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

Dysregulation of the ghrelin/RANKL/OPG pathway in bone mass is related to AIS osteopenia

BACKGROUND

Osteopenia has been well documented in adolescent idiopathic scoliosis (AIS), and ghrelin has been shown to have a positive effect on bone metabolism. However, the circulating level of ghrelin is increased in AIS osteopenia, and the relationship between ghrelin and low bone mass in AIS osteopenia remains unclear.

METHOD

A total of 563 AIS and 281 age-matched controls were recruited for this study. Anthropometry and bone mass were measured in all participants. Plasma ghrelin levels were determined by enzyme-linked immunosorbent assay (ELISA) in both AIS and control groups. An improved multiplex ligation detection reaction was performed to analyze single-nucleotide polymorphisms (SNPs). Facet joints were collected and subjected to immunohistochemistry; osteogenic gene and protein expression was also measured. Furthermore, primary cells were extracted from facet joints and bone marrow to observe the response to ghrelin stimulation.

RESULTS

The body mass index was lower and circulating ghrelin was markedly higher in the AIS osteopenia group than in the control group. No significant difference was observed in four ghrelin level-related SNPs between the AIS osteopenia and control groups. RNA and protein analyses revealed higher RANKL/OPG and lower runx2 levels in AIS cancellous bone. Compared with normal primary osteoblasts and BMSCs, AIS osteopenia primary cells were insensitive to the same ghrelin concentration gradient and showed lower osteogenic ability, increases in OPG and decreases in RANKL.

CONCLUSION

Our results indicate that high circulating ghrelin levels may not result from gene variations in AIS osteopenia. Dysregulation of the ghrelin/RANKL/OPG pathway may lead to decreased osteogenic ability of osteoblasts and BMSCs, which may be related to lower bone mass in AIS osteopenia.

Quantitation Analysis of PCDH10 Methylation in Adolescent Idiopathic Scoliosis Using Pyrosequencing Study

STUDY DESIGN

A retrospective and comparative study.

OBJECTIVE

To evaluate the difference of DNA methylation in protocadherin10 (PCDH10) genes between adolescent idiopathic scoliosis (AIS) and normal controls, and to assess the association between DNA methylation and the etiology of AIS.

SUMMARY OF BACKGROUND DATA

The PCDH10 gene showed abnormal expression in AIS. However, the mechanism was still unclear. DNA methylation was an important epigenetic mechanism at the interface between genetics and environmental phenotype, seeming to be a suitable epigenetic mark for the abnormal expression of PCDH10 in AIS.

METHODS

There were 50 AIS patients and 50 healthy controls included in the study. The peripheral blood sample of each participant was taken. The pyrosequencing assay was used to assess the methylation status of PCDH10 promoter and real time PCR (RT-PCR) was used to detect the PCDH10 gene expression. The comparison analysis was performed using independent t test and 2-tailed Pearson coefficients was calculated for the correlation analysis.

RESULTS

The average methylation level was 4.32 ± 0.73 in AIS patients and 3.14 ± 0.97 in healthy controls (P < 0.001). The PCDH10 gene expression was 0.23 ± 0.04 in AIS patients and 0.36 ± 0.08 in normal controls (P < 0.0001). Statistically significant linear correlation was found between PCDH10 gene methylation level and Cobb angle of major curve (P < 0.001). Besides, a significant negative correlation between PCDH10 methylation and PCDH10 gene expression was found (P < 0.001).

CONCLUSION

AIS patients were associated with high DNA methylation level and low gene expression of PCDH10 gene rather than normal controls. The high methylation level indicated high Cobb angle of major curves in AIS. The abnormal DNA methylation may widely exist and serve as a potential mechanism for AIS.

LEVEL OF EVIDENCE

3.

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

STUDY DESIGN

A genetic case-control association study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

PIEZO2: A Novel Molecule Involved in the Development of AIS

STUDY DESIGN

A case-control study.

OBJECTIVE

This study aimed to investigate the potential role of PIEZO2 gene in the development of AIS.

