Reproduction：Homozygote x Homozygote
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease and acromegaly, is a fatal progressive neurodegenerative disease. ALS is caused by the degeneration and death of motor neurons that control skeletal muscles in the central nervous system, resulting in progressive muscle weakness and atrophy. Eventually, the brain completely loses the ability to control random movements and ALS can cause disorders of articulation, swallowing, and breathing. Unlike Alzheimer's disease, ALS does not necessarily affect higher neural activity. On the contrary, patients with advanced disease can always maintain clear thinking and retain their pre-onset memory, personality, and intelligence. The identified ALS-causing genes include SOD1 (Superoxide Dismutase 1), ALS2 (Alsin Rho Guanine Nucleotide Exchange Factor ALS2), TARDBP (Transactive response DNA-binding protein), and FUS (Fused in sarcoma), etc.
TARDBP (TAR DNA Binding Protein) is a protein-coding gene involved in the positive regulation of protein import into the nucleus and the regulation of circadian rhythms and protein stability. Mutations in the TARDBP gene are associated with ALS. Mutations in TARDBP (TDP-43) cause abnormal protein accumulation and its mislocalization in the cytoplasm is an important pathological hallmark of ALS.
TARDBP-targeted drugs are mainly monoclonal drugs and most of them are currently in the preclinical stage. The indications include amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and other neurological diseases. TARDBP is a relatively new and hot target for the treatment of ALS. The disease models are mainly TG and PM. Gene therapies such as ASO have been reported. Cyagen developed fully humanized mice to advance drug therapies related to TARDBP, especially gene therapy.
This strain is a mouse Tardbp gene humanized model. The sequences from the ATG start codon to the TAG stop codon of the endogenous mouse Tardbp gene were replaced with the sequences from the ATG start codon to the TAG stop codon of the human TARDBP gene by gene editing technology, which can be used for the research of neurological diseases such as ALS and FTD. Homozygous B6-hTARDBP mice are viable and fertile. Leveraging its proprietary TurboKnockout fusion BAC recombination technology, Cyagen can also generate hot spot disease related-mutation models based on this strain and provide customized services for specific point mutations to meet the experimental needs of researchers in pharmacology and other fields related to ALS, FTD, and so on.
Figure 1. Diagram of the gene editing strategy of B6-hTARDBP mice. The sequences from the ATG start codon to the TAG stop codon of the endogenous mouse Tardbp gene were replaced with the sequences from the ATG start codon to the TAG stop codon of the human TARDBP gene by TurboKnockout targeting technology.
● Research on amyotrophic lateral sclerosis (ALS);
● Research on frontotemporal dementia (FTD);
● Research on other neurodegenerative diseases.
1. Detection of human TARDBP gene expression
Figure 2. Detection of human TARDBP gene expression in the brain and thymus of wild-type mice (WT) and B6-hTARDBP mice (hTARDBP). The RT-qPCR analysis results showed that the human TARDBP gene was expressed in both the brain and thymus of B6-hTARDBP mice, while there was no expression of the human TARDBP gene in WT mice.
ND: Not detected
2. Detection of mouse Tardbp gene expression
Figure 3. Detection of mouse Tardbp gene expression in the brain and thymus of wild-type mice (WT) and B6-hTARDBP mice (hTARDBP). The RT-qPCR analysis results showed that the mouse Tardbp gene was expressed in both the brain and thymus of WT mice, while there was no expression of the mouse Tardbp gene in B6-hTARDBP mice.
1.Basic information about the TARDBP gene
2. TARDBP clinical variants
3. Disease introduction
The majority of ALS is sporadic ALS (sALS) with no family history of ALS, accounting for about 90%. A small proportion of ALS is familial ALS (fALS), which means that there is more than one ALS patient in the family, accounting for about 10%. There are approximately 50 pathogenic genes that cause ALS. Mutations in the following genes have been studied more frequently: Superoxide dismutase 1 (SOD1) gene, Chromosome 9 open reading frame 72 (C9orf72) gene, Fused in sarcoma (FUS) gene, and TARDBP gene.
4. TARDBP gene and mutations
The human TARDBP gene is located on chromosome 1. TDP-43 is a DNA and RNA binding protein expressed mainly in the nucleus and performs several important functions under normal physiological conditions, such as transcription, translation, mRNA transport, mRNA stabilization, microRNA (miRNA) and long non-coding RNA (lncRNA) processing, etc. Under normal physiological conditions, TDP-43 can shuttle in the nucleus and cytoplasm. However, TDP-43 will function preferentially in the nucleus. In contrast, under pathological conditions, TDP-43 aggregates toward the cytoplasm and shows high phosphorylation or ubiquitination, resulting in greatly reduced solubility. Abnormal localization of TDP-43 to the cytoplasm can lead to the development of cytotoxicity or, as TDP-43 continues to bind RNA in the cytoplasm, which causes functional abnormalities, resulting in degenerative neuronal lesions. The majority of ALS-related mutations in the TARDBP gene occur in exon 6, which encodes the C-terminal glycine-rich region of TDP-43. The most common missense mutations are A382T, M337V, A315T, etc.
5. Function of non-coding DNA sequences
According to published reports, mutations in the C-terminal region of TDP-43 enhance its propensity for intrinsic aggregation. TARDBP has pathogenic mutations in both the intron and UTR regions.
6. TARDBP-targeted gene therapy
Drugs targeting TARDBP are dominated by monoclonal antibodies. Among the drug pipelines for ALS, those targeting SOD1 are the most numerous, followed by TARDBP. The current pipeline focused on targeting TARDBP is primarily in the preclinical stage, which signifies the significant interest in preclinical research on drugs that target TARDBP. The application of fully humanized models can help drive the translation of relevant potential TARDBP-targeted therapies to clinical trials.
In summary, the TARDBP gene is an important pathogenic gene in amyotrophic lateral sclerosis with a complex pathogenic mechanism. This clinical drug development is based on monoclonal antibodies. Using humanized models can facilitate the preclinical development of the drug. Cyagen's TARDBP fully humanized mice can be used in preclinical research for ALS and FTD gene therapy. Custom modeling services are available for different point mutations.
 Motor Neuron Diseases Fact Sheet. National Institute of Neurological Disorders and Stroke (NINDS).
 Ederle H , Dormann D .TDP‐43 and FUS en route from the nucleus to the cytoplasm[J].FEBS Letters, 2017, 591(11).DOI:10.1002/1873-3468.12646.
 Prasad A, Bharathi V, Sivalingam V, et al.Molecular Mechanisms of TDP-43 Misfolding and Pathology in Amyotrophic Lateral Sclerosis[J].Frontiers in Molecular Neuroscience, 2019, 12:25-.DOI:10.3389/fnmol.2019.00025.