Splicing biomarkers of disease severity in myotonic dystrophy.
OBJECTIVE
To develop RNA splicing biomarkers of disease severity and therapeutic response in myotonic dystrophy type 1 (DM1) and type 2 (DM2).


METHODS
In a discovery cohort, we used microarrays to perform global analysis of alternative splicing in DM1 and DM2. The newly identified splicing changes were combined with previous data to create a panel of 50 putative splicing defects. In a validation cohort of 50 DM1 subjects, we measured the strength of ankle dorsiflexion (ADF) and then obtained a needle biopsy of tibialis anterior (TA) to analyze splice events in muscle RNA. The specificity of DM-associated splicing defects was assessed in disease controls. The CTG expansion size in muscle tissue was determined by Southern blot. The reversibility of splicing defects was assessed in transgenic mice by using antisense oligonucleotides to reduce levels of toxic RNA.


RESULTS
Forty-two splicing defects were confirmed in TA muscle in the validation cohort. Among these, 20 events showed graded changes that correlated with ADF weakness. Five other splice events were strongly affected in DM1 subjects with normal ADF strength. Comparison to disease controls and mouse models indicated that splicing changes were DM-specific, mainly attributable to MBNL1 sequestration, and reversible in mice by targeted knockdown of toxic RNA. Splicing defects and weakness were not correlated with CTG expansion size in muscle tissue.


CONCLUSIONS
Alternative splicing changes in skeletal muscle may serve as biomarkers of disease severity and therapeutic response in myotonic dystrophy.
Department of Neurology, University of Rochester Medical Center, Rochester, NY; Center for Neural Development and Disease, University of Rochester Medical Center, Rochester, NY.
Masayuki
M
Nakamori
Krzysztof
K
Sobczak
Araya
A
Puwanant
Steve
S
Welle
Katy
K
Eichinger
Shree
S
Pandya
Jeannne
J
Dekdebrun
Chad R
CR
Heatwole
Michael P
MP
McDermott
Tian
T
Chen
Melissa
M
Cline
Rabi
R
Tawil
Robert J
RJ
Osborne
Thurman M
TM
Wheeler
Maurice S
MS
Swanson
Richard T
RT
Moxley
Charles A
CA
Thornton
D000293:Adolescent; D000328:Adult; D000368:Aged; D017398:Alternative Splicing; D000818:Animals; D015415:Biomarkers; D015331:Cohort Studies; D004268:DNA-Binding Proteins / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology; D020967:Myotonic Disorders / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D009223:Myotonic Dystrophy / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D016376:Oligonucleotides, Antisense / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics; D012720:Severity of Illness Index; D055815:Young Adult
D015415:Biomarkers; D004268:DNA-Binding Proteins; C479922:Mbnl1 protein, mouse; D016376:Oligonucleotides, Antisense; D016601:RNA-Binding Proteins