The huC3/huC5 mice are a dual-gene humanized model obtained by mating huC3 mice (catalog number: C001955) with huC5 mice (catalog number: C001824). This model can be used in research on the complement system, immunotherapy, tumors, etc., as well as in the development of C3/C5-targeted drugs.

Complement component C3 plays a central role in activating the complement system and is the most abundant complement protein in human plasma, primarily synthesized in the liver. As part of the innate immune system, the complement system is activated during tissue damage and pathogen invasion, playing a crucial role in the inflammatory response, host homeostasis, and pathogen defense. The complement cascade is activated through the classical pathway, alternative pathway, and lectin pathway, all of which generate C3 convertase, which cleaves C3 into C3a and C3b. C3a is a potent anaphylatoxin with pro-inflammatory activity, while C3b is a regulator that induces C5 cleavage, thereby participating in the dissolution and clearance of immune complexes. Mutations in this gene are associated with atypical hemolytic uremic syndrome (aHUS) and age-related macular degeneration (AMD). Deficiencies in C3 and C3-derived peptides can lead to autoimmune diseases (such as rheumatoid arthritis, systemic lupus erythematosus, and vasculitis) and make individuals susceptible to recurrent respiratory infections and infections caused by encapsulated organisms. Conversely, excessive activation of C3 and related complement components is associated with kidney diseases (immune complex glomerulonephritis, hemolytic uremic syndrome, lupus nephritis, membranous nephropathy, and immune-mediated nephropathy) ^[1-2]. The Transferrin receptor (TFRC) gene encodes Transferrin Receptor 1 (TFR1), a protein that is expressed at low levels in most normal cells but shows increased expression in highly proliferative cells, such as basal epidermal cells, intestinal epithelium, and certain activated immune cells. Brain capillary endothelial cells, which constitute the blood-brain barrier (BBB), also express this receptor at high levels ^[3]. TFR1 plays a critical role in maintaining iron metabolism and homeostasis by facilitating receptor-mediated endocytosis of iron-bound transferrin (Tf) via Tf cycling, thereby promoting iron uptake ^[4]. Cellular iron deficiency can lead to apoptosis, while cellular transformation requires substantial iron to sustain proliferation, with iron overload contributing to tumor progression. The high expression of TFR1 in many tumors makes it a potential tumor marker, offering a target for therapies to inhibit tumor growth and metastasis ^[3]. Moreover, TFR1 is implicated in anemia and iron metabolism disorders. Studies have shown that elevated TFR1 expression in cardiomyocytes is associated with exacerbated inflammation in myocarditis patients ^[5]. Various clinical drugs targeting TFR1 are currently under development, including antisense oligonucleotides (ASOs), antibody-drug conjugates (ADCs), and antibody-oligonucleotide conjugates, applicable to diseases such as cancer, anemia, and neurodegenerative disorders. Research indicates that enhancing antibody transport across the blood-brain barrier via TFR1, by forming specific bispecific antibodies with anti-β-amyloid antibodies, can improve therapeutic outcomes in Alzheimer's patients ^[6-7]. As research progresses, TFR1 is expected to become an effective clinical target for multiple diseases and a synergistic target for drug delivery across the blood-brain barrier (BBB). The hTFRC/huC3 mouse model is a humanized model obtained by breeding huC3 mice (Catalog No.: C001955) with hTFRC mice (Catalog No.: C001584). This model can be used for research on complement-mediated diseases, iron metabolism disorders, neurodegenerative diseases, and tumor development, aiding in studying C3/TFRC-targeted drugs.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a critical protein that maintains the salt and water balance across various human organs, including the lungs, pancreas, and sweat glands. The primary function of CFTR is to act as a chloride channel, regulating the transport of chloride and bicarbonate ions across epithelial cell membranes, thereby maintaining tissue fluid balance and pH. This process is ATP-dependent and also modulates the activity of other ion channels and transport proteins ^[1-2]. Mutations in the CFTR gene can lead to chloride channel dysfunction, resulting in various diseases, with cystic fibrosis (CF) being the most common. CF is the most prevalent lethal genetic disease among Caucasians, with an incidence of approximately 1/2,500 to 1/1,800, and about 90,000 cases globally ^[3-4]. The disease is characterized by thickened mucus in the lungs, frequent respiratory infections, pancreatic insufficiency, and male infertility, typically due to vas deferens obstruction. The c.3718-2477C>T mutation is a relatively rare pathogenic cause of Cystic Fibrosis (CF). As a deep intronic variant, c.3718-2477C>T is classified as a splicing mutation, meaning its primary effect is likely to disrupt the normal process of mRNA splicing (the removal of non-coding introns and joining of coding exons) after transcription. This disruption can lead to a faulty or absent CFTR protein, ultimately resulting in the clinical manifestations of CF. Current treatments for CF mainly focus on CFTR modulators to restore the function of the mutated CFTR protein. CFTR modulators are classified into potentiators (which enhance CFTR function) and correctors (which assist in the proper folding and trafficking of CFTR to the cell membrane). Representative drugs include Ivacaftor, Lumacaftor, and triple-combination CFTR modulating therapy Elexacaftor-Tezacaftor-Ivacaftor ^[5]. B6-huCFTR*c.3718-2477C>T mice were developed by introducing the c.3718-2477C>T mutation into the CFTR-humanized mouse model (Catalog Number: C001964), creating a humanized disease model. It is suitable for research into CF mechanisms and the development of therapies targeting the CFTR c.3718-2477C>T mutation. This strain requires feeding with intestinal cleansers to maintain survival. In addition, based on the independently developed TurboKnockout fusion BAC recombination technology, Cyagen can also generate hot mutation models based on the CFTR-humanized strain and provide customized services for specific mutations to meet the experimental needs in pharmacology and other fields.