between a polymorphic locus near the LBX1 gene and predisposition of idiopathic scoliosis in Southeastern European population

Idiopathic scoliosis (IS) is a common medical condition in children, characterized by three-dimensional spinal curve and strong evidence of genetic predisposition. The purpose of the present case-control study is to examine the association between the polymorphic variant rs11190870 (T/C), near the LBX1 gene, and IS predisposition in distinct subgroups based on age at onset, family history and gender. A total of 127 IS patients and 254 unrelated controls of Southeastern European descent were recruited. The genotyping was carried out by TaqMan real-time amplification technology. The results were analyzed by the Pearson's Chi-squared Test and the Fisher's Exact Test with a value of p less than 0.05 as statistically significant. The T allele and homozygous TT genotype were associated with a greater incidence of IS. Our results suggest that there is a genetic association with IS in adolescents, familial and non-familial cases, and in females. Larger case-control studies are necessary to examine the genetic factors of IS/AIS etiology in infants, juveniles and males. In conclusion, the molecular genetic identification of diagnostic and prognostic molecular markers would make an early treatment including minimally invasive procedures possible.

Association between ladybird homeobox 1 gene polymorphisms and adolescent idiopathic scoliosis: A MOOSE-compliant meta-analysis

The Ladybird Homeobox 1 (LBX1) gene has been implicated in the etiology of adolescent idiopathic scoliosis (AIS). The association between LBX1 gene polymorphisms and AIS has been investigated in several studies. However, these findings have yield contradictory results rather than conclusive evidence.This study is to provide a meta-analysis of the published case-control studies on the association between LBX1 gene polymorphisms and AIS in Asian and Caucasian populations.This meta-analysis conformed to the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines. We conducted a literature research on PubMed, Embase, Web of Science, and Cochrane Library until February 10, 2018. We included all case-control or cohort studies about association between LBX1 gene polymorphisms and AIS. The Risk Of Bias In Non-randomised Studies-of Interventions and Critical Appraisal Skills Programme were used to evaluate the risk of bias and study quality. We assessed the strength of association by pooled odds ratios (ORs) and 95% confidence intervals (CIs) in all genetic models under a fixed-effect model or random-effect model. We further performed subgroup analysis by ethnicity and sex. Sensitivity analysis and publication bias were also undertaken.A total of 10 studies (11,411 cases and 26,609 controls) were included in this meta-analysis. The pooled results showed a statistically significant association between LBX1 gene polymorphisms and AIS (for rs11190870, T vs C, OR = 1.54, 95% CI = 1.48-1.61, P < .00001; for rs625039, G vs A, OR = 1.50, 95% CI: 1.38-1.62; P < .00001; for rs678741, G vs A, OR = 0.74, 95% CI: 0.63-0.86; P < .0001; for rs11598564, G vs A, OR = 1.41, 95% CI: 1.31-1.51; P < .0001). For stratified analyses by ethnicity and sex, robust significant associations were detected in Asian and Caucasian populations, and in women and men under all genetic models.T allele of rs11190870 and G alleles of rs625039 and rs11598564 represent risk factors for AIS, but G allele of rs678741 may play a protective role in the occurrence of AIS. Further research is needed to confirm this finding and to understand its implications.

Replication Study for the Association of GWAS-associated Loci With Adolescent Idiopathic Scoliosis Susceptibility and Curve Progression in a Chinese Population

STUDY DESIGN

A genetic association (replication) study.

OBJECTIVE

The aim of this study was to replicate and further evaluate the association among seven genome-wide association studies (GWAS)-identified single nucleotide polymorphisms (SNPs) in Chinese girls with adolescent idiopathic scoliosis (AIS) with disease onset, curve types, and progression.

SUMMARY OF BACKGROUND DATA

AIS is the most common pediatric spinal deformity with a strong genetic predisposition. Recent GWAS identified 10 new disease predisposition loci for AIS.

METHODS

Three hundred nineteen female AIS patients with Cobb angle ≥ 10 and 201 healthy controls were studied for the association with disease onset. Seven GWAS-identified SNPs (rs11190870 in LBX1, rs12946942 in SOX9/KCNJ2, rs13398147 in PAX3/EPH4, rs241215 in AJAP1, rs3904778 in BNC2, rs6570507 in GPR126, and rs678741 in LBX1-AS1) were analyzed. In subgroup analysis, AIS patients were subdivided by curve types and disease progression to examine for genotype association.

