Mice carrying this spontaneous mutation of the Down syndrome cell adhesion molecule exhibit degeneration of spinal joints, dystrophic axons in the lumbar spinal cord, small areas of degenerating epaxial skeletal muscle, and disorganization of inner nuclear and retinal ganglion layers. These mice may be useful for studies of neural development.Read More +
Mice homozygous for the Dscam2J mutation can be identified as early as 2 days of age resting on their backs instead of their stomachs and struggling to maintain balance. They develop overt thoracic kyphosis and a domed skull and appear to walk on their toes. Homozygotes fail swim tests wherein they are unable to swim in a straight line, curl up their bodies, and sink to the bottom. However, they have normal auditory brain stem responses indicative of normal cochlear hair cell function and connectivity. Degeneration of spinal joints, dystrophic axons in the lumbar spinal cord and small areas of degenerating epaxial skeletal muscle are found in aging homozygotes. On this background, in the presence of the Pde6brd1 mutation, the inner nuclear layer and retinal ganglion layer are disorganized, a phenotype beyond the retinal degeneration inherent in the background. Additionally, the dopaminergic amacrine cells have fasciculated neurites and are organized in clumps instead of mosaics. When bred onto a C3H background that lacks the Pde6brd1 mutation, it was revealed that homozygotes have defective lamination of the processes of cholinergic, calbindin-positive, and nitric oxide synthetase 1-positive amacrine cells in the retina and that distinct from Dscamdel17 homozygotes the central calbindin-positive amacrine cell band loses organized lamination so that three distinct calbindin-positive bands are not found. It is noteworthy that on this C3H inbred background homozygotes survive to adulthood, while other mutations of this gene on the C57BL/6J background suffer postnatal lethality which is diminished by the introduction of hybrid vigor.
The Dscam2J mutation arose spontaneously in 1981 on the C3H/HeDiSn background at The Jackson Laboratory and was maintained by sibling mating until 1983 when hysterectomy rederivation was performed with a homozygous ovarian transplanted female bred to a C3H/HeSnJ male, the progeny of which have subsequently been maintained by sibling mating.
|Allele Name||2 Jackson|
|Gene Symbol and Name||Dscam, DS cell adhesion molecule|
|Strain of Origin||C3H/HeDiSnJ|
|Molecular Note||This spontaneous mutation has a 4 base pair duplication in exon 19 resulting in a frameshift with 84 novel amino acids and a premature stop codon that truncates the protein at approximately halfway through the extracellular domain.|