Can homosexuals have children? ——Research results of new academicians

Dear friends, do you feel that the Internet has been very busy recently, with too many hot searches? Not only is there the discovery of the smallpox virus by an American pharmaceutical company, which is closely related to human safety, but also the election of 149 new members of the two academies in my country this year. It is really a cause for celebration that so many people have been elected!

Some friends said that the smallpox virus incident was a hot topic, which is understandable, but the election of this academician seems to have little to do with us, right? Let’s put it this way, Zhong Nanshan and Yuan Longping are both academicians, do you understand this?

Now, let me introduce you to a very hot topic: how to make same-sex couples reproduce? This is a small study by the newly elected academician Li Jinsong. In fact, I have written about Academician Li before.

01. Same-sex reproductive issues

In junior high school biology knowledge, we know that under normal circumstances, to give birth to a child, the sperm and egg need to combine to produce a fertilized egg, which then implants in the uterus. The fertilized egg continues to differentiate and divide, and eventually develops into a fetus.

If it is two women, the uterus problem is easy to solve, but if it is two men, it is not easy to solve, after all, surrogacy is still illegal in our country. The most critical issue is that since the fertilized egg is called a fertilized egg, it must be produced by the combination of sperm and egg. If there are only two eggs or two sperms, offspring cannot be formed. This is written into our genes. In other words, humans cannot reproduce asexually.

However, scientists are not convinced by this, because biologically, both sperm and eggs carry a complete set of chromosomes, so why can't two sperm or two eggs fuse?

So scientists began to study how to allow same-sex couples to reproduce.

However, research must start from the simplest place, so scientists first chose eggs. Because eggs are large in size and have a complete set of biological systems, such as the familiar organelles and mitochondria, and also have a series of cytoplasm, enzymes, nutrients and other materials that allow various biological reactions to proceed.

Sperm is much smaller. In order to facilitate movement, the volume of sperm is less than one percent of the egg, and it lacks sufficient organelles, enzymes and other substances.

02. Integration Problem

However, the first step of the fusion experiment failed.

Why? The reason is that the two eggs cannot fuse at all. When scientists put the two eggs together, they still maintain their own independent state. You are you and I am me. This is very embarrassing. After all, if they cannot even fuse in the first step, then don't even think about the follow-up.

Some scientists have tried some methods, such as using electric current to stimulate, but it has no effect. If you use reagents that dissolve cell membranes, you can make two egg cells fuse, but the result is that the egg cells die.

The reason is that there are a series of barriers and corresponding signal molecules on the cell surface. They are like secret codes. If you can't answer the secret codes, then sorry, you will be rejected. This is one of the reasons why two egg cells cannot fuse.

However, this does not pose a problem for scientists.

The sperm fertilization process is essentially the sperm finding the signal pathway on the surface of the egg through the acrosome reaction, and then injecting the DNA in the sperm into the egg. This is the core process.

So scientists began to simulate the fertilization nature of sperm by directly extracting the DNA of one egg and then injecting it into another egg.

This simulates the sperm-egg fertilization process and realizes the process of two egg cell genomes being integrated into one egg cell.

Is this OK?

Ideals are beautiful, but reality is cruel.

Although the two egg cells appeared to have fused, they did not develop further.

03. Epigenetic Dilemma

After careful study, it was found that the genomes of the two egg cells remained very independent in the new cell, each of which was separate. This is completely different from fertilization, because during fertilization, the genomes of the sperm and egg will communicate with each other, but the genomes of the two egg cells do not communicate with each other, so naturally it is impossible to proceed to the next step.

The problem lies in epigenetics.

The human genome has a special way of recording information, which is not a change in the DNA sequence, but exists in an epigenetic way, which directly affects the fusion of the genome. If you do not eliminate these imprints, then if you put the DNA of two eggs together, they will remain independent and will not interact with each other like the two sets of chromosomes of a normal diploid.

How to solve this problem? The answer is to remove these marks.

