Exon 1b of the mouse Ank3 (AnkG) gene is disrupted to create a knock-out of the cerebellar isoform. Homozygous mutant mice exhibit a progressive ataxia beginning around postnatal day P16 and subsequent loss of Purkinje neurons.
Vann Bennett, Duke University Medical Center
Exon 1b of the mouse Ank3 (ankyrin 3, epithelial; also called AnkG) gene is strongly expressed in the cerebellum, but it is also detectable in the brain stem and thalamus at low levels. A neomycin cassette was introduced to the exon to create a knock-out of the associated cerebellar isoform. No exon 1b-containing transcripts are detected in the homozygous mutant mice, and expression levels of transcripts containing exon 1e are unaffected.
Homozygous mutant mice are born in nearly Mendelian ratios and exhibit a progressive ataxia beginning around postnatal day P16 and subsequent loss of Purkinje neurons. This phenotype is reported to have a variable onset and severity. In mutant mouse cerebella, voltage-gated sodium channels (NaCh) are absent from axon initial segments of granule cell neurons, and Purkinje cells show deficiencies in their ability to initiate action potentials and support rapid, repetitive firing. Neurofascin, a member of the L1CAM family of ankyrin-binding cell adhesion molecules, as well as beta-4 spectrin (Sptbn4) and KCNQ2/3 channels also exhibit impaired localization to initial segments of Purkinje cell neurons. In addition, ponceau synapses of GABAergic neurons are absent at the axon initial segment. Results suggest that this gene is essential for assembly of axon initial segments and is required for physiological levels of sodium channel activity. Some premature death of homozygous mice may occur between 4 and 6 months of age, and in some cases may be preceded by uncontrollable jumping and convulsions. Although homozygotes are fertile, they do not breed well. Heterozygotes are phenotypically normal. PMID 9832557)
A neomycin cassette was introduced to a SmaI restriction site within exon 1b via homologous recombination in (129X1/SvJ x 129S1/Sv)F1- Kitl+-derived R1 embryonic stem (ES) cells. Resultant chimeric males were crossed with C57BL/6J females. This strain was backcrossed to a C57BL/6 inbred strain for 10 generations by the donating laboratory.
|Allele Name||targeted mutation 1, Vann Bennett|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||Ank3 exon 1b-; ankG-; cs-AnkG-KO|
|Gene Symbol and Name||Ank3, ankyrin 3, epithelial|
|Strain of Origin||(129X1/SvJ x 129S1/Sv)F1-Kitl+|
|Molecular Note||A neomycin resistance cassette was inserted into exon 1b, which is an alternatively spliced exon found in transcripts only in brain. Northern blot analysis on RNA derived from homozygous brains demonstrated that no transcript containing exon 1b was expressed, while expression of transcripts containing other alternaltively spliced exons remained unaffected. Western blot analysis and immunohistochemistry experiments confirmed that little or no protein was seen in cerebellum.|
Heterozygotes are viable and fertile. Although homozygotes are fertile, they do not breed well.
When using the exon1b-null mouse strain in a publication, please cite the originating article(s) and include JAX stock #029799 in your Materials and Methods section.