RESULTS

We replicated the association with disease onset in four common SNPs rs11190870, rs3904778, rs6570507, and rs678741. In addition, rs1190870 and rs678741 remained significantly associated in the right thoracic curves only subgroup. However, no significant difference was observed with both clinical curve progression or Cobb angle.

CONCLUSION

This study replicated the associations of four GWAS-associated SNPs with occurrence of AIS in our Chinese population. However, none of these SNPs was associated with curve severity and progression. The results suggest that curve progression may be determined by environmental (nongenetic) factor, but further study with a larger sample size is required to address this issue.

LEVEL OF EVIDENCE

4.

A Genetic Variant in GPR126 Causing a Decreased Inclusion of Exon 6 Is Associated with Cartilage Development in Adolescent Idiopathic Scoliosis Population

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity disease in adolescents but its etiology and pathogenesis are still unclear. The current study aims to identify the relationship between single nucleotide polymorphisms (SNPs) of G protein-coupled receptor 126 (GPR126) gene and AIS predisposition. GPR126 contains 26 exons and alternative splicing of exon 6 and exon 25 produces 4 protein-coding transcripts. We genotyped SNPs of GPR126 gene around exon 6 and exon 25 in 131 Chinese AIS patients and 132 healthy controls and provided evidence that SNP rs41289839 G>A is strongly associated with AIS susceptibility. Linkage disequilibrium analysis suggests that rs41289839 and other AIS-related SNPs were in strong LD. Next, we demonstrated that rs41289839 G>A inhibits the inclusion of exon 6 during alternative splicing, resulting in a decreased expression level of exon 6-included transcript (GPR126-exon6ⁱⁿ) relative to the exon 6 excluded transcript (GPR126-exon6^ex) by minigene assay. Chondrogenic differentiation experiment showed that GPR126-exon6ⁱⁿ has a high expression level relative to GPR126-exon6^ex during chondrogenic differentiation of hMSCs. Our findings indicate that newly discovered SNP is related to cartilage development and may provide valuable insights into the etiology and pathogenesis of adolescent idiopathic scoliosis.

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.

A Replication Study for the Association of rs11190870 With Curve Severity in Adolescent Idiopathic Scoliosis in Japanese

STUDY DESIGN

Case-only study.

OBJECTIVE

The aim of this study was to confirm the association of rs11190870 with adolescent idiopathic scoliosis (AIS) severity in Japanese patients with AIS.

SUMMARY OF BACKGROUND DATA

Although the association of rs11190870 with AIS susceptibility is replicated in multiple ethnics, the association of rs11190870 with curve severity is controversial. Since the previous studies are of small, we performed a replication study using far larger number of patients than previous studies.

METHODS

A total of 1860 Japanese patients with AIS who had reached skeletal maturity or undergone surgical fusion were included in the study. We evaluated the association between rs11190870 and AIS progression for the entire group, and then for patients grouped according to a severe curve (a Cobb angle of ≥40°) or mild curve (a Cobb angle <30°). Because braces could affect the results of the present study, patients in the mild-curve group were divided according to whether or not they had worn a brace. We then evaluated associations between rs11190870 genotype and curve severity in these groups.

RESULTS

The mean Cobb angles were 54.8° ± 12.1° in the severe-curve group and 24.4° ± 4.0° in the mild-curve group. The difference in rs11190870 risk-allele frequency between the severe- and mild-curve groups was evaluated. No significant differences were observed. We then examined the association of rs11190870 risk-allele frequency between patients in the mild- and severe-curve groups using the χ test for three models, and found a marginal association between rs11190870 and curve severity in the dominant model (P = 0.035, odds ratio = 1.51).

CONCLUSION

We found no association between rs11190870 and curve severity using the criteria of previous study. However, we found a marginal association between rs11190870 and curve severity. Large-scale replication studies that consider skeletal maturity and brace history, including replication studies in other ethnic groups, would be helpful for clarifying the association.

LEVEL OF EVIDENCE

4.

An international meta-analysis confirms the association of BNC2 with adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a common spinal deformity with the prevalence of approximately 3%. We previously conducted a genome-wide association study (GWAS) using a Japanese cohort and identified a novel locus on chromosome 9p22.2. However, a replication study using multi-population cohorts has not been conducted. To confirm the association of 9p22.2 locus with AIS in multi-ethnic populations, we conducted international meta-analysis using eight cohorts. In total, we analyzed 8,756 cases and 27,822 controls. The analysis showed a convincing evidence of association between rs3904778 and AIS. Seven out of eight cohorts had significant P value, and remaining one cohort also had the same trend as the seven. The combined P was 3.28 × 10⁻¹⁸ (odds ratio = 1.19, 95% confidence interval = 1.14–1.24). In silico analyses suggested that BNC2 is the AIS susceptibility gene in this locus.

