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

Genetics and pathogenesis of scoliosis

Background

Scoliosis is defined as a lateral spine curvature of at least 10° with vertebral rotation, as seen on a posterior-anterior radiograph, often accompanied by reduced thoracic kyphosis. Scoliosis affects all age groups: idiopathic scoliosis is the most common spinal disorder in children and adolescents, while adult degenerative scoliosis typically affects individuals over fifty. In the United States, approximately 3 million new cases of scoliosis are diagnosed annually, with a predicted increase in part due to global aging. Despite its prevalence, the etiopathogenesis of scoliosis remains unclear.

Methods

This comprehensive review analyzes the literature on the etiopathogenetic evidence for both idiopathic and adult degenerative scoliosis. PubMed and Google Scholar databases were searched for studies on the genetic factors and etiopathogenetic mechanisms of scoliosis development and progression, with the search limited to articles in English.

Results

For idiopathic scoliosis, genetic factors are categorized into three groups: genes associated with susceptibility, disease progression, and both. We identify gene groups related to different biological processes and explore multifaceted pathogenesis of idiopathic scoliosis, including evolutionary adaptations to bipedalism and developmental and homeostatic spinal aberrations. For adult degenerative scoliosis, we segregate genetic and pathogenic evidence into categories of angiogenesis and inflammation, extracellular matrix degradation, neural associations, and hormonal influences. Finally, we compare findings in idiopathic scoliosis and adult degenerative scoliosis, discuss current limitations in scoliosis research, propose a new model for scoliosis etiopathogenesis, and highlight promising areas for future studies.

Conclusions

Scoliosis is a complex, multifaceted disease with largely enigmatic origins and mechanisms of progression, keeping it under continuous scientific scrutiny.

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.

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.

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.

Differential Regulation of POC5 by ERα in Human Normal and Scoliotic Cells

Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional spinal deformity. The incidence of AIS in females is 8.4 times higher than in males. Several hypotheses on the role of estrogen have been postulated for the progression of AIS. Recently, Centriolar protein gene POC5 (POC5) was identified as a causative gene of AIS. POC5 is a centriolar protein that is important for cell cycle progression and centriole elongation. However, the hormonal regulation of POC5 remains to be determined. Here, we identify POC5 as an estrogen-responsive gene under the regulation of estrogen receptor ERα in normal osteoblasts (NOBs) and other ERα-positive cells. Using promoter activity, gene, and protein expression assays, we found that the POC5 gene was upregulated by the treatment of osteoblasts with estradiol (E2) through direct genomic signaling. We observed different effects of E2 in NOBs and mutant POC5^A429V AIS osteoblasts. Using promoter assays, we identified an estrogen response element (ERE) in the proximal promoter of POC5, which conferred estrogen responsiveness through ERα. The recruitment of ERα to the ERE of the POC5 promoter was also potentiated by estrogen. Collectively, these findings suggest that estrogen is an etiological factor in scoliosis through the deregulation of POC5.

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.

Exploring the association between specific genes and the onset of idiopathic scoliosis: a systematic review

Background

Idiopathic Scoliosis (IS) is the most common spinal deformity in adolescents, accounting for 80% of all spinal deformities. However, the etiology remains uncertain in most cases, being identified as Adolescent Idiopathic Scoliosis (AIS). IS treatments range from observation and sport to bracing or surgery. Several risk factors including sex and familiarity, have been linked with IS. Although there are still many uncertainties regarding the cause of this pathology, several studies report a greater incidence of the defect in families in which at least one other first degree relative is affected. This study systematically reviews the available literature to identify the most significant genes or variants related to the development and onset of IS.

Methods

The research question was formulated using a PIOS approach on the following databases: Medline, Embase, Cinahl, Scopus, Web of Science and Google Scholar. The search was performed from July to August 2021, and articles from the inception of the database to August 2021 were searched.

