PDF(Pubmed)
Abstract：
BACKGROUND: Abnormalities in cilia ultrastructure and function lead to a range of human phenotypes termed ciliopathies. Many tetratricopeptide repeat domain (TTC) family members have been reported to play critical roles in cilium organization and function.
RESULTS: Here, we describe five unrelated family trios with multisystem ciliopathy syndromes, including situs abnormality, complex congenital heart disease, nephronophthisis or neonatal cholestasis. Through whole-exome sequencing and Sanger sequencing confirmation, we identified compound heterozygous mutations of TTC12 and TTC21B in six affected individuals of Chinese origin. These nonsynonymous mutations affected highly conserved residues and were consistently predicted to be pathogenic. Furthermore, ex vivo cDNA amplification demonstrated that homozygous c.1464 + 2 T > C of TTC12 would cause a whole exon 16 skipping. Both mRNA and protein levels of TTC12 were significantly downregulated in the cells derived from the patient carrying TTC12 mutation c.1464 + 2 T > C by real-time qPCR and immunofluorescence assays when compared with two healthy controls. Transmission electron microscopy analysis further identified ultrastructural defects of the inner dynein arms in this patient. Finally, the effect of TTC12 deficiency on cardiac LR patterning was recapitulated by employing a morpholino-mediated knockdown of ttc12 in zebrafish.
CONCLUSIONS: To the best of our knowledge, this is the first study reporting the association between TTC12 variants and ciliopathies in a Chinese population. In addition to nephronophthisis and laterality defects, our findings demonstrated that TTC21B should also be considered a candidate gene for biliary ciliopathy, such as TTC26, which further expands the phenotypic spectrum of TTC21B deficiency in humans.
RESULTS: Here, we describe five unrelated family trios with multisystem ciliopathy syndromes, including situs abnormality, complex congenital heart disease, nephronophthisis or neonatal cholestasis. Through whole-exome sequencing and Sanger sequencing confirmation, we identified compound heterozygous mutations of TTC12 and TTC21B in six affected individuals of Chinese origin. These nonsynonymous mutations affected highly conserved residues and were consistently predicted to be pathogenic. Furthermore, ex vivo cDNA amplification demonstrated that homozygous c.1464 + 2 T > C of TTC12 would cause a whole exon 16 skipping. Both mRNA and protein levels of TTC12 were significantly downregulated in the cells derived from the patient carrying TTC12 mutation c.1464 + 2 T > C by real-time qPCR and immunofluorescence assays when compared with two healthy controls. Transmission electron microscopy analysis further identified ultrastructural defects of the inner dynein arms in this patient. Finally, the effect of TTC12 deficiency on cardiac LR patterning was recapitulated by employing a morpholino-mediated knockdown of ttc12 in zebrafish.
CONCLUSIONS: To the best of our knowledge, this is the first study reporting the association between TTC12 variants and ciliopathies in a Chinese population. In addition to nephronophthisis and laterality defects, our findings demonstrated that TTC21B should also be considered a candidate gene for biliary ciliopathy, such as TTC26, which further expands the phenotypic spectrum of TTC21B deficiency in humans.
摘要：
背景：纤毛超微结构和功能的异常导致一系列称为纤毛病的人类表型。据报道，许多四肽重复结构域（TTC）家族成员在纤毛的组织和功能中起着关键作用。
结果：这里，我们描述了五个不相关的家庭三重奏与多系统纤毛病综合征，包括situs异常,复杂的先天性心脏病，肾单位或新生儿胆汁淤积。通过全外显子组测序和Sanger测序确认,我们在6个中国血统的受影响个体中鉴定了TTC12和TTC21B的复合杂合突变.这些非同义突变影响高度保守的残基,并且一致地预测为致病性的。此外，离体cDNA扩增表明，TTC12的纯合c.1464+2T>C会导致整个外显子16跳跃。通过实时qPCR和免疫荧光测定，与两个健康对照相比，在来自携带TTC12突变c.14642T>C的患者的细胞中，TTC12的mRNA和蛋白质水平均显着下调。透射电子显微镜分析进一步确定了该患者内动力蛋白臂的超微结构缺陷。最后,通过在斑马鱼中使用吗啉代介导的ttc12基因敲低,可以概括TTC12缺乏对心脏LR模式的影响.
结论：据我们所知，这是第一项报道中国人群中TTC12变异与纤毛病变之间关联的研究.除了肾软骨和侧向缺陷，我们的发现表明TTC21B也应该被认为是胆道纤毛病的候选基因，例如TTC26，它进一步扩展了人类TTC21B缺乏症的表型谱。
结果：这里，我们描述了五个不相关的家庭三重奏与多系统纤毛病综合征，包括situs异常,复杂的先天性心脏病，肾单位或新生儿胆汁淤积。通过全外显子组测序和Sanger测序确认,我们在6个中国血统的受影响个体中鉴定了TTC12和TTC21B的复合杂合突变.这些非同义突变影响高度保守的残基,并且一致地预测为致病性的。此外，离体cDNA扩增表明，TTC12的纯合c.1464+2T>C会导致整个外显子16跳跃。通过实时qPCR和免疫荧光测定，与两个健康对照相比，在来自携带TTC12突变c.14642T>C的患者的细胞中，TTC12的mRNA和蛋白质水平均显着下调。透射电子显微镜分析进一步确定了该患者内动力蛋白臂的超微结构缺陷。最后,通过在斑马鱼中使用吗啉代介导的ttc12基因敲低,可以概括TTC12缺乏对心脏LR模式的影响.
结论：据我们所知，这是第一项报道中国人群中TTC12变异与纤毛病变之间关联的研究.除了肾软骨和侧向缺陷，我们的发现表明TTC21B也应该被认为是胆道纤毛病的候选基因，例如TTC26，它进一步扩展了人类TTC21B缺乏症的表型谱。
