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 W1282X mutation is a prevalent and severe class I nonsense mutation (c.3846G>A, p.Trp1282Ter) in the CFTR gene, notably common in the Ashkenazi Jewish population ^[5]. This genetic alteration introduces a premature termination codon at position 1282, which prematurely truncates the synthesis of the CFTR protein. Consequently, the resulting shortened polypeptide is unstable and the corresponding mRNA is often degraded via the nonsense-mediated mRNA decay (NMD) pathway, leading to a near-complete absence of functional CFTR protein and an associated severe clinical phenotype of Cystic Fibrosis (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 ^[6]. B6-huCFTR*W1282X mice were developed by introducing the W1282X mutation into the CFTR-humanized mouse model (Catalog Number: I001132), creating a humanized disease model. It is suitable for research into CF mechanisms and the development of therapies targeting the CFTR W1282X 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.

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 G551D mutation is a clinically significant genetic defect in the CFTR gene, which is classified as a Class III mutation and is the third most common CF-associated mutation worldwide, occurring in about 3% of CF patients ^[5]. This missense mutation involves a single amino acid substitution where Glycine (G) is replaced by Aspartic Acid (D) at position 551 within the first Nucleotide Binding Domain (NBD1) of the CFTR protein. The defining molecular pathology is a severe gating defect; while the CFTR chloride channel is correctly processed and successfully trafficked to the apical membrane of epithelial cells, its probability of opening is drastically reduced (approximately 100-fold lower than the wild-type channel). This impairment in channel opening results in a critical reduction in chloride and bicarbonate transport, leading to the characteristic buildup of thick, dehydrated mucus in multiple organs and a severe clinical phenotype. 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 ^[6]. The G551D mutation holds particular importance in CF research and therapy as it was the first genotype-specific mutation to be successfully targeted by a CFTR potentiator drug, Ivacaftor, which functions by increasing the opening probability of the mutant channel. B6-huCFTR*G551D mice were developed by introducing the G551D mutation into the CFTR-humanized mouse model (Catalog Number: I001132), creating a humanized disease model. It is suitable for research into CF mechanisms and the development of therapies targeting the CFTR G551D 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.

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 ^[1]. 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 ^[2]. 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 ^[1]. 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 ^[3]. As a target for antibody-mediated cancer therapy, TFR1 can be leveraged through two approaches: one involves the use of antibodies conjugated to anti-cancer drugs, which are indirectly internalized via receptor-mediated endocytosis; the other employs antibodies that directly disrupt receptor function or induce Fc effector functions such as antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), or complement-dependent cytotoxicity (CDC). 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 ^[4-5]. 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). B6-huTFRC mouse model was generated by replacing the mouse Tfrc endogenous extracellular domain with the human TFRC extracellular domain. The murine cytoplasmic and helical will be kept. This model is valuable for studying iron metabolism disorders, neurodegenerative diseases, and tumor development, supporting the development of TFR1-targeted therapeutics and preclinical pharmacological evaluations.

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 F508del and G542X are the most common mutations found in US patients, accounting for 86.4% and 4.6% of all mutations, respectively ^[5]. The G542X mutation is a common and severe cause of Cystic Fibrosis (CF), resulting from a single point mutation in the CFTR gene that creates a premature termination codon (PTC) at amino acid position 542; this classifies G542X as a Class I nonsense mutation. The presence of this PTC triggers a cellular quality control mechanism known as Nonsense-Mediated Decay (NMD), which targets the mutant mRNA for degradation, leading to a near-complete absence of functional CFTR protein at the epithelial cell surface. Consequently, patients with two copies of G542X often exhibit a severe form of CF, characterized by major organ dysfunction, and this lack of protein makes it a primary target for novel therapeutic strategies, such as readthrough agents and gene editing. 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 ^[6]. B6-huCFTR*G542X mice were developed by introducing the G542X mutation into the CFTR-humanized mouse model (Catalog Number: I001132), creating a humanized disease model. It is suitable for research into CF mechanisms and the development of therapies targeting the CFTR G542X 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.

