Editing Human Genes in Embryos to Correct Inherited Diseases

For many years now, scientific advancements are capable of altering genetic material in a cell by utilizing a technique called CRISPR.

Our genome comprises of DNA. These DNAs are made up of long sequences of base pairs. Each base is represented by one of the four letters- A, T, G and C (Adenine, Thymine, Guanine and Cytosine respectively). These genetic alphabets sequence in a particular order of letters to form “words” or “sentences”, which are the genes that determine our traits.

At times when these words get “misspelled”, it results in a disorder or disease. The scientific community came up with genetic engineering to fix such mistakes. They use a genome editing tool called CRISPR to eliminate the misspelled section of the sequence and insert the “correct” sequence”. It works just like MS Word’s search-and-replace function.

CRISPR has been the key tool used in the last decade for editing genes- be it human, animal, plant or any other organism. This tool was used in experiments for producing genetically modified disease-resistant plants, malaria-resistant mosquitoes, etc; exploring the possibility of genetically engineered livestock and pets; and potentially treating certain human diseases such as leukemia, hemophilia and HIV.

Until the recent years, genetic engineering focused on modifying the cells of a single individual, and not the germline cells such as early embryos, sperms and eggs- which are involved in passing on the traits to the next generations. This is because of the theory that working with non-germline cells would restrain any unforeseen long-term impact of genetic modifications on the off-springs. However, this has its disadvantage too – the technique has to be applied in every generation, which affects its potential therapeutic value.

A ground-breaking study
A new research at Oregon Health and Science University, Portland, Oregon, has announced the successful modification of the genetic material of a human embryo. This study avoided the potential errors that could occur with CRISPR- such as modifications in the untargeted sections of the genome, or the failed occurrence of the intended modification in all cells. Both of these issues had restricted scientists from applying CRISP to modify embryos that subsequently might be used in a human pregnancy. Thus, the more successful and safer use of CRISPR can lead to further research involving human embryos.

Limitations of the study
The researchers used early stage embryos, outside the womb, which were not allowed to develop for more than a few days. Some limiting factors, both scientific and ethical, restrict the implantation of the modified embryo in a human womb to achieve child birth.

A federal ban restrains the funding of embryo gene editing studies; and in some states, there is a complete ban of embryo research, irrespective of the funding. Further, the implantation of a modified human embryo would be governed under the Food, Drug and Cosmetic Act, the federal human research regulations; and potential federal regulations concerning testing in clinical laboratories.

As for the scientific limitation, a lot more scientific knowledge in this field is required to design human progenies. While the Oregon research focused on a single gene edition to acquired diseases, there are cases where a single gene controls more than one human trait. So, this type of genetic engineering will not be efficient in bringing the desired changes in conditions involving multiple genes or a gene/environment interaction. And, certainly the characteristics which we might be interesting in editing – such as personality, intelligence, artistic, musical or athletic ability – are much more complex.

Further, though this study is significantly ground-breaking in the use of the CRISPR technique, it is only one step forward. There is still a long way to go from this point to providing genetic solutions for disorders and diseases. So, the use of this technique as a mainstream medical practice will take some time.

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