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Human Germline Engineering is the process by which the genome of an individual is edited in such a way that the change is heritable. This is achieved through genetic alterations within the germinal cells, or the reproductive cells, such as the oocyte and spermatogonium. The first attempt to edit the human germline was reported in 2015, when a group of Chinese scientists used the gene editing technique CRISPR/Cas9 to edit single-celled, non-viable embryos to see the effectiveness of this technique. This attempt was rather unsuccessful; only a small fraction of the embryos succesfully spliced the new genetic material and many of the embryos contained a large amount of random mutations. The non-viable embryos that were used contained an extra set of chromosomes, which may have been problematic. In 2016, a different study performed in China, using similar methods to the first study of human germline engineering, was published. This study also used non-viable embryos with extra sets of chromosomes, and this study showed very similar results to the first; there were successful integrations of the desired gene, yet the majority of the attempts failed, or produced undesirable mutations.

Human germline engineering should not be confused with gene therapy. Gene therapy consists of altering somatic cells, which are all cells that make up the body and are not involved in reproduction. While gene therapy does change the genome of the targeted cells, these cells are not within the germline, so the alterations are not heritable.

Conceivable Uses

Currently, there are no successfully engineered humans, but there are many prospective uses such as curing genetic diseases and disorders. In the first study published regarding human germline engineering, the researchers attempted to edit the HBB gene which codes for the human β-globin protein. Mutations in the HBB gene result in the disorder β-thalassaemia, which can be fatal. Perfect editing of the genome in patients who have these HBB mutations would result in copies of the gene which do not possess any mutations, effectively curing the disease. The importance of editing the germline would be to pass on this normal copy of the HBB genes to future generations.

Another possible use of human germline engineering would be eugenic modifications to humans which would result in what are known as "designer babies". The concept of a "designer baby" is that its entire genetic composition could be selected for. In an extreme case, people would be able to effectively create the offspring that they want, with traits of their choosing. Not only does human germline engineering allow for the selection of specific traits, but it also allows for enhancement of these traits. Using human germline editing for selection and enhancement is currently very heavily scrutinzied, and the main driving force behind the movement of trying to ban human germline engineering.

State of Research

The topic of human germline engineering is a widely debated topic. Currently, 15 of 22 Western European nations have outlawed human germline engineering. There is no current legislation in the United States that explicitly prohibits germline engineering, however, the Consolidated Appropriation Act of 2016 banned the use of U.S. Food and Drug Administration (FDA) funds to engage in research regarding human germline modifications.

References

1. ^ Stock, Gregory; Campbell, John (2000-02-03). Engineering the Human Germline: An Exploration of the Science and Ethics of Altering the Genes We Pass to Our Children. Oxford University Press. ISBN 9780195350937.
2. ^ Cyranoski, David; Reardon, Sara. "Chinese scientists genetically modify human embryos". Nature. doi:10.1038/nature.2015.17378.
3. ^ Callaway, Ewen. "Second Chinese team reports gene editing in human embryos". Nature. doi:10.1038/nature.2016.19718.
4. ^ National Academies of Sciences, Engineering, and Medicine. 2017. Human Genome Editing: Science, Ethics, and Governance. Washington, DC: The National Academies Press. doi: 10.17226/24623.
5. Lock, Margaret; Nichter, Mark (2003-09-02). New Horizons in Medical Anthropology: Essays in Honour of Charles Leslie. Routledge. ISBN 9781134471287.
6. Lanphier, Edward; Urnov, Fyodor; Haecker, Sarah Ehlen; Werner, Michael; Smolenski, Joanna (2015-03-26). "Don't edit the human germ line". Nature. 519 (7544): 410–411. doi:10.1038/519410a.
7. Cohen, I. Glenn; Adashi, Eli Y. (2016-08-05). "The FDA is prohibited from going germline". Science. 353 (6299): 545–546. doi:10.1126/science.aag2960. ISSN 0036-8075. PMID 27493171.