Manage the genes of "I"

Release date: 2016-06-15

After learning that the second child in her arms also suffered from congenital deafness, Du Shaohui and his wife had no choice but to abort.

The first child of the couple had congenital deafness. In order to treat the child, two people living in Shandong should often go to Beijing. There is no problem with the hearing of the Du Shaohui couple, but they are carriers of the deafness gene, which means that their children have a 25% probability of congenital deafness.

They are eager to have a hearing-impaired child - this is understandable, and they want to know if their child is healthy before they get pregnant.

In order to have a healthy child, Du Shaohui and his wife came to the reproductive center of the General Hospital of the People's Liberation Army. The doctor told them that the use of the latest IVF technology can block the family hereditary deafness. Its core name is “Multiple Annealing Cyclic Amplification Technology” (MALBAC technology), which is the most advanced whole-genome amplification technology that can identify healthy embryos and then implant the embryos into the mother.

Du Shaohui and his wife accepted the doctor's advice. After a long period of pregnancy, on December 10, 2015, they got a pair of healthy twins. This is the first case in China to use MALBAC technology, preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS).

It is essentially a battle for time to detect whether an embryo can develop into a healthy fetus before conception.

In vitro, the IVF is to be cultured in vitro. After the fertilized egg divides and differentiates, the formed cell population is called an embryo. These embryos that later become fetal will not leave the mother for a long time, and will be implanted in the mother's body after a period of development.

After the genetic testing company gets multiple embryos, it needs to sequence the embryos and quickly determine which embryos can develop into healthy fetuses, and which ones are to be abandoned. The Yikang gene for the sequencing of the Du Shaohui couple was originally obtained. Of the 17 embryos, it must immediately identify which embryos do not carry the deafness gene, and then transplant the embryo without the defective gene into the maternal uterus.

A fertilized egg divides into 2 cells after 36 hours, and after 16 hours, it splits into 16 cells, and when it reaches the 5th day, it becomes more than 100 cells. Usually, genetic testing companies will take 1 to 3 cells on these embryos that have been cultured for 3 to 5 days - this number sounds pitiful, but early embryos have a strong ability to divide and divide, not because of a few The absence of cells results in a defective fetus.

After the cells are removed, they will be lysed and the tester will isolate the DNA. Although there are 23 pairs of chromosomes in each cell and one DNA molecule on each chromosome, this number is too small for genetic testing. Therefore, one of the more important issues facing single-cell gene sequencing or gene sequencing of a small number of cells is how to replicate DNA quickly and accurately.

Depending on the rate of cell division, it may take 15 to 20 days to get the DNA that meets the genetic testing requirements, but the tester now has to shorten the time to a few hours. Therefore, the genetic testing company lets the DNA-cleaving link break away from the cell, allowing DNA to be copied as quickly as a virus.

Viruses don't wrap heavy proteins for self-replication, but copy them directly, which is faster. Similarly, when the gene company removes the cells from the embryo, it also separates the DNA and replicates it separately, ie, whole genome amplification. In this way, the genetic testing company can obtain a sufficient amount of DNA after 3 to 4 hours.

In fact, many technologies have achieved faster genome-wide amplification before the concept of MALBAC technology first appeared in Science in 2013. However, during the process of replication, the amplification speed of different fragments on DNA is not the same, and the faster part will inhibit the amplification of the adjacent gene fragments. This can cause the disease-causing gene to be submerged in “background noise” and the test results will be affected.

"If you use the 100-meter race to analogize gene amplification, then the young man is a fast-replicating segment, and the slower copy is the old lady. If there is no control over the process of amplification, then the old lady can’t see the place at the end. Where the image is. The MALBAC technology is to let young people run the old lady together." Lu Sijia, one of the developers of this amplification technology, told CBN Weekly.

Consistency in gene amplification is at the heart of the MALBAC technology, which allows the first amplified fragment to form a circular structure. Once such a structure is formed, the first amplified fragment "knows" its own subsequent amplification. It should be slower, allowing the entire genome to be amplified simultaneously.

The ring structure also prevents errors during amplification. Once a minor error occurs during the copying process, the information of the wrong copy is quickly copied during the next index copying process, and the error will continue to be amplified. But the ring structure can lock the copy so that the copy has no way to copy itself, so all copies can only be sourced from the parent, enabling more accurate copying.

