@article {954, title = {Human and mouse studies establish TBX6 in Mendelian CAKUT and as a potential driver of kidney defects associated with the 16p11.2 microdeletion syndrome.}, journal = {Kidney Int}, volume = {98}, year = {2020}, month = {2020 10}, pages = {1020-1030}, abstract = {

Congenital anomalies of the kidney and urinary tract (CAKUTs) are the most common cause of chronic kidney disease in children. Human 16p11.2 deletions have been associated with CAKUT, but the responsible molecular mechanism remains to be illuminated. To explore this, we investigated 102 carriers of 16p11.2 deletion from multi-center cohorts, among which we retrospectively ascertained kidney morphologic and functional data from 37 individuals (12 Chinese and 25 Caucasian/Hispanic). Significantly higher CAKUT rates were observed in 16p11.2 deletion carriers (about 25\% in Chinese and 16\% in Caucasian/Hispanic) than those found in the non-clinically ascertained general populations (about 1/1000 found at autopsy). Furthermore, we identified seven additional individuals with heterozygous loss-of-function variants in TBX6, a gene that maps to the 16p11.2 region. Four of these seven cases showed obvious CAKUT. To further investigate the role of TBX6 in kidney development, we engineered mice with mutated Tbx6 alleles. The Tbx6 heterozygous null (i.e., loss-of-function) mutant (Tbx6) resulted in 13\% solitary kidneys. Remarkably, this incidence increased to 29\% in a compound heterozygous model (Tbx6) that reduced Tbx6 gene dosage to below haploinsufficiency, by combining the null allele with a novel mild hypomorphic allele (mh). Renal hypoplasia was also frequently observed in these Tbx6-mutated mouse models. Thus, our findings in patients and mice establish TBX6 as a novel gene involved in CAKUT and its gene dosage insufficiency as a potential driver for kidney defects observed in the 16p11.2 microdeletion syndrome.

}, issn = {1523-1755}, doi = {10.1016/j.kint.2020.04.045}, author = {Yang, Nan and Wu, Nan and Dong, Shuangshuang and Zhang, Ling and Zhao, Yanxue and Chen, Weisheng and Du, Renqian and Song, Chengcheng and Ren, Xiaojun and Liu, Jiaqi and Pehlivan, Davut and Liu, Zhenlei and Rao, Jia and Wang, Chunyan and Zhao, Sen and Breman, Amy M and Xue, Huadan and Sun, Hao and Shen, Jianxiong and Zhang, Shuyang and Posey, Jennifer E and Xu, Hong and Jin, Li and Zhang, Jianguo and Liu, Pengfei and Sanna-Cherchi, Simone and Qiu, Guixing and Wu, Zhihong and Lupski, James R and Zhang, Feng} } @article {793, title = {Increased gene dosages induce congenital cervical vertebral malformations in humans and mice.}, journal = {J Med Genet}, volume = {57}, year = {2020}, month = {2020 06}, pages = {371-379}, abstract = {

BACKGROUND: Congenital vertebral malformations (CVMs) manifest with abnormal vertebral morphology. Genetic factors have been implicated in CVM pathogenesis, but the underlying pathogenic mechanisms remain unclear in most subjects. We previously reported that the human 16p11.2 BP4-BP5 deletion and its associated dosage reduction caused CVMs. We aim to investigate the reciprocal 16p11.2 BP4-BP5 duplication and its potential genetic contributions to CVMs.

METHODS AND RESULTS: Patients who were found to carry the 16p11.2 BP4-BP5 duplication by chromosomal microarray analysis were retrospectively analysed for their vertebral phenotypes. The spinal assessments in seven duplication carriers showed that four (57\%) presented characteristics of CVMs, supporting the contention that increased dosage could induce CVMs. For further in vivo functional investigation in a model organism, we conducted genome editing of the upstream regulatory region of mouse using CRISPR-Cas9 and obtained three mouse mutant alleles ( to ) with elevated expression levels of . Luciferase reporter assays showed that the allele presented with the 160\% expression level of that observed in the reference (+) allele. Therefore, the homozygous mice could functionally mimic the dosage of heterozygous carriers of 16p11.2 BP4-BP5 duplication (approximately 150\%, ie, 3/2 gene dosage of the normal level). Remarkably, 60\% of the mice manifested with CVMs. Consistent with our observations in humans, the CVMs induced by increased dosage in mice mainly affected the cervical vertebrae.

CONCLUSION: Our findings in humans and mice consistently support that an increased dosage contributes to the risk of developing cervical CVMs.

}, issn = {1468-6244}, doi = {10.1136/jmedgenet-2019-106333}, author = {Ren, Xiaojun and Yang, Nan and Wu, Nan and Xu, Ximing and Chen, Weisheng and Zhang, Ling and Li, Yingping and Du, Ren-Qian and Dong, Shuangshuang and Zhao, Sen and Chen, Shuxia and Jiang, Li-Ping and Wang, Lianlei and Zhang, Jianguo and Wu, Zhihong and Jin, Li and Qiu, Guixing and Lupski, James R and Shi, Jiangang and Zhang, Feng and Liu, Pengfei} } @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} }