At the end of 2015, Li Jinsong's team from the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, successfully produced complete offspring using two eggs.

We know that egg cells do not fuse with each other, otherwise the Virgin Mary would really appear.

But the core reason is because of two genes, H19 and Gtl2, whose epigenetic differences affect the fusion of two eggs with each other (Differentially Methylated Region (DMR)).

So they controlled the expression of these two genes (deletion of IG-DMR and H19-DMR using CRISPR-Cas9)

Their approach is as shown below

Simply put, through demethylation gene modification, an egg cell is turned into a "sperm-like cell", and then this sperm-like cell combines with the egg cell, thus completing fertilization and developing into a complete mouse.

The picture above shows a pure mouse, which comes from the fusion of two egg cells.

Zhong C, Xie Z, Yin Q, et al. Partthenogenetic haploid embryonic stem cells efficiently support mouse generation by oocyte injection[J]. Cell research, 2015.

This is one of the important scientific research achievements of Academician Li Jinsong. Academician Li Jinsong mainly studies somatic cell reprogramming, that is, how to restore a cell to its original state. This process is a necessary step in the development of stem cells and fertilized eggs.

04. Reprogramming and Same-Sex Reproduction

In fact, it is not only female-female reproduction, but also male-male reproduction that has similar problems.

In fact, the issue behind reproduction is how to enable these sperm and eggs to initiate the reprogramming process, which involves many important epigenetic processes and has also been a hot topic in recent years.

The introduction basically ends here. In fact, in this year's list of academicians of the Academy of Sciences in biology, I have some intersections with three big guys (they don’t know me, haha), but these people are indeed top researchers in the field and deserve to be academicians.

Attached is the main scientific research achievements of Academician Li Jinsong.

1. Jiang, Jing*; Lv, Wenjian; Ye, Xiaoying; Wang, Lingbo; Zhang, Man; Yang, Hui; Okuka, Maja; Zhou, Chikai; Zhang, Xuan; Liu, Lin#; 23(1):92-16.

2. Yang, Hui*; Shi, Linyu; Wang, Bang-An; Liang, Dan; Zhong, Cuiqing; Liu, Wei; Nie, Yongzhan; Liu, Jie; Zhao, Jing; Gao, Xiang; Li, Dangsheng; Xu, Guo-Liang#; Li, Jinsong#. Generation of Genetically Modified Mice by Oocyte Injection of Androgenetic Haploid Embryonic Stem Cells. CELL. 2012. 149(3):65-617.

3. Gu, Tian-Peng*; Guo, Fan; Yang, Hui; Wu, Hai-Ping; Xu, Gui-Fang; Liu, Wei; Xie, Zhi-Guo; Shi, Linyu; He, Xinyi; Jin, Seung-gi; Iqbal, Khursheed; Shi, Yujiang Geno; Deng, Zixin; Szabo, Piroska E.; Pfeifer, Gerd P.; Li, Jinsong#; Xu, Guo-Liang#.The role of Tet3 DNA dioxygenase in epigenetic reprogramming by oocytes.NATURE. 2011. 477(7366):606-U136.

4. Jiang, Jing*; Ding, Guohui; Lin, Jiangwei; Zhang, Man; Shi, Linyu; Lv, Wenjian; Yang, Hui; Xiao, Huasheng; Pei, Gang; Li, Yixue; Wu, Jiarui#; Li, Jinsong#.Different developmental potential of pluripotent stem cells generated by different reprogramming strategies.JOURNAL OF MOLECULAR CELL BIOLOGY. 2011. 3(3):197-199.

5. Lin, Jiangwei*; Shi, Linyu; Zhang, Man; Yang, Hui; Qin, Yiren; Zhang, Jun; Gong, Daoqing; Zhang, Xuan; Li, Dangsheng; Li, Jinsong#. Defects in Trophoblast Cell Lineage Account for the Impaired In Vivo Development of Cloned Embryos Generated by Somatic Nuclear