@article {708, title = {Genetic and molecular mechanism for distinct clinical phenotypes conveyed by allelic truncating mutations implicated in FBN1.}, journal = {Mol Genet Genomic Med}, volume = {8}, year = {2020}, month = {2020 01}, pages = {e1023}, abstract = {

BACKGROUND: The molecular and genetic mechanisms by which different single nucleotide variant alleles in specific genes, or at the same genetic locus, cause distinct disease phenotypes often remain unclear. Allelic truncating mutations of FBN1 could cause either classical Marfan syndrome (MFS) or a more complicated phenotype associated with Marfanoid-progeroid-lipodystrophy syndrome (MPLS).

METHODS: We investigated a small cohort, encompassing two classical MFS and one MPLS subjects~from China, whose clinical presentation included scoliosis potentially requiring surgical intervention. Targeted next generation sequencing was performed on all the participants. We analyzed the molecular diagnosis, clinical features, and the potential molecular mechanism involved in the MPLS subject in our cohort.

RESULTS: We report a novel de novo FBN1 mutation for the first Chinese subject~with MPLS, a more complicated fibrillinopathy, and two subjects~with more classical MFS. We further predict that the MPLS truncating mutation, and others previously reported, is prone to escape the nonsense-mediated decay (NMD), while MFS mutations are predicted to be subjected to NMD. Also, the MPLS mutation occurs within the glucogenic hormone asprosin domain of FBN1. In vitro experiments showed that the single MPLS mutation p.Glu2759Cysfs*9 appears to perturb proper FBN1 protein aggregation as compared with the~classical MFS mutation p.Tyr2596Thrfs*86. Both mutations appear to upregulate SMAD2 phosphorylation in vitro.

CONCLUSION: We provide direct evidence that a dominant-negative interaction of FBN1 potentially explains the complex MPLS phenotypes through genetic and functional analysis. Our study expands the mutation spectrum of FBN1 and highlights the potential molecular mechanism for MPLS.

}, keywords = {Adolescent, Adult, Child, Female, Fibrillin-1, HEK293 Cells, Humans, Lipodystrophy, Marfan Syndrome, Mutation, Phenotype, Progeria, Protein Domains, Smad2 Protein}, issn = {2324-9269}, doi = {10.1002/mgg3.1023}, author = {Lin, Mao and Liu, Zhenlei and Liu, Gang and Zhao, Sen and Li, Chao and Chen, Weisheng and Coban Akdemir, Zeynep and Lin, Jiachen and Song, Xiaofei and Wang, Shengru and Xu, Qiming and Zhao, Yanxue and Wang, Lianlei and Zhang, Yuanqiang and Yan, Zihui and Liu, Sen and Liu, Jiaqi and Chen, Yixin and Zuo, Yuzhi and Yang, Xu and Sun, Tianshu and Yang, Xin-Zhuang and Niu, Yuchen and Li, Xiaoxin and You, Wesley and Qiu, Bintao and Ding, Chen and Liu, Pengfei and Zhang, Shuyang and Carvalho, Claudia M B and Posey, Jennifer E and Qiu, Guixing and Lupski, James R and Wu, Zhihong and Zhang, Jianguo 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 {526, title = {The coexistence of copy number variations (CNVs) and single nucleotide polymorphisms (SNPs) at a locus can result in distorted calculations of the significance in associating SNPs to disease.}, journal = {Hum Genet}, volume = {137}, year = {2018}, month = {2018 Jul}, pages = {553-567}, abstract = {

With the recent advance in genome-wide association studies (GWAS), disease-associated single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) have been extensively reported. Accordingly, the issue of incorrect identification of recombination events that can induce the distortion of multi-allelic or hemizygous variants has received more attention. However, the potential distorted calculation bias or significance of a detected association in a GWAS due to the coexistence of CNVs and SNPs in the same genomic region may remain under-recognized. Here we performed the association study within a congenital scoliosis (CS) cohort whose genetic etiology was recently elucidated as a compound inheritance model, including mostly one rare variant deletion CNV null allele and one common variant non-coding hypomorphic haplotype of the TBX6 gene. We demonstrated that the existence of a deletion in TBX6 led to an overestimation of the contribution of the SNPs on the hypomorphic allele. Furthermore, we generalized a model to explain the calculation bias, or distorted significance calculation for an association study, that can be {\textquoteright}induced{\textquoteright} by CNVs at a locus. Meanwhile, overlapping between the disease-associated SNPs from published GWAS and common CNVs (overlap 10\%) and pathogenic/likely pathogenic CNVs (overlap 99.69\%) was significantly higher than the random distribution (p < 1 {\texttimes} 10 and p = 0.034, respectively), indicating that such co-existence of CNV and SNV alleles might generally influence data interpretation and potential outcomes of a GWAS. We also verified and assessed the influence of colocalizing CNVs to the detection sensitivity of disease-associated SNP variant alleles in another adolescent idiopathic scoliosis (AIS) genome-wide association study. We proposed that detecting co-existent CNVs when evaluating the association signals between SNPs and disease traits could improve genetic model analyses and better integrate GWAS with robust Mendelian principles.

}, keywords = {Adolescent, Congenital Abnormalities, DNA Copy Number Variations, Female, Genetic Predisposition to Disease, Genome, Human, Genome-Wide Association Study, Genomics, Genotype, Haplotypes, Humans, Phenotype, Polymorphism, Single Nucleotide, Scoliosis}, issn = {1432-1203}, doi = {10.1007/s00439-018-1910-3}, author = {Liu, Jiaqi and Zhou, Yangzhong and Liu, Sen and Song, Xiaofei and Yang, Xin-Zhuang and Fan, Yanhui and Chen, Weisheng and Akdemir, Zeynep Coban and Yan, Zihui and Zuo, Yuzhi and Du, Renqian and Liu, Zhenlei and Yuan, Bo and Zhao, Sen and Liu, Gang and Chen, Yixin and Zhao, Yanxue and Lin, Mao and Zhu, Qiankun and Niu, Yuchen and Liu, Pengfei and Ikegawa, Shiro and Song, You-Qiang and Posey, Jennifer E and Qiu, Guixing and Zhang, Feng and Wu, Zhihong and Lupski, James R and Wu, Nan} }