These mice exhibit laterally protruding ears, small body size; some exhibit microphthalmia, and a proportion of homozygotes die within the first three days of life. This strain is a model for oculo-auricular syndrome.
Dr. Ken Johnson, JAX
Mice homozygous for the dumbo mutation have low set, laterally protruding ears. They are smaller in overall body size than normal, with males weighing about half that of normal littermates at three days of age and lagging behind through nine days of age. Most have microphthalmia. This mutation causes perinatal lethality such that approximately 40% fewer homozygotes than predicted by standard Mendelian genetics are found at three weeks of age. Further assessment showed that most of the homozygous death occurs within the first three days of life and is strongly associated with exencephaly. This strain is a model for oculo-auricular syndrome.
The dumbo mutation was generated by treatment of 8 to 10 week old C57BL/6J males with intraperitoneal injections of 80 or 85 mg/kg body weight N-ethyl-N-nitrosourea (ENU) followed 10 weeks later by breeding with C3Fe.Cg-Rw heterozygous females. The G1 offspring carrying Rw, identified by the areas of white coat, were then bred to mice carrying Rw in trans to Hm, a mutation causing webbed digits. Rw has an inversion of the proximal third of Chromosome 5 and is homozygous lethal. Therefore, viable G2 progeny that did not have webbed digits were known to have inherited Rw from the Rw/Hm parent and thus to carry the Rw-spanning stretch of Chromosome 5 from the original ENU treated male ancestor. The G2 mice with normal feet were intercrossed and any viable offspring that did not have Rw were known to be homozygous for the region of Chromosome 5 from the ENU treated ancestor. Visual screen revealed an array of mutants in this population, including dumbo. This mutant was subsequently crossed to a Rw heterozygote in order to introduce a dominant visual marker for tracking the recessive dumbo mutation. This strain was maintained by breeding Hmx1dmbo/Rw females with Hmx1dmbo/Hmx1dmbo males for several years and distributed as stock #008677, and in 2011 sperm from Hmx1dmbo homozygotes was cryopreserved thereby removing Rw from this subline.