[September 2011] Two exciting new papers have been published recently on possible approaches for treating FSHD using a form of genetic treatment called RNA interference (RNAi).
The details emerged within one month of each other in the highly regarded international journal Molecular Therapy. The two complementary studies were performed by different teams of scientists: the Harper Laboratory, at The Ohio State University and Nationwide Children’s Hospital in Columbus, Ohio, with a collaborator in Modena, Italy; and the Gabellini and Chamberlain laboratories, in Milan, Italy, and Seattle, Washington, respectively.
For this work, Drs. Gabellini and Tupler were funded by research grants totalling $240,000 from FSHD Global Research Foundation. We at FSHD Global Research Foundation remain cautiously optimistic about this new technology as being applicable for treatment of human FSHD. However, we believe that this work is a major step forward in development of a treatment for FSHD sufferers.
FSHD Global Research Foundation’s funding of local and international Basic Research into FSHD is critical at this exciting and important time in the development of potential treatments for FSHD. In addition to funding of Basic Research into the causes of FSHD, and the testing of potential treatments in animals, FSHD Global Research Foundation plans to form a new Therapeutic Strategy Committee during late 2011 or early 2012. The aims of this committee are to recommend potential human treatments, based on the findings from the types of animal studies described below, and to assist in bringing these treatments to the clinic. FSHD Global Research Foundation will be releasing more information on this new committee in the near future.
More About The New Findings
RNA interference (RNAi) is a natural process that controls the effects of genes. It operates like a volume control knob for the gene’s effects. Over several years, many scientists have been working to apply this natural gene control mechanism for treating diseases. The triggers of RNAi in the body can be designed in the laboratory to reduce the effects of disease associated genes. In the two studies published in the journal Molecular Therapy, the research teams designed RNAi’s to inhibit the gene producing the toxic protein FRG1and then used them to treat the muscles of dystrophic mice exhibiting FSHD symptoms.
The first study, published by Wallace and co-workers on July 5, 2011, reported that FRG1 RNAi’s reduced toxic FRG1 levels and improved the microscopic appearance and abnormal function of muscles seen in these mice. Drs. Wallace and Harper wrote that since using RNAi worked in this instance, that RNAi-based treatment shows promise for treatment of frequently inherited muscle diseases, regardless of the faulty gene. The Harper Laboratory is now applying this strategy to another FSHD associated gene, called DUX4, as well as genes involved in other frequently inherited muscle diseases, including Limb Girdle Muscular Dystrophy (LGMD).
The second study, published on August 9, 2011, by Bortolanza and co-workers, noted that from a single injection they reached all of the muscles and obtained a lasting effect. This treatment resulted in improvements of the muscle structure under the microscope, and muscle function, and lowered toxic FRG1 protein levels. There were no ill effects of the treatment in these adult animals that initially had signs of muscular dystrophy. While this work targeted the FRG1 gene, the same approach is possible for other faulty genes, such as DUX4, that are associated with FSHD.
Both papers are important for several reasons. Firstly, they are proof of concept of a possible treatment for human FSHD. Secondly, this form of treatment is relevant for frequently inherited muscle diseases in general. There are at least 29 genes thought to be responsible for these inherited muscle diseases. In total, these inherited muscle diseases may affect as many as 1 individual in 2,400 making them the most frequent muscle disorders. Indeed, of the three most important muscle diseases (FSHD, Myotonic and Duchenne), FSHD and Myotonic are frequently inherited disorders. Nevertheless, these frequently inherited muscle diseases have been largely neglected. New approaches using synthetic genetic material such as RNAi were unavailable until a few years ago. Based on the results obtained by the two groups described above, they predict that similar approaches to the one they described could be applicable to a large number of patients affected by frequently inherited muscle diseases.
The financial support of FSHD Global Research Foundation was instrumental in obtaining the results described in these scientific publications, which are referenced below.