Results

24 of the 919 initially identified studies were included in the present review. The 24 included studies observed a total of 16,316 cases and 81,567 controls. All the considered studies stated either the affected gene and/or specific SNPs. CHD7, SH2B1, ESR, CALM1, LBX1, MATN1, CHL1, FBN1 and FBN2 genes were associated with IS development.

Conclusions

Although association can be found in some candidate genes the field of research regarding genetic association with the onset of IS still requires more information.

Genetic and serum markers in adult degenerative scoliosis: a literature review

STUDY DESIGN

Literature review.

OBJECTIVE

Adult degenerative scoliosis (ADS) is becoming a more prevalent diagnosis with an increasing elderly population. Our objective is to provide a literature review of genetic and serum markers in ADS.

METHODS

A literature review was conducted in the various databases from their inception to July 2020. Studies that reviewed any genetic or serum markers of ADS whether in detection or progression were selected. Studies that reviewed congenital scoliosis or adolescent idiopathic scoliosis (AIS) were excluded.

RESULTS

A total of 1447 titles were identified of which 14 were included in the final review. Two papers reported on serum markers pertaining to serum cartilage metabolites and pentosidine. Twelve studies reported on genetic markers including gene polymorphisms in estrogen receptors, parathyroid hormone receptors, interleukin 6, cyclooxygenase-2 (COX-2), COL2A1, GPRIN1, TRAIL, GRIN receptor, RIMS, LBX1 as well as copy number variations.

CONCLUSIONS

Serum markers of osteoarthritis and sarcopenia have been found to be significantly elevated in ADS patients as well. Numerous polymorphisms have been found in a variety of genes playing key roles in bone formation and regulation. Further research is needed in validating previous studies as well as identifying other biomarkers for patients at risk for developing ADS.

The landscape of GWAS validation; systematic review identifying 309 validated non-coding variants across 130 human diseases

Background

The remarkable growth of genome-wide association studies (GWAS) has created a critical need to experimentally validate the disease-associated variants, 90% of which involve non-coding variants.

Methods

To determine how the field is addressing this urgent need, we performed a comprehensive literature review identifying 36,676 articles. These were reduced to 1454 articles through a set of filters using natural language processing and ontology-based text-mining. This was followed by manual curation and cross-referencing against the GWAS catalog, yielding a final set of 286 articles.

Results

We identified 309 experimentally validated non-coding GWAS variants, regulating 252 genes across 130 human disease traits. These variants covered a variety of regulatory mechanisms. Interestingly, 70% (215/309) acted through cis-regulatory elements, with the remaining through promoters (22%, 70/309) or non-coding RNAs (8%, 24/309). Several validation approaches were utilized in these studies, including gene expression (n = 272), transcription factor binding (n = 175), reporter assays (n = 171), in vivo models (n = 104), genome editing (n = 96) and chromatin interaction (n = 33).

Conclusions

This review of the literature is the first to systematically evaluate the status and the landscape of experimentation being used to validate non-coding GWAS-identified variants. Our results clearly underscore the multifaceted approach needed for experimental validation, have practical implications on variant prioritization and considerations of target gene nomination. While the field has a long way to go to validate the thousands of GWAS associations, we show that progress is being made and provide exemplars of validation studies covering a wide variety of mechanisms, target genes, and disease areas.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01216-w.

Undergraduate laboratory series that employs a complete polymerase chain reaction-restriction fragment length polymorphism experiment for determination of a single nucleotide polymorphism in CYP2R1 gene

Nowadays, novel Biochemistry lab techniques are being introduced at a very fast pace in scientific research. This requires development of new labs for undergraduate Biochemistry courses to equip the students with up-to-date techniques. However, the time limit of Biochemistry labs for undergraduate students represents a major obstacle. This article presents a clear set of laboratory exercises designed to introduce students to the use of polymerase chain reaction-restriction-fragment length polymorphism (PCR-RFLP) as a means of detection of genetic variants. Three consecutive lab experiments have been designed for the undergraduate students to serve this purpose. The first session was performed in a computer lab (dry lab) where students were taught how to obtain a specific gene sequence, identify an exact single nucleotide polymorphism location, choose the target sequence for amplification, design specific primers for this particular sequence and choose the most suitable restriction enzyme from web tools. The second and third lab sessions were performed as wet labs where in the second lab session, students optimized PCR conditions and performed a successful PCR. The PCR products were kept for use in the third lab session where they utilized the selected restriction enzyme and carried out gel electrophoresis to determine the exact genotype.

