C57BL/6J-Gtpbp2^nmf205/J

Stock number: 004823
Research areas: Cell Biology Research, Neurobiology Research, Sensorineural Research

Description

This strain, which combines the n-Tr20^m1J and Gtpbp2^nmf205 mutations, has strong ribosomal stalling in the brain and is valuable for characterizing molecular interactions and pathways involved in protein translation.

Detailed description

The animals exhibit an unsteady gait, with 'high' hind limbs (walking on hind toes), which can be observed at approximately 4 weeks of age (mean 4.6+/-0.7; n=21, but as early as 3 weeks of age); the impairment progresses over time, i.e. hind limbs become weaker, and the animals show a staggering gait. Because of phenotypic similarities to nmf291, allele tests between nmf205 and nmf291 were performed but did not produce any affected mice.

Standard pathology work-up on four mutants (38 to 51 days of age) revealed loss of cerebellar granule cells in all four animals and cortical laminar necrosis in three animals. Subsequent characterization by Ishimura et al, 2014, revealed that the nmf205 mutation in Gtpbp2 requires the presence of the n-Tr20^m1J point mutation, a strain characteristic of C57BL/6J and C57BL/6JEiJ, in order for the neurodegenerative phenotype to present. The phenotype results from ribosomal stalling at AGA codons, which requires the presence of both mutations for full phenotypic expression. The phenotypic assessment was further characterized and found to include neurodegeneration in the retina including photoreceptor degeneration, and degeneration of amacrine, horizontal, and ganglion cells. Mice die by 8 to 9 weeks of age with progressive neuronal apoptosis. Apoptotic loss is found between 3 and 4 weeks of age the inner granule layer, and between 5 and 8 weeks of age also in the granule cells of the dentate gyrus, CA2 pyramidal neurons, and layer IV cortical neurons.

Development

This phenotypic deviant was generated by ethylnitrosourea (ENU) mutagenesis in C57BL/6J males (Stock No. 000664), in the Neuroscience Mutagenesis facility at The Jackson Laboratory. Mutagenized males were crossed to C57BL/6J females; G3 descendants of the mutagenized males were selected for neurological impairment. In 2004 sperm was cryopreserved from males, then at generation N4F1, one of which was homozygous and the other heterozygous. Cryorecovered animals will thus be a mixture of heterozygotes and wildtype siblings.

Allele

Symbol: n-TRtct5^m1J
Name: mutation 1, Jackson
MGI accession ID: MGI:5575489
Generation method: Spontaneous
Attributes: Not Specified
Marker symbol: n-TRtct5
Marker name: nuclear encoded tRNA arginine 5 (anticodon TCT)
Chromosome: 1
Strain of origin: C57BL/6J
Molecular note: This C-to-T transition, the T variant of SNP rs46447118, found in C57BL/6J and C57BL/6JEiJ but not any of the other 18 inbred strains tested, is in nucleotide 50 in the stem of the T loop and impairs maturation, leading to accumulation of a 105 nucleotide pre-tRNA band with leader and trailer sequences instead of the usual 115 nucleotide pre-tRNA, and also diminishes aminoacylation of this isodecoder.

Allele

Symbol: Gtpbp2^nmf205
Name: neuroscience mutagenesis facility, 205
MGI accession ID: MGI:2681955
Generation method: Chemically induced (ENU)
Attributes: Null/Knockout
Marker symbol: Gtpbp2
Marker name: GTP binding protein 2
Chromosome: 17
Strain of origin: C57BL/6J
Molecular note: This ENU-induced T to C point mutation in the consensus splice donor site of intron 6 results in misspliced mRNAs with premature stop codons. Western blot analysis failed to detect this protein in cerebellar extracts from homozygotes.