Mutant mice are identified visibly at three weeks of age by the presence of a tilted head and a tremor visible when walking. When picked up by the tail mutant mice display increased agitation followed by an increase in tremor and hyperactivity. Most mutant mice lean to one side, and this is most noticeable by their tilted head. The tilted head is not completely penetrant as some mutants appear only to tremble. Progeny from the tremor-only mice yield both mice with tremor and mice with tremor and head tilt. The two phenotypic characteristics are inseparable. Female mutant mice breed and raise their pups successfully while male mutant mice do not breed. Sperm from mutants are 66-75% motile and appear to have normal morphology, thus male infertility is not likely due to defective sperm. Auditory brain stem response (ABR) results reveal no significant differences in hearing thresholds between homozygous mutant animals and controls, and no inner ear abnormalities were detected.
The tth mutation arose spontaneously on the C57BL/6JEi background when it was at F46 in 1997. It has been maintained by sibling mating, primarily homozygous female x heterozygous male and was backcrossed to C57BL/6JEi once.
Male homozygotes have not successfully bred but no sperm defects have been identified that would explain this.
When using the tremor with tilted head mouse strain in a publication, please cite the originating article(s) and include JAX stock #004667 in your Materials and Methods section.