@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} }