Using RNA interference to correct an error in the genetic code of patients with Fukuyama muscular dystrophy

New method with implications for the treatment of Fukuyama muscular dystrophy, a common neuromuscular disorder

RNAi treatment restores normal FKTN protein production and alpha-dystroglycan glycosylation in cells derived from Fukuyama muscular dystrophy patients carrying the deep intronic variant. Credit: Mariko Taniguchi-Ikeda of Fujita Health University

Muscular dystrophy is a debilitating disease that causes progressive weakening and loss of muscle. Fukuyama congenital muscular dystrophy (FCMD), the second most common form of childhood muscular dystrophy in Japan, is a severe neuromuscular disorder characterized by generalized muscle weakness, decreased muscle tone, eye abnormalities, brain malformation, cardiomyopathy, epilepsy and seizures associated with intellectual disorders. disability.

FCMD is caused by a genetic defect in the “fukutin” (FKTN) gene. Japanese researchers led by Dr. Mariko Taniguchi-Ikeda, Associate Professor in the Department of Clinical Genetics at Fujita Health University Hospital, recently succeeded in overcoming this defect in the FKTN gene and restoring its normal biological function.

Using the experimental technique called exon skipping by antisense oligonucleotides the team corrected an error in the FKTN gene that blocks the chemical glycosylation of a biologically important protein. To this end, the team designed specific antisense oligonucleotides, small pieces of DNA or RNA that can bind to specific RNA molecules. The researchers then conducted experiments on patient-derived cells using these antisense oligonucleotides to validate their hypothesis.

Dr. Taniguchi-Ikeda says, “I have seen patients with FCMD for over 20 years. The goal of our research was to find a cure for this incurable disease. FCMD is the second most common childhood type. muscular dystrophy in the Japanese population. Our previous studies show that patients with a retrotransposal insertion can be treated by introducing antisense oligonucleotides.”

“Clinical trials are currently underway. However, no therapeutic methods are available for patients carrying a heterozygous variant with deep enthronement. Our results suggest that exon skipping by antisense oligonucleotides as a treatment for patients with the deep enthronement variant has tremendous potential.”

The basic principle of the research is based on a physiological mechanism involving FKTN. The FKTN gene is responsible for the production of “ribitol-phosphate transferase” – an enzyme that chemically transfers a glycosyl group to alpha-dystroglycan (α-DG). α-DG is a key protein found in the cytoskeleton – an extensive network of protein filaments and tubules that give living cells shape and coherence.

New method with implications for the treatment of Fukuyama muscular dystrophy, a common neuromuscular disorder

Fluorescent microscopy images showing absent and restored glycosylated alpha-dystroglycan and its function (laminin-binding capacity) in patient-derived myotube. Credit: Mariko Taniguchi-Ikeda of Fujita Health University

The genetic defect in the FKTN gene prevents it from expressing a fully functional form of ribitol-phosphate transferase. This reduced functionality, in turn, blocks a critical process in the biological relay, α-DG glycosylation. Incidentally, glycosylation, or the attachment of sugar molecules to non-sugar moieties like lipids and proteins, such as α-DG in this case, is important to ensure the structural stability as well as the functionality of these moieties.

The findings, which were published in Human Molecular Geneticshave immediate implications, since the specifically designed antisense oligonucleotides, when introduced into patient-derived cells via RNAi, were able to bypass the affected region of the gene, thus restoring normal production of the FKTN protein and the subsequent glycosylation of α-DG.

Radical therapies for certain types of neuromuscular disorders have evolved considerably in recent years. Although no effective therapy was available until recently, several therapeutic approaches have reached the clinical stage in recent years. Specifically, the pharmacological modulation of RNA splicing aimed at altering RNA processing and function has made remarkable progress in recent years.

Co-author Hiroki Kurahashi, a professor at Fujita Health University, adds, “FCMD patients who carry the abnormal FKTN gene produce unglycosylated α-DG, which makes them bedridden by adolescence. They also need respiratory support, a feeding tube, and lifelong care from their families. Our initial experiences are therefore of paramount importance.

Encouraged by their in vitro findings, the research team is now offering translational work by setting up large-scale clinical trials involving patients with FCMD. Lead author Sarantuya Enkhjargal, Ph.D. student at Fujita Health University Hospital concludes: “The United States Food and Drug Administration has approved eight antisense oligonucleotides for the treatment of several diseases. Our findings are promising at the in vitro level. Further in vivo efficacy and safety studies in animal models will be needed before this approach is finally used in clinical trials, however. »

These results nevertheless offer a glimmer of hope for the multitude of patients and their families affected by this serious disease.

More information:
Sarantuya Enkhjargal et al, Antisense oligonucleotide-induced pseudoexon skipping and functional protein restoration for Fukuyama muscular dystrophy caused by deep intronic variant, Human Molecular Genetics (2022). DOI: 10.1093/hmg/ddac286

Provided by Fujita Health University

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