A Generic Assay to Detect Aberrant ARSB Splicing and mRNA Degradation for the Molecular Diagnosis of MPS VI

• Main Authors: Mike Broeders, Kasper Smits, Busra Goynuk, Esmee Oussoren, Hannerieke J.M.P. van den Hout, Atze J. Bergsma, Ans T. van der Ploeg, W.W.M. Pim Pijnappel
• Format: Article
• Language: English
• Published: Elsevier 2020-12-01
• Series: Molecular Therapy: Methods & Clinical Development
• Subjects: lysosomal disease; splicing; antisense oligonucleotides; pseudo exon; diagnosis; nonsense mediated decay
• Online Access: http://www.sciencedirect.com/science/article/pii/S2329050120301893

Identification and characterization of disease-associated variants in monogenic disorders is an important aspect of diagnosis, genetic counseling, prediction of disease severity, and development of therapy. However, the effects of disease-associated variants on pre-mRNA splicing and mRNA degradation are difficult to predict and often missed. Here we present a generic assay for unbiased identification and quantification of arylsulfatase B (ARSB) mRNA for molecular diagnosis of patients with mucopolysaccharidosis VI (MPS VI). We found that healthy control individuals have inefficient ARSB splicing because of natural skipping of exon 5 and inclusion of two pseudoexons in introns 5 and 6. Analyses of 12 MPS VI patients with 10 different genotypes resulted in identification of a 151-bp intron inclusion caused by the c.1142+2T>C variant and detection of low ARSB expression from alleles with the c.629A>G variant. A special case showed skipping of exon 4 and low ARSB expression. Although no disease-associated DNA variant could be identified in this patient, the molecular diagnosis could be made based on RNA. These results highlight the relevance of RNA-based analyses to establish a molecular diagnosis of MPS VI. We speculate that inefficient natural splicing of ARSB may be a target for therapy based on promotion of canonical splicing.