Animal models of disease model diseases in transgenic animals have contributed to the development of medicine. However, many diseases are difficult to manufacture animal models by artificially induced methods, or many diseases do not occur in experimental animals or only in higher mammals, so it is difficult to obtain animal models by spontaneous or artificial directed cultivation. The emergence of transgenic technology has made it possible for humans to accurately study the relationship between genes and diseases, and can use any individual to analyze the genetic function in each stage of individual occurrence. Therefore, the development of animal models of transgenic diseases has become a hot spot for transgenic animals, and some have entered the application stage.
Virus model
(1) Poliovirus receptor transgenic mice: Human poliovirus receptors were cloned and transgenic mice were made. The poliovirus cell line receptor gene (human PVR gene) was microinjected into early embryos of C57BL/10 mice to prepare transgenic mice and the finished product line. This mouse expresses a human receptor and has the susceptibility to poliovirus. Moreover, mice infected with this virus exhibit the same clinical symptoms as humans, and the specificity to the virus strain also exhibits the same properties as humans. Therefore, in addition to being a human disease model, this mouse may also be used as a substitute for monkeys for the determination of the efficacy and specificity of poliovirus, and has a wide range of uses.
(2) Hepatitis B virus carrier model: Hepatitis B virus (HBV) carriers have a liver cancer rate 100 to 200 times that of normal people, but there is still no effective treatment. HBV only infects humans or gorillas, and other suitable animal models have not yet been developed. It is generally believed that the immune response to HBV is genetically controlled, and the immune response is insufficient to become chronic hepatitis; the mechanism of liver cancer is not unique, and there are various problems in hepatocyte necrosis and regeneration caused by the presence of chronic hepatitis. Genetic variation and canceration. The HBV genome is a circular double-stranded DNA molecule containing a partially single-stranded region. The length of the two single strands is different, the long strand is the minus strand (3.2 kb), and the short strand is the positive strand, which is about 50% to 80% of the minus strand. . So if you make l. The DNA of 2HB-BS is a double-stranded linear DNA for transduction, enabling genome-wide expression. On the other hand, when only HBS antigen expression is required, only the 1.2HB-BS gene needs to be introduced. The HBV DNA to which l.2HB-BS was added was introduced into C57BL/6J mice, and HBV was replicated in the liver to release virions in the blood. Gene expression occurs during the embryonic phase, but exhibits immunopotentiation (passivation status) against these viral antigens, does not exhibit any pathological changes, and thus can be used as a model for human HBV carriers. The mice that lead the human gene have no abnormalities in clinical manifestations like humans.
(3) Hepatitis B surface antigen transgenic animal model: The human hepatitis B surface antigen (HBsAg) gene is introduced into a mouse, and a mouse HBsAg gene can be obtained, and HBsAg can be produced in the liver of the transgenic mouse. This transgenic mouse can simulate the patient's toxic state without causing disease. Chisari found that HBsAg-positive transgenic mice were immunized with HBsAg plus Freund's complete or incomplete adjuvant and were unable to induce specific antibodies, whereas HBsAg-negative transgenic mice responded with HBsAg-positive The transgenic mice did not show any pathological changes within 6 months, but showed a continuous poisoning state. The results of these tests indicate that hepatocyte damage in patients with hepatitis B is not directly caused by HBsAg expression, but is caused by an immune response to viral antigens on the membrane of liver cells. This transgenic mouse model can be used to study the relationship between immune response tolerance and hepatocyte injury, and to explore the pathogenesis, persistent toxic state and its clearance, drug screening experiments, HBV DNA replication, expression and regulation in the host and type B. The relationship between the onset of hepatitis and other issues related to HBV pathology and therapeutics.
In addition to the establishment of animal models of transgenic mice as described above, animal models of transgenic mice with other viral diseases have also been established. Transgenic mice obtained by injecting the JC virus genome can be used as a transgenic mouse animal model of progressive multifocal leukoencephalopathy (PML) using tyrosine aminotransferase of human T lymphocyte type 1 virus (HTLV-1). The transgenic mouse prepared by the (TAT) gene can be used as an animal model of a disease of human nerve fiber tendon.
Gene therapy
Gene therapy uses molecular biology techniques to introduce foreign genes into target cells to correct, compensate for gene defects or to inhibit and block the overexpression of abnormal genes, thereby achieving the goal of treating diseases. Gene therapy includes gene compensation, gene correction, cytokine gene import, antisense RNA technology, and the like. As a new means of treating diseases, this technology has developed extremely fast, and several cases have entered the clinical practical stage, solving the clinical problems that traditional methods cannot solve. This novel and unique treatment is also derived from the study of transgenic mice.
In the production of animal models for gene therapy, retroviruses are currently widely used as vectors to introduce foreign genes of interest. This recombinant antibody retrovirus can integrate the functional gene carried into the chromosome of the recipient cell, and the expression product of the introduced gene will make up for the original gene product. A mouse lacking growth hormone is usually smaller and male than the normal mouse. The growth hormone gene is introduced into the mouse, and the expression of the exogenous growth hormone gene can increase the number of A and murine individuals with the dwarf by a factor of three, and restore the male fertility; Mice with the major histocompatibility complex (MHC) gene have an immune response against synthetic anti-Ig, but MHC-transgenic mice can restore immune response; mice with beta thalassemia are introduced into mice. After the human globulin gene, the degree of anemia is slowed down.
For the production of animal models for gene therapy, an antisense gene method can also be used. This method is suitable for diseases caused by abnormal expression of certain genes. Specifically, the antisense DNA is injected into the fertilized egg, integrated into the genome, and the RNA complementary to the pathogenic mRNA sequence is expressed, and the pathogenic mRNA is not translated by forming the RNA duplex. Human neurotic tremor is a disease caused by a decrease in myelin basic protein (MBP). The antisense DNA of MBP was integrated into the mouse chromosomal gene, and its MBP synthesis was reduced to 50% to 70% of normal, and thus tremor occurred, and an animal model of tremor was prepared. In mice, mutants of MBP deficiency were also found to exhibit spontaneous tremors. In contrast, when MBP DNA is transferred into these mutants, a myelin basic antibody proteins is formed. When the mRNA expression reached more than 25% of the normal MBP, the symptoms disappeared, showing significant symptom recovery (treatment) and the relationship between onset and MBP expression levels, providing another way for gene therapy of transgenic animals.
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