Jojy Cheriyan MD,MPH--February 7, 2015

After years of discussions British House of Commons voted (382 to 128) in favor of creating embryos with genetic material from two women and one man. The House of Lords will probably pass the bill, which amends the 2008 Human Fertilization and Embryology Act, later this year.

Controversy has erupted among scientists and bioethicists, with more religious groups reacting against implementing this law. Supporters describe it as just a "mitochondrial transfer" where as opponents call it "three parent embryo".

This technique is an in-vitro fertilization that involves taking the nucleus of one egg (from a woman whose egg contains the defective mitochondria) and inserting that nucleus into the cytoplasm of another egg (from a donor-woman with healthy mitochondrial DNA) which has had its nucleus removed, and then fertilizing the hybrid egg with a sperm (from a man). The purpose of this procedure is to remove the nucleus from a cell with defective mitochondria and place it in a donor cell with healthy mitochondria, which after fertilization will contain a nucleus with genetic material from only the two parents. The two techniques currently tested are pronuclear transfer and spindle transfer.

This mitochondrial gene replacement raises ethical and social concerns. The technique as such involves modification of germ-line and these modifications would pass on to subsequent generations. Another ethical concern is the psychological and emotional impacts on a child's life, regarding sense of identity. According to bioethicists, the genetic make-up of children born as a result of mitochondrial replacement affect their emotional well-being when they become aware that they are different from other healthy children (siblings) conceived from the two parents.

Britain is the first country in the world to allow mitochondrial transfer, which has been banned elsewhere because it alters the human germ-line and could be described as “genetic engineering”. The Food and Drug Administration in the US is currently studying the issue. If U.S FDA gives green-light to the technique, it could rapidly spread elsewhere.

The technique is meant to help families whose children would otherwise live with a mitochondrial disease. Mitochondria are responsible for creating more than 90% of the energy needed by the body to sustain life and support growth. When they fail, less and less energy is generated within the cell. Cell injury and even cell death follow. If this process is repeated throughout the body, all systems begin to fail, and the life of the person is severely compromised. The diseases primarily affect children, but adult onset is becoming more and more common. These vary greatly in severity, but at their worst the children suffer damage to cells of the brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems.

Not all scientists welcome this decision. They all agree that mitochondrial diseases are truly terrible and need to be addressed. But, the potential outcomes from the technology are still vague with safety concerns, and it raises profound ethical issues such as changing the human genome heritably. Recently researchers found that the mitochondrial genome produces thousands of potentially powerful non-coding RNAs with largely unknown functions. Nobody has any clue how these RNAs might behave in the context of mitochondrial transfer.