Deafness Gene GJB2 Edited in Human Eggs

Denis Rebrikov is a Russian biologist that started editing the GJB2 gene, associated with deafness, in human eggs donated by women who can hear. The GJB2 gene produces a protein in gap junctions, the channels that help move chemical signals like potassium between cells, including in the inner ear. Rebrikov told Science that he plans to do extensive safety checks before seeking approval to implant an edited embryo. First, he wants to sequence the entire genomes of each parent to get a baseline for assessing off-target mutations in their edited embryos. He then wants to stimulate the woman’s ovaries, obtain about 20 eggs, fertilize them with her partner’s sperm, and finally add the mutation fixing CRISPR. He’ll grow these embryos for 5 days, at which point they will have about 250 cells and be in the blastocyst stage. Then he will do repeated rounds of whole-genome sequencing of 10 of these blastocysts, which will reveal all mutations that differ from the genomes of the parents. he will move to the next stage with the remaining edited embryos: a preimplantation test, then he will check the cells for many types of genetic defects and for mosaicism for the CRISPR edit.

He does not plan to create gene-edited babies just yet. He is studying normal copies of GJB2 to better understand potentially harmful mutations associated with using CRISPR. His eventual goal is to edit the eggs of deaf women in order to allow deaf couples with GJB2 mutations to have children with functioning copies of the gene and typical hearing. The experiment is similar to work done by researcher He Jiankui, who announced last year that he had created CRISPR-edited twin babies whose genomes were modified in hopes of making them resistant to HIV.



Article: https://www.the-scientist.com/news-opinion/deafness-gene-gjb2-edited-in-human-eggs-66600

Related Article: https://www.sciencemag.org/news/2019/10/embattled-russian-scientist-sharpens-plans-create-gene-edited-babies

Embryo cells from skin cells

An article at ScienceDaily summarizes the findings of a research conducted at the Hebrew University of Jerusalem (HU). With this study, researchers have found a way of transforming skin cells into the three major stem cell types that comprise early-stage embryos, (embryo, placenta and extra-embryonic tissue), using mouse cells. This was achieved by using retroviruses to insert a series of genes into the skin cells.

In a different article, the author notes that human skin cells have already been tested, and were successfully transformed using the same techniques used in mouse cells. Although successful, the technique with retroviruses could cause tumors in the tissue. The next step is finding a way of altering or switching genes existing in the cells, instead of inserting new copies.

Scientists say that in the future, it could be possible to create whole human embryos out of skin cells. The findings are significant since embryonic cells can be used to model and study embryonic diseases and placental dysfunctions as well as other complications without using "real embryos" or oocytes; therefore escaping some of the ethical debates that surround the field. With this I think that humans are getting closer to find a way of creating life without even the need of sex cells.  

4-cell stage mouse embryos

U.S. Scientists Sucessfully Use CRISPR to Research a Cure for Genetic Diseases in Human Embryos

The U.S. was not the first scientists to do research with CRISPR to cut DNA to edit the genomes of human embryos. Chinese scientists attempted similar experiments, but not enough embryos were viable after the use of CRISPR for it to be considered successful. These Chinese scientists collaborated with Shoukhrat Mitalipov (Oregon Health and Science University) and other researchers from South Korea to find more successful results to their study. The earliest stage possible of a human embryo is when it is only one cell, at this point is when they added CRISPR. As the embryo developed and cells divided the genetic traits were passed on to all cells. For ethical and legal reasons, the embryos that were used were made for research only and are not capable of developing past three days. The genetic defect in these embryos caused serious heart problems and after the CRISPR cut the DNA of the human embryo and additional genome editing technology was used, successful results were shown and 72% of the embryos had no sign of the genetic defects anymore several days later. This does not mean that tomorrow these procedures will be available to everyone in real human embryos; but it does mean that we are one giant step closer to ending genetic diseases. Many people believe using human embryos is not ethical and should not be done, but what these people do not understand is that the research is being done on specially designed human embryos for research purpose only so they will never have the potential to one day become life. This research needs to continue because it is truly amazing how far we have come with CRISPR considering it was only discovered as a possible way to fix genetic diseases just in 2012.

Article URL: http://time.com/4882855/crispr-gene-editing-human-embryo/

Additional Information: https://www.nature.com/articles/nature23305.pdf