The association of rs11190870 near LBX1 with the susceptibility and severity of AIS, a meta-analysis

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is the most common structural deformity of the spine. Genetics constitute largely to AIS, and the rs11190870 polymorphism has the potential for use in public health and clinical settings as a predictor of AIS risk. The aim of the present meta-analysis was to provide exhaustive evidence to evaluate the association of rs11190870 with the susceptibility and severity of adolescent idiopathic scoliosis (AIS) in multiple ethnic groups and different genders.

MATERIALS AND METHODS

The professional databases, including PubMed, Embase, Social Sciences Citation Index, CINAHL, and International Bibliography of the Social Sciences, were searched from 1966 to October 2015. No language restriction was applied. Reference lists of all the selected articles were hand-searched for any additional studies. Three authors independently extracted data from all eligible studies. The data were analyzed by meta-analysis using fixed-effects or random-effects models with mean differences and risk ratios for continuous and dichotomous variables, respectively.

RESULTS

Eight studies were included, and the pooled analysis suggested that the T genotype of SNP rs11190870 leads to a higher risk of AIS in multiple ethnic groups regardless of gender (Total:OR, 1.66, 95% CI 1.53, 1.79; I² = 37.3%, P = 0.000, Female: OR, 1.62, 95% CI 1.50, 1.73; I² = 26.7%, P = 0.000, Male: OR, 1.79, 95% CI 1.38, 2.20; I2 = 0.00%, P = 0.000). Additionally, the TT and TC genotype had a larger Cobb angle than those with the CC genotype in the overall and female Asian populations.

CONCLUSION

A significant association of rs11190870 with AIS was observed in multiple ethnic groups regardless of gender. Additionally, a significant association was found between rs11190870 and curve severity in the overall and female Asian populations. Due to the limited data and clinical heterogeneity, further studies with large sample sizes are required.

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.

Etiological Theories of Adolescent Idiopathic Scoliosis: Past and Present

Adolescent idiopathic scoliosis is one of the most common spinal deformities, yet its cause is unknown. Various theories look to biomechanical, neuromuscular, genetic, and environmental origins, yet our understanding of scoliosis etiology is still limited. Determining the cause of a disease is crucial to developing the most effective treatment. Associations made with scoliosis do not necessarily point to causality, and it is difficult to determine whether said associations are primary (playing a role in development) or secondary (develop as a result of scoliosis). Scoliosis is a complex condition with highly variable expression, even among family members, and likely has many causes. These causes could be similar among homogenous groups of AIS patients, or they could be individual. Here, we review the most prevalent theories of scoliosis etiology and recent trends in research.

Genetic Polymorphism of LBX1 Is Associated With Adolescent Idiopathic Scoliosis in Northern Chinese Han Population

STUDY DESIGN

A case-control association study was performed to investigate the relationship between ladybird homeobox (LBX1) and adolescent idiopathic scoliosis (AIS) in northern Chinese Han population.

OBJECTIVE

To explore the prevalence and functional importance of LBX1 polymorphisms in patients with AIS within the northern Chinese Han population.

SUMMARY OF BACKGROUND DATA

AIS is the most common subtype of idiopathic scoliosis. Genetic factors such as LBX1 polymorphisms have been recently proved to be associated with AIS in some populations. In this study we explored the prevalence and functional importance of the polymorphisms around LBX1 in patients with AIS within the northern Chinese Han population.

METHODS

Five tag single nucleotide polymorphisms (SNPs) around or in LBX1 were genotyped in 180 patients with AIS and 182 controls. And the luciferase assay was performed to explore the functional importance of the most significant SNPs.

RESULTS

We replicated that rs11190870, previously reported as the most significantly associated SNP, was enriched in our AIS cohort. In addition, we found that the T allele of rs1322331 was associated with a novel risk allele (odds ratio = 3.349, 95% confidence interval 1.742-6.436). In the following luciferase assay, the TT-type promoter showed significantly reduced transcription activity in vitro.

