Analysis of an ADTKD family with a novel frameshift mutation in MUC1 reveals characteristic features of mutant MUC1 protein
Analysis of an ADTKD family with a novel frameshift mutation in MUC1 reveals characteristic features of mutant MUC1 protein
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DOI：
10.1093/ndt/gfx083
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发表时间：
2017-12-01
影响因子：
6.1
通讯作者：
Isaka, Yoshitaka
中科院分区：
文献类型：
--
作者：
Yamamoto, Satoko;Kaimori, Jun-Ya;Isaka, Yoshitaka
背景髓质囊性肾病1型是一种常染色体显性遗传的肾小管间质性肾病（ADTKD）。最近，粘蛋白1（MUC 1）被确定为髓样囊性肾病（ADTKD-MUC 1）的致病基因。然而，MUC 1突变被发现是在富含GC的可变数目串联重复序列（VNTR）的单个拷贝中的单个胞嘧啶插入，这是非常难以通过下一代测序分析的。迄今为止，在ADTKD-MUC 1中尚未检测到其他突变，并且由于难以遗传修饰VNTR序列，因此尚未分析突变MUC 1蛋白。我们通过下一代测序对ADTKD家族进行了全外显子组分析。我们还对一个家系成员的肾活检进行了组织病理学分析。我们根据患者基因组序列构建了突变蛋白表达载体，并对突变蛋白的性质进行了鉴定。我们在MUC 1基因的VNTR之前发现了一个新的移码突变。得到的突变MUC 1蛋白具有非常相似的氨基酸序列和预测的3D结构，以先前报道的突变蛋白。值得注意的是，重组突变MUC 1蛋白被困在细胞质中，并出现自我聚集。在尿外泌体中也发现了患者天然突变蛋白。这种新的移码突变MUC 1基因和随之而来的突变蛋白可能有助于未来发现ADTKD-MUC 1的病理生理学。尿外泌体中的突变MUC 1蛋白可用于非DNA相关的诊断。
Background. Medullary cystic kidney disease Type 1 is an autosomal dominant tubulointerstitial kidney disease (ADTKD). Recently, mucin 1 (MUC1) was identified as a causal gene of medullary cystic kidney disease (ADTKD-MUC1). However, the MUC1 mutation was found to be a single cytosine insertion in a single copy of the GC-rich variable number of tandem repeats (VNTRs), which are very difficult to analyze by next-generation sequencing. To date, other mutations have not been detected in ADTKD-MUC1, and the mutant MUC1 protein has not been analyzed because of the difficulty of genetically modifying the VNTR sequence.Methods. We conducted whole-exome analyses of an ADTKD family by next-generation sequencing. We also performed histopathological analyses of a renal biopsy from a pedigree family member. We constructed a mutant protein expression vector based on the patient genome sequence and characterized the nature of the mutant protein.Results. We found a novel frameshift mutation before the VNTR in the MUC1 gene. The resulting mutant MUC1 protein had a very similar amino acid sequence and predicted 3D structure to the previously reported mutant protein. Notably, the recombinant mutant MUC1 protein was trapped in the cytoplasm and appeared to self-aggregate. The patient native mutant protein was also found in urine exosomes.Conclusions. This novel frameshift mutation in the MUC1 gene and consequent mutant protein may contribute to the future discovery of the pathophysiology of ADTKD-MUC1. The mutant MUC1 protein in urine exosomes may be used for non-DNA-related diagnosis.