In 2018 two babies, Lulu and Nana, were born as the result of a procedure called heritable human genome editing (HHGE) done by Dr. He Jiankui from the Southern University of Science and Technology in China. The procedure was against Chinese regulations and raised serious ethical questions. Dr. Jiankui is now in prison.
As a result of their genomes being edited, Lulu and Nana could face serious health conditions. Lulu and Nana’s DNA was modified long before they were born, when they shared one single cell, so they are at risk of mosaicism. Mosaicism occurs when an organism has different genetic information in different cells, as opposed to having the same genetic information in every single cell.
Genetic abnormalities in an early embryo can be detected before being implanted in the mother through genetic testing, using biological samples from the outer layer of the embryo. These tests do not reflect the genetic information of the whole embryo, and the occurrence of undetected mosaicism could affect the results.
Recently a group of scientists showed the efficiency of a new, non-invasive preimplantation genetic testing. Researchers used a sample from the inner cavity of an early embryo instead of the outer layer. As a result, this test was more reliable for detecting mosaicism in the embryo. The development of this non-invasive genetic testing could help to detect genetic abnormalities in embryos in assisted reproduction procedures and to detect mosaicism in HHGE experiments.
However, just because this procedure can detect mosaicism does not mean that HHGE is safe or a good idea. Undesired and unwanted potentially dangerous changes performed with genome editing can be passed down to future generations, and significant, legitimate ethical concerns remain. Currently, the scientific community recommends not to perform genome editing intended for pregnancy, and to regulate such experiments.