Mice homozygous for the rb allele of Epha4 can be visibly identified by 2.5 - 3 weeks of age by a constant hopping gait of the hind limbs; the forelimbs may show a hopping gait or move normally. When picked up by the tail homozygotes clasp their hindlimbs and show reduced ability to hold on to an edge; forelimbs show normal strength.
The rb mutation arose spontaneously on the C57BL/6J background in 1964 at The Jackson Laboratory. It was outcrossed to C3H in approximately 1968 and in later years was crossed to C57BL/6J or (B6 x C3H)F1 to improve colony maintenance prior to cryopreservation in 1984. To generate embryos for cryopreservation, C57BL/6J females were bred with heterozygous males that were the F1 of either a cross to C57BL/6J or (B6 x C3H)F1.
|Gene Symbol and Name||Epha4, Eph receptor A4|
|Strain of Origin||C57BL/6J|
|Molecular Note||The rb mouse arose in 1964 at the Jackson Laboratory. This mouse was identified as an allele at the Epha4 locus based complementation analysis using the Epha4Gt(pGT1TM)38Wcs allele. The mutation at the level of the sequence has not been reported.|