SUMMARY OF BACKGROUND DATA

Mutations of PIEZO2 gene have been reported to be associated with progressive scoliosis and impaired proprioception. Previous studies showed that patients with AIS may have impaired proprioception. However, there is lack of knowledge concerning the mechanism underlying the proprioception of AIS patients and the role of PIEZO2 gene in the etiology of AIS.

METHODS

Proprioception tests were performed in both AIS patients and age-matched healthy controls. Based on the falling risk scores, AIS patients were divided into impaired proprioception group and unimpaired proprioception group. Paraspinal muscle was collected from 34 AIS patients during surgery. The tissue expression of PIEZO2 was compared between the impaired group and the unimpaired group. In addition, the average number of muscle fibers in the muscle spindle was compared between the two groups.

RESULTS

Proprioception test showed that patients had significantly higher falling index (41.7 ± 16.5 vs. 11.3 ± 8.3, P = 0.004). In addition, the expression of PIEZO2 gene was remarkably decreased in the impaired group (0.51 ± 0.24 vs. 1.00 ± 0.33, P = 0.04). The average number of muscle fibers in the muscle spindle was significantly decreased in AIS patients of the impaired group than those of the unimpaired group (2.2 ± 1.3 vs. 3.5 ± 2.1, P = 0.04). PIEZO2 expression level was remarkably correlated with the average number of muscle fibers in the muscle spindle (r = 0.352, P = 0.04).

CONCLUSION

Proprioception is remarkably impaired in patients with AIS. Abnormal expression of PIEZO2 may play a role in AIS via altered proprioception and number of muscle fibers in the muscle spindles. Further investigation is warranted to illustrate the mechanism regulating PIEZO2 expression in AIS.

LEVEL OF EVIDENCE

4.

CHD7 gene polymorphisms in female patients with idiopathic scoliosis

BACKGROUND

The CHD7 (chromosome domain helicase DNA binding protein 7) gene has been associated with familial idiopathic scoliosis (IS) in families of European descent. The CHD7 single-nucleotide polymorphisms have never been studied in Polish Caucasian IS patients.

METHODS

The aim of this study was to investigate the relationship of CHD7 gene polymorphisms with susceptibility to or progression of IS in Polish Caucasian females. The study group comprised 211 females who underwent clinical, radiological and genetic examination. The study group was analyzed in three subgroups according to: (1) Cobb angle (Cobb angle ≤30° vs. Cobb angle ≥35°), (2) age of diagnosis (adolescent IS vs. early-onset IS) and (3) rate of progression (non-progressive vs. slowly progressive vs. rapidly progressive IS). The control group comprised 83 females with no scoliosis and with a negative family history who underwent clinical and genetic examination. In total six CHD7 gene polymorphisms were examined. Three polymorphisms (rs1017861, rs13248429, and rs4738813) were examined by RFLP (restriction fragment length polymorphism) analysis, and three were quantified by Sanger sequencing (rs78874766, rs4738824, and rs74797613).

RESULTS

In rs13248429, rs78874766, and rs74797613 polymorphisms only the wild allele was present. The rs1017861 polymorphism demonstrated an association with IS susceptibility (p < 0.01). Two polymorphisms, rs1017861 and rs4738813, were associated with curve severity and progression rate (p < 0.05). None of the evaluated polymorphisms in CHD7 gene showed any association with the age of IS onset.

CONCLUSIONS

The polymorphism rs1017861 in CHD7 gene showed an association with IS susceptibility. Two polymorphisms (rs1017861 and rs4738813) were associated with curve severity and progression rate. None of the evaluated polymorphisms in CHD7 gene showed any association with the age of IS onset. Further evaluation of CHD7 gene should be considered as IS modifying factor.

ARL3, a small GTPase with a functionally conserved role in primary cilia and immune synapses

The primary cilium and the immunological synapse are both specialized functional plasma membrane domains that share several similarities. Signalling output of membrane domains is regulated, spatially and temporally, by segregating and focusing lipids and proteins. ARL3, a small GTPase, plays a major role in concentrating lipid-modified proteins in both the immunological synapse and the primary cilia. Here in this review we will introduce the role of ARL3 in health and disease and its role in polarizing signalling at the primary cilia and immunological synapses.

