Stargardt disease (STGD), a hereditary macular dystrophy, is characterized by the presence of yellowish flecks within the retinal pigment epithelium (RPE), ultimately culminating in macular atrophy. Typically manifesting in childhood and adolescence, STGD leads to progressive central vision loss and mild dyschromatopsia. Fundoscopic examination may reveal pale yellow lesions exhibiting a characteristic gold foil-like sheen, accompanied by yellow-white spots surrounding the posterior pole. In advanced stages, atrophy of the RPE, photoreceptors, and choriocapillaris is observed. This bilateral and typically synchronous condition affects both eyes with comparable incidence across sexes, estimated between 1/8,000 and 1/13,000. STGD is predominantly an autosomal recessive disorder, with mutations in the ABCA4 gene accounting for approximately 95% of cases. ABCA4 encodes a retina-specific ABC transporter protein crucial for the clearance of retinal derivatives and toxic metabolites generated during rhodopsin photobleaching. Consequently, ABCA4 mutations result in the accumulation of these cytotoxic substances, triggering apoptosis of both RPE and photoreceptor cells and ultimately driving retinal degeneration. Notably, ABCA4 mutations have been implicated in a spectrum of retinal diseases, including STGD, cone-rod dystrophy (CRD), age-related macular degeneration (AMD), and retinitis pigmentosa (RP), with the specific clinical phenotype correlating with the nature and severity of the ABCA4 mutation. This strain is an Abca4 gene knockout (KO) mouse model. Gene-editing technology was used to delete the protein-coding sequence of the Abca4 gene (the homolog of the human ABCA4 gene) in mice. Previous studies have demonstrated that Abca4 KO mice exhibit delayed dark adaptation following photobleaching and a slow progression of photoreceptor degeneration^[1]. Homozygous Abca4 KO mice are viable and fertile.

B6-huCFB/huC5 mice are a dual-gene humanized model obtained by mating B6-huCFB mice (catalog No.: C001710) with B6-huC5 mice (catalog No.: C001824). This model can be used for research on immune-related diseases such as age-related macular degeneration (AMD), atypical hemolytic uremic syndrome (aHUS), and systemic lupus erythematosus (SLE), as well as for the development of CFB/C5-targeted drugs.

Retinitis pigmentosa (RP) is a hereditary retinal disease with a global prevalence of approximately 1:5000-1:3000. RP is highly clinically and genetically heterogeneous, with mutations in the rhodopsin (RHO) gene causing approximately 25% of dominant RP ^[1]. The rhodopsin encoded by the RHO gene is closely associated with visual light transduction and GPCR downstream signals. Rhodopsin is essential for the transmission of light signals in the process of vision formation. Most RHO mutations lead to high levels of rhodopsin expression in photoreceptor cells, causing many mutant proteins to be abnormally located and aggregated in cells. This results in the apoptosis of photoreceptor cells, which cannot perform normal light signal transduction functions. Additionally, mutations in the RHO gene are associated with congenital stationary night blindness (CSNB) ^[2-6]. Mutations in the RHO gene can lead to rhodopsin-mediated autosomal dominant retinitis pigmentosa (RHO-adRP). In 25% of autosomal dominant inherited RP (adRP) cases, there are over 150 different RHO gene mutations. Notably, the P23H mutation is one of the most prevalent, accounting for 10% of adRP cases ^[2]. Previous studies have shown that mice carrying the heterozygous human RHO P23H mutation exhibit retinopathy and progressive retinal degeneration similar to the patient's disease process, which could be used for visual signaling and retinitis pigmentosa (RP) studies ^[3]. Current gene therapy targeting the RHO gene to treat retinitis pigmentosa includes ASO, CRISPR, and others. Applying fully humanized animal models will promote the further development of RHO-related potential therapies in clinical trials ^[7-11]. B6-hRHO (Promoter) /hRHO*P23H (Promoter) mouse is an F1 humanized model generated by crossing homozygous B6-hRHO (Promoter) mice (Catalog No.: C001646) with homozygous B6-hRHO*P23H (Promoter) mice (Catalog No.: C001727). This model carries two human RHO gene alleles, both with humanized promoter regions. One allele is the wild-type human RHO (without mutation), while the other is the human RHO carrying a pathogenic point mutation (P23H) (hRHO*P23H). The abnormal proteins encoded by the human genes are expressed in mice, resulting in abnormal retinal morphology, functional impairments, and visual defects in this model. Additionally, leveraging the technological innovation of independently developed TurboKnockout-fused BAC recombination, Cyagen Biosciences can provide customized services for different point mutations based on B6-hRHO humanized mice to meet the experimental needs of researchers, such as pharmacodynamic studies related to retinitis pigmentosa (RP).

