These mice carry an ENU-induced mutation at the Scn8a locus and exhibit abnormal body movements resulting from neurogenic myopathy.
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In these mutants hind and fore limbs are affected, and the mice show a tottering walk, torso swaying, intense body tremor, and head tossing movements. The hind limbs are pulled closely to the body with impaired movement ability, front limbs show intermittently clonus like movements; when mice are lifted up, hind limbs do not spread apart, and the torso ventroflects backward. This overt phenotype can be observed at 3.7 weeks of age (+/- 1.2 weeks; n=91). Map position and phenotype similarities made NMF335 a candidate for complementation analysis with Scn8a; a mating of heterozygotes (NMF335 by C57BL/6J-Scn8med-jo/J [JR#3799]) resulted in 4 mutants in a total of 8 progeny, confirming that NMF335 represents an allele of Scn8a. Standard pathology work-up was performed on five mutants (20 - 110 days of age). Neurogenic myopathy in the hind limb characterized by areas of very small muscle fibers with degenerating nerve fibers and replacement of muscle by fat was revealed in the three oldest mice (77, 78 or 110 days of age). A loss of granule cells in the cerebellum was also observed in these three mutants, with vacuolation of the ventral roots of the spinal cord noted in one. No abnormalities were observed in the two youngest animals (20 days of age). Ovarian transplants are needed to maintain a colony.
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.
|Allele Name||7 Jackson|
|Allele Type||Chemically induced (ENU)|
|Allele Synonym(s)||neuroscience mutagenesis facility, 335; NMF335; Scn8anmf335|
|Gene Symbol and Name||Scn8a, sodium channel, voltage-gated, type VIII, alpha|
|Strain of Origin||C57BL/6J|
|Molecular Note||This phenotypic mutation was identified in an ENU mutagenesis screen and was shown by complementation testing to be allelic with the jolting mutation of this gene.|