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

Background:

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

Methods:

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

Results:

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

Conclusion:

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

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

STUDY DESIGN

A genetic association study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

N/A.

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

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

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

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 organizing principle of GABAB receptor complexes: Physiological and pharmacological implications

GABA_B receptors (GBRs), the G protein-coupled receptors for the neurotransmitter γ-aminobutyric acid (GABA), regulate synaptic transmission at most synapses in the brain. Proteomic approaches revealed that native GBR complexes assemble from an inventory of ~30 proteins that provide a molecular basis for the functional diversity observed with these receptors. Studies with reconstituted GBR complexes in heterologous cells and complementary knockout studies have allowed to identify cellular and physiological functions for obligate and several non-obligate receptor components. It emerges that modular association of receptor components in space and time generates a variety of multiprotein receptor complexes with different localizations, kinetic properties and effector channels. This article summarizes current knowledge on the organizing principle of GBR complexes. We further discuss unanticipated receptor functions, links to disease and opportunities for drug discovery arising from the identification of novel receptor components.

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.

Investigating Role of IRX Family in Development of Female Adolescent Idiopathic Scoliosis: Which One Is Real Cause?

BACKGROUND

Previous studies showed that several variants located around the IRX family may have functional roles in the development of adolescent idiopathic scoliosis (AIS). However, there was lack of knowledge concerning the target gene of the region on 5p13.3 and the role of IRX genes in the etiology of AIS. This study aimed to validate the relationship between the IRX family and AIS in a large-scale general population and to further investigate the target gene of the region, which was associated with AIS.

METHODS

SNP rs12517904 and rs117273909 were genotyped in 1323 patients and 1670 age-matched healthy controls. Paraspinal muscle was collected from 70 AIS patients and 20 congenital scoliosis patients. Student's t-test was used to compare the IRX1 expression between AIS patients and controls. The 1-way analysis of variance test was used to compare the expression of the IRX genes among different genotypes.

RESULTS

For rs12517904, patients were found to have a significantly higher frequency of allele T than the controls (37.6% vs. 34.7%, P = 0.02). Allele T can significantly add to the risk of AIS with an odds ratio of 1.14. AIS patients were found to have significantly lower IRX1 expression than the controls. Patients with genotype TT were found to have significantly lower IRX1 expression than those with genotype GG.

CONCLUSIONS

Our large-scale case control study validated that the IRX1 gene could be the disease-associated gene of AIS. The variant rs12517904 of the IRX1 gene is functionally associated with the development of AIS in the Chinese population. The role of IRX1 in the onset of AIS is worthy of further investigation.

Adiponectin regulates bone mass in AIS osteopenia via RANKL/OPG and IL6 pathway

BACKGROUND

Osteopenia have been well documented in adolescent idiopathic scoliosis (AIS). Adiponectin has been shown to be inversely proportional to body mass index and to affect bone metabolism. However, the circulating levels of adiponectin and the relationship between adiponectin and low bone mass in AIS remain unclear.

METHODS

A total of 563 AIS and 281 age-matched controls were recruited for this study. Anthropometry and bone mass were measured in all participants. Plasma adiponectin levels were determined by enzyme-linked immunosorbent assay (ELISA) in the AIS and control groups. An improved multiplex ligation detection reaction was performed to study on single nucleotide polymorphism. Facet joints were collected and used to measure the microstructure, the expression of RANKL, OPG, osteoblast-related genes, inflammatory factors, adiponectin and its receptors by qPCR, western blotting and immunohistochemistry. Furthermore, primary cells were extracted from facet joints to observe the reaction after adiponectin stimulation.

RESULTS

Compared with the controls, lower body mass index and a marked increase in circulating adiponectin were observed in AIS osteopenia (17.09 ± 1.09 kg/m² and 21.63 ± 10.30 mg/L). A significant difference in the presence of rs7639352
was detected in the AIS osteopenia, AIS normal bone mass and control groups. The T allele showed a significant higher proportion in AIS osteopenia than AIS normal bone mass and control groups (41.75% vs 31.3% vs 25.7%, p < 0.05). micro-CT demonstrated that the AIS convex side had a significant lower bone volume than concave side. RNA and protein analyses showed that in cancellous bone, higher RANKL/OPG and adipoR1 levels and lower runx2 levels were observed, and in cartilage, higher adipoR1 and IL6 levels were observed in AIS. Furthermore, convex side had higher RANKL/OPG, IL6 and adipoR1 than concave side. Compared with normal primary cells, convex side primary cells showed the most acute action, and concave side primary cells showed the second-most acute action when exposed under same adiponectin concentration gradient.

