title: Detailed molecular characterization of a novel IDS exonic mutation associated with multiple pseudoexon activation.
abstract: Mutations affecting splicing underlie the development of many human genetic diseases, but rather rarely through mechanisms of pseudoexon activation. Here, we describe a novel c.1092T>A mutation in the iduronate-2-sulfatase (IDS) gene detected in a patient with significantly decreased IDS activity and a clinical diagnosis of mild mucopolysaccharidosis II form. The mutation created an exonic de novo acceptor splice site and resulted in a complex splicing pattern with multiple pseudoexon activation in the patient's fibroblasts. Using an extensive series of minigene splicing experiments, we showed that the competition itself between the de novo and authentic splice site led to the bypass of the authentic one. This event then resulted in activation of several cryptic acceptor and donor sites in the upstream intron. As this was an unexpected and previously unreported mechanism of aberrant pseudoexon inclusion, we systematically analysed and disproved that the patient's mutation induced any relevant change in surrounding splicing regulatory elements. Interestingly, all pseudoexons included in the mature transcripts overlapped with the IDS alternative terminal exon 7b suggesting that this sequence represents a key element in the IDS pre-mRNA architecture. These findings extend the spectrum of mechanisms enabling pseudoexon activation and underscore the complexity of mutation-induced splicing aberrations.
  
  
  
  Novel exonic IDS gene mutation leads to a complex splicing pattern. Mutation activates multiple pseudoexons through a previously unreported mechanism. Multiple cryptic splice site (ss) activation results from a bypass of authentic ss. Authentic ss bypass is due to a competition between de novo and authentic ss.
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.|Molecular Genetics Laboratory, Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.
authors.forename: L
authors.initials: L
authors.lastname: Grodecká
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.|Molecular Genetics Laboratory, Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.
authors.forename: T
authors.initials: T
authors.lastname: Kováčová
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Kramárek
authors.affiliation: Center for Medical Genetics, UZ Brussel and Vrije Universiteit Brussel, 1090, Brussels, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Seneca
authors.affiliation: Center for Medical Genetics, UZ Brussel and Vrije Universiteit Brussel, 1090, Brussels, Belgium.
authors.forename: K
authors.initials: K
authors.lastname: Stouffs
authors.affiliation: Nutrition and Metabolism Unit, University Children's Hospital Queen Fabiola, Free University of Brussels (ULB), 1020, Brussels, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: De Laet
authors.affiliation: Institute of Inherited Metabolic Disorders, First Faculty of Medicine, Charles University, Prague, Czech Republic.
authors.forename: F
authors.initials: F
authors.lastname: Majer
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: T
authors.initials: T
authors.lastname: Kršjaková
authors.affiliation: Molecular Genetics Laboratory, Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic.
authors.forename: P
authors.initials: P
authors.lastname: Hujová
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: K
authors.initials: K
authors.lastname: Hrnčířová
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: P
authors.initials: P
authors.lastname: Souček
authors.affiliation: Center for Medical Genetics, UZ Brussel and Vrije Universiteit Brussel, 1090, Brussels, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Lissens
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Buratti
authors.affiliation: Central European Institute of Technology, Masaryk University, Brno, Czech Republic. tomas.freiberger@cktch.cz.|Molecular Genetics Laboratory, Centre for Cardiovascular Surgery and Transplantation, Pekařská 53, 656 91, Brno, Czech Republic. tomas.freiberger@cktch.cz.|Institute of Clinical Immunology and Allergology, St. Anne's University Hospital and Masaryk University, Brno, Czech Republic. tomas.freiberger@cktch.cz.
authors.forename: Tomas
authors.identifier: 0000-0001-6532-7053
authors.initials: T
authors.lastname: Freiberger
mesh_terms: D000293:Adolescent; D005091:Exons; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D007438:Introns; D008297:Male; D016532:Mucopolysaccharidosis II / Q000235:genetics*; D009154:Mutation; D017354:Point Mutation; D022821:RNA Splice Sites; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D006023:Glycoproteins; C018322:IDS protein, human; D022821:RNA Splice Sites; D012333:RNA, Messenger
keywords: Complex splicing aberration; De novo splice site; IDS; Pseudoexon; Splice site competition