Differences in aberrant expression and splicing of sarcomeric proteins in the myotonic dystrophies DM1 and DM2.
Aberrant transcription and mRNA processing of multiple genes due to RNA-mediated toxic gain-of-function has been suggested to cause the complex phenotype in myotonic dystrophies type 1 and 2 (DM1 and DM2). However, the molecular basis of muscle weakness and wasting and the different pattern of muscle involvement in DM1 and DM2 are not well understood. We have analyzed the mRNA expression of genes encoding muscle-specific proteins and transcription factors by microarray profiling and studied selected genes for abnormal splicing. A subset of the abnormally regulated genes was further analyzed at the protein level. TNNT3 and LDB3 showed abnormal splicing with significant differences in proportions between DM2 and DM1. The differential abnormal splicing patterns for TNNT3 and LDB3 appeared more pronounced in DM2 relative to DM1 and are among the first molecular differences reported between the two diseases. In addition to these specific differences, the majority of the analyzed genes showed an overall increased expression at the mRNA level. In particular, there was a more global abnormality of all different myosin isoforms in both DM1 and DM2 with increased transcript levels and a differential pattern of protein expression. Atrophic fibers in DM2 patients expressed only the fast myosin isoform, while in DM1 patients they co-expressed fast and slow isoforms. However, there was no increase of total myosin protein levels, suggesting that aberrant protein translation and/or turnover may also be involved.
Vihola
Anna
A
Department of Medical Genetics, Folkhälsan Institute of Genetics, University of Helsinki, 00014 Helsinki, Finland.
Bachinski
Linda L
LL
Sirito
Mario
M
Olufemi
Shodimu-Emmanuel
SE
Hajibashi
Shohrae
S
Baggerly
Keith A
KA
Raheem
Olayinka
O
Haapasalo
Hannu
H
Suominen
Tiina
T
Holmlund-Hampf
Jeanette
J
Paetau
Anders
A
Cardani
Rosanna
R
Meola
Giovanni
G
Kalimo
Hannu
H
Edström
Lars
L
Krahe
Ralf
R
Udd
Bjarne
B
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D017398:Alternative Splicing; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D060588:LIM Domain Proteins; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000473:pathology; D009133:Muscular Atrophy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009218:Myosins / Q000235:genetics* / Q000378:metabolism; D009223:Myotonic Dystrophy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020107:Troponin T / Q000235:genetics* / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C120696:LDB3 protein, human; D060588:LIM Domain Proteins; D020033:Protein Isoforms; C518660:TNNT3 protein, human; D014157:Transcription Factors; D020107:Troponin T; D009218:Myosins