By Daniel Paul Perez & June Kinoshita
One of the blue-sky dreams for those of us working toward treatments for FSH muscular dystrophy is regenerative therapy—treatments to generate healthy muscles to restore or replace those damaged by disease. We have taken an important step toward realizing this dream with our latest grant award for a project that will test stem cell therapy in a mouse model of FSHD.
A second award goes to a new tactic to prevent DUX4 protein from setting off a series of unfortunate events that lead to muscle cell death. The third grant given out in this cycle takes aim at a prevailing mystery—why males (on average) develop symptoms a decade earlier than females. Unraveling this secret could point the way to treatments that harness the mechanisms that help slow down the disease process in women.
These proposals, representing a total commitment of $388,445, were received for the February 2018 cycle of grant submissions and approved at the Society’s Board of Directors Meeting on September 25, 2018. Here are our latest grant awards:
DETERMINING THE THERAPEUTIC POTENTIAL OF PLURIPOTENT STEM CELL-DERIVED MYOGENIC PROGENITORS IN THE IDUX4PA MOUSE MODEL. Rita Perlingeiro, PhD, University of Minnesota, Minneapolis, USA. US$99,998 total (US$49,999 annually for two years)
There has been tremendous excitement for the therapeutic potential of induced pluripotent stem (iPS) cells in treating genetic diseases. These cells are derived from patients’ skin cells, which are genetically “reprogrammed” to become stem cells, with the ability to develop into muscle. This project builds on the Perlingeiro lab’s successful studies developing such cell therapies specifically in mouse models of Duchenne and limb-girdle muscular dystrophy (LGMD).
The intent of this cell product is to replace diseased muscle with normal functional muscle fibers as well as muscle stem cells, which have the potential to provide long-term therapeutic effect in Duchenne and other devastating types of muscular dystrophies, including FSHD. Because all of the Perlingeiro lab’s work to date has been with Duchenne and LGMD models, it will be essential to understand how effectively cell replacement can address muscle damage due to the distinct mechanism underlying FSHD.
Now that an FSHD mouse model (iDUX4pA; see FSH Watch 2018 Issue 1, page 1) is available that can be induced to produce very low levels of DUX4, resulting in a slow decline in muscle over several months, it will be possible to evaluate the effectiveness of cell therapy in the context of such a relevant muscle damage mechanism. The work proposed in this grant will provide proof of principle for including FSHD in the pipeline for future clinical trials of cell-based regenerative therapies.
A DECOY TRAPPING DUX4 FOR THE TREATMENT OF FACIOSCAPULOHUMERAL MUSCULAR DYSTROPHY. Virginie Mariot, PhD, University College London; Great Ormond Street Institute of Child Health, London, United Kingdom. US$163,447 for 18 months
Nearly 20 laboratories (including Drs. Mariot’s and Dumonceaux’s) have proposed therapeutic approaches for FSHD, but no one can predict whether any of these approaches will be successful in human patients. It is therefore important to continue to develop new strategies. This application uses a “decoy” approach, which represents a new conceptual approach in the neuromuscular field.
Unlike antisense oligonucleotides (ASO/AO) or siRNAs which target DUX4 messenger (mRNA) prior to the creation of the DUX4 protein, the decoy mechanism of action is to trap the DUX4 protein itself post-RNA translation. The decoy will attach to the DUX4 protein so that it cannot bind to DNA and trigger the downstream toxic effects of DUX4. Notably, this method is independent of the nucleus that produces DUX4 mRNA (which can be one out of 1000 nuclei) allowing the decoy to sequester the DUX4 protein during its cellular journey wherever it occurs. This decoy strategy may be highly powerful as shown by proof-of-principle studies already performed. The aim of this project is now to validate these results in the FLEx ACTA MCM mice (see FSH Watch 2017 issue 1, page 12).
THE ROLE OF ESTROGEN RECEPTORS IN FSHD1 MECHANISM. Anna Pakula, PhD, Boston Children’s Hospital, Boston, Massachusetts USA. US$125,000 for one year
FSHD individuals with shorter D4Z4 repeats are reported to be more severely affected, but there is still an unsolved conundrum on different disease manifestation in women and men. Sexual dimorphism in FSHD has been studied among American, Brazilian, Italian, and Dutch FSHD patients. Clinical (e.g., MRI) and neurological data revealed that in these populations, men manifest the disease earlier in their life and are more severely affected than women. The underlying mechanism explaining these noticeable sex differences in disease severity remains yet unsolved and will be the goal of these studies.
Dr. Pakula utilizes fish embryos, which when programmed to synthesize Dux4, develop features that resemble FSHD symptoms. This model is very helpful for studying the mechanism and potential treatments of this disease (see FSH Watch 2013 Winter, page 10). By performing analysis of DUX4 binding sites, her team has discovered that, at 12 hours of embryo development, ER-like (estrogen receptor-like) protein interacts with DUX4. The advantage of their model is that DUX4 and estrogen receptor (ER) interaction can be detected at the very early stages of disease development, which is not feasible in humans.
The investigators hypothesize that one of the estrogen receptors could help DUX4 reach its binding sites in DNA. Their hypothesis is that in males (having less estrogen than females), DUX4 binds to different DNA regions and regulates different genes, which possibly leads to more severe disease.
Dr. Kunkel and Dr. Pakula, together with Drs. Martha Bulyk and Yuliya Sytnikova from Brigham and Women’s Hospital, who are well established in studying transcription factors and chromatin, will unravel the mechanism of ER-like driven recruitment of the DUX4, which they believe may help to uncover new ways to treat FSHD.
Editor’s note: The FSH Society funded the development of the zebrafish, the FLEx mouse, and characterization of the iDUX4pA mouse models used in these projects. Project summaries submitted by investigators are found at https://www.fshdsociety.org/grants/funded-grants/