动物造模,亨廷顿病 z-bio 2021-12-01 629

　　Summary: Animal models that simulate human diseases are an important tool for studying the causes of diseases and finding treatments. There is no doubt that small animal models provide a wealth of information about the causes of diseases and provide a widely used tool for formulating treatment strategies. This rodent model is used to understand the potential mechanisms of misfolded protein-mediated neurological dysfunction and behavioral phenotypes in various neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease. It is very useful for researchers. value. However, most transgenic rodent models of these diseases lack the obvious and selective neurodegeneration found in the patient's brain. Large animal models are more likely to mimic important human neuropathological features, because large animals are closer to humans than small animals and rodents. In this article, I will use HD large animal models as a research topic to explain the application of large animal models in neurodegenerative disease research, hoping to inspire the application of animal models in neurodegenerative disease research. disease. Yes.

　　Huntington's disease is an autosomal dominant neurodegenerative disease. It is caused by CAG amplification of the first exon repeat of the HD gene. As a result, CAG expanded to encode polyglutamine (polyQ) repeats in the terminal region of the diseased Huntingtin protein (Htt). The identification of HD gene mutations has created a variety of animal models expressing polyQ, including Htt. By expressing mutant Htt containing amplified CAG repeats in different species, various HD transgenic animal models have been established and identified. Among these models, the mouse HD model is widely used and provides valuable information about the pathogenesis and treatment progress of HD. These animal models provide clear evidence that small-end Htt fragments with PolyQ amplification are prone to misfolding and aggregation, and are more toxic than full-length mutant Htt. The expressing transgenic Htt mice died. It showed a more severe behavioral phenotype earlier than mice expressing the full-length mutant Htt. These HD mouse models show neurological symptoms related to the accumulation of age-related mutations Htt, but have obvious and selective neurodegeneration, which is a typical pathological feature of HD. I missed. Like the HD mouse model, other transgenic mouse models, including AD and PD models, express different types of misfolded proteins and do not show selective neurodegeneration. The huge differences between species are believed to be responsible for the differences in pathology between rodents and humans.

　　Non-human primates have been used to generate transgenic monkey models expressing disease genes or foreign genes. Among them, the transgenic rhesus monkey is the first monkey model suffering from human diseases, expressing the 84Q exon 1 mutant Htt under the control of the human ubiquitin promoter. Lentivirus was injected into fertilized eggs to produce HD monkeys expressing mutant Htt. However, compared to the HD mouse model generated in the same way, the HD monkey model exhibits a more severe phenotype. Unlike transgenic mice, if the same exon 1 variant Htt is expressed in a longer polyQ repeat sequence (150Q), the mice can survive after birth, but 6 84Q HD transgenic monkeys died after birth The possibility is great. The transgenic monkeys died very early, but still had important clinical HD features such as dystonia, chorea, and epilepsy. Small animal models such as mice could not reproduce 14 features. In addition, the brains of HD monkeys have a large amount of Htt accumulation and axonal degeneration. The above results indicate that large animals are more sensitive to the toxic HTT protein than rodents. To support this view, the transgenic pig model expressing terminal mutation Htt (N208-105Q) obtained by somatic cell nuclear transfer (SCNT) also has a postnatal death phenotype and abundant Htt accumulation. In addition, the transgenic HD pig model showed apoptosis and chorea, but the transgenic HD mouse model did not.

　　The main difference between a large transgenic HD animal model and a small transgenic HD animal model emphasizes the importance of using large animals to study HD neuropathology. These differences also indicate that the overexpression of the terminal mutant Htt is very harmful to large animals. Therefore, the establishment of large animal models representing full-length mutant Htt at the endogenous level is essential for neuropathology and phenotypic research. Non-human primates are closer to humans than other animals and are ideal models for HD research. However, due to their long reproduction period, high cost, and difficulty in modifying monkey endogenous genes, they are an endogenous expression. Htt has many challenges. On the other hand, compared with non-human primates, pigs have several advantages in creating transgenic animal models. Existing genetic engineering tools can generate a variety of pig disease models. Somatic cell nuclear transfer (SCNT) combined with CRISPR/Cas9 can genetically change the endogenous genes of pigs. SCNT caused the first generation of non-chimeric animals to replicate the phenotype associated with endogenous gene mutations. In addition, considering the timeline for establishing large-scale animal models of human diseases, pigs have a fast reproductive period (5-6 months of sexual maturity) and a large number of litters (average 7-8 piglets). -Human primates. . Advantage.

　　Recently, Yang and her colleagues successfully established the first large animal model using pig endogenous expression of full-length mutant Htt. They used CRISPR/Cas9 to create a large CAG and inserted a repetitive sequence (150 CAG) into the pig. The endogenous porcine Htt gene of fibroblasts is then used to replace 150 polyglutamic acid repeats with somatic cell nuclear transfer technology. The full-length mutant Htt was knocked down by a pig. HD-KI pigs exhibit age-dependent neurological symptoms such as weight loss, premature death, and movement disorders. The accumulation of Htt aggregates was also observed in the brains of HD-KI pigs, similar to other HD animal models. More importantly, the brains of HD-KI pigs showed selective neurodegeneration of the striatum, which reproduced important pathological features of HD patients. In addition, F1-KI pig phenotype and neurodegeneration are transmitted through the reproductive lineage. The establishment of the HD-KI pig model proved for the first time that large mammals can reproduce major and selective neurodegeneration and severe symptoms caused by endogenous expression of mutant proteins. The obvious differences in pathology and phenotype between small and large animal HD models can be attributed to the following facts: First, species-dependent differences in life cycle, genomics, anatomy, and physiology determine the severity of neurodegeneration in different species Aspect plays an important role. In fact, the lack of distinguishable caudate and shell structures in the rodent striatum makes it impossible to simulate the preferential caudate nucleus degeneration in HD. Secondly, there are big differences in the development of the central nervous system of different species. The rapid development and maturation of the rodent brain can make nerve cells resistant to toxic proteins.

　　The example of using large animals to study HD emphasizes the importance of large animal models in the research of other neurodegenerative diseases. Although rodent models provide valuable tools for studying the etiology of neurodegenerative diseases, large animal models can be used as important tools for validating important findings and therapeutic targets. In addition, the evidence of HDKI porcine neurodegeneration has paved the way for the establishment of animal models that simulate selective neurodegeneration of other important neurodegenerative diseases (such as AD and PD). Large animal models allow the use of small molecule chemicals, gene therapy, and stem cell replacement to develop effective treatment strategies.