B6-hFUS Mice

Catalog Number: I001191

Strain Name: C57BL/6JCya-Fustm2(hFUS)/Cya

Genetic Background: C57BL/6JCya

Reproduction: Homozygote x Homozygote

One of Cyagen’s HUGO-GTTM (Humanized Genomic Ortholog for Gene Therapy) Strains

 

Strain Description

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, is a fatal progressive neurodegenerative disease. The disease is caused by the degeneration and death of motor neurons that control skeletal muscles in the central nervous system, leading to gradual muscle weakness and atrophy, and ultimately complete loss of voluntary movement control by the brain [1]. Unlike Alzheimer’s disease, ALS does not necessarily affect higher brain functions. On the contrary, late-stage patients can maintain clear thinking and retain memories, personality, and intelligence before the onset of the disease. The known ALS-causing genes include SOD1, ALS2, TARDBP, and FUS, among others.

FUS is a multifunctional DNA/RNA binding protein typically located in the cell nucleus and can shuttle between the nucleus and cytoplasm. FUS protein plays an important role in RNA transcription, splicing, and microRNA processing. Mutations in the FUS gene are closely related to frontotemporal lobar degeneration/dementia (FTLD-FUS) and amyotrophic lateral sclerosis (ALS-FUS). More than 50 FUS gene mutations have been identified in familial and sporadic ALS patients, most of which are autosomal dominant and most of which affect the nuclear localization signal (NLS) of FUS protein [2]. ALS-FUS patients have a histopathological feature of FUS protein mislocalization to the cytoplasm and formation of FUS-positive inclusions in spinal motor neurons and glial cells. However, in current cases, only some patients exhibit FUS mislocalization, and changes in the nuclear function of FUS mutants can also cause ALS. Studies have found that FUS pathological mice can induce neurodegeneration without cytoplasmic pathology or obvious mislocalization, which strongly suggests that the nuclear toxic function of FUS mutants may be a potential pathogenic mechanism [2].

Most FUS-targeting drugs in development are gene therapies, including antisense oligonucleotides (ASOs). The ASO drug ION363 developed by Ionis Pharmaceuticals can effectively reduce abnormal expression of FUS in diseased mice [3]. Humanizing mouse genes, given the genetic differences between animals and humans, can accelerate the development of FUS-targeted gene therapy for clinical use. This strain is a mouse Fus gene humanized model and can be used for research on ALS. The homozygous B6-hFUS mice are viable and fertile. In addition, based on the independently developed TurboKnockout fusion BAC recombination technology, Cyagen can also generate hot mutation models based on this strain (e.g. FUS (p.R521C)) and provide customized services for specific mutations to meet the experimental needs in pharmacology and other fields related to ALS.

Strain Strategy


Figure 1. Gene editing strategy of B6-hFUS mice. The sequences from the ATG start codon to ~1 kb downstream of exon 15 of the endogenous mouse Fus gene were replaced with the sequences from the ATG start codon to ~1 kb downstream of exon 15 of the human FUS gene.

Application

  • Research on amyotrophic lateral sclerosis (ALS);
  • Research on frontotemporal lobar degeneration/dementia (FTLD-FUS).

Validation Data

1. Expression of human FUS gene and mouse Fus gene


Figure 2. RT-qPCR detection of human FUS gene and mouse Fus gene expression in the brains and spleens of 6-week-old female wild-type mice (WT) and B6-hFUS mice (hFUS). The results show significant expression of the human FUS gene in both the brain and spleen of B6-hFUS mice, while mouse Fus gene expression is absent. In WT mice, human FUS gene expression is not detected, with only mouse Fus gene expression observed.

Expanded Information: The Rare Disease Data Center (RDDC)

1. Basic information about the FUS gene

2. FUS clinical variants

3. Disease introduction

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, Lou Gehrig’s disease, and Charcot’s disease, is a fatal progressive neurodegenerative disease. The disease is caused by the degeneration and death of motor neurons that control skeletal muscles in the central nervous system, leading to gradual muscle weakness and atrophy, and ultimately complete loss of voluntary movement control by the brain. Patients may experience difficulties in speaking, swallowing, and breathing [1]. Unlike Alzheimer’s disease, ALS does not necessarily affect higher brain functions. On the contrary, late-stage patients can maintain clear thinking and retain memories, personality, and intelligence before the onset of the disease. In familial ALS, SOD1 gene mutations account for 10%-20% of cases, C9orf72 gene mutations account for 20%-50% of cases, TARDBP, also known as TDP-43 gene mutations account for 5%, and FUS gene mutations account for 5%.

