U1 snRNA is an experimental treatment being developed for aromatic L-amino acid decarboxylase (AADC) deficiency.
What is AADC deficiency?
AADC deficiency is a rare disorder caused by mutations in a gene called DDC, which provides instructions for making an important enzyme (AADC) in the brain. AADC is involved in making two important signaling molecules in the brain (dopamine and serotonin). Mutations in DDC mean that not enough AADC is made, resulting in not enough serotonin and dopamine in the brain, causing the symptoms of the disease.
In order to make a protein from a gene (a DNA sequence within the genome), a temporary copy of the gene has to be made. This is called a messenger RNA or mRNA. This mRNA must then be processed to produce a mature mRNA that is ready to be “translated” into a protein. The processing of this mRNA involves editing out some non-coding sequences (called introns). This process is tightly controlled. Some mutations in DDC can cause the processing to stall or fail, meaning that no AADC protein is made.
How could U1 snRNA treat AADC deficiency?
U1 snRNA is a small, non-coding RNA (i.e. the RNA does not code for a protein) that is part of the complex involved in mRNA maturation. By introducing a modified form of U1 snRNA to the brain, it may be possible for cells to overcome the stall during mRNA maturation that prevents AADC protein from being made. The modified snRNA recognizes the specific mutations in the DDC mRNA, correcting the editing process so that a more normal protein can be made.
U1 snRNA in research
Researchers in Taiwan recently conducted a study in which they described the modified U1 snRNA that they designed to treat some forms of AADC deficiency. The results of this study were published in the scientific journal Human Molecular Genetics.
The authors performed an experiment, demonstrating that the snRNA would correct the editing events of DDC mRNA maturation. They followed up this experiment with a test in a mouse model of AADC deficiency. They used a virus to deliver the modified U1 snRNA to the brains of the mice. Following treatment, the mice showed improved production of dopamine and serotonin, and their survival was also improved.
The authors concluded that these results were promising, but more research is needed to translate these findings into human clinical trials.
Last updated: Sept. 23, 2019.
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