CONCLUSION

Two SNPs around LBX1, rs11190870 and rs1322331 are associated with AIS in northern Chinese Han population. The T allele of rs1322331 is a novel risk allele. We hypothesize that rs1322331 might increase patients' susceptibility to AIS by reducing LBX1-AS1 transcription and thus upregulating the function of LBX1.

LEVEL OF EVIDENCE

3.

Genetics and pathogenesis of idiopathic scoliosis

Idiopathic scoliosis (IS), the most common spinal deformity, affects otherwise healthy children and adolescents during growth. The aetiology is still unknown, although genetic factors are believed to be important. The present review corroborates the understanding of IS as a complex disease with a polygenic background. Presumably IS can be due to a spectrum of genetic risk variants, ranging from very rare or even private to very common. The most promising candidate genes are highlighted.

Associations of LBX1 gene and adolescent idiopathic scoliosis susceptibility: a meta-analysis based on 34,626 subjects

Background

The results of studies investigating the association between the ladybird homeobox 1 (LBX1) gene polymorphisms and the risk of adolescent idiopathic scoliosis (AIS) are not all the same. As such, we performed a meta-analysis to estimate the association between LBX1 gene polymorphisms and AIS susceptibility.

Methods

Relevant studies published before 15 November 2015 were identified by searching PubMed, EMBASE, ISI web of knowledge, EBSCO, CNKI and CBM. The strength of relationship was assessed by using odds ratios (ORs) and 95 % confidence interval (CI).

Results

A total number of eight case-control studies including 10,088 cases and 24,538 controls were identified. The results showed that T allele of rs111090870 increased AIS susceptibility in Asians (T vs. C, OR = 1.22, 95 % CI: 1.16–1.29, P < 0.001), Caucasians (T vs. C, OR = 1.17, 95 % CI: 1.14–1.21, P < 0.001) and in female (T vs. C, OR = 1.21, 95 % CI: 1.17–1.25, P < 0.001). The G allele of rs678741 decreased AIS risk in female (G vs. A, OR = 0.83, 95 % CI: 0.81–0.85, P < 0.001), and the G allele of the rs625039 increased AIS susceptibility in Asians (G vs. A, OR = 1.14, 95 % CI: 1.11–1.17, P < 0.001).

Conclusions

Our meta-analysis provides evidence that rs111090870, rs678741 and rs625039 polymorphisms near LBX1 gene are associated with AIS susceptibility in some populations. However, our findings are based on only a limited number of studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1139-z) contains supplementary material, which is available to authorized users.

Genomic study of adolescent idiopathic scoliosis in Japan

Adolescent idiopathic scoliosis (AIS) is a common disease. It is a multi-factorial (polygenic) disease controlled by genetic and environmental factors. Studies searching for genetic factors of AIS using linkage and association analyses have been conducted and several susceptibility genes have been reported. This paper reviews the recent progress in the genome-wide association study of AIS in Japan and comments on its future task.

Functional Investigation of a Non-coding Variant Associated with Adolescent Idiopathic Scoliosis in Zebrafish: Elevated Expression of the Ladybird Homeobox Gene Causes Body Axis Deformation

Previously, we identified an adolescent idiopathic scoliosis susceptibility locus near human ladybird homeobox 1 (LBX1) and FLJ41350 by a genome-wide association study. Here, we characterized the associated non-coding variant and investigated the function of these genes. A chromosome conformation capture assay revealed that the genome region with the most significantly associated single nucleotide polymorphism (rs11190870) physically interacted with the promoter region of LBX1-FLJ41350. The promoter in the direction of LBX1, combined with a 590-bp region including rs11190870, had higher transcriptional activity with the risk allele than that with the non-risk allele in HEK 293T cells. The ubiquitous overexpression of human LBX1 or either of the zebrafish lbx genes (lbx1a, lbx1b, and lbx2), but not FLJ41350, in zebrafish embryos caused body curvature followed by death prior to vertebral column formation. Such body axis deformation was not observed in transcription activator-like effector nucleases mediated knockout zebrafish of lbx1b or lbx2. Mosaic expression of lbx1b driven by the GATA2 minimal promoter and the lbx1b enhancer in zebrafish significantly alleviated the embryonic lethal phenotype to allow observation of the later onset of the spinal curvature with or without vertebral malformation. Deformation of the embryonic body axis by lbx1b overexpression was associated with defects in convergent extension, which is a component of the main axis-elongation machinery in gastrulating embryos. In embryos overexpressing lbx1b, wnt5b, a ligand of the non-canonical Wnt/planar cell polarity (PCP) pathway, was significantly downregulated. Injection of mRNA for wnt5b or RhoA, a key downstream effector of Wnt/PCP signaling, rescued the defective convergent extension phenotype and attenuated the lbx1b-induced curvature of the body axis. Thus, our study presents a novel pathological feature of LBX1 and its zebrafish homologs in body axis deformation at various stages of embryonic and subsequent growth in zebrafish.