The CD19 gene encodes a member of the immunoglobulin gene superfamily. As a key co-receptor in the B cell receptor (BCR) signaling pathway, it is crucial for B cell development, activation, and differentiation. CD19, a pan-B-cell marker exclusively expressed in the B cell lineage, remains stable throughout B cell development, from pro-B cells to mature and memory B cells. It acts as a positive regulator of BCR signal transduction by forming a B cell-specific signaling complex with CD21 (complement receptor 2), CD81 (tetraspanin), and CD225 (Leu13), which lowers the threshold for antigen-induced B cell activation ^[1]. Dysregulation of CD19 is strongly linked to autoimmune diseases such as systemic lupus erythematosus (SLE) and B cell malignancies like acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma. Mutations in this gene are associated with common variable immunodeficiency 3 (CVID3), characterized by impaired B cell differentiation and hypogammaglobulinemia. Owing to its B cell-specific expression, CD19 has become a pivotal target for immunotherapy. For example, anti-CD19 CAR-T cell therapy (e.g., Tisagenlecleucel) has shown remarkable efficacy in refractory or relapsed ALL ^[2]. Recent studies have also explored CD19-targeted bispecific antibodies (e.g., blinatumomab) to enhance tumor cell clearance ^[3]. B6-hCD19 mice are a humanized model generated by replacing the mouse endogenous Cd19 gene sequence from the ATG start codon to part of intron 4 with the corresponding human CD19 gene sequence using gene editing technology. This model is applicable for studying B cell development and function, as well as therapeutic research on autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and B cell malignancies. It is an ideal research platform for preclinical efficacy evaluation of anti-human CD19 CAR-T cell therapy, and the development of bispecific antibodies and combination therapies.

Proprotein convertase subtilisin/kexin 9 (PCSK9) is a serine protease primarily produced in the liver but expressed in other tissues, including the intestine, heart, and neurons. The N-terminal domain of the PCSK9 protein is responsible for protein localization and stability, while the C-terminal domain is responsible for protein enzymatic activity ^[1]. The Low-density lipoprotein receptor (LDLR) is a receptor that is responsible for clearing low-density lipoprotein cholesterol (LDL-C) from the blood. PCSK9 cleaves the intracellular domain of LDLR on the cell surface, causing it to detach from the cell membrane and be transported to the lysosome for degradation, promoting LDLR degradation, and increasing plasma LDL-C. Overexpression or gain-of-function mutations of the PCSK9 gene can lead to LDL-C accumulation by reducing LDLR levels. This can cause hypercholesterolemia, which increases the risk of cardiovascular diseases, such as atherosclerosis and coronary heart disease, and neurodegenerative diseases, such as Alzheimer's disease ^[2]. PCSK9 has become an important target for the development of lipid-lowering drugs. Several PCSK9-targeted antibodies or small nucleic acid drugs have been approved for marketing worldwide, including evolocumab from Amgen, alirocumab from Sanofi and Regeneron, and inclisiran from Novartis. These drugs primarily work by inhibiting PCSK9 activity or preventing PCSK9 protein from binding to LDLR, lowering LDL-C levels in the blood to treat hypercholesterolemia ^[3-4]. In addition, PCSK9 can promote tumor growth and development by regulating cell proliferation, migration, and invasion. It can also regulate the expression of inflammatory factors that contribute to inflammation. Therefore, targeting the expression of PCSK9 has been investigated in tumor immunotherapy and autoimmune disease therapy ^[5-6]. B6-hPCSK9 mice are a humanized model generated by gene editing technology to replace the mouse Pcsk9 gene with the human PCSK9 gene sequence. These mice express human PCSK9 protein and can be used for research on various metabolic diseases, neurodegenerative diseases, tumor development, autoimmune disease mechanisms, and for the preclinical pharmacological evaluation of PCSK9-targeted drugs. In addition, Cyagen has developed a similar model, the B6-hPCSK9(CDS) mouse (PCSK9 coding sequence humanized model, Catalog Number: C001593). Compared to the B6-hPCSK9 mouse model, the B6-hPCSK9(CDS) mouse expresses higher levels of human PCSK9 and exhibits LDLR protein expression closer to physiological levels. It is recommended to choose the appropriate model based on the type of drug or research direction.

