malf homozygotes have craniofacial defects that include primarily misplaced ears and, in some instances, significant asymmetry of the snout. The ear pinnae can be smaller than normal, misshapen, and positioned lower than normal and this can affect one or both ears. The phenotype ranges from subtle to pronounced. Of 37 mutants 28 had the left pinna affected, 8 had the right pinna affected and 1 had both affected. The parental phenotype does not appear to instruct which ear is affected. Of 117 offspring from homozygous x heterozygous or heterozygous x homozygous crosses only 39 (33%) were clearly mutant, indicative of either incomplete penetrance or partial embryonic lethality. In a mapping cross to C3H/HeSnJ only nine mutants were identified in one hundred seven F2 hybrids (8.4%). No mutants were identified in twenty-eight F2 hybrids with FVB/NJ, thirty-four F2 hybrids with CAST/EiJ, or nine F2 hybrids with A/J.
The malformed ear mutation arose spontaneously in the CXB5/ByJ strain at The Jackson Laboratory in 2005 when that strain was at generation F117. It was maintained by sibling intercrossing, primarily heterozygotes with homozygotes and vice versa. Sperm was cryopreserved from homozygous males at generation F6 and cryo-recovery will use BALB/cByJ oocytes since this has provided a successful recovery.
Some homozygotes with a twisted snout require tooth trimming due to malocclusion.
When using the malformed ear mouse strain in a publication, please cite the originating article(s) and include JAX stock #008260 in your Materials and Methods section.