Of the nearly 3 billion molecules that make up our genome, only 1.1% code for genetic instructions. When scientists sequenced the genome, they originally estimated that as much as 24% was useless. MicroRNAs, are tiny sequences of molecules that are vital to our development, growth, survival and regulate many of our genes. While they are “cast-off” parts of our genome, they are should not be overlooked as scientists have matched microRNAs to the development of diseases such as Alzheimer’s and cancer.
MicroRNAs can stop genes from using their instructions to make protein molecules by blocking and binding to the genetic code. In the case of Alzheimer’s, microRNAs are involved in the build-up of the tangles of proteins that accumulate in the brain and in cancer development, some microRNAs are tumour suppressors, so when they lose their function, cancerous cells can develop.
When microRNAs are known to be involved in the development of a disease, they can be looked at as a biological target or a biomarker for the condition. MicroRNAs are better markers for a disease than most other molecules because they are so small they do not become trapped in inaccessible regions of the body such as the brain, and are found well-preserved in bodily samples such as blood, urine or tissue.
However, due to their small size, they degrade rather quickly and can be hard to detect. Researchers are developing tools which can be used as biosensors, to give off fluorescent signals once they bind with a microRNA. They are also trialling the use of microRNAs as biomarkers for disease diagnosis and treatment targets or using microRNAs themselves as a form of treatment. The first treatment to target RNA was a drug patisiran (Onpattro), which targets a small interfering RNA and works by binding to the RNA molecule that is linked to a rare form of nerve disease. Now scientists are researching how we can target and use microRNAs for treatment.
While there is a lot of ongoing research in the area, there are significant challenges to overcome, such as how we might deliver microRNAs to the body as they are relatively unstable. Using modified or synthetic microRNAs may help to increase their stability and make them a viable treatment option in the future.