CONCLUSION

Our results indicated that high circulating adiponectin levels may result from gene variations in AIS osteopenia. Adiponectin has a negative effect on bone metabolism, and this negative effect might be mediated by the ADR1-RANKL/OPG and ADR1-IL6 pathways.

Distal chromosome 16p11.2 duplications containing SH2B1 in patients with scoliosis

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) is a common musculoskeletal disorder with strong evidence for a genetic contribution. CNVs play an important role in congenital scoliosis, but their role in idiopathic scoliosis has been largely unexplored.

METHODS

Exome sequence data from 1197 AIS cases and 1664 in-house controls was analysed using coverage data to identify rare CNVs. CNV calls were filtered to include only highly confident CNVs with >10 average reads per region and mean log-ratio of coverage consistent with single-copy duplication or deletion. The frequency of 55 common recurrent CNVs was determined and correlated with clinical characteristics.

RESULTS

Distal chromosome 16p11.2 microduplications containing the gene SH2B1 were found in 0.7% of AIS cases (8/1197). We replicated this finding in two additional AIS cohorts (8/1097 and 2/433), resulting in 0.7% (18/2727) of all AIS cases harbouring a chromosome 16p11.2 microduplication, compared with 0.06% of local controls (1/1664) and 0.04% of published controls (8/19584) (p=2.28×10^-11, OR=16.15). Furthermore, examination of electronic health records of 92 455 patients from the Geisinger health system showed scoliosis in 30% (20/66) patients with chromosome 16p11.2 microduplications containing SH2B1 compared with 7.6% (10/132) of controls (p=5.6×10^-4, OR=3.9).

CONCLUSIONS

Recurrent distal chromosome 16p11.2 duplications explain nearly 1% of AIS. Distal chromosome 16p11.2 duplications may contribute to scoliosis pathogenesis by directly impairing growth or by altering expression of nearby genes, such as TBX6. Individuals with distal chromosome 16p11.2 microduplications should be screened for scoliosis to facilitate early treatment.

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

STUDY DESIGN

A genetic association study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Spinal instrumentation in infants, children, and adolescents: a review

OBJECTIVEThe evolution of pediatric spinal instrumentation has progressed in the last 70 years since the popularization of the Harrington rod showing the feasibility of placing spinal instrumentation into the pediatric spine. Although lacking in pediatric-specific spinal instrumentation, when possible, adult instrumentation techniques and tools have been adapted for the pediatric spine. A new generation of pediatric neurosurgeons with interest in complex spine disorder has pushed the field forward, while keeping the special nuances of the growing immature spine in mind. The authors sought to review their own experience with various types of spinal instrumentation in the pediatric spine and document the state of the art for pediatric spine surgery.METHODSThe authors retrospectively reviewed patients in their practice who underwent complex spine surgery. Patient demographics, operative data, and perioperative complications were recorded. At the same time, the authors surveyed the literature for spinal instrumentation techniques that have been utilized in the pediatric spine. The authors chronicle the past and present of pediatric spinal instrumentation, and speculate about its future.RESULTSThe medical records of the first 361 patients who underwent 384 procedures involving spinal instrumentation from July 1, 2007, to May 31, 2018, were analyzed. The mean age at surgery was 12 years and 6 months (range 3 months to 21 years and 4 months). The types of spinal instrumentation utilized included occipital screws (94 cases); C1 lateral mass screws (115 cases); C2 pars/translaminar screws (143 cases); subaxial cervical lateral mass screws (95 cases); thoracic and lumbar spine traditional-trajectory and cortical-trajectory pedicle screws (234 cases); thoracic and lumbar sublaminar, subtransverse, and subcostal polyester bands (65 cases); S1 pedicle screws (103 cases); and S2 alar-iliac/iliac screws (56 cases). Complications related to spinal instrumentation included hardware-related skin breakdown (1.8%), infection (1.8%), proximal junctional kyphosis (1.0%), pseudarthroses (1.0%), screw malpositioning (0.5%), CSF leak (0.5%), hardware failure (0.5%), graft migration (0.3%), nerve root injury (0.3%), and vertebral artery injury (0.3%).CONCLUSIONSPediatric neurosurgeons with an interest in complex spine disorders in children should develop a comprehensive armamentarium of safe techniques for placing rigid and nonrigid spinal instrumentation even in the smallest of children, with low complication rates. The authors' review provides some benchmarks and outcomes for comparison, and furnishes a historical perspective of the past and future of pediatric spine surgery.