Aberrant interaction between mutated ADAMTSL2 and LTBP4 is associated with adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a complex spinal structure deformity with a prevalence of 1%-3%. Genetic and hereditary factors have been associated with the etiology of AIS. However, previous studies mainly focused on common single nucleotide polymorphisms which confer modest disease risk. Recently, rare variants in FBN1 and other extracellular matrix genes have been implicated in AIS, suggesting a potential overlapping disease etiology between AIS and hereditary connective tissue disorders (HCTD). In this study, we systematically analyzed rare variants in a set of HCTD-related genes in 302 AIS patients using exome sequencing. We firstly focused on pathogenic variants based on a monogenic inheritance and identified nine disease-associated variants in FBN1, COL11A1, COL11A2 and TGFBR2. We then explored the potential interactions between variants in different genes based on the case-control statistics. We identified three ADAMTSL2-LTBP4 variant pairs in three AIS patients and none in controls. Furthermore, we revealed that the variant pairs identified in these genes could affect the interaction between ADAMTSL2 and LTBP4 and upregulate TGF-β signaling pathway in human fibroblasts. Our findings supported that the aberrant interaction between mutated ADAMTSL2 and LTBP4 was associated with AIS.

Characterization of a novel Lbx1 mouse loss of function strain

Adolescent Idiopathic Scoliosis (AIS) is the most common type of spine deformity affecting 2-3% of the population worldwide. The etiology of this disease is still poorly understood. Several GWAS studies have identified single nucleotide polymorphisms (SNPs) located near the gene LBX1 that is significantly correlated with AIS risk. LBX1 is a transcription factor with roles in myocyte precursor migration, cardiac neural crest specification, and neuronal fate determination in the neural tube. Here, we further investigated the role of LBX1 in the developing spinal cord of mouse embryos using a CRISPR-generated mouse model expressing a truncated version of LBX1 (Lbx1^Δ). Homozygous mice died at birth, likely due to cardiac abnormalities. To further study the neural tube phenotype, we used RNA-sequencing to identify 410 genes differentially expressed between the neural tubes of E12.5 wildtype and Lbx1^Δ/Δ embryos. Genes with increased expression in the deletion line were involved in neurogenesis and those with broad roles in embryonic development. Many of these genes have also been associated with scoliotic phenotypes. In comparison, genes with decreased expression were primarily involved in skeletal development. Subsequent skeletal and immunohistochemistry analysis further confirmed these results. This study aids in understanding the significance of links between LBX1 function and AIS susceptibility.

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.

The role of gene therapy as a valuable treatment modality for multiple spinal pathologies

The world of biomedical research has led to several breakthroughs in the treatment of various spinal pathologies. As we investigate chronic pathologies of the spine, we start to unravel the underlying molecular mechanisms through a careful analysis of mutated genetic sequences. Investigations have led to gene therapy being explored for its potential as a treatment modality. Despite only about 2% of current gene therapy trials being centered for spinal pathologies, spinal diseases are valuable targets in gene therapy administration. Through a comprehensive literature review, our objective is to discuss the molecular mechanisms behind gene therapy for spinal pathologies, the genetic targets, along with the outcomes, success, and possible pitfalls in gene therapy research and administration. The emerging development of robotic technologies and intelligent carriers are recognized as a promising innovative technique for increasing the efficiency of gene therapy and potentially resolving spinal pathologies.

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.

Estrogen Receptors (ESRs) Mutations in Adolescent Idiopathic Scoliosis: A Cross-Sectional Study

Background

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity, but its etiology is unclear. Multiple genetic mutations have been reported to be associated with AIS.

