Mom, Dad and the Mitochondrial Donor


They say three is a party. But in this case, three parents may be just enough parents to save future babies from suffering a crippling disease for the rest of their lives.

We are talking about the mitochondrial replacement procedure. Found in the cytoplasm of a cell, mitochondria are powerhouses which supply it with energy to function and survive. However, they are not perfect organelles, and may sometimes have mutations which cause disease. Unfortunately, this can be passed on to children, since when fertilisation occurs, it uses the mother’s egg cell as the starter cell, and so all of her mitochondria, meaning that any subsequent cells that form from that zygote will carry the mother’s defective mitochondria.

zygote

A human zygote, which would contain a nucleus with genes from the mother and the father, and mitochondria from a donor

To prevent this, scientists have designed a new process, called mitochondrial replacement, to be carried out on women with mitochondrial diseases, allowing them to have children and prevent these from also suffering from the disease. It is done by a form of In Vitro Fertilisation. An egg cell from the mother and a sperm cell from the father are taken, like in normal IVF. The change comes when we add another egg cell, this time from a different woman (a donor). The nucleus of the mother’s egg cell is taken and it replaces the nucleus from the donor egg cell. The sperm is then allowed to fertilise the new egg cell and a zygote is formed which can then be implanted onto the mother and allowed to grow into a healthy baby. This way, the zygote will develop from a cell which contains the mother’s genes, but none of her mitochondria, so the baby is safe.

Messing around with zygotes is never child’s play, and always carries some controversy. In this case, it is due to the questionable effects of adding a third group of genes to a person. Since mitochondria are essential for life, having them come from a different source than the rest of the genome could have unpredictable consequences.

Despite some uncertainty, the UK government has approved this measure, saying there is no real proof it is unsafe. Rest assured, there will be plenty of human trials before it becomes a standard procedure, but at least it’s a brave step towards helping people suffering from these diseases improve their lives.

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