What is the ACTN3 variant?
In any one gene there may be subtle variations in the DNA code. It is often these subtle variations, in conjunction with the environment that makes each person unique. Within the DNA code of the ACTN3 gene, there is a variation known as the R577X variant. The R577X variant stops the developing muscle cells in the body from being able to read the entire code of the ACTN3 gene. If a person is shown to have the R577X variant in both copies of their ACTN3 gene, it stops them from producing the alpha-actinin-3 protein. In such a person, the alpha-actinin-3 is completely absent from the fast twitch muscle fibres. This doesn’t stop the muscles from working properly: the person’s muscles appear to use a different gene (ACTN2) to compensate for the loss of alpha-actinin-3. It is currently estimated that approximately 18% of the world’s population carries the R577X variant in both copies of their ACTN3 gene. In other words, the R577X variant is a very common genetic alteration in the population,