Material/Methods

We enrolled a cohort of 113 surgically treated AIS patients with available parental subjects from the Peking Union Medical College Hospital. We performed whole-exome sequencing in 10 trio families and whole-genome sequencing in 103 singleton patients. Luciferase assay was used to detect the functional alterations of candidate ESR1 and ESR2 variants.

Results

Using a de novo strategy, a missense variant in ESR1 (c.868A>G) was selected as a candidate gene for AIS. The main Cobb angle of this patient was 41° (T6–T10). Another potential pathogenic variant in ESR2 (c.236T>C) was identified. The main curve of the patient was 45° at T10–L3. The transactivation capacities of the mutated ESR1 and ESR2 protein were both significantly decreased (p=0.026 and 0.014, respectively).

Conclusions

Potential pathogenic variants in ESR1 and ESR2 were identified in 113 AIS patients, suggesting that genetic mutations in ESR1/2 were associated with the risk of AIS.

Whole-Genome Methylation Analysis of Phenotype Discordant Monozygotic Twins Reveals Novel Epigenetic Perturbation Contributing to the Pathogenesis of Adolescent Idiopathic Scoliosis

Background: Adolescent idiopathic scoliosis (AIS) is a complex disease affecting a large number of teenagers, especially in female. This study reveals novel epigenetic perturbation to the pathogenesis of AIS.

Methods: A female monozygotic (MZ) twin pair discordant for AIS were examined for whole-exome sequencing and epigenome difference. Sets of differentially methylated regions (DMRs) were validated using MethylTarget™ method in 20 AIS female patients and 20 healthy female controls.

Results: Few exome difference but several potential DMRs were found between the MZ twins. We identified 313 hypermethylated DMRs and 397 hypomethylated DMRs, respectively. Most of them were enriched in the MAPK and PI3K-Akt signaling pathway, which may contribute to the discordance of AIS. Several DMRs related to scoliosis genes were tested, and the NDN: TSS-DMR (chr15:23932133-23932304, hg19) was confirmed in additional samples. The methylation level of this DMR was significantly higher in the AIS group than in the control group (p = 0.04).

Conclusions: We described the epigenome difference in an AIS female discordant MZ twin pair using Whole Genome Bisulfite Sequencing (WGBS). The NDN: TSS-DMR had higher methylation level in female AIS, which can help elucidate the potential etiology of AIS.

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.

The Progress of CRISPR/Cas9-Mediated Gene Editing in Generating Mouse/Zebrafish Models of Human Skeletal Diseases

Genetic factors play a substantial role in the etiology of skeletal diseases, which involve 1) defects in skeletal development, including intramembranous ossification and endochondral ossification; 2) defects in skeletal metabolism, including late bone growth and bone remodeling; 3) defects in early developmental processes related to skeletal diseases, such as neural crest cell (NCC) and cilia functions; 4) disturbance of the cellular signaling pathways which potentially affect bone growth. Efficient and high-throughput genetic methods have enabled the exploration and verification of disease-causing genes and variants. Animal models including mouse and zebrafish have been extensively used in functional mechanism studies of causal genes and variants. The conventional approaches of generating mutant animal models include spontaneous mutagenesis, random integration, and targeted integration via mouse embryonic stem cells. These approaches are costly and time-consuming. Recent development and application of gene-editing tools, especially the CRISPR/Cas9 system, has significantly accelerated the process of gene-editing in diverse organisms. Here we review both mice and zebrafish models of human skeletal diseases generated by CRISPR/Cas9 system, and their contributions to deciphering the underpins of disease mechanisms.

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.

