Tooth hopper heterozygotes are smaller than normal in size, and have a hopping gait rather than a normal stride. They may lean or fall over when trying to move around the cage. They grow long teeth that require trimming. This may be due to abnormal jaw length or additional lower teeth resulting in malocclusion. Some heterozygotes die before weaning, and those that survive will require ongoing trimming of the teeth. Female heterozygotes are poor mothers and do not produce large litters. This congenic carries the agouti allele in coupling with Thpr in the congenic interval.
The Thpr mutation arose spontaneously and was identified in a (C57BL/6J x C3H/HeJ)F1 mouse at The Jackson laboratory. This dominant mutation was maintained for several generations by breeding a heterozygote to a (C57BL/6J x C3H/HeJ)F1. It was subsequently backcrossed onto C57BL/6JEi and carried with it the agouti allele, indicating that this mutation arose in C3H/HeJ derived sequence. After reaching backcross generation N6 in 2001, the congenic host was changed to C57BL/6J, beginning with one generation of in vitro fertilization using a heterozygous male and C57BL/6J oocytes, and continuing to backcross to C57BL/6J thereafter. In 2013 this strain reached backcross generation N15 on C57BL/6J still carrying the agouti allele in the congenic interval. Sperm was cryopreserved from heterozygous males at generation N12 and N13 that were also agouti in color.
Tooth overgrowth requires weekly cutting throughout life. Nestlets are beneficial to improve survival of these mutant pups. Female heterozygotes are poor mothers and produce small litters so it is preferred to maintain this strain by breeding heterozygous males.
When using the B6.C3(B6Ei)-A Thpr/GrsrJ mouse strain in a publication, please cite the originating article(s) and include JAX stock #003400 in your Materials and Methods section.