@article {774, title = {TBX6 missense variants expand the mutational spectrum in a non-Mendelian inheritance disease.}, journal = {Hum Mutat}, volume = {41}, year = {2020}, month = {2020 01}, pages = {182-195}, abstract = {

Congenital scoliosis (CS) is a birth defect with variable clinical and anatomical manifestations due to spinal malformation. The genetic etiology underlying about 10\% of CS cases in the Chinese population is compound inheritance by which the gene dosage is reduced below that of haploinsufficiency. In this genetic model, the trait manifests as a result of the combined effect of a rare variant and common pathogenic variant allele at a locus. From exome sequencing (ES) data of 523 patients in Asia and two patients in Texas, we identified six TBX6 gene-disruptive variants from 11 unrelated CS patients via ES and in vitro functional testing. The in trans mild hypomorphic allele was identified in 10 of the 11 subjects; as anticipated these 10 shared a similar spinal deformity of hemivertebrae. The remaining case has a homozygous variant in TBX6 (c.418C>T) and presents a more severe spinal deformity phenotype. We found decreased transcriptional activity and abnormal cellular localization as the molecular mechanisms for TBX6 missense loss-of-function alleles. Expanding the mutational spectrum of TBX6 pathogenic alleles enabled an increased molecular diagnostic detection rate, provided further evidence for the gene dosage-dependent genetic model underlying CS, and refined clinical classification.

}, keywords = {Alleles, Cell Line, Female, Gene Expression, Genes, Reporter, Genetic Association Studies, Genetic Predisposition to Disease, Genotype, Haplotypes, Humans, Inheritance Patterns, Male, Models, Molecular, Molecular Diagnostic Techniques, Mutation, Missense, Phenotype, Protein Conformation, Radiography, Sequence Analysis, DNA, Spine, Structure-Activity Relationship, T-Box Domain Proteins, Whole Exome Sequencing}, issn = {1098-1004}, doi = {10.1002/humu.23907}, author = {Chen, Weisheng and Lin, Jiachen and Wang, Lianlei and Li, Xiaoxin and Zhao, Sen and Liu, Jiaqi and Akdemir, Zeynep C and Zhao, Yanxue and Du, Renqian and Ye, Yongyu and Song, Xiaofei and Zhang, Yuanqiang and Yan, Zihui and Yang, Xinzhuang and Lin, Mao and Shen, Jianxiong and Wang, Shengru and Gao, Na and Yang, Ying and Liu, Ying and Li, Wenli and Liu, Jia and Zhang, Na and Yang, Xu and Xu, Yuan and Zhang, Jianguo and Delgado, Mauricio R and Posey, Jennifer E and Qiu, Guixing and Rios, Jonathan J and Liu, Pengfei and Wise, Carol A and Zhang, Feng and Wu, Zhihong and Lupski, James R and Wu, Nan} } @article {570, title = {TBX6 compound inheritance leads to congenital vertebral malformations in humans and mice.}, journal = {Hum Mol Genet}, volume = {28}, year = {2019}, month = {2019 02 15}, pages = {539-547}, abstract = {

Congenital vertebral malformations (CVMs) are associated with human TBX6 compound inheritance that combines a rare null allele and a common hypomorphic allele at the TBX6 locus. Our previous in vitro evidence suggested that this compound inheritance resulted in a TBX6 gene dosage of less than haploinsufficiency (i.e. <50\%) as a potential mechanism of TBX6-associated CVMs. To further investigate this pathogenetic model, we ascertained and collected 108 Chinese CVM cases and found that 10 (9.3\%) of them carried TBX6 null mutations in combination with common hypomorphic variants at the second TBX6 allele. For in vivo functional verification and genetic analysis of TBX6 compound inheritance, we generated both null and hypomorphic mutations in mouse Tbx6 using the CRISPR-Cas9 method. These Tbx6 mutants are not identical to the patient variants at the DNA sequence level, but instead functionally mimic disease-associated TBX6 variants. Intriguingly, as anticipated by the compound inheritance model, a high penetrance of CVM phenotype was only observed in the mice with combined null and hypomorphic alleles of Tbx6. These findings are consistent with our experimental observations in humans and supported the dosage effect of TBX6 in CVM etiology. In conclusion, our findings in the newly collected human CVM subjects and Tbx6 mouse models consistently support the contention that TBX6 compound inheritance causes CVMs, potentially via a gene dosage-dependent mechanism. Furthermore, mouse Tbx6 mutants mimicking human CVM-associated variants will be useful models for further mechanistic investigations of CVM pathogenesis in the cases associated with TBX6.

