Using RNA interference to correct a mistake in the genetic code of patients with Fukuyama muscular dystrophy

Muscular dystrophy is a debilitating disease that causes progressive wasting 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, ocular abnormalities, brain malformation, cardiomyopathy, epilepsy, and associated seizures. with intellectual problems. disability.

FCMD is caused by a genetic abnormality in the “fukutin” gene (FKTN). Researchers in Japan led by Dr. Mariko Taniguchi-Ikeda, associate professor in the Department of Clinical Genetics at Fujita Health University Hospital, were recently able to overcome this defect in the FKTN gene and restore 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 fragments of DNA or RNA that can bind to specific RNA molecules. The researchers then performed experiments on patient-derived cells using these antisense oligonucleotides to validate their hypothesis.

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

“Clinical trials are currently underway. However, there are no therapeutic methods available for patients who carry a heterozygous deep intronic variant. Our findings suggest that exon skipping by antisense oligonucleotides as a treatment for patients with the deep intronic variant has enormous potential.” “.

The basic premise 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 present in the cytoskeleton, a large network of protein filaments and tubules that gives living cells shape and coherence.

The genetic abnormality 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. By the way, glycosylation, or the attachment of sugar molecules to non-sugar moieties such as lipids and proteins, like α-DG in this case, is important to ensure the structural stability and functionality of these moieties.

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

Radical therapies for certain types of neuromuscular disorders have evolved significantly in recent years. Although effective therapies were not available until recently, several therapeutic approaches have advanced to the clinical stage in recent years. More specifically, modulation of pharmacological RNA splicing aimed at modifying RNA processing and function has made marked progress in recent years.

Co-author Hiroki Kurahashi, a professor at Fujita Health University adds: “FCMD patients who carry the abnormal FKTN gene produce non-glycosylated α-DG, rendering them bedridden since adolescence. They also require respiratory support, a feeding tube, and lifelong care for their families. Our initial experiments are therefore of paramount importance.”

Encouraged by their in vitro findings, the research team now proposes translational work by establishing large-scale clinical trials involving FCMD patients. Lead author Sarantuya Enkhjargal, Ph.D. Fujita Health University Hospital student concludes: “The US Food and Drug Administration has approved eight antisense oligonucleotides for the treatment of various diseases. Our findings are promising at the in vitro level. Further studies on efficacy and safety will follow.” in vivo in animal models”. However, it will be necessary before this approach is finally used in clinical trials.”

These findings, however, offer a glimmer of hope for the multitude of patients and their families affected by this serious condition.

Provided by Fujita Health University