Intra-familial tests of association between familial idiopathic scoliosis and linked regions on 9q31.3-q34.3 and 16p12.3-q22.2

Genetic variant of TTLL11 gene and subsequent ciliary defects are associated with idiopathic scoliosis in a 5-generation UK family

Idiopathic scoliosis (IS) is a complex 3D deformation of the spine with a strong genetic component, most commonly found in adolescent girls. Adolescent idiopathic scoliosis (AIS) affects around 3% of the general population. In a 5-generation UK family, linkage analysis identified the locus 9q31.2-q34.2 as a candidate region for AIS; however, the causative gene remained unidentified. Here, using exome sequencing we identified a rare insertion c.1569_1570insTT in the tubulin tyrosine ligase like gene, member 11 (TTLL11) within that locus, as the IS causative gene in this British family. Two other TTLL11 mutations were also identified in two additional AIS cases in the same cohort. Analyses of primary cells of individuals carrying the c.1569_1570insTT (NM_194252) mutation reveal a defect at the primary cilia level, which is less present, smaller and less polyglutamylated compared to control. Further, in a zebrafish, the knock down of ttll11, and the mutated ttll11 confirmed its role in spine development and ciliary function in the fish retina. These findings provide evidence that mutations in TTLL11, a ciliary gene, contribute to the pathogenesis of IS.

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

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

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.

The polymorphisms of melatonin receptor 1B gene (MTNR1B) (rs4753426 and rs10830963) and susceptibility to adolescent idiopathic scoliosis: a meta-analysis

OBJECTIVE

To determine whether MTNR1B rs4753426 and rs10830963 polymorphisms are correlated with AIS. Adolescent idiopathic scoliosis (AIS) is the most common form of spinal deformity, while its etiology remains uncertain. Melatonin receptor 1B (MTNR1B) gene polymorphisms have been found to be significantly associated with AIS risk; however, some of these results are controversial.

METHODS

An systematic online search was performed using PubMed, EMBASE, Web of Science and the Cochrane Library to identify case-control studies investigating the relationship between MTNR1B rs4753426 and rs10830963 polymorphisms and the susceptibility of AIS. The pooled odds ratio (OR) with 95 % confidence interval (95 % CI) was calculated to assess the associations, and subgroup meta-analyses were performed according to the ethnicity of the study populations.

RESULTS

A total of five studies involving 2395 cases and 3645 controls met the inclusion criteria after assessment by two reviewers. Overall, no significant associations were found between MTNR1B rs4753426 polymorphism and AIS risk (C vs. T: OR = 1.11, 95 % CI 0.94-1.30, P = 0.21; CC vs. TT: OR = 1.15, 95 % CI 0.97-1.36, P = 0.12; CT vs. TT: OR = 1.14, 95 % CI 0.97-1.35, P = 0.10; CC/CT vs. TT: OR = 1.14, 95 % CI 0.98-1.33, P = 0.09; CC vs.

CT/TT

OR = 1.10, 95 % CI 0.84-1.45, P = 0.48), as well as the MTNR1B rs10830963 polymorphism (G vs. C: OR = 0.99, 95 % CI 0.88-1.12, P = 0.91; GG vs. CC: OR = 0.99, 95 % CI 0.74-1.33, P = 0.96; CG vs. CC: OR = 1.00, 95 % CI 0.84-1.18, P = 0.88; GG/CG vs. CC: OR = 0.99, 95 % CI 0.84-1.17, P = 0.93; GG vs.

CG/CC

OR = 0.99, 95 % CI 0.75-1.30, P = 0.92). When stratified by ethnicity, there were no significant associations between MTNR1B rs4753426 and MTNR1B rs10830963 polymorphisms and AIS risk in either Asian or Caucasian populations.

CONCLUSION

MTNR1B rs4753426 and MTNR1B rs10830963 polymorphisms are not obviously associated with risk of AIS in either Asian populations or Caucasian populations.

Sequencing of the TBX6 Gene in Families with Familial Idiopathic Scoliosis

STUDY DESIGN

A hypothesis-driven study was conducted in a familial cohort to determine the potential association between variants within the TBX6 gene and Familial Idiopathic Scoliosis (FIS).

OBJECTIVE

To determine if variants within exons of the TBX6 gene segregate with the FIS phenotype within a sample of families with FIS.

SUMMARY OF BACKGROUND DATA

Idiopathic Scoliosis (IS) is a structural curvature of the spine whose underlying genetic etiology has not been established. IS has been reported to occur at a higher rate than expected in family members of individuals with congenital scoliosis (CS), suggesting that the two diseases might have a shared etiology. The TBX6 gene on chromosome 16p, essential to somite development, has been associated with CS in a Chinese population. Previous studies have identified linkage to this locus in families with FIS, and specifically with rs8060511, located in an intron of the TBX6 gene.

METHODS

Parent-offspring trios from 11 families (13 trios, 42 individuals) with FIS were selected for Sanger sequencing of the TBX6 gene. Trios were selected from a large population of families with FIS in which a genome-wide scan had resulted in linkage to 16p.