Asymmetric expression of H19 and ADIPOQ in concave/convex paravertebral muscles is associated with severe adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is the most common paediatric spinal deformity. The etiology and pathology of AIS remain unexplained, and have been reported to involve a combination of genetic and epigenetic factors. Since paravertebral muscle imbalance plays an important role in the onset and progression of scoliosis, we aimed to investigate transcriptomic differences by RNA-seq and identify significantly differentially expressed transcripts in two sides of paravertebral muscle in AIS.

Methods

RNA-seq was performed on 5 pairs of paravertebral muscle from 5 AIS patients. Significantly differentially expressed transcripts were validated by quantitative reverse polymerase chain reaction. Gene expression difference was correlated to clinical characteristics.

Results

We demonstrated that ADIPOQ mRNA and H19 is significantly differentially expressed between two sides of paravertebral muscle, relatively specific in the context of AIS. Relatively low H19 and high ADIPOQ mRNA expression levels in concave-sided muscle are associated with larger spinal curve and earlier age at initiation. We identified miR-675-5p encoded by H19 as a mechanistic regulator of ADIPOQ expression in AIS. We demonstrated that significantly reduced CCCTC-binding factor (CCTF) occupancy in the imprinting control region (ICR) of the H19 gene in the concave-sided muscle contributes to down-regulated H19 expression.

Conclusions

RNA-seq revealed transcriptomic differences between two sides of paravertebral muscle in AIS patients. Our findings imply that transcriptomic differences caused by epigenetic factors in affected individuals may account for the structural and functional imbalance of paravertebral muscle, which can expand our etiologic understanding of this disease.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0049-y) contains supplementary material, which is available to authorized users.

A multi-ethnic meta-analysis confirms the association of rs6570507 with adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity and has a significant genetic background. Genome-wide association studies (GWASs) identified several susceptibility loci associated with AIS. Among them is a locus on chromosome 6q24.1 that we identified by a GWAS in a Japanese cohort. The locus is represented by rs6570507 located within GPR126. To ensure the association of rs6570507 with AIS, we conducted a meta-analysis using eight cohorts from East Asia, Northern Europe and USA. The analysis included a total of 6,873 cases and 38,916 controls and yielded significant association (combined P = 2.95 × 10^-20; odds ratio = 1.22), providing convincing evidence of the worldwide association between rs6570507 and AIS susceptibility. In silico analyses strongly suggested that GPR126 is a susceptibility gene at this locus.

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

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

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

STUDY DESIGN

A case-control study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

4.

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

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

VANGL1 Is Not Associated With the Susceptibility of Adolescent Idiopathic Scoliosis in the Chinese Population

STUDY DESIGN

A case-control study.

OBJECTIVE

To replicate the association between the VANGL1 gene and the susceptibility of AIS in the Chinese population.

SUMMARY OF BACKGROUND DATA

The mutations of VANGL1 gene were recently reported to be associated with AIS in the Danish population. However, there is a lack of replication in other populations. Further analysis of the functional role of VANGL1 in AIS was warranted.

METHODS

A total of 1481 female AIS patients and 1372 age-matched healthy controls were included in this study. single nucleotide variant (SNV)s c.407T > A and c.1318T > G were genotyped using allelic-specific multiple ligase detection reactions. single nucleotide polymorphism (SNP)s covering VANGL1 gene were selected using Haploview (v2.6). The associations between theses SNPs and AIS were investigated through Cochran-Armitage trend test by PLINK (v1.90). Relative mRNA expression of VANGL1 in the paraspinal muscles was analyzed for 30 patients and 24 age-matched controls. The difference of mRNA expression level between the two groups was analyzed with the Student t test.