RNA Interference Improves Myopathic Phenotypes in Mice Over-expressing FSHD Region Gene 1 (FRG1)
Molecular Therapy 2011 Jul 5. doi: 10.1038/mt.2011.118. [Epub ahead of print] Wallace LM, Garwick-Coppens SE, Tupler R, Harper SQ
Molecular, Cellular, and Developmental Biology Graduate Program, The Ohio State University, Columbus, Ohio, Center for Gene Therapy, The Research Institute at Nationwide Children’s Hospital, Columbus, Ohio, USA.
In the summary, Wallace, Harper and co-workers reported that the mice used in their study, were originally developed to prove that high levels of the FRG1 protein were a primary cause of FSHD. Although the disease symptoms in these mice strongly supported this concept, there were arguments against the role of FRG1 in causing FSHD, or minimizing its importance. Thus, FRG1 was controversial as a cause of FSHD. In their study, the primary goal was to demonstrate efficacy for RNAi therapy of frequently inherited muscle diseases, in general, and that these mice mimicked the human disease. The group reasoned that lack of confirmation of FRG1 as the cause of FSHD, was not important to the goal of their study, which was to reduce toxic levels of human FRG1 protein in the mouse muscles. They reported that treatment with RNAi reduced toxic FRG1protein levels and improved muscle structure under the microscope and muscle function in the diseased muscles caused by high FRG1 protein levels in these mice. Their work suggests that RNAi has great potential for treatment of frequently inherited muscle diseases, in general. Not only could this form of treatment be applied to target FRG1, but it could be modified to target other faulty genes associated with FSHD, such as DUX4.
AAV6-mediated Systemic shRNA Delivery Reverses Disease in a Mouse Model of Facioscapulohumeral Muscular Dystrophy
Molecular Therapy , (9 August 2011) | doi:10.1038/mt.2011.153
Bortolanza S, Nonis A, Sanvito F, Maciotta S, Sitia G, Wei J, Torrente Y, Di Serio C, Chamberlain JR, Gabellini D Dulbecco Telethon Institute and Division of Regenerative Medicine, San Raffaele Scientific Institute, Milano, Italy
There were several conclusions from the results obtained by Bortolanza, Gabellini and co-workers. They stated that although several interesting genes have been proposed as the cause of FSHD, no single gene has been definitely proven to cause FSHD, thus far. It was reported that in an area on one of the human chromosomes called the D4Z4 repeat, there is genetic material (DNA) that codes for a protein involved in development of the body, named DUX4. DUX4 has been detected in early muscle cell progenitors from FSHD sufferers, but not from non-FSHD progenitors. This suggests that changes in the D4Z4 repeat region of the DNA may affect the disease by faulty production of DUX4 protein. Several studies on muscle function have described toxic effects of DUX4 protein. The toxicity of DUX4 protein coupled with usual very low DUX4 protein levels in humans is a difficult challenge to workers trying to mimic the human disease in mice. However, if production of a DUX4 mouse is successful, the group’s RNAi treatment could be adapted to reduce DUX4 protein levels in the affected muscles of these mice.
The group reported that a growing understanding of the FRG1 protein’s function strongly suggests that high FRG1 protein levels play an important role in FSHD. Based on their results, FRG1 inhibition should lead to an effective treatment for FSHD. They used the unique FSHD mice to demonstrate the potential benefit of RNAi treatment for FSHD. In their study, they showed a long-lasting reduction in FRG1 protein in all the muscles analysed. Moreover, the FRG1 protein levels decreased as the dose given to the mice increased. Benefits were observed in all of the mice treated with either low or high doses.
In conclusion, the group showed that they could prevent development of the disease by injection of FRG1 RNAi after onset of the disease. Their work demonstrated the power and selectivity of RNAi in targeting widespread disease in muscles in a living animal and offers a potential treatment for individuals who have already developed symptoms of disease. The efficient, stable, and lasting reduction of symptoms in these mice suggests that clinical benefit may be obtained with limited dosing. This treatment could potentially be translated into treatments for human patients. The knowledge gained from their studies could therefore eventually lead to new treatments for FSHD and other dominant diseases in humans.
For more information on FSHD Global Research sponsored projects, please contact Glenn Pilkington, Manager, Grants and Research Development. Email:glenn.pilkington@fshdglobal.org.