Neuroinflammatory signals drive spinal curve formation in zebrafish models of idiopathic scoliosis

The etiopathogenesis of idiopathic scoliosis (IS), a highly prevalent spinal deformity that occurs in the absence of obvious congenital or physiological abnormalities, is poorly understood. Although recent zebrafish genetic studies have linked cilia motility and cerebrospinal fluid (CSF) flow defects with scoliosis progression, underlying mechanisms were not identified. Here, we use next-generation sequencing and conditional genetic methodologies to define the spatial and biological origins of spinal curve formation in ptk7 mutant zebrafish, a faithful IS model. We demonstrate that focal activation of proinflammatory signals within the spinal cord is associated with, and sufficient for, induction of spinal curvatures. Furthermore, administration of acetylsalicylic acid (aspirin) or N-acetylcysteine (NAC) to juvenile ptk7 mutants significantly reduces the incidence and/or severity of scoliosis phenotypes. Together, our results implicate neuroinflammation, downstream of CSF defects, in spinal curve formation and provide intriguing evidence that simple immunomodulating therapies might prove effective in managing idiopathic-like spinal deformities.

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.

The coexistence of copy number variations (CNVs) and single nucleotide polymorphisms (SNPs) at a locus can result in distorted calculations of the significance in associating SNPs to disease

With the recent advance in genome-wide association studies (GWAS), disease-associated single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) have been extensively reported. Accordingly, the issue of incorrect identification of recombination events that can induce the distortion of multi-allelic or hemizygous variants has received more attention. However, the potential distorted calculation bias or significance of a detected association in a GWAS due to the coexistence of CNVs and SNPs in the same genomic region may remain under-recognized. Here we performed the association study within a congenital scoliosis (CS) cohort whose genetic etiology was recently elucidated as a compound inheritance model, including mostly one rare variant deletion CNV null allele and one common variant non-coding hypomorphic haplotype of the TBX6 gene. We demonstrated that the existence of a deletion in TBX6 led to an overestimation of the contribution of the SNPs on the hypomorphic allele. Furthermore, we generalized a model to explain the calculation bias, or distorted significance calculation for an association study, that can be 'induced' by CNVs at a locus. Meanwhile, overlapping between the disease-associated SNPs from published GWAS and common CNVs (overlap 10%) and pathogenic/likely pathogenic CNVs (overlap 99.69%) was significantly higher than the random distribution (p < 1 × 10^-6 and p = 0.034, respectively), indicating that such co-existence of CNV and SNV alleles might generally influence data interpretation and potential outcomes of a GWAS. We also verified and assessed the influence of colocalizing CNVs to the detection sensitivity of disease-associated SNP variant alleles in another adolescent idiopathic scoliosis (AIS) genome-wide association study. We proposed that detecting co-existent CNVs when evaluating the association signals between SNPs and disease traits could improve genetic model analyses and better integrate GWAS with robust Mendelian principles.

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.

Genetic polymorphisms of GPR126 are functionally associated with PUMC classifications of adolescent idiopathic scoliosis in a Northern Han population

GPR126 has been identified to be associated with AIS (Adolescent Idiopathic Scoliosis) in different populations, but data on the northern Chinese population are unavailable. Additionally, it is important to know the exact clinical phenotypes associated with specific genetic polymorphisms. Fourteen SNP (single nucleotide polymorphism) loci in GPR126 were genotyped in 480 northern Chinese Han AIS patients and 841 controls. These patients were classified into three types based on the PUMC classification system. Luciferase assays were used to investigate their regulation of GPR126 transcription activity. Combined and stratified genotype-phenotype association analyses were conducted. The alleles rs225694, rs7774095 and rs2294773 were significantly associated with AIS (P = 0.021, 0.048 and 0.023, respectively). rs225694 and rs7774095 potentially have regulatory functions for the GRP126 gene. Correlation analysis revealed that allele A of rs225694 was a risk allele only for PUMC type II AIS (P = 0.036) and allele G of rs2294773 was a risk allele only for PUMC type I AIS (P = 0.018). In summary, rs225694, rs7774095 and rs2294773 are significantly associated with disease in northern Chinese Han AIS patients. The SNPs rs225694 and rs2294773 are associated with different AIS PUMC classifications.