RESULTS

There was no case of mutation for all the subjects. A total of 22 SNPs covering VANGL1 were analyzed. All the SNPs were found to have comparable distribution of genotype and allele frequency in the cases and the controls. Moreover, there was no significant difference regarding the mRNA expression of VANGL1 in the two groups.

CONCLUSION

VANGL1 gene is not associated with AIS in the Chinese population. Replication studies in other ethnic groups are warranted to further clarify the role of the VANGL1 gene in AIS.

LEVEL OF EVIDENCE

4.

Abnormal PITX1 gene methylation in adolescent idiopathic scoliosis: a pilot study

Background

The gene of pituitary homeobox 1 (PITX1) has been reported to be down-regulated in adolescent idiopathic scoliosis (AIS), of which the cause has not been well addressed. The abnormal DNA methylation was recently assumed to be an important mechanism for the down-regulated genes expression. However, the association between PITX1 promoter methylation and the etiology of AIS was not clear.

Methods

The peripheral blood samples of 50 AIS patients and 50 healthy controls were collected and the genomic DNA was extracted. The pyrosequencing assay was used to assess the methylation status of PITX1 promoter and real-time quantitative polymerase chain reaction (PCR) was used to detect the PITX1 gene expression. Comparison analysis was performed using independent t test and Chi-square tests, while correlation analysis were performed with 2-tailed Pearson coefficients.

Results

The mean methylation level was (3.52 ± 0.96)% in AIS and (1.40 ± 0.81)% in healthy controls (P < 0.0001). The PITX1 gene expression was 0.15 ± 0.08 in AIS and 0.80 ± 0.55 in healthy controls (P < 0.0001). The comparative analysis showed significant difference in age (P = 0.021) and Cobb angle of the main curve (P = 0.0001) between AIS groups with positive and negative methylation. The methylation level of 6 CpG sites in PITX1 promoters was significantly associated with Cobb angle of the main curve (P < 0.001) in AIS. No statistical relationship between PITX1 promoter methylation and gene expression was found in AIS (P = 0.842).

Conclusion

Significantly higher methylation level and lower PITX1 gene expression are found in AIS patients. PITX1 methylation is associated with Cobb angles of the main curves in AIS. DNA methylation thus plays an important role in the etiology and curve progression in AIS.

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

STUDY DESIGN

This is a genetic association study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Level III.

Genetic Variant of PAX1 Gene Is Functionally Associated With Adolescent Idiopathic Scoliosis in the Chinese Population

STUDY DESIGN

A genetic association study.

OBJECTIVE

To investigate the association between PAX1 gene and the susceptibility of adolescent idiopathic scoliosis (AIS) in the Chinese population and to further determine the functional variant regulating PAX1 expression in patients with AIS.

SUMMARY OF BACKGROUND DATA

In a previous study an enhancer locus of PAX1 was reported to be associated with the development of AIS in the Caucasian and the Japanese population. However, there is a paucity of knowledge concerning the functional role of PAX1 in the Chinese AIS population.

METHODS

The single-nucleotide polymorphisms rs6137473 and rs169311 were genotyped in 2914 patients and 3924 controls. The differences of genotype and allele distributions between patients and controls were calculated using chi-square test. Paraspinal muscles were collected from 84 patients with AIS. The one-way analysis of variance test was used to compare the mRNA expression of PAX1 among different genotypes.

RESULTS

Both rs6137473 and rs169311 were significantly associated with the susceptibility of AIS. Allele G of rs6137473 and allele A of rs169311 can significantly add to the risk of AIS with an odds ratio of 1.17 and 1.22, respectively. Moreover, there was significant difference regarding the expression of the PAX1 between the concave side and convex side of the patients. Patients with genotype AA of rs169311 had significantly decreased expression of PAX1 than those with genotype CC. As for rs6137473, no remarkable difference of PAX1 expression was found among the three genotypes.