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]. Specifically, the C3*R102G mutation involves a substitution of the amino acid arginine (R) with glycine (G) at position 102 of the mature C3 protein, often leading to a gain-of-function that results in the protein being more susceptible to cleavage and thus causing uncontrolled complement activation ^[3]. The B6-huC3*R102G mouse is a humanized disease model constructed by gene-editing technology. The sequences from upstream of exon 1 to the TGA stop codon of mouse C3 were replaced with the sequences from upstream of exon 1 to downstream of exon 41 of human C3. The p.R102G (CGC to GGC) mutation was introduced into human C3 exon 3. This model is suitable for the mechanistic study of immune-related diseases caused by uncontrolled activation of the complement system (such as age-related macular degeneration (AMD), etc.) and the development of therapies targeting C3 R102G.

Complement factor B (CFB) is a circulating serine protease that plays a central role in the alternative pathway of the complement system, a critical component of innate immunity. Encoded by the CFB gene, this protein is primarily synthesized by hepatocytes, adipocytes, and monocytes, reflecting its systemic and local involvement in immune surveillance and inflammation ^[1]. Upon activation by factor D, CFB forms the active enzyme factor Bb, which, in complex with complement component C3b, constitutes the alternative pathway C3 convertase (C3bBb). This convertase catalyzes the cleavage of C3 into the anaphylatoxin C3a and the opsonin C3b, leading to the amplification of the complement cascade and the subsequent elimination of pathogens and damaged cells ^[2]. Dysregulation of CFB activity, often stemming from genetic polymorphisms within the CFB locus, has been implicated in the pathogenesis of several human diseases, including age-related macular degeneration (AMD), atypical hemolytic uremic syndrome (aHUS), and systemic lupus erythematosus (SLE), underscoring the delicate balance required for proper complement regulation and immune homeostasis ^[3-4]. These associations highlight CFB as a key mediator of both protective and pathological immune responses. The MASP2 gene encodes MASP-2, a serum serine protease that serves as a key mediator in complement system activation. MASP-2 initiates the lectin pathway by forming complexes with pattern recognition molecules such as mannose-binding lectin (MBL) and ficolins. Upon pathogen recognition by MBL, MASP-2 is activated and subsequently cleaves complement components C4 and C2, leading to the generation of C3 convertase and triggering downstream complement activation. Beyond its role in the complement cascade, MASP-2 also contributes to the coagulation pathway by cleaving prothrombin to generate thrombin, thereby linking innate immunity and hemostasis ^[5]. Emerging evidence highlights the clinical significance of MASP2 gene polymorphisms, which are associated with altered susceptibility to infectious diseases and immune-related disorders. Reduced plasma levels of MASP-2 have been linked to increased vulnerability to HIV infection, while elevated MASP-2 activity may exacerbate inflammatory responses ^[6]. Given its pivotal role in immune regulation, MASP-2 has emerged as a promising therapeutic target. Inhibition of MASP-2 is currently under investigation as a potential strategy for treating a range of conditions, including IgA nephropathy (IgAN) ^[7], atypical hemolytic uremic syndrome (aHUS), and transplant-associated thrombotic microangiopathy (TA-TMA) ^[8]. The B6-huCFB/hMASP2 mouse is a dual-gene humanized model obtained by mating B6-huCFB mice (catalog number: C001710) with B6-hMASP2 mice (catalog number: C001592). This model can be used for research on the pathological mechanisms and treatment methods of autoimmune diseases and infectious diseases, as well as the development of CFB/MASP2-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.