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 ^[1]. 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 ^[2]. 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 ^[1]. 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 ^[3]. 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 ^[4-5]. 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). Parkinson's disease (PD) is a neurodegenerative disease with a high prevalence mainly in the middle-aged and elderly population. It is the second most common neurodegenerative disease after Alzheimer's disease (AD). The main clinical symptoms include resting tremors, limb stiffness, bradykinesia, loss of voluntary movement, etc. The typical pathological process of PD is the formation of Lewy bodies (LB) in the central nervous system (CNS), which results in the gradual death and loss of dopaminergic neurons, leading to the disease ^[6-7]. The main components of Lewy bodies are insoluble aggregates of abnormal α-synuclein (α-syn), and the SNCA gene, which encodes α-synuclein, is one of the key causative genes in Parkinson's disease. Mutations in this gene cause overexpression of α-syn, leading to the formation of Lewy bodies, ultimately leading to PD ^[8]. In addition, SNCA mutations are also associated with diseases such as dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). B6-huTFRC/huSNCA(3'UTR) mice are a dual-gene humanized model generated by crossing B6-huTFRC mice (Catalog No.: C001860) with B6-hSNCA (3'UTR) mice (Catalog No.: C001698). This model can be used for research on neurodegenerative diseases such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), as well as iron metabolism disorders and tumorigenesis and development. It is also applicable for the development of TFRC/SNCA-targeted drugs.

Asialoglycoprotein receptor 1 (ASGR1), encoded by the ASGR1 gene, is central to cholesterol homeostasis and liver pathophysiology. Primarily localized to the hepatocyte plasma membrane, ASGR1 mediates ligand internalization and lysosomal degradation ^[1-2]. Ligand binding triggers ASGR1-dependent metabolism, involving the formation of a heteromeric complex with ASGR2, which recognizes glycoproteins with terminal galactose or N-acetylgalactosamine residues. Through modulation of the liver X receptor (LXR)/breast cancer susceptibility gene 1 (BRCA1)/BRCA1-associated ring domain protein 1 (BARD1) pathway, ASGR1 facilitates cholesterol excretion into bile, thereby influencing systemic lipid levels ^[1-2]. Beyond cholesterol regulation, ASGR1 participates in liver lesion processes, underscoring its broader role in liver health ^[3]. Notably, loss-of-function mutations in ASGR1 correlate with reduced circulating cholesterol and decreased cardiovascular disease risk. Conversely, elevated serum soluble ASGR1 (sASGR1) levels are associated with increased low-density lipoprotein cholesterol (LDL-C), particularly in hypertensive individuals ^[3]. Consequently, ASGR1 has emerged as a therapeutic target for cardiovascular and hepatic disorders, including hypercholesterolemia, atherosclerosis, non-alcoholic fatty liver disease, and cirrhosis ^[2-4]. The B6-huASGR1 mouse model was generated by replacing sequences from the ATG start codon to the TAG stop codon of the endogenous mouse Asgr1 gene with the sequences from the ATG start codon to the TAA stop codon of the human ASGR1 gene. This model can be used to study the pathological mechanisms and therapeutic approaches for cardiovascular and liver diseases, as well as for the development of ASGR1-targeted drugs.

