Egg Cells from Skin Cells?

     In this article, scientists are working to create a human egg from an adult cell. They used a technique that combines cloning with fertilization, along with a small amount of chemical coaxing. Researchers had succeeded in producing egg cells of many other types of animals, so the hunt to produce egg and sperm of humans has been on.

    An attempt was made when the nucleus from a human egg cell was taken out and replaced with the nucleus of a skin cell, which is called somatic cell nuclear transfer. In this case, the researchers weren't trying to clone a human, but wanted to make an egg cell, which is half of the DNA of a skin cell. When done on mice, once the cloned egg was fertilized, it removed half of its chromosomes in order to take in the chromosomes of the sperm. In human eggs, this did not happen, so the researchers added roscovitine to persuade the egg to allow the chromosomes to be removed. This led to no viable eggs, since many would kick out the wrong half of chromosomes or end up with an incorrect number of chromosomes. It is theorized that it's due to the chromosomes pairing up randomly instead of with their specific other half, like in normal meiosis.

    This is still being tested in Japan, and hopefully, these trials are getting us a step closer to creating viable eggs. I think this is such an interesting idea that can help many people who would like biological children, but have reasons they wouldn't be able to. The fact that similar tests have been proven possible in other animals makes me optimistic about the probability of this becoming an option in the future.

ReTro Experiences Adulthood

    Meet ReTro. He is extraordinary because he is the first cloned Rhesus monkey to reach adulthood. In the article written about ReTro on the Scientific American website, we get a full overview of the meaning of this experiment and its success. 

    ReTro was cloned the same way as Dolly the Sheep, through a process known as somatic cell nuclear transfer (SCNT). In this process, a nucleus from a somatic cell is inserted into an egg cell whose nucleus has been removed. It is noted there are extremely low survival rates with this process, which is why ReTro is so amazing to have fully developed into an adult. They had tried this experiment in 2022, but that rhesus monkey survived 12 hours after birth. At the Chinese Academy of Sciences, they researched all the errors within the cloning process. Their outcome: 484 SCNT and 499 ICSI (intracytoplasmic sperm injection) monkeys were compared, all developing through the same stages before reaching surrogates. Only 35 SCNT embryos were successfully implanted, compared to 74 ICSI embryos successfully implanted. The SCNT placentas were deformed and thick. They found SCNT embryos had serious genetic modification, resulting in a decrease in DNA methylation. To fix these issues, they used trophoblasts from ICSI embryos to form natural placentas around a cloned fetus. Once this was completed only two of the pregnancies evolved with only one survival, which we know as ReTro. Even with this success, cloning is still highly difficult, with a very low success rate. They wanted to use these animals to study drug efficacy. 

    In my opinion, it's amazing to believe we have found the basis of cloning, but not the exact way to do it yet. If universities across the globe keep putting their best foot forward in the science of genetics, there are so many things we will be able to discover and cure. If we successfully begin cloning other species, will this evolve into a future experiment with humans? Will cloning help us test genetic medical trials for illnesses? There are so many questions revolving around the process and if it is truly something we need to do. Dolly the sheep made people begin to wonder if human cloning was the next step, and if it would be humane to study. Yet Dolly was born in 1996, almost 20 years ago!

Sources:

Naddaf M, Magazine N. 2024 Jan 17. Meet ReTro, the First Cloned Rhesus Monkey to Reach Adulthood. Scientific American. https://www.scientificamerican.com/article/meet-retro-the-first-cloned-rhesus-monkey-to-reach-adulthood/.

Dolly the sheep. National Museums Scotland. https://www.nms.ac.uk/explore-our-collections/stories/natural-sciences/dolly-the-sheep/.

'Cow Gene' Explains Failure of Cloned Genes

A recent study conducted at the University of California showed a cow gene that demonstrated why most clones fail. Cloning mammals has proven to be a challenge; however, it was just twenty years ago that Dolly the sheep was successfully cloned. Using the technique of somatic cell nuclear transfer was originally how Dolly was cloned, or rather when a nucleus from an adult cell is transferred into unfertilized egg that has had its nucleus removed, and then begins cell growth by an electric shock. Recipient mothers then carry the transferred embryos until the clones are born.

The process of cloning cattle can be used to study development in mammals, and is important technology for agriculture; however, the success rate remains very low - less than ten percent of cloned animals survive until birth. Losses of the cloned animals may be due to a variety of reasons: failure during implantation of the embryo, embryonic death in general, or the possible development of a defective placenta. However, with recent developments into why there is so much reoccurring failure, it may be possible to get to the root of the issue. Scientists used RNA sequencing in order to look at gene expression in cows that had been cloned during implantation and attempt to understand the molecular mechanisms that lead to such a high rate of failure during pregnancy.



In this study, the researchers studied tissue from cloned cow embryos--all derived from the same cell line--at 18 and 34 days of development, as well as the corresponding endometrial lining of the pregnant cows. They also used cows that were not cloned, conceived using the process of artificial insemination. By use of RNA sequencing, multiple genes were found to be expressed abnormally, that could potentially lead to the high mortality rate of cloned embryos, as well as their failure to be implanted in the uterus and to develop a normal placenta. Researchers were able to find anomalies in expression of more than five thousand genes looking at the extra embryonic tissue of those of the cloned cows by day 18. Hopefully researchers will be able to use this find to uncover more developmental issues of the cloned embryo, and eventually lead to a higher survival rate.

As much as I find cloning of genes interesting, I do wonder about the possible risk factors involved, besides those listed above. It makes me very curious to see the future of these processes, and what could potentially come out of then. I also do think that cloning of genes as a whole could be a very useful practice, especially with genes that may be correlated to positive human growth and health. I'm sure that there is a lot left to learn about the future of cloning, and I am excited to see where it goes.