However, although it allows the mother to determine whether she can conceive a fetus without a genetic defect before pregnancy, it is rarely used at home and abroad because of the damage to the embryo. The solution currently being tried by Gene is to collect apoptotic cells in the culture medium of the embryos and then extract the DNA from the cells for genetic testing. These subtle signals are likely to contribute to the early diagnosis of tumors and even help monitor the effectiveness of later medications.

"Gene detection has been progressing from the end of the disease treatment to the front-end genetic testing and prevention." Yin Wei, executive director of Huada Gene, told China Business Weekly.

When Lin Wenli, who lives in Shenzhen, made prenatal diagnosis, she did not choose traditional amniocentesis because she was afraid of pain and worried about infection. Instead, she did a non-invasive prenatal genetic test at a promotional price of 999 yuan. Similar maternal and child health services are representative of the front-end of genetic testing technology. The non-invasive prenatal genetic testing of Qantas has 1 million users worldwide. It is also the first Chinese institution to apply high-throughput genetic technology to clinical testing.

This method only needs to collect 5 ml of pregnant women's peripheral blood and extract free DNA from it, which can be used to calculate whether the fetus suffers from Down's syndrome through high-throughput sequencing technology, which greatly reduces the cost of genetic testing. The risk of genetic diseases.

A week later, Lin Wenli got the test report from the hospital. Her baby is very healthy. Now, the child is 4 months old.

In January 2015, US President Barack Obama proposed the “Precision Medicine Program” in his State of the Union address. The so-called “precise medicine” is an emerging method for disease prevention and treatment that takes into account differences in personal genes, environment and living habits. "The combination of genomic data and clinical data has enabled the formation of a complete real-time, panoramic medical system. It is possible to achieve individualized precision medicine and health management in the next two to three years," Yin said. In terms of birth defects, cancer prevention, etc., Huada Gene has also launched a precision medicine program.

Because each person's situation is different, they should take different treatments after they become ill. However, the current situation is that almost every drug used to treat each disease is suitable for most patients by default.

Professor Thorben Hansen of the University of Copenhagen has been working with Huada Gene for more than three years in metabolic diseases. He is also the head of metabolic genomics at the Novo Nordisk Center for Metabolic Research.

Among them, there is single-gene diabetes. It is a special type of diabetes that does not fall into the so-called type 1 or type 2 diabetes, but is often misdiagnosed as the latter. However, if the treatment method of injecting insulin against the latter is used, it will not only have an effect, but may even aggravate the condition or cause other organ damage. In this case, genetic testing is required in advance. Hansen and Huada have now developed a method for screening for the diagnosis of monogenic diabetes using gene chips at a price of only $300.

This method is also being applied to mother and child testing. “We found that many pregnant women develop diabetes during pregnancy, but some will get better after giving birth, while others still have diabetes,” Hansen told CBN Weekly. He followed 380 gestational diabetes patients and found that the latter case was about 11%.

Combined with a single-gene diabetes chip test, Hansen found a total of 18 gene mutations in the genes of most women still suffering from diabetes, and it is these mutations that increase the probability of developing diabetes in patients with gestational diabetes. “If pregnant women have an understanding of their genetic status in advance, they can take appropriate risk control and interventions.”

Fifteen years ago, American geneticist Francis Collins predicted that by 2020, scientists would be able to use "custom drugs" to treat diseases such as breast cancer and heart disease. By 2030, genetic drugs will extend the average life expectancy of developed country residents to 90 years.

In developed countries such as the United States, a new occupation called genetic counseling has emerged. After people have obtained the results of genome-wide testing, they can use the advice and guidance of genetic counselors to conduct targeted and regular testing.

In the future, perhaps more than 90% of the diseases will no longer be solved by the hospital, because before we were born, even when we just formed embryos, we can “know” what diseases are most likely to happen in the future through genetic testing, and how to prevent them. . Even with this disease, you can get a treatment that is more suitable for your body's condition - everything is personalized and precise.

Of course, all of this must be based on a large amount of genetic data and a powerful ability to interpret the data - if it can be achieved, maybe you can find someone who matches your genes after "shake".

Source: First Finance

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