The NRL (neural retina leucine zipper) gene encodes a basic motif-leucine zipper (bZIP) transcription factor of the Maf subfamily, which plays a critical role in the development and function of photoreceptor cells, particularly rods, in the mammalian retina. Gene expression of NRL is highly specific to the retina, appearing in postmitotic neuronal cells during embryonic development and maintaining high levels in mature neural retina. It functions as a master regulator of rod photoreceptor cell fate, working in conjunction with other transcription factors like CRX and NR2E3 to activate rod-specific genes (e.g., rhodopsin) and repress cone-specific genes. Cellular tissues predominantly labeled by NRL include rod photoreceptor nuclei, with some labeling also observed in rod and cone inner segments, somata, and synapses, and weak labeling in the cytoplasm of scattered cells in the inner nuclear and ganglion cell layers. Mutations in the NRL gene are associated with various inherited retinal degenerative diseases, most notably Retinitis Pigmentosa (RP), which can manifest as autosomal dominant (Retinitis Pigmentosa 27) or autosomal recessive forms (clumped pigmentary retinal degeneration, resembling Enhanced S-cone Syndrome), leading to progressive loss of vision ^[1-3]. The B6-hNRL mouse is a humanized model, constructed by replacing the sequences from 5'UTR to 3'UTR of the endogenous mouse Nrl gene with the corresponding human NRL gene sequence. B6-hNRL mice can be used for research into the pathogenesis of various inherited retinal degenerative diseases such as Retinitis Pigmentosa (RP). They are also useful for the screening, development, and safety evaluation of NRL-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 B6-hC3/hTFRC(CDS) mouse model is a humanized model obtained by breeding B6-hC3 mice (Catalog No.: I001135) with B6-hTFRC(CDS) 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 PRPF31 gene, located on chromosome 19q13.4, encodes the PRP31 protein, a crucial component of the spliceosome, a large molecular machine essential for pre-mRNA splicing. This gene is ubiquitously expressed, meaning it is active in nearly all cell types and tissues throughout the body, as its function is fundamental to general cell metabolism and survival ^[1]. The encoded protein, also known as Protein 61K, plays a critical role in the assembly of the U4/U6·U5 tri-snRNP complex, a vital step in the splicing process ^[2]. Mutations in the PRPF31 gene are primarily associated with autosomal dominant retinitis pigmentosa (adRP), a progressive inherited retinal disease. Although the gene is expressed ubiquitously, the disease phenotype is retina-specific, with cellular labeling and studies showing that photoreceptor and retinal pigment epithelial (RPE) cells are the most affected, leading to their dysfunction and death ^[3]. This is often attributed to haploinsufficiency, where a single mutated copy of the gene is not sufficient to produce the necessary amount of functional protein, particularly in the retina which has a high demand for splicing activity ^[4]. The B6-huPRPF31 mouse model was generated by replacing sequences from the ATG start codon to the TGA stop codon of the endogenous mouse Prpf31 gene with the sequences from the ATG start codon to the TGA stop codon of the human PRPF31 gene. This model can be used to study the pathological mechanisms and therapeutic approaches for autosomal dominant retinitis pigmentosa (adRP), as well as for the development of PRPF31-targeted drugs.

Retinitis pigmentosa (RP) is a hereditary retinal disease with a global prevalence of approximately 1:5000-1:3000. RP is highly clinically and genetically heterogeneous, with mutations in the rhodopsin (RHO) gene causing approximately 25% of dominant RP ^[1]. The rhodopsin encoded by the RHO gene is closely associated with visual light transduction and GPCR downstream signals. Rhodopsin is essential for the transmission of light signals in the process of vision formation. Most RHO mutations lead to high levels of rhodopsin expression in photoreceptor cells, causing many mutant proteins to be abnormally located and aggregated in cells. This results in the apoptosis of photoreceptor cells, which cannot perform normal light signal transduction functions. Additionally, mutations in the RHO gene are associated with congenital stationary night blindness (CSNB) ^[2-6]. Current gene therapy targeting the RHO gene to treat retinitis pigmentosa includes ASO, CRISPR, and others. Applying fully humanized animal models will promote the further development of RHO-related potential therapies in clinical trials ^[7-12]. This strain is a humanized model of the Rho gene with a heterozygous P23H mutation. It is obtained by mating homozygous B6J-hRHO mice (Catalog Number: C001396) with homozygous B6-hRHO-P23H mice (Catalog Number: C001495). In this model, the mouse Rho gene is replaced by the human RHO gene carrying the pathogenic mutation (P23H) and the human RHO gene without the mutation, respectively. The abnormal protein encoded by the mutant human gene is expressed in the mice. Therefore, the model exhibits abnormalities in the appearance and function of the retina, as well as visual defects. In addition, based on the technological innovation of TurboKnockout combined with BAC recombination developed independently, Cyagen Biosciences can also provide customized services for different point mutations based on B6-hRHO humanized mice to meet the experimental needs related to retinitis pigmentosa (RP) diseases. Mutations in the RHO gene are a major cause of RHO-mediated autosomal dominant retinitis pigmentosa (RHO-adRP). In 25% of autosomal dominant RP (adRP) cases, over 150 different RHO gene mutants have been identified. The P23H mutation is one of the most common causes of autosomal dominant retinitis pigmentosa, accounting for approximately 10% of adRP cases ^[2]. Previous studies have demonstrated that heterozygous mice carrying this mutation exhibit retinal pathology and progressive retinal degeneration similar to the disease progression in patients ^[3], making them valuable for studying visual signal transduction and retinitis pigmentosa (RP). Homozygous mice develop the disease earlier and have more severe phenotypes compared to heterozygous mice. Considering the uncertainty of the growth status and survival period of homozygous mice due to blindness in the later stage, it is generally recommended to use heterozygous mice (B6-hRHO*P23H/hRHO, Catalog Number: C001517) for experiments.