B6.Cg-Atxn1^em2Hzo/J

Stock number: 036101
Product name: Atxn1 154Q[S776A] , Atxn1^{154Q[S776A]/2Q} , SCA1 S776A
Research areas: Cancer Research, Neurobiology Research

Description

Atxn1^{154Q[S776A]/2Q} (SCA1 S776A) mice carry a serine to alanine mutation in the mouse Ataxin-1 (Atxn1) gene at amino acid 751 (ENSEMBL Atxn1-201 ENSMUST00000091628.11) that is homologous to human S776A in addition to an expanded CAG repeat tract. The mice can be used for studying the importance of ATXN1's S776 phosphorylation in Spinocerebellar Ataxia Type 1. Compared to Atxn1^154Q/2Q SCA1 mice (Atxn1[154Q], see Stock No. 005601), disruption of S776 phosphorylation on ATXN1[154Q] not only improves motor coordination, but also partially ameliorates the neuromuscular respiratory dysfunction and extends the lifespan, while having no effect on the hippocampal learning and memory deficits.

Update: Sequencing demonstrates a CAG (polyQ) copy number between 139-141 in The Jackson Laboratory stocks. (October, 2021)

Detailed description

Spinocerebellar ataxia type 1 (SCA1) is an adult-onset neurodegenerative disorder characterized by motor incoordination, mild cognitive decline, respiratory dysfunction, and early lethality. It is caused by the expansion of the polyglutamine (polyQ) tract in Ataxin-1 (ATXN1) which stabilizes the protein, leading to its toxic accumulation in neurons. Serine 776 (S776) phosphorylation is critical for ATXN1 stability in humans and contributes to its toxicity.

Atxn1^{154Q[S776A]/2Q} (SCA1 S776A) mice carry a serine to alanine mutation at amino acid 751 (ENSEMBL Atxn1-201 ENSMUST00000091628.11) that is homologous to an S776A mutation found in humans. It is carried on a C57BL/6J background that has been modified to carry one expanded Atxn1 allele with 154 CAG repeats encoding the 154Q glutamines in the polyQ tract of ATXN1 (Atxn1[154Q], see Stock No. 005601). The serine to alanine mutation abolishes phosphorylation at position S751 of the mouse protein, as confirmed by western blotting. ATXN1[154Q] protein levels are reduced in all tested brain regions.

Update: Sequencing demonstrates a CAG (polyQ) copy number between 139-141 in The Jackson Laboratory stocks. (October, 2021)

Atxn1^{154Q[S776A]/2Q} heterozygotes fail to gain weight, develop kyphosis, motor coordination difficulties, learning and memory deficits, breathing dysfunction, and show early lethality. Slight motor coordination phenotypes can be observed at 7 weeks of age; at 24 weeks of age mice are significantly worse than wildtype animals. Mice show altered breathing at 6 months of age. The onset of the kyphosis phenotype is estimated to begin around 24 weeks of age and is strongly visible at 40 weeks of age. After 5-6 months the mice become more progressively affected and are less fertile. All phenotypes besides the learning and memory deficits are delayed compared to Atxn1^[154Q]/2Q heterozygotes (Stock No. 005601) which recapitulate all major human SCA1 features.

Atxn1^2Q[S776A] (WT S776A) mutant mice (Stock No. 036100), carrying 2 CAG repeats (2Q) in the polyQ tract of Atxn1 in addition to the serine to alanine mutation, are also available as potential controls.

Development

A serine to alanine (TCG to GCG; amino acid 751; ENSEMBL Atxn1-201 ENSMUST00000091628.11) mutation and additional synonymous mutations (altering the PAM motif to increase editing efficiency and facilitate genotyping) were introduced by CRISPR/Cas9 to exon 8 of the mouse Atxn1 gene of Atxn1^154Q/2Q embryos (allele Atxn1[154Q]; see Stock No. 005601).

Founders were backcrossed to inbred C57BL/6J mice. Sanger sequencing confirmed the correct mutations in the F1 heterozygous offspring and the segregation of the Atxn1[154Q] allele with S776A genotyping confirmed the correct location of the serine-to-alanine mutation on the Atxn1[154Q] allele. The mice were backcrossed for over 10 generations by the donating laboratory.

Update: Sequencing demonstrates a CAG (polyQ) copy number between 139-141 in The Jackson Laboratory stocks. (October, 2021)

Allele

Symbol: Atxn1^em2Hzo
Name: endonuclease-mediated mutation 2, Huda Y Zoghbi
MGI accession ID: MGI:6501717
Generation method: Endonuclease-mediated
Attributes: Not Applicable
Synonyms: Atxn1^154Q[S776A]
Marker symbol: Atxn1
Marker name: ataxin 1
Marker synonyms: 2900016G23Rik; Atx1; D6S504E; Sca1
Chromosome: 13
Strain of origin: B6.129S7-Atxn1^tm1Hzo/J
Molecular note: CRISPR/cas9 genome editing was used to introduce a p.S751A (serine to alanine, TCG to GCG) mutation and additional synonymous mutations (altering the PAM motif to increase editing efficiency and facilitate genotyping) in zygotes containing the Atxn1^tm1Hzo allele. The p.S751A mutation in mouse is homologous to p.S776A in human. The mutation abolishes phosphorylation of the protein, as confirmed by western blotting. ATXN1 protein levels are reduced in all tested brain regions.