CONCLUSION

The association between PAX1 and the susceptibility of AIS was successfully replicated in the Chinese population. Moreover, rs169311 could be a functional variant regulating the expression of PAX1 in the paraspinal muscles of AIS. Further functional analysis is warranted for a comprehensive knowledge on the contribution of this variant to the development of AIS.

LEVEL OF EVIDENCE

3.

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.

Circulating miRNAs as diagnostic biomarkers for adolescent idiopathic scoliosis

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

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

STUDY DESIGN

A case-control association study.

OBJECTIVES

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

Lack of association between AKAP2 and the susceptibility of adolescent idiopathic scoliosis in the Chinese population

Background

Adolescent idiopathic scoliosis (AIS) is a well characterized spinal deformity that affects millions of children world-wide. The role of genetic factor in the development of AIS has been of great interest, since obvious hereditary trend has been observed in AIS families. In a recent study of Chinese population, a novel mutation of AKAP2 was observed in a family with AIS, which was believed to play a role in the aetiopathogenesis of AIS. The purpose of this study was to investigate whether genetic variants of AKAP2 are associated with the susceptibility of AIS in Chinese population.

Methods

SNV c.2645A > C of AKAP2 was genotyped in 1254 AIS patients and 1232 normal controls using allelic-specific multiple ligase detection reactions. SNPs located within 5′ untranslated regions (UTR) and 3′ UTR of AKAP2 gene were selected using Haploview (v2.6). The GWAS database composed of 961 AIS patients and 1499 controls was referred to for the genotyping information. Relative mRNA expression of AKAP2 in peripheral blood was analyzed for 33 patients and 18 age-matched controls. Comparison between the cases and controls were performed using the Student’s t test. PLINK (v1.90) was used to calculate the association of each SNP with the disease by Cochran-Armitage trend test.

Results

All the patients and the controls presented a genotype of AA in c.2645A > C of AKAP2, and there was no case of mutation in any subject. A total of 116 SNPs covering AKAP2 were analyzed, and none of these SNPs was found to have significantly different allele frequency between the cases and the controls. The mRNA expression of AKAP2 in patients was comparable with that in the controls (1.9 ± 0.8 vs. 1.8 ± 0.7, p = 0.66).

Conclusions

Our large-scale replication study of the variants in AKAP2 gene did not support its association with the susceptibility of AIS in the Chinese population. In future study, functional studies of the previously reported rare variant are warranted to clarify whether the variant can regulate the expression of AKAP2. The whole AKAP2 gene can be sequenced in larger AIS cohorts to identify potentially missing mutations.

Knockdown of JARID2 inhibits the proliferation and invasion of ovarian cancer through the PI3K/Akt signaling pathway

Protein Jumonji (JARID2), a member of the family of JmjC domain-containing proteins, has been reported to serve an important role in tumor growth and metastasis. However, the expression pattern and role of JARID2 in ovarian cancer remains unclear. Therefore, in the present study, the role of JARID2 in ovarian cancer was investigated, as well as the underlying mechanisms. The results of the present study demonstrated that the expression of JARID2 is upregulated in human ovarian cancer cell lines. Furthermore, downregulation of JARID2 significantly suppressed proliferation, migration, invasion and epithelial‑mesenchymal transition in human ovarian cancer cells. Mechanistically, downregulation of JARID2 decreased the protein expression levels of phosphorylated phosphoinositide 3‑kinase (PI3K) and protein kinase B (Akt) in ovarian cancer cells. In conclusion the observations suggested that knockdown of JARID2 inhibited proliferation, migration and invasion in vitro through the inactivation of the PI3K/Akt signaling pathway. Therefore, JARID2 may represent a potential therapeutic target for the treatment of ovarian cancer.