RESULTS

Sequencing analyses of the subset of families resulted in the identification of five coding variants. Three of the five variants were novel; the remaining two variants were previously characterized and account for 90% of the observed variants in these trios. In all cases, there was no correlation between transmission of the TBX6 variant allele and FIS phenotype. However, an analysis of regulatory markers in osteoblasts showed that rs8060511 is in a putative enhancer element.

CONCLUSIONS

Although this study did not identify any TBX6 coding variants that segregate with FIS, we identified a variant that is located in a potential TBX6 enhancer element. Therefore, further investigation of the region is needed.

Exome sequencing identifies a rare HSPG2 variant associated with familial idiopathic scoliosis

Idiopathic scoliosis occurs in 3% of individuals and has an unknown etiology. The objective of this study was to identify rare variants that contribute to the etiology of idiopathic scoliosis by using exome sequencing in a multigenerational family with idiopathic scoliosis. Exome sequencing was completed for three members of this multigenerational family with idiopathic scoliosis, resulting in the identification of a variant in the HSPG2 gene as a potential contributor to the phenotype. The HSPG2 gene was sequenced in a separate cohort of 100 unrelated individuals affected with idiopathic scoliosis and also was examined in an independent idiopathic scoliosis population. The exome sequencing and subsequent bioinformatics filtering resulted in 16 potentially damaging and rare coding variants. One of these variants, p.Asn786Ser, is located in the HSPG2 gene. The variant p.Asn786Ser also is overrepresented in a larger cohort of idiopathic scoliosis cases compared with a control population (P = 0.024). Furthermore, we identified additional rare HSPG2 variants that are predicted to be damaging in two independent cohorts of individuals with idiopathic scoliosis. The HSPG2 gene encodes for a ubiquitous multifunctional protein within the extracellular matrix in which loss of function mutation are known to result in a musculoskeletal phenotype in both mouse and humans. Based on these results, we conclude that rare variants in the HSPG2 gene potentially contribute to the idiopathic scoliosis phenotype in a subset of patients with idiopathic scoliosis. Further studies must be completed to confirm the effect of the HSPG2 gene on the idiopathic scoliosis phenotype.

Are copy number variants associated with adolescent idiopathic scoliosis?

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a complex genetic disorder that causes spinal deformity in approximately 3% of the population. Candidate gene, linkage, and genome-wide association studies have sought to identify genetic variation that predisposes individuals to AIS, but the genetic basis remains unclear. Copy number variants are associated with several isolated skeletal phenotypes, but their role in AIS, to our knowledge, has not been assessed.

QUESTIONS/PURPOSES

We determined the frequency of recurrent copy number rearrangements, chromosome aneuploidy, and rare copy number variants in patients with AIS.

METHODS

Between January 2010 and August 2014, we evaluated 150 patients with isolated AIS and spinal curvatures measuring 10° or greater, and 148 agreed to participate. Genomic copy number analysis was performed on patients and 1079 control subjects using the Affymetrix(®) Genome-wide Human SNP Array 6.0. After removing poor quality samples, 143 (97%) patients with AIS were evaluated for copy number variation.

RESULTS

We identified a duplication of chromosome 1q21.1 in 2.1% (N = 3/143) of patients with AIS, which was enriched compared with 0.09% (N = 1/1079) of control subjects (p = 0.0057) and 0.07% (N = 6/8329) of a large published control cohort (p = 0.0004). Other notable findings include trisomy X, which was identified in 1.8% (N = 2/114) of female patients with AIS, and rearrangements of chromosome 15q11.2 and 16p11.2 that previously have been associated with spinal phenotypes. Finally, we report rare copy number variants that will be useful in future studies investigating candidate genes for AIS.

CONCLUSIONS

Copy number variation and chromosomal aneuploidy may contribute to the pathogenesis of adolescent idiopathic scoliosis.

CLINICAL RELEVANCE

Chromosomal microarray may reveal clinically useful abnormalities in some patients with AIS.

Scoliosis and vertebral anomalies: additional abnormal phenotypes associated with chromosome 16p11.2 rearrangement

The typical chromosome 16p11.2 rearrangements are estimated to occur at a frequency of approximately 0.6% of all samples tested clinically and have been identified as a major cause of autism spectrum disorders, developmental delay, behavioral abnormalities, and seizures. Careful examination of patients with these rearrangements revealed association with abnormal head size, obesity, dysmorphism, and congenital abnormalities. In this report, we extend this list of phenotypic abnormalities to include scoliosis and vertebral anomalies. We present detailed characterization of phenotypic and radiological data of 10 new patients, nine with the 16p11.2 deletion and one with the duplication within the coordinates chr16:29,366,195 and 30,306,956 (hg19) with a minimal size of 555 kb. We discuss the phenotypical and radiological findings in our patients and review 5 previously reported patients with 16p11.2 rearrangement and similar skeletal abnormalities. Our data suggest that patients with the recurrent 16p11.2 rearrangement have increased incidence of scoliosis and vertebral anomalies. However, additional studies are required to confirm this observation and to establish the incidence of these anomalies. We discuss the potential implications of our findings on the diagnosis, surveillance and genetic counseling of patients with 16p11.2 rearrangement.