The roundabout 2 Jackson mutation causes hearing and balance defects due to degeneration of cochlear hair cells. Homozyogtes can be identified by 3 weeks of age by their bi-directional circling. They are deaf by 5 weeks of age, the youngest age tested, as assessed by auditory brainstem response measurements. The deafness is also reflected in the lack of an acoustic startle response. Although the cochlear hair cells are normal at birth, by 7 and 10 days of age a few of the outer hair cells have abnormal hair bundles with degeneration of stereocilla directly adjacent to the kinocillum. By 15 days of age all outer hair cells have stereocilla degeneration, some completely lacking bundles, and inner hair cells begin to display striking elongation and fusion of stereocillia. By 4 months of age complete degeneration of the organ of Corti and decreased density of spiral ganglion cells is found.
The roundabout 2 Jackson mutation arose spontaneously in the strain B10.BR-H2k H2-T18a/SgSnJ at The Jackson Laboratory in 1999 and was later backcrossed onto the C57BL/6J inbred strain for 8 backcross generations and maintained by sibling intercrossing heterozygous females with homozygous males. In 2012 this congenic strain reached generation N8F4.
|Allele Name||roundabout 2 Jackson|
|Allele Type||Spontaneous (Null/Knockout)|
|Gene Symbol and Name||Elmod1, ELMO/CED-12 domain containing 1|
|Strain of Origin||B10.BR-H2k2 H2-T18a/SgSnJ|
|Molecular Note||A spontaneous mutation results in a 606 bp intragenic duplication of exons 3 through 8. Western blot analysis confirmed the absence of a 62 kDa protein compared with the wild-type 36 kDa.|
Homozygous females should not be used as mothers since their circling phenotype may cause them to trample the pups.
When using the roundabout-2J mouse strain in a publication, please cite the originating article(s) and include JAX stock #006018 in your Materials and Methods section.