title: Muscleblind-like 1 knockout mice reveal novel splicing defects in the myotonic dystrophy brain.
abstract: Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by a CTG trinucleotide repeat expansion (CTG(exp)) in the DMPK gene. In skeletal muscle, nuclear sequestration of the alternative splicing factor muscleblind-like 1 (MBNL1) explains the majority of the alternative splicing defects observed in the HSA(LR) transgenic mouse model which expresses a pathogenic range CTG(exp). In the present study, we addressed the possibility that MBNL1 sequestration by CUG(exp) RNA also contributes to splicing defects in the mammalian brain. We examined RNA from the brains of homozygous Mbnl1(ΔE3/ΔE3) knockout mice using splicing-sensitive microarrays. We used RT-PCR to validate a subset of alternative cassette exons identified by microarray analysis with brain tissues from Mbnl1(ΔE3/ΔE3) knockout mice and post-mortem DM1 patients. Surprisingly, splicing-sensitive microarray analysis of Mbnl1(ΔE3/ΔE3) brains yielded only 14 candidates for mis-spliced exons. While we confirmed that several of these splicing events are perturbed in both Mbnl1 knockout and DM1 brains, the extent of splicing mis-regulation in the mouse model was significantly less than observed in DM1. Additionally, several alternative exons, including Grin1 exon 4, App exon 7 and Mapt exons 3 and 9, which have previously been reported to be aberrantly spliced in human DM1 brain, were spliced normally in the Mbnl1 knockout brain. The sequestration of MBNL1 by CUG(exp) RNA results in some of the aberrant splicing events in the DM1 brain. However, we conclude that other factors, possibly other MBNL proteins, likely contribute to splicing mis-regulation in the DM1 brain.
authors.affiliation: Division of Neurology, Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Suenaga
authors.forename: Kuang-Yung
authors.initials: KY
authors.lastname: Lee
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakamori
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Tatsumi
authors.forename: Masanori P
authors.initials: MP
authors.lastname: Takahashi
authors.forename: Harutoshi
authors.initials: H
authors.lastname: Fujimura
authors.forename: Kenji
authors.initials: K
authors.lastname: Jinnai
authors.forename: Hiroo
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Hongqing
authors.initials: H
authors.lastname: Du
authors.forename: Manuel
authors.initials: M
authors.lastname: Ares
authors.forename: Maurice S
authors.initials: MS
authors.lastname: Swanson
authors.forename: Takashi
authors.initials: T
authors.lastname: Kimura
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D015139:Blotting, Southern; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005091:Exons / Q000235:genetics; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D046228:Microarray Analysis; D009223:Myotonic Dystrophy / Q000473:pathology*; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
chemical_list: C585517:DMPK protein, human; C585516:DMPK protein, mouse; D004268:DNA-Binding Proteins; C479922:Mbnl1 protein, mouse; D016601:RNA-Binding Proteins; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases