Gene-silencing oligonucleotides work by preventing the production of the protein product of gene transcription. This is significant in FSHD because they can be used to stop the production of toxic proteins produced through the lack of inhibition in the D4Z4 region.
Gene silencing oligonucleotides have been studied previously in models of FSHD with some promising results. The oligonucleotides that Professor Chen will be using for this newly funded grant represent a significant advancement on these early oligonucleotides. In addition, Idera Pharmaceuticals have identified four potential oligonucleotides that effectively inhibit DUX4 mRNA transcripts in cells.
The aims of this grant are to further develop these potential therapeutics in human FSHD cells and a mouse model of FSHD.
Update June 2016
The goal of the proposed study is to test a new generation of gene silencing agents called gene-silencing oligonucleotides (GSOs) for their efficacy in suppressing the pathogenic DUX4 expression in FSHD myoblasts and an FSHD mouse model. Several innovative designs of the GSOs by Idera Pharmaceuticals made them promising therapeutic agents. In the past six months, we have tested five GSOs and showed that all five successfully suppressed the DUX4 expression in patients’ muscle cells in culture. Higher concentration of the GSOs suppressed DUX4 expression more. Several genes that are regulated by DUX4 were also suppressed by the GSOs, indicating that the GSO treatments successfully reduced the harmful DUX4 expression effects in the human FSHD muscle cells. We are currently studying how the treatments correct the physiological defects that have been reported in the cells. We thank the FSHD Global Research Foundation for supporting this work.
Update January 2017
The goal of the proposed study is to test a new gene silencing agents called gene-silencing oligonucleotides (GSOs) for their efficacy in suppressing the pathogenic DUX4 expression in FSHD myoblasts and an FSHD mouse model. In the past grant period, we have tested five GSOs and showed that the GSOs successfully suppressed the DUX4 expression and genes that are regulated by DUX4. Higher concentration of the GSOs suppressed DUX4 expression more. We then studied whether the treatments could correct the cellular defects that had been reported previously. The defects include lower fusion index and higher number of atrophic myotubes in FSHD muscle cells, both suggest that the cells cannot form mature muscles well. In our studies, we showed that the GSO treatments completely or partially corrected the defects by increasing the fusion indexes and reducing the numbers of atrophic myotubes in cell culture. The results suggested that the treatments improved the ability of muscle growth. Currently, we are studying efficacy of the GSOs using a new mouse model of FSHD. We thank the FSHD Global Research Foundation for supporting this work.
Update July 2017
Gene-silencing oligonucleotides (GSOs) produced by Idera Pharmaceutical are designed to reduce the expression of the pathogenic DUX4 expression in FSHD. The goal of this study is to determine their efficacy using both human cell and mouse models of FSHD. In the first part of the study, we have tested five GSOs using FSHD muscle cells and showed that the GSOs reduced DUX4 levels in the cells. In addition, the FSHD cells behaved more similar to the healthy cells after the treatments. In this report period, we started animal studies to determine whether we can successfully deliver GSOs to muscles and whether the GSOs reduce expression of DUX4 and genes regulated by DUX4. To allow us visualize the GSOs, we added a florescent tag to the GSO compounds before we injected them into the mice. Our results showed that GSOs were able to enter muscle cells after intramuscular injection (direct injection into muscle), as well as after the subcutaneous injection (injection under the skin which allows systemic delivery). The results showed that the GSOs entered the muscles after either intramuscular or subcutaneous injection. Higher amount of GSOs was observed in muscles when the GSOs were delivered by intramuscular injection. We also showed that a gene regulated by DUX4 reduced its expression level after systemic delivery of GSOs for 12 days (6 subcutaneous injections). Our next step will be to increase the number of injections of GSOs to determine the efficacy of GSOs when delivered for longer period of time. We thank the FSHD Global Research Foundation for supporting this work.