Apolipoprotein E ε2 (APOE2) is one of the three major human APOE isoforms, characterized by the amino acid signature Cys112/Cys158. The APOE gene is primarily expressed in the liver and central nervous system, where it is synthesized by hepatocytes and astrocytes to encode a 299-amino acid glycoprotein ^[1]. As a key ligand for the low-density lipoprotein (LDL) receptor family, APOE plays a critical role in cholesterol and triglyceride transport, lipoprotein metabolism, neuronal membrane repair, and the maintenance of synaptic plasticity ^[1-2]. Compared to APOE3, APOE2 exhibits significantly reduced binding affinity for LDL receptors, which impairs lipid clearance efficiency. Under specific genetic backgrounds, the APOE2 homozygous state can lead to Familial Dysbetalipoproteinemia (Type III Hyperlipoproteinemia) ^[2]. Furthermore, in contrast to APOE4, APOE2 is generally considered to possess neuroprotective properties and is associated with a reduced risk of Alzheimer's disease (AD) ^[3]. The huAPOE2 mouse is a humanized model generated via gene editing. The exons 2-4 plus partial flanking sequences of the mouse Apoe gene were replaced with the human APOE gene sequence including exons 2-4 and some downstream sequence of 3'UTR. The point mutation p.R176C (CGC to TGC) was introduced into the human APOE exon 4. This model is suitable for studying dyslipidemia, atherosclerosis, Type III hyperlipoproteinemia, neuroinflammation, Alzheimer's disease (AD), and other APOE2-associated disorders.

The APOE3 (Apolipoprotein E epsilon 3) gene represents the most prevalent isoform within the human population and is typically categorized as the functionally "neutral" or wild-type allele. Predominantly expressed in the liver and central nervous system, it is produced by hepatocytes and astrocytes to encode the 299-amino acid Apolipoprotein E glycoprotein ^[1]. This protein serves as a vital ligand for LDL receptors, facilitating the systemic transport and redistribution of cholesterol and triglycerides necessary for membrane stability and neural synaptic repair. While APOE3 generally supports healthy lipid homeostasis, the APOE4 isoform is associated with increased risk of cardiovascular pathologies like atherosclerosis, whereas APOE2 homozygosity (or rare APOE variants) can lead to familial dysbetalipoproteinemia in specific genetic contexts ^[2]. Furthermore, it serves as the baseline for assessing neurodegenerative risk, sitting between the neuroprotective effects of the APOE2 variant and the significantly increased Alzheimer's disease risk associated with APOE4 ^[3]. The huAPOE3 mouse is a humanized model constructed by using gene-editing technology to replace exons 2-4 and part of the flanking sequences of the mouse Apoe gene with the human APOE gene sequences, including exons 2, 3, 4, and some downstream sequence of 3’UTR. This model can be used for research on cardiovascular diseases, such as atherosclerosis, and neurodegenerative diseases, such as Alzheimer's disease (AD), as well as for the development of APOE3-targeted drugs.

Apolipoprotein E (APOE) is a critical apolipoprotein involved in lipid transport mediated by lipoproteins. As a core component of plasma lipoproteins, APOE facilitates the transport of lipids through plasma and interstitial fluid between organs, and it plays a pivotal role in the generation, conversion, and clearance of lipoproteins. In humans, the APOE gene has three isoforms (E2, E3, E4) associated with atherosclerosis and Alzheimer’s disease (AD), with the E4 allele present in approximately 14% of the population ^[1]. The ApoE4 isoform is a major genetic risk factor for late-onset Alzheimer’s disease (AD), exacerbating neurodegeneration. ApoE4-associated damage to vascular systems in the brain could have a key role in AD pathogenesis ^[2]. Beyond AD, APOE4 is linked to cardiovascular diseases due to its influence on lipid homeostasis ^[3]. huAPOE4 mice are humanized models constructed through gene editing technology. Exons 2-4 plus partial flanking sequences of the mouse Apoe gene were replaced in situ with the Mutant human APOE gene sequence, including exons 2, 3, and 4 and some downstream sequence of 3’UTR. The p.C130R (TGC to CGC) was introduced into the mutant human APOE gene. This model can be used for research on the pathogenic mechanisms and treatment methods of cardiovascular diseases such as diet-induced hypercholesterolemia, atherosclerosis, and lipid metabolism. It can also be used to study the role of human APOE gene polymorphisms in Alzheimer's disease.

Try5 is located on chromosome 6 of mice. SgRNA and ssDNA will be designed using Nuclease Technology; Try5 conditional knockout mice will be obtained by high-throughput electroporation of fertilized eggs. After sexual maturity, sperm will be collected for cryopreservation.