Scoliosis is the most common type of spinal deformity with a lateral spinal curvature of at least 10 degrees, affecting 2–4% of the population. Scoliosis caused by a primary problem related to the spine itself is classified into congenital scoliosis (CS) and idiopathic scoliosis (IS). Among these, adolescent idiopathic scoliosis (AIS), the most common form of scoliosis, is known as a common polygenic disease. Severe curving of the spine in scoliosis leads to profound psychological and social impacts, but etiology-based therapies have not been established since the precise pathological mechanisms of both IS and CS remain undefined. Previously, we identified an AIS susceptibility locus near human ladybird homeobox 1 (LBX1) by a genome-wide association study. Here, we report the functional characterization of the most significantly associated single nucleotide polymorphism (SNP), rs11190870 and LBX1 as well as its zebrafish homologues. Overexpression of LBX1 and zebrafish lbx genes caused lateral body curvature in association with the impairment of non-canonical Wnt/planar cell polarity signaling. Thus, our study presents a novel pathological feature of LBX1 in body axis deformation.

Candidate gene analysis and exome sequencing confirm LBX1 as a susceptibility gene for idiopathic scoliosis

BACKGROUND CONTEXT

Idiopathic scoliosis is a spinal deformity affecting approximately 3% of otherwise healthy children or adolescents. The etiology is still largely unknown but has an important genetic component. Genome-wide association studies have identified a number of common genetic variants that are significantly associated with idiopathic scoliosis in Asian and Caucasian populations, rs11190870 close to the LBX1 gene being the most replicated finding.

PURPOSE

The aim of the present study was to investigate the genetics of idiopathic scoliosis in a Scandinavian cohort by performing a candidate gene study of four variants previously shown to be associated with idiopathic scoliosis and exome sequencing of idiopathic scoliosis patients with a severe phenotype to identify possible novel scoliosis risk variants.

STUDY DESIGN

This was a case control study.

PATIENT SAMPLE

A total of 1,739 patients with idiopathic scoliosis and 1,812 controls were included.

OUTCOME MEASURE

The outcome measure was idiopathic scoliosis.

METHODS

The variants rs10510181, rs11190870, rs12946942, and rs6570507 were genotyped in 1,739 patients with idiopathic scoliosis and 1,812 controls. Exome sequencing was performed on pooled samples from 100 surgically treated idiopathic scoliosis patients. Novel or rare missense, nonsense, or splice site variants were selected for individual genotyping in the 1,739 cases and 1,812 controls. In addition, the 5'UTR, noncoding exon and promoter regions of LBX1, not covered by exome sequencing, were Sanger sequenced in the 100 pooled samples.

RESULTS

Of the four candidate genes, an intergenic variant, rs11190870, downstream of the LBX1 gene, showed a highly significant association to idiopathic scoliosis in 1,739 cases and 1,812 controls (p=7.0×10(-18)). We identified 20 novel variants by exome sequencing after filtration and an initial genotyping validation. However, we could not verify any association to idiopathic scoliosis in the large cohort of 1,739 cases and 1,812 controls. We did not find any variants in the 5'UTR, noncoding exon and promoter regions of LBX1.

CONCLUSIONS

Here, we confirm LBX1 as a susceptibility gene for idiopathic scoliosis in a Scandinavian population and report that we are unable to find evidence of other genes of similar or stronger effect.

Genome-wide association study identifies new susceptibility loci for adolescent idiopathic scoliosis in Chinese girls

Adolescent idiopathic scoliosis (AIS) is a structural deformity of the spine affecting millions of children. As a complex disease, the genetic aetiology of AIS remains obscure. Here we report the results of a four-stage genome-wide association study (GWAS) conducted in a sample of 4,317 AIS patients and 6,016 controls. Overall, we identify three new susceptibility loci at 1p36.32 near AJAP1 (rs241215, Pcombined=2.95 × 10(-9)), 2q36.1 between PAX3 and EPHA4 (rs13398147, Pcombined=7.59 × 10(-13)) and 18q21.33 near BCL-2 (rs4940576, Pcombined=2.22 × 10(-12)). In addition, we refine a previously reported region associated with AIS at 10q24.32 (rs678741, Pcombined=9.68 × 10(-37)), which suggests LBX1AS1, encoding an antisense transcript of LBX1, might be a functional variant of AIS. This is the first GWAS investigating genetic variants associated with AIS in Chinese population, and the findings provide new insight into the multiple aetiological mechanisms of AIS.

