A novel synonymous KMT2B variant in a patient with dystonia causes aberrant splicing

Molecular Genetics & Genomic Medicine

Michel C. Tchan¹  Renee Smyth¹  Sophie Devery¹  Alison McLean¹  Susan E. Tomlinson²  Stephen Tisch²  Paul Darveniza²  Manju A. Kurian³  Avi Fellner⁴  Marina L. Kennerson⁵  Bianca R. Grosz⁵  Kathy H. C. Wu⁶  Kishore R. Kumar⁷  Victor S. C. Fung⁷ 

[1] Clinical Genomics St Vincent's Hospital Darlinghurst New South Wales Australia;Department of Neurology St Vincent's Hospital Darlinghurst New South Wales Australia;Developmental Neurosciences, Zayed Centre for Research into Rare Disease in Children London UK;Kinghorn Centre for Clinical Genomics Garvan Institute of Medical Research Darlinghurst New South Wales Australia;Northcott Neuroscience Laboratory ANZAC Research Institute Concord New South Wales Australia;School of Medicine University of New South Wales Sydney New South Wales Australia;Sydney Medical School, Faculty of Medicine and Health University of Sydney Sydney New South Wales Australia;

关键词: deep brain stimulation;    dystonia;    KMT2B;    splicing;    synonymous;   

DOI  :  10.1002/mgg3.1923

来源: DOAJ

【 摘 要 】

Abstract Background Heterozygous KMT2B variants are a common cause of dystonia. A novel synonymous KMT2B variant, c.5073C>T (p.Gly1691=) was identified in an individual with childhood‐onset progressive dystonia. Methods The splicing impact of c.5073C>T was assessed using an in vitro exon‐trapping assay. The genomic region of KMT2B exons 23–26 was cloned into the pSpliceExpress plasmid between exon 2 and 3 of the rat Ins2 gene. The c.5073C>T variant was then introduced through site‐directed mutagenesis. The KMT2B wild‐type and c.5073C>T plasmids were transfected separately into HeLa cells and RNA was extracted 48 hours after transfection. The RNA was reverse transcribed to produce cDNA, which was PCR amplified using primers annealing to the flanking rat Ins2 sequences. Results Sanger sequencing of the PCR products revealed that c.5073C>T caused a novel splice donor site and therefore a 5‐bp deletion of KMT2B exon 23 in mature mRNA, leading to a coding frameshift and premature stop codon (p.Lys1692AsnfsTer7). Conclusion To our knowledge, this is the first report of a KMT2B synonymous variant associated with dystonia. Reassessment of synonymous variants may increase diagnostic yield for inherited disorders including monogenic dystonia. This is of clinical importance, given the generally favourable response to deep brain stimulation for KMT2B‐related dystonia.

【 授权许可】

Unknown