}, keywords = {Adolescent, Alleles, Animals, Child, Child, Preschool, Congenital Abnormalities, CRISPR-Cas Systems, Disease Models, Animal, Female, Haploinsufficiency, Humans, Infant, Male, Mice, Mutation, Phenotype, Scoliosis, Spine, T-Box Domain Proteins}, issn = {1460-2083}, doi = {10.1093/hmg/ddy358}, author = {Yang, Nan and Wu, Nan and Zhang, Ling and Zhao, Yanxue and Liu, Jiaqi and Liang, Xiangyu and Ren, Xiaojun and Li, Weiyu and Chen, Weisheng and Dong, Shuangshuang and Zhao, Sen and Lin, Jiachen and Xiang, Hang and Xue, Huadan and Chen, Lu and Sun, Hao and Zhang, Jianguo and Shi, Jiangang and Zhang, Shuyang and Lu, Daru and Wu, Xiaohui and Jin, Li and Ding, Jiandong and Qiu, Guixing and Wu, Zhihong and Lupski, James R and Zhang, Feng} } @article {682, title = {TBX6-associated congenital scoliosis (TACS) as a clinically distinguishable subtype of congenital scoliosis: further evidence supporting the compound inheritance and TBX6 gene dosage model.}, journal = {Genet Med}, volume = {21}, year = {2019}, month = {2019 07}, pages = {1548-1558}, abstract = {

PURPOSE: To characterize clinically measurable endophenotypes, implicating the TBX6 compound inheritance model.

METHODS: Patients with congenital scoliosis (CS) from China(N = 345, cohort 1), Japan (N = 142, cohort 2), and the United States (N = 10, cohort 3) were studied. Clinically measurable endophenotypes were compared according to the TBX6 genotypes. A mouse model for Tbx6 compound inheritance (N = 52) was investigated by micro computed tomography (micro-CT). A clinical diagnostic algorithm (TACScore) was developed to assist in clinical recognition of TBX6-associated CS (TACS).

RESULTS: In cohort 1, TACS patients (N = 33) were significantly younger at onset than the remaining CS patients (P = 0.02), presented with one or more hemivertebrae/butterfly vertebrae (P = 4.9 {\texttimes} 10), and exhibited vertebral malformations involving the lower part of the spine (T8-S5, P = 4.4 {\texttimes} 10); observations were confirmed in two replication cohorts. Simple rib anomalies were prevalent in TACS patients (P = 3.1 {\texttimes} 10), while intraspinal anomalies were uncommon (P = 7.0 {\texttimes} 10). A clinically usable TACScore was developed with an area under the curve (AUC) of 0.9 (P = 1.6 {\texttimes} 10). A Tbx6 mouse model supported that a~gene dosage effect underlies the TACS phenotype.

CONCLUSION: TACS is a clinically distinguishable entity with consistent clinically measurable endophenotypes. The type and distribution of vertebral column abnormalities in TBX6/Tbx6 compound inheritance implicate subtle perturbations in gene dosage as a cause of spine developmental birth defects responsible for about 10\% of CS.

}, issn = {1530-0366}, doi = {10.1038/s41436-018-0377-x}, author = {Liu, Jiaqi and Wu, Nan and Yang, Nan and Takeda, Kazuki and Chen, Weisheng and Li, Weiyu and Du, Renqian and Liu, Sen and Zhou, Yangzhong and Zhang, Ling and Liu, Zhenlei and Zuo, Yuzhi and Zhao, Sen and Blank, Robert and Pehlivan, Davut and Dong, Shuangshuang and Zhang, Jianguo and Shen, Jianxiong and Si, Nuo and Wang, Yipeng and Liu, Gang and Li, Shugang and Zhao, Yanxue and Zhao, Hong and Chen, Yixin and Zhao, Yu and Song, Xiaofei and Hu, Jianhua and Lin, Mao and Tian, Ye and Yuan, Bo and Yu, Keyi and Niu, Yuchen and Yu, Bin and Li, Xiaoxin and Chen, Jia and Yan, Zihui and Zhu, Qiankun and Meng, Xiaolu and Chen, Xiaoli and Su, Jianzhong and Zhao, Xiuli and Wang, Xiaoyue and Ming, Yue and Li, Xiao and Raggio, Cathleen L and Zhang, Baozhong and Weng, Xisheng and Zhang, Shuyang and Zhang, Xue and Watanabe, Kota and Matsumoto, Morio and Jin, Li and Shen, Yiping and Sobreira, Nara L and Posey, Jennifer E and Giampietro, Philip F and Valle, David and Liu, Pengfei and Wu, Zhihong and Ikegawa, Shiro and Lupski, James R and Zhang, Feng and Qiu, Guixing} }