Investigation of the 53 Markers in a DNA-Based Prognostic Test Revealing New Predisposition Genes for Adolescent Idiopathic Scoliosis

STUDY DESIGN

A genetic association study of 53 single nucleotide polymorphisms (SNPs) with adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To explore new predisposition genes of AIS in Chinese Han population SUMMARY OF BACKGROUND DATA.: A panel of 53 SNPs were reported to be associated with curve severity of AIS. However, there is still a lack of knowledge concerning the association of these SNPs with the susceptibility of AIS in the Chinese Han population.

METHODS

A gene-based association study was conducted by genotyping the 53 SNPs of a prognostic test. DNA samples of 990 female patients with AIS and 1188 age-matched healthy controls were analyzed using the polymerase chain reaction-based Invader assay. The χ test was carried out to compare the differences of genotype and allele distributions between patients with AIS and healthy controls.

RESULTS

A total of 4 SNPs were found to present significant differences in allele or genotype frequencies between the 2 groups. Compared with normal controls, patients were found to have significantly higher allele G of rs12618119 and allele A of rs9945359. Besides, patients were found to have significantly lower allele T of rs4661748 and allele C of rs4782809 than the normal controls. BIN1, CDH13, SETBP1, and SPATA21 genes could be associated with the susceptibility of AIS.

CONCLUSION

Four new predisposition genes of AIS were identified on the basis of a large-scale case-control study. Putting all these findings together, it suggests that AIS is a multifactorial disease possibly involving different pathways such as development of central neural system and bone formation. Further studies exploring more predisposition gene are essential to illustrate the etiology of AIS and to guide the prevention or prognosis of the disease.

LEVEL OF EVIDENCE

3.

Haplotypes at LBX1 have distinct inheritance patterns with opposite effects in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a clinically significant disorder with high heritability that affects 2–4% of the population. Genome-wide association studies have identified LBX1 as a strong susceptibility locus for AIS in Asian and Caucasian populations. Here we further dissect the genetic association with AIS in a Caucasian population. To identify genetic markers associated with AIS we employed a genome-wide association study (GWAS) design comparing 620 female Caucasian patients who developed idiopathic scoliosis during adolescence with 1,287 ethnically matched females who had normal spinal curves by skeletal maturity. The genomic region around LBX1 was imputed and haplotypes investigated for genetic signals under different inheritance models. The strongest signal was identified upstream of LBX1 (rs11190878, P_trend = 4.18×10^-9, OR = 0.63[0.54–0.74]). None of the remaining SNPs pass the genome-wide significance threshold. We found rs11190870, downstream of LBX1 and previously associated with AIS in Asian populations, to be in modest linkage disequilibrium (LD) with rs11190878 (r² = 0.40, D' = 0.81). Haplotype analysis shows that rs11190870 and rs11190878 track a single risk factor that resides on the ancestral haplotype and is shared across ethnic groups. We identify six haplotypes at the LBX1 locus including two strongly associated haplotypes; a recessive risk haplotype (TTA, Control_freq = 0.52, P = 1.25×10^-9, OR = 1.56), and a co-dominant protective haplotype (CCG, Control_freq = 0.28, P = 2.75×10^-7, OR = 0.65). Together the association signals from LBX1 explain 1.4% of phenotypic variance. Our results identify two clinically relevant haplotypes in the LBX1-region with opposite effects on AIS risk. The study demonstrates the utility of haplotypes over un-phased SNPs for individualized risk assessment by more strongly delineating individuals at risk for AIS without compromising the effect size.