4. FUS gene and mutations

FUS is a multifunctional DNA/RNA binding protein typically located in the cell nucleus and can shuttle between the nucleus and cytoplasm. FUS protein plays an important role in RNA transcription, splicing, and microRNA processing. Mutations in the FUS gene are closely related to frontotemporal lobar degeneration/dementia (FTLD-FUS) and motor neuron diseases such as amyotrophic lateral sclerosis (ALS-FUS). FUS gene mutations can cause about 5% of familial ALS and about 1% of sporadic ALS. More than 50 FUS gene mutations have been identified in familial and sporadic ALS patients, most of which are autosomal dominant and most of which affect the nuclear localization signal (NLS) of FUS protein [2]. ALS-FUS patients have a histopathological feature of FUS protein mislocalization to the cytoplasm and formation of FUS-positive inclusions in spinal motor neurons and glial cells. However, in current cases, only some patients exhibit FUS mislocalization, and changes in the nuclear function of FUS mutants can also cause ALS. Studies have found that FUS pathological mice can induce neurodegeneration without cytoplasmic pathology or obvious mislocalization, which strongly suggests that the nuclear toxic function of FUS mutants may be a potential pathogenic mechanism [2]. Most FUS gene mutations are missense mutations, mainly concentrated in two regions: about 2/3 of the mutations occur in exons 14 and 15, which encode the nuclear localization signal; the other 1/3 are located in exons 3, 5, and 6.

5. Function of non-coding DNA sequences

Studies have found that the pathogenic mutation c.1542-1G>T in the intron 14 of the FUS gene can lead to a reduction of more than half of FUS mRNA expression [4]. In addition, mutations in the 3’UTR region of the FUS gene are overexpressed in ALS patients and lead to translation dysregulation of FUS [5].

6. FUS-targeted gene therapy

Most FUS-targeting drugs in development are gene therapies, including antisense oligonucleotides (ASOs). The ASO drug ION363 developed by Ionis Pharmaceuticals, a leading gene therapy company, is currently in Phase III clinical trials. This drug can effectively reduce the levels of wild-type and mutant FUS proteins in the brains and spinal cords of MN-P517L/Δ14 mice by targeting the intron 6 of the FUS gene, thereby significantly reducing the toxicity of FUS aggregates and delaying motor neuron degeneration [3]. Humanizing mouse genes, given the genetic differences between animals and humans, can accelerate the development of FUS-targeted gene therapy for clinical use. In response to the research on the mechanism and pharmacology, Cyagen has also independently developed a disease model carrying FUS (p.R521C) mutation.

7. Summary

The FUS gene is an important pathogenic gene for Amyotrophic lateral sclerosis (ALS). FUS gene humanized mice from Cyagen can be used for preclinical research on ALS, and customized services can also be provided for different point mutations.




References
[1]Motor Neuron Diseases Fact Sheet. National Institute of Neurological Disorders and Stroke (NINDS).
[2]An, H., Skelt, L., Notaro, A. et al. ALS-linked FUS mutations confer loss and gain of function in the nucleus by promoting excessive formation of dysfunctional paraspeckles. acta neuropathol commun 7, 7 (2019).
[3]Korobeynikov VA, Lyashchenko AK, Blanco-Redondo B, Jafar-Nejad P, Shneider NA. Antisense oligonucleotide silencing of FUS expression as a therapeutic approach in amyotrophic lateral sclerosis. Nat Med. 2022 Jan;28(1):104-116.
[4]Canosa A, Lomartire A, De Marco G, Grassano M, Brunetti M, Manera U, Vasta R, Salamone P, Fuda G, Sbaiz L, Gallone S, Moglia C, Calvo A, Chiò A. A novel splice site FUS mutation in a familial ALS case: effects on protein expression. Amyotroph Lateral Scler Frontotemporal Degener. 2022 Feb;23(1-2):128-136. doi: 10.1080/21678421.2021.1909065. Epub 2021 Apr 21. PMID: 33879000.
[5]Sabatelli M, Moncada A, Conte A, Lattante S, Marangi G, Luigetti M, Lucchini M, Mirabella M, Romano A, Del Grande A, Bisogni G, Doronzio PN, Rossini PM, Zollino M. Mutations in the 3'untranslated region of FUS causing FUS overexpression are associated with amyotrophic lateral sclerosis. Hum Mol Genet. 2013 Dec 1;22(23):4748-55. doi: 10.1093/hmg/ddt328. Epub 2013 Jul 11. PMID: 23847048.