Yue Han1,2, Xiangzhong Zhao2, Sai Wang1,2, Cui Wang1,2, Dongxu Tian3, Yanhua Lang4, Irene Bottillo5, Xinsheng Wang6, Leping Shao7,8. 1. Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, No.5 Donghai Middle Road, 266071, Qingdao, People's Republic of China. 2. Central Laboratory, The Affiliated Hospital of Qingdao University, 266003, Qingdao, People's Republic of China. 3. Department of Urology, The Affiliated Hospital of Qingdao University, 266003, Qingdao, People's Republic of China. 4. Department of Nursing, The Affiliated Hospital of Qingdao University, 266003, Qingdao, People's Republic of China. 5. Division of Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, 00185, Italy. 6. Department of Urology, The Affiliated Hospital of Qingdao University, 266003, Qingdao, People's Republic of China. qy_wangxs@126.com. 7. Department of Nephrology, The Affiliated Qingdao Municipal Hospital of Qingdao University, No.5 Donghai Middle Road, 266071, Qingdao, People's Republic of China. lepingshao@163.com. 8. Central Laboratory, The Affiliated Hospital of Qingdao University, 266003, Qingdao, People's Republic of China. lepingshao@163.com.
Abstract
INTRODUCTION: Bartter syndrome type I (BS1) has been rarely reported in large groups. On the other hand, the phenomenon of exon skipping, in which exonic mutations result in abnormal splicing, has been reported to be associated with various diseases. Specifically, mutations that result in the disruption of exonic splicing enhancers (ESEs) and/or the creation of exonic splicing silencers (ESSs) can promote exon skipping. However, the aberrant exon skipping caused by an exonic variant in such splicing regulatory elements (SREs) sequences has never been reported in the causal gene of SLC12A1 in BS1. METHODS: We analyze the variants in nine Chinese families with BS1, including eight with antenatal BS (aBS) and one presenting as classical BS (cBS), by next-generation sequencing. Then we used bioinformatics programs to analyze all these variants found in this study and identify candidate mutations that may induce exon skipping. Furthermore, the effects of identified variants were classified according to the 2015 American College of Medical Genetics and Genomics (ACMG) standards and guidelines. RESULTS: Fifteen different variants of SLC12A1 gene were identified, including 11 novel ones. Two of the nine probands were homozygotes, the rest seven ones were compound heterozygotes. One candidate variant (c.1435C>G), not only significantly reduced ESEs scores but also markedly increased ESSs scores, were further investigated by mini-gene splicing assay, and found this single-nucleotide substitution causes abnormal splicing in vitro (exclusion of exon 11). Finally, among 15 variants, 9, 3, and 3 were classified as "pathogenic variants", "likely pathogenic variants", "variants with uncertain significance", respectively. CONCLUSION: These data would enrich the human gene mutation database (HGMD) and would provide valuable references to the genetic counseling and diagnosis of BS1 for Chinese population. Additionally, our results suggest that aberrant exon skipping is one previously unrecognized mechanism by which an exonic variant in SLC12A1 can lead to BS1.
INTRODUCTION:Bartter syndrome type I (BS1) has been rarely reported in large groups. On the other hand, the phenomenon of exon skipping, in which exonic mutations result in abnormal splicing, has been reported to be associated with various diseases. Specifically, mutations that result in the disruption of exonic splicing enhancers (ESEs) and/or the creation of exonic splicing silencers (ESSs) can promote exon skipping. However, the aberrant exon skipping caused by an exonic variant in such splicing regulatory elements (SREs) sequences has never been reported in the causal gene of SLC12A1 in BS1. METHODS: We analyze the variants in nine Chinese families with BS1, including eight with antenatal BS (aBS) and one presenting as classical BS (cBS), by next-generation sequencing. Then we used bioinformatics programs to analyze all these variants found in this study and identify candidate mutations that may induce exon skipping. Furthermore, the effects of identified variants were classified according to the 2015 American College of Medical Genetics and Genomics (ACMG) standards and guidelines. RESULTS: Fifteen different variants of SLC12A1 gene were identified, including 11 novel ones. Two of the nine probands were homozygotes, the rest seven ones were compound heterozygotes. One candidate variant (c.1435C>G), not only significantly reduced ESEs scores but also markedly increased ESSs scores, were further investigated by mini-gene splicing assay, and found this single-nucleotide substitution causes abnormal splicing in vitro (exclusion of exon 11). Finally, among 15 variants, 9, 3, and 3 were classified as "pathogenic variants", "likely pathogenic variants", "variants with uncertain significance", respectively. CONCLUSION: These data would enrich the human gene mutation database (HGMD) and would provide valuable references to the genetic counseling and diagnosis of BS1 for Chinese population. Additionally, our results suggest that aberrant exon skipping is one previously unrecognized mechanism by which an exonic variant in SLC12A1 can lead to BS1.
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