Regulatory mechanisms of aberrant splicing in the deseases

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17026027
• Research Category: Grant-in-Aid for Scientific Research on Priority Areas
• Allocation Type: Single-year Grants
• Review Section: Biological Sciences
• Research Institution: University of Miyazaki
• Principal Investigator: IMAIZUMI Kazunori University of Miyazaki, Department of Anatomy, Faculty of Medicine, Prof. (90332767)
• Project Period (FY): 2005 – 2006
• Keywords: splicing / dystrophy / Muscleblind / SERCA / trinucleotide repeats

Research Abstract

Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disorder associated with an expansion of CTG trinucleotide repeats in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. The RNA gain-of-function hypothesis proposes that mutant DMPK mRNA alters the function and localization of alternative splicing regulators, which are critical for normal RNA processing. Previously, we found alternative splicing variants of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1 (SERCA1), which excluded exon 22, in skeletal muscle of DM1 patients. In the present study, we analyzed the molecular mechanisms responsible for the splicing dysregulation of SERCA1. Five 'YGCU(U/G)Y' motifs that could potentially serve as Muscleblind, (MBNL)-binding motifs, are included downstream from the SERCA1 exon 22. Exon trapping experiments showed that MBNL acts on the 'YGCU(U/G)Y' motif, and positively regulates the exon 22 splicing. Of the five MBNL motifs in intron 22, the second and third sites were important for regulation of exon 22 splicing, but the other three binding sites were not required. Overexpression of the CUG repeat expansion of DMPK mRNA resulted in exclusion of the exon 22 of SERCA1. These results suggest that sequestration of MBNL into the CUG repeat expansion of DMPK mRNA could cause the exclusion of SERCA1 exon 22, and expression of this aberrant splicing form of SERCA1 could affect the regulation of Ca2+ concentration of sarcoplasmic reticulum in the DM patients.

Research Products

• [Journal Article] Molecular mechanisms responsible for aberrant splicing of SERCA1 in myotonic dystrophy type 1. (2007)
  • Author(s): Hino S-I, Kondo S, Sekiya H, Saito A, Kanemoto S, Murakami T, Chihara K, Aoki Y, Nakamori M, Takahashi MP, Imaizumi K.
  • Journal Title: Human Molecular Genetics 16 Pages: 2834-2843
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Candidates for tumor-specific alternative splicing. (2005)
  • Author(s): Okumura M, Kondo S, Ogata M, Kanemoto S, Murakami T, Yanagida K, Saito A, Imaizumi K.
  • Journal Title: Biochem Biophys Res Commun 334 Pages: 23-29
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Presentation] 筋強直性ジストロフィータイプ1におけるSERCA1の異常スプライシングの分子機構 (2007)
  • Author(s): 日野真一郎, 高橋正紀, 今泉和則
  • Organizer: 第30回日本分子生物学会年会(BMB2007)
  • Place of Presentation: 横浜
  • Year and Date: 2007-12-14
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] Molecular mechanisms responsible for aberrant splicing of sarcoplasmic/endoplasmic reticulum Ca^<2+>-ATPase 1 (SERCA1) in myotonic dystrophy type1. (2007)
  • Author(s): Hino S-I, Takahashi MP, Imaizumi K.
  • Organizer: The 30^<th> Annual Meeting of the Molecular Biology Society of Japan
  • Place of Presentation: Yokohama, Japan
  • Year and Date: 2007-12-14
  • Description: 「研究成果報告書概要(欧文)」より