Association of GPR126 gene polymorphism with adolescent idiopathic scoliosis in Chinese populations

Idiopathic scoliosis is the most common pediatric spinal deformity affecting 1% to 3% of the population, and adolescent idiopathic scoliosis (AIS) accounts for approximately 80% of these cases; however, the etiology and pathogenesis of AIS are still uncertain. The current study aims to identify the relationship between G protein-coupled receptor 126 (GPR126) gene and AIS predisposition, to identify the relationship between the genotypes of the GPR126 SNPs and the clinical phenotypes of AIS. We conducted a case-control study and genotyped twenty SNPs of GPR126 gene including ten exonic SNPs and ten intronic polymorphisms in 352 Chinese sporadic AIS patients and 149 healthy controls. We provided evidence for strong association of three intronic SNPs of the GPR126 gene with AIS susceptibility: rs6570507 A > G (p =0 .0035, OR = 1.729), rs7774095 A > C (p = 0.0078, OR = 1.687), and rs7755109 A > G (p = 0.0078, OR = 1.687). However, we did not identify any significant association between ten exonic SNPs of GPR126 and AIS. Linkage disequilibrium analysis indicated that rs7774095 A > C and rs7755109 A > G could be parsed into one block. The association between the intronic haplotype and AIS was further confirmed in an independent population with 110 AIS individuals and 130 healthy controls (p = 0.046, OR = 1.680). Furthermore, molecular mechanisms underlying intronic SNP regulation of GPR126 gene were studied. Although intronic SNPs associated with AIS didn't influence GPR126 mRNA alternative splicing, there was a strong association of rs7755109 A > G with decreased GPR126 mRNA level and protein levels. Our findings indicate that genetic variants of GPR126 gene are associated with AIS susceptibility in Chinese populations. The genetic association of GPR126 gene and AIS might provide valuable insights into the pathogenesis of adolescent idiopathic scoliosis.

Association of rs11190870 near LBX1 with adolescent idiopathic scoliosis in East Asians: a systematic review and meta-analysis

BACKGROUND CONTEXT

The rs11190870 single nucleotide polymorphism in the 3'-flanking region of the LBX1 gene has been implicated in the etiology of adolescent idiopathic scoliosis (AIS). A thorough appraisal of the evidence supporting this association has not been previously attempted.

PURPOSE

To provide a comprehensive assessment and synthesis of the currently available evidence on the association between rs11190870 and AIS.

STUDY DESIGN

A systematic review and meta-analysis.

METHODS

This review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. PubMed (MEDLINE), EMBASE, Scopus, and HuGE Literature Finder databases were systematically searched through November 2013 to identify relevant studies following a sensitive strategy. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using the fixed-effect inverse variance model for allelic (T vs. C) and genotypic comparisons.

RESULTS

Meta-analysis of four studies conducted in East Asian populations (n=3,215 AIS cases and n=15,347 controls) found a highly statistically significant and robust association between rs11190870 and AIS. Comparison of summary ORs indicated a codominant model effect of the T allele. Carriers of the TC and TT genotypes were 69% (OR=1.69, 95% CI: 1.48-1.94, p<.001) and 162% (OR=2.62, 95% CI: 2.28-3.02, p<.001), respectively, more likely to have AIS compared with carriers of the CC genotype.

CONCLUSIONS

Based on a comprehensive analysis of the currently available evidence, rs11190870 is likely a susceptibility variant for AIS in East Asians. Further investigation of this association is necessary in other populations.

Association Between rs11190870 Polymorphism Near LBX1 and Susceptibility to Adolescent Idiopathic Scoliosis in East Asian Population: A Genetic Meta-Analysis

STUDY DESIGN

Meta-analysis to collect all the relevant studies to date to further investigate whether or not the rs11190870 polymorphism is associated with susceptibility to adolescent idiopathic scoliosis (AIS) in East Asian population.

OBJECTIVE

To investigate whether or not the rs11190870 polymorphism is associated with susceptibility to AIS in East Asian population.

SUMMARY OF BACKGROUND DATA

To date, the single nucleotide polymorphism rs11190870 was identified as the most significant common variant in Japanese females. Three association studies conducted in Chinese Han population from Hong Kong, Yangtze River region, and Southern region of mainland China replicated the association between AIS and rs1190870. However, there is limited published data about the association of rs11190870 with AIS in East Asian population.

METHODS

A systematic search of all relevant studies published through August 2013 was conducted using the MEDLINE, EMBASE, OVID, and ScienceDirect. Single nucleotide polymorphism of rs11190870 was evaluated. The included studies were assessed in the analysis of the following allele model: T allele versus C allele for the allele-level comparison; (b) TC + TT versus CC for dominant model of T allele; (c) TT versus TC + CC for recessive model of T allele, and (d) TT versus CC for extreme genotype.