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

The genetic architecture of adolescent idiopathic scoliosis (AIS) remains poorly understood. Here we present the result of a 4-stage genome-wide association study composed of 5,953 AIS patients and 8,137 controls. Overall, we identified three novel susceptible loci including rs7593846 at 2p14 near MEIS1 (Pcombined = 1.19 × 10-13, OR = 1.21, 95% CI = 1.10-1.32), rs7633294 at 3p14.1 near MAGI1 (Pcombined = 1.85 × 10-12, OR = 1.20, 95% CI = 1.09-1.32), and rs9810566 at 3q26.2 near TNIK (Pcombined = 1.14 × 10-11, OR = 1.19, 95% CI = 1.08-1.32). We also confirmed a recently reported region associated with AIS at 20p11.22 (Pcombined = 1.61 × 10-15, OR = 1.22, 95% CI = 1.12-1.34). Furthermore, we observed significantly asymmetric expression of Wnt/beta-catenin pathway in the bilateral paraspinal muscle of AIS patients, including beta-catenin, TNIK, and LBX1. This is the first study that unveils the potential role of Wnt/beta-catenin pathway in the development of AIS, and our findings may shed new light on the etiopathogenesis of AIS.

Volumetric and Fatty Infiltration Imbalance of Deep Paravertebral Muscles in Adolescent Idiopathic Scoliosis

Background

Several studies have described the differences in electromyographic activity and histological changes of paravertebral muscles in patients with adolescent idiopathic scoliosis (AIS). However, there is little knowledge about the muscle volumetric and fatty infiltration imbalance of patients with AIS.

Material/Methods

Thirty-four patients with AIS were evaluated with standardized anteroposterior (AP) and lateral standing films for the location and direction of the apex of scoliosis, coronal Cobb angle, apex vertebra translation, and thoracic kyphosis; and with magnetic resonance imaging (MRI) scan of the spine at the level of T4–L1. The muscle volume and fatty infiltration rate of bilateral deep paravertebral muscles at the level of upper end, apex, and lower end vertebra were measured.

Results

All patients had major thoracic curve with apex of curves on the right side. The muscle volume on the convex side was larger relative to the concave side at the three levels, while the fatty infiltration rate was significantly higher on the concave side. The difference index of the muscle volume was significantly larger at the apex vertebra level than at the upper end vertebra level (p=0.002) or lower end vertebra level (p<0.001). The difference index of muscle volume correlated with apex vertebra translation (r=−0.749, p=0.032), and the difference index of fatty involution correlated with apex vertebra translation (r=0.727, p=0.041) and Cobb angle (r=0.866, p=0.005).

Conclusions

Our findings demonstrated significant imbalance of muscle volume and fatty infiltration in deep paravertebral muscles of AIS patients. Moreover, these changes affected different vertebra levels, with the most imbalance of muscle volume at the apex vertebra. We interpreted this as morphological changes corresponding with known altered muscle function of AIS.

Identification of Elongated Primary Cilia with Impaired Mechanotransduction in Idiopathic Scoliosis Patients

The primary cilium is an outward projecting antenna-like organelle with an important role in bone mechanotransduction. The capacity to sense mechanical stimuli can affect important cellular and molecular aspects of bone tissue. Idiopathic scoliosis (IS) is a complex pediatric disease of unknown cause, defined by abnormal spinal curvatures. We demonstrate significant elongation of primary cilia in IS patient bone cells. In response to mechanical stimulation, these IS cells differentially express osteogenic factors, mechanosensitive genes, and signaling genes. Considering that numerous ciliary genes are associated with a scoliosis phenotype, among ciliopathies and knockout animal models, we expected IS patients to have an accumulation of rare variants in ciliary genes. Instead, our SKAT-O analysis of whole exomes showed an enrichment among IS patients for rare variants in genes with a role in cellular mechanotransduction. Our data indicates defective cilia in IS bone cells, which may be linked to heterogeneous gene variants pertaining to cellular mechanotransduction.

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.

Adolescent idiopathic scoliosis: current concepts on neurological and muscular etiologies

Adolescent idiopathic scoliosis (AIS) is a frequent disease but its etiology remains unknown. Gender prevalence in females is already known and there are many suggested hypotheses to explain its origin and manifestation, like associated neurologic, muscular and connective tissue disorders. Literature reports have tried to analyze disease prevalence in selected populations, possible ways of inheritance, related genes location and their polymorphisms, which may play a role in the development of the deformity. The purpose of this paper is to review and update concepts on the origin and genetic influence on AIS.