Transthyretin amyloidosis (ATTR) is a protein disorder caused by the abnormal accumulation of misfolded transthyretin (TTR) protein in organs and tissues throughout the body, primarily affecting the peripheral nervous system and heart ^[1]. ATTR can be divided into hereditary ATTR and wild-type ATTR, with hereditary ATTR being caused by genetic mutations in the TTR gene. The TTR gene encodes transthyretin (TTR), also known as prealbumin, which is mainly synthesized in the liver and to a lesser extent in the brain’s choroid plexus or ocular photoreceptor tissue (such as the retina). TTR is a transport protein that exists as a homotetramer in peripheral blood under normal physiological conditions and participates in the transport of thyroxine and retinol-binding protein. Mutations in the TTR gene can lead to hereditary familial amyloidosis, such as Transthyretin Cardiac Amyloidosis Myocardiopathy (ATTR-CM) and Transthyretin Amyloid Polyneuropathy (ATTR-PN). The pathogenic mechanism is that structurally unstable TTR protein tetramers develop into pathological aggregates in tissues such as the peripheral nervous system, heart, eyes, kidneys, and meninges, forming insoluble amyloid deposits, eventually leading to ATTR. The treatments for ATTR-CM and ATTR-PN mainly involve inhibiting the production of mutant TTR mRNA or stabilizing the structure of TTR protein tetramers. At present, various drug pipelines have emerged in the field of gene therapy targeting the TTR gene, including ASO, siRNA, and CRISPR-based gene therapies. Among them, Inotersen Sodium, developed by Ionis, the leading oligonucleic acid drug (ASO) therapy company, is the first approved ASO drug for this disease. It targets the conserved sequence of the 3’ untranslated region (UTR) of TTR mRNA to induce mRNA degradation and reduce TTR synthesis in liver cells ^[2]. Since most ASO, siRNA, and CRISPR-based therapies target human TTR genes, considering the differences between animals and humans at the genetic level, humanizing mouse genes will help advance gene therapy drug pipelines into clinical stages. This strain is a mouse Ttr gene humanized model and can be used for research on transthyretin amyloidosis. The homozygous B6-hTTR mice are viable and fertile ^[3-6]. Additionally, 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 experimental needs in pharmacology.

Transthyretin amyloidosis (ATTR) is a protein misfolding disorder caused by the abnormal accumulation of misfolded transthyretin (TTR) protein in organs and tissues throughout the body. It primarily affects the peripheral nervous system and the heart ^[1]. Hereditary ATTR (ATTRv) results from genetic mutations in the TTR gene. The TTR gene encodes transthyretin, also known as prealbumin. This protein is primarily synthesized in the liver, with a smaller amount produced in the choroid plexus of the brain or the light-sensitive tissue in the eye (such as the retina). TTR functions as a transport protein and normally exists in the peripheral blood as a homotetramer, participating in the transport of thyroid hormones and retinol-binding protein. Over 130 TTR variants have been identified, among which the Val50Met (V50M) mutation, also known as c.148G>A and V30M, is the most common in patients with hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) ^[2-6]. Most ATTRv patients with the Val50Met mutation, if left untreated, will progress to complete disability or even death within 10 to 15 years after diagnosis. Their neurological symptoms may also be accompanied by gastrointestinal dysfunction, cardiomyopathy, renal disease, or ocular deposits ^[7]. The primary treatment for ATTR mainly involves inhibiting the production of mutant TTR gene mRNA or stabilizing the structure of TTR protein tetramers. In the current stage of research targeting TTR, several innovative therapeutic pipelines have emerged, including ASO (antisense oligonucleotide) drugs, siRNA drugs, and CRISPR-based gene therapies. Inotersen Sodium, developed by the leading nucleic acid drug company Ionis, specifically targets the conservative sequence in the 3’ untranslated region of TTR mRNA, inducing mRNA degradation to reduce TTR synthesis in liver cells. It is the first ASO drug approved for this disease ^[8]. Given that most ASO, siRNA, and CRISPR-based therapies target the human TTR gene, humanizing mouse genes can accelerate the TTR-targeted treatments into clinical stages. This strain is a Ttr humanized model and can be used for research on ATTRv-PN. A human TTR gene fragment carrying the V50M mutation, driven by the mouse Alb promoter (liver-specific promoter), is inserted at the H11 safe harbor. This modification does not affect the expression of the mouse Ttr gene. The homozygous H11-Alb-hTTR*V50M mice are viable and fertile. In addition, based on the independently developed TurboKnockout fusion BAC recombination technology, Cyagen can also provide customized services to meet experimental needs.

Chil6 is located on chromosome 3 of mice. SgRNA and ssDNA will be designed using Nuclease Technology; Chil6 conditional knockout mice will be obtained by high-throughput electroporation of fertilized eggs. After sexual maturity, sperm will be collected for cryopreservation.

Cntnap5b is located on chromosome 1 of mice. Nuclease Technology will be used to design sgRNA; Cntnap5b knockout mice will be obtained by applying high-throughput electroporation of fertilized eggs. After sexual maturity, sperm were collected for cryopreservation.