RESULTS

Four studies with 8415 total participants (2889 patients with AIS and 5526 controls), who were all East Asian population, were eligible for inclusion. We searched for genotypes T allele versus C allele, TT versus TC + CC, TC + TT versus CC, and TT versus CC in a fixed/random-effects model. The effect summary odds ratios and 95 % confidence intervals were obtained, which shows significant association between rs11190870 and AIS in East Asian populations (all genetic models P < 0.001). Subgroup analyses were conducted according to sex. The results showed a significant association between rs11190870 and AIS in female (all genetic models, P < 0.001) but not in male (all genetic models, P > 0.05).

CONCLUSION

The present meta-analysis demonstrated that the T allele of single nucleotide polymorphism rs11190870 may be a major susceptibility locus in the East Asian population with AIS, especially in female.

LEVEL OF EVIDENCE

1.

Microduplication 10q24.31 in a Spanish girl with scoliosis and myopathy: the critical role of LBX

LBX1 plays a cardinal role in neuronal and muscular development in animal models. Its function in humans is unknown; it has been reported as a candidate gene for idiopathic scoliosis. Our goal is to document the first clinical case of a microduplication at 10q24.31 (chr10:102927883-103053612, hg19), affecting exclusively LBX1. The patient, a 12-year-old girl, showed attention problems, dyspraxia, idiopathic congenital scoliosis, and marked hypotrophy of paravertebral muscles. Her paternal aunt had a severe and progressive myopathy with a genetic study that revealed the same duplication. We propose to consider genetic studies, particularly of LBX1, in patients with scoliosis and/or hypotrophy-hypoplasia of paravertebral muscles of unknown etiology.

Ultrastructure of Intervertebral Disc and Vertebra-Disc Junctions Zones as a Link in Etiopathogenesis of Idiopathic Scoliosis

Background Context. There is no general accepted theory on the etiology of idiopathic scoliosis (IS). An important role of the vertebrae endplate physes (VEPh) and intervertebral discs (IVD) in spinal curve progression is acknowledged, but ultrastructural mechanisms are not well understood. Purpose. To analyze the current literature on ultrastructural characteristics of VEPh and IVD in the context of IS etiology. Study Design/Setting. A literature review. Results. There is strong evidence for multifactorial etiology of IS. Early wedging of vertebra bodies is likely due to laterally directed appositional bone growth at the concave side, caused by a combination of increased cell proliferation at the vertebrae endplate and altered mechanical properties of the outer annulus fibrosus of the adjacent IVD. Genetic defects in bending proteins necessary for IVD lamellar organization underlie altered mechanical properties. Asymmetrical ligaments, muscular stretch, and spine instability may also play roles in curve formation. Conclusions. Development of a reliable, cost effective method for identifying patients at high risk for curve progression is needed and could lead to a paradigm shift in treatment options. Unnecessary anxiety, bracing, and radiation could potentially be minimized and high risk patient could receive surgery earlier, rendering better outcomes with fewer fused segments needed to mitigate curve progression.

The association study of calmodulin 1 gene polymorphisms with susceptibility to adolescent idiopathic scoliosis

Objective. Idiopathic scoliosis is the most common pediatric spinal deformity affecting 1% to 3% of the population, and adolescent idiopathic scoliosis (AIS) accounts for approximately 80% of these cases; however, the etiology and pathogenesis of AIS are still uncertain. The current study aims to identify the relationship between calmodulin 1 (CALM1) gene and AIS predisposition, to identify the relationship between the genotypes of the SNPs and the clinical phenotypes of AIS. Methods. 146 AIS patients and 146 healthy controls were enrolled into this case-control study. 12 single nucleotide polymorphisms (SNPs) candidates in CALM1 gene were selected to determine the relationship between CALM1 gene and AIS predisposition. Case-only study was performed to determine the effects of these variants on the severity of the condition. Results. Three SNPs from 12 candidates were found to be associated with AIS predisposition. The ORs were observed as 0.549 (95% CI 0.3519–0.8579, P = 0.0079), 0.549 (95% CI 0.3519–0.8579, P = 0.0079), and 1.6139 (95% CI 1.0576–2.4634, P = 0.0257) for rs2300496, rs2300500, and rs3231718, respectively. There was no statistical difference between main curve, severity, and genotype distributions of all of 12 SNPs. Conclusion. Genetic variants of CALM1 gene are associated with AIS susceptibility.