Myotonic Dystrophy Drug Discovery Service

The development of novel relevant disease models remains of high importance to investigate pathophysiologic mechanisms and assess new therapeutic approaches. In addition to animal models, in vitro cell culture provides a unique resource for basic and translational research. Creative Biolabs has vast experience in providing one-stop-shop solutions to numerous and diverse pharmaceutical research companies.

Overview

DM (myotonic dystrophy) is a multisystemic disorder and the second most common form of muscular dystrophy. The main features of the disease include muscular rigidity, cataracts, muscle loss, heart conduction defects, insulin resistance, cognitive impairment, and mental retardation in the most serious congenital condition. There are two distinct genetic subtypes DM1 and DM2.

Creative Biolabs' Services for the Genetic Mechanism Studies of DM

DM is inherited in an autosomal dominant pattern. Both DM1 and DM2 are generated by the extension of nucleotide repeats. DM1 is extended from a trinucleotide sequence on chromosome 19, while DM2 is extended from a tetranucleotide repeat on chromosome 3. In a series of elegant studies, it has been shown that RNA expression of the repeat expansion is pathogenic itself. This mechanism of "gain-of-function toxic RNA" is thought to mediate disease through the formation of aggregates of double-stranded RNA in the nucleus. The expanded RNA accumulates as double-stranded structures in the nucleus and sequesters splicing regulators, rendering them unable to facilitate normal splicing of genes. The current understanding of DM molecular pathology emphasizes that double-stranded RNA aggregates are the main mediators of pathology.

Fig.1 DM1 is caused by an expansion in a CTG repeat on chromosome 19. (McNally, 2011)

Creative Biolabs' Mouse Models of DM

Nearly 20 mouse models have provided important additional insights into specific aspects of this novel disease mechanism. These models provide a unique resource for testing pharmacological, antisense, and gene therapy treatment strategies for specific events in the pathological cascade.

• Transgenic Mouse Models

DM1 transgenic mouse models have been developed to investigate the multisystemic pathophysiology and mechanisms of trinucleotide repeat dynamics. Existing mouse models are derived from (i) gene inactivation at DM1 locus, (ii) overexpression of toxic CTG repeats, (iii) abnormal splicing regulation through Mbnl inactivation or Celf overexpression, and (iv) introduction of unstable CTG expansion.

• Models of Abnormal Splicing Regulators

The characterization of the molecular and physiological phenotypes resulting from MBNL (RNA-binding Protein Muscleblind-like) inactivation and CELF (CUG-BP and ETR-3-like factor) upregulation in mice, independently of repeat expansion, has illustrated the central role of these two families of splicing regulators in DM1 pathogenesis.

Strategies for Treating DM

The dissection of molecular mechanisms opens new avenues for rationally targeting multiple disease intermediates: DNA amplification, toxic transcripts, RNA-interacting proteins, splicing regulators, and misspliced transcripts.

• Reducing RNA Toxicity by Silencing Transcription

For repeat expansion mutations there are indications that transcription elongation is a promising therapeutic target.

• Post-transcriptional Silencing of DMPK or CNBP

Various nucleic acid-based techniques have been used to obtain the post-transcriptional knockout of toxic RNA. The most widely used strategy in clinical development is the use of RNase H1-active ASOs. In this case, the targeted sequence lies outside the repeat sequence and thus retains the main advantage of the antisense technique, its significant target specificity.

• Small Molecules to Inhibit MBNL:(C)CUG-repeat Interactions or Disperse RNA Foci

The biophysical properties of expanded CUG- or CCUG-repeats are favorable for drug development. In the DM1 model system, the drug-induced release of MBNL protein in CUG repeats restores MBNL activity and repairs splicing defects.

• Targeting Signaling Pathways Downstream of CUG/CCUG Expression

Another therapeutic strategy is to target signaling pathways activated downstream of CUG^exp expression, including protein kinase C (PKC), glycogen synthase kinase 3 beta (GSK3beta), and AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR).

Fig.2 Strategies for treating DM. (Thornton, 2017)

Creative Biolabs' Services for DM Preclinical Drug Discovery

• In Vitro Services
• In Vivo Services
• Ex Vivo Services
• Discovery Services
• Development Services

Creative Biolabs is a customer-driven organization that is oriented toward quick knowledgeable responses to your needs. You can rely on our know-how, understanding, experience, and passion for providing the most comprehensive research program in the field of neuroscience, in a reliable manner with quick turnaround times and the utmost respect for customer confidentiality. Contact us to get a quote for your DM research project.

References

1. McNally, E.M.; Sparano, D. Mechanisms and management of the heart in myotonic dystrophy. Heart. 2011, 97(13): 1094-1100.
2. Thornton, C.A.; et al. Myotonic dystrophy: approach to therapy. Current opinion in genetics & development. 2017, 44: 135-140.