Usher syndrome (USH), also referred to as hereditary deafness-retinitis pigmentosa syndrome or retinitis pigmentosa-neurosensory deafness syndrome, is an autosomal recessive disorder marked by genetic heterogeneity. The primary clinical manifestations include congenital sensorineural hearing loss, progressive retinitis pigmentosa (RP), and visual impairment. USH is the leading disorder resulting in deafness and blindness, with an estimated prevalence ranging from 1 in 5,000 to 1 in 16,000 individuals. USH is classified into three subtypes—USH1, USH2, and USH3—based on the age of onset and effects on hearing and vestibular function. Patients with USH1 present with profound congenital deafness and vestibular dysfunction, typically developing RP before adulthood. USH2 is characterized by moderate to severe hearing loss without vestibular dysfunction, with RP symptoms manifesting later in adulthood. USH3 patients are born with normal hearing, which progressively declines alongside the onset of RP. USH1 is the most severe form, while USH2 is the most prevalent, accounting for 40%–50% of cases. However, underdiagnosis and the gradual progression of the disease suggest that the true prevalence of USH2 may be underestimated. The USH2A gene is the primary causative gene for USH2, with 75%–90% of USH2 cases linked to mutations in this gene ^[1]. The USH2A gene encodes Usherin, a protein featuring laminin EGF-like, pentraxin, and fibronectin type III domains, predominantly expressed in the basement membrane of the inner ear and retina. Usherin plays a critical role in developing hair cells in the inner ear, auditory signal transduction, and the maintenance of adhesion via interactions with fibronectin in the retinal basement membrane. Mutations in the USH2A gene disrupt the normal development and function of hair cells, impair fibronectin assembly, and compromise the adhesive properties of the retinal basement membrane, leading to hearing loss and RP symptoms. Currently, there are no effective therapies for Usher syndrome. Ongoing research focuses on elucidating the genetic mechanisms underlying the disorder and developing gene-based therapeutic strategies. While gene therapy remains preclinical, promising advances have been made with antisense oligonucleotides (ASO) and CRISPR-based gene-editing technologies. QR-421a, an RNA-based oligonucleotide therapy developed by ProQR Therapeutics, targets exon 13 mutations in the USH2A gene associated with USH and non-syndromic RP. This therapeutic approach aims to restore Usherin expression by correcting exon 13 deletions through exon skipping. Given the focus of ASO and CRISPR therapies on the human USH2A gene, developing humanized mouse models is critical to advancing gene therapies toward clinical applications. Exon 13 of the USH2A gene harbors a hotspot for pathogenic mutations associated with USH, including two common mutations, c.2299delG and c.2276G>T, which are the subject of several therapeutic investigations ^{[2-4, 6]}. The B6-hUSH2A(E10-15) mouse model, in which the corresponding mouse Ush2a gene sequence was replaced with human USH2A exons 10 to 15 and their flanking regions, provides a valuable tool for studying USH pathogenesis and evaluating preclinical treatments. Homozygous B6-hUSH2A(E10-15) mice are viable and fertile, making them suitable for drug evaluation and disease modeling. In addition, based on the independently developed TurboKnockout fusion BAC recombination technology, Cyagen can also generate hot mutation models based on this strain and provide customized services for specific mutations to meet the experimental needs in pharmacology and other fields.

Marfan syndrome (MFS) is an autosomal dominant systemic connective tissue disorder with a prevalence of 1/3,000–1/5,000, unaffected by race or geographic location. Patients typically exhibit disproportionately long limbs, fingers, and toes, and significantly exceed average height. Clinically, the disease presents with diverse manifestations, with the most life-threatening complications involving the cardiovascular system, including mitral valve prolapse, aortic valve regurgitation, aortic root dilation, and aortic dissection. This connective tissue disorder affects multiple organ systems, including the skeletal, pulmonary, ocular, central nervous, and cardiovascular systems ^[1]. The FBN1 gene is the causative gene for MFS, which encodes fibrillin-1, a connective tissue protein that provides structural support to cells as an extracellular matrix component and imparts elasticity and strength to connective tissues. FBN1 mutations can lead to a spectrum of type I fibrillinopathies, including Marfan syndrome (MFS), dominant Weill-Marchesani syndrome, and scleroderma. Current therapeutic strategies for MFS primarily focus on preventive and symptomatic treatments, while gene therapy, potentially addressing both prevention and symptom management, shows promise as the next frontier in research. Studies have demonstrated that gene editing technologies can correct mutations in patient-derived induced pluripotent stem cells (iPSCs), marking a critical first step toward developing efficient and precise gene therapies for MFS ^[2-3]. Subsequent in vivo animal studies are indispensable for preclinical research. As gene therapies act on the human FBN1 gene, the development of fully humanized animal models is scientifically robust and adaptable to diverse drug targeting sites, accelerating the FBN1-targeted therapeutic approaches into clinical trials. The B6-hFBN1 mouse is a humanized model, generated by in situ replacement of the mouse Fbn1 gene sequence (including 3'UTR) with the corresponding human FBN1 sequence while retaining the mouse signal peptide. This model is suitable for research on the pathogenesis and therapeutic agents for Marfan syndrome (MFS), dominant Weill-Marchesani syndrome, scleroderma, and other related disorders. Additionally, leveraging its proprietary TurboKnockout fusion BAC recombination technology, Cyagen can provide popular mutation disease models based on this platform or offer customized services for different mutations to meet the experimental needs of researchers.