Mice homozygous for the gummy intragenic inversion have osteopetrotic bone development with dramatically denser bones, filled medullary spaces in the long bones, failed tooth eruption, and a much smaller overall body size. The skulls are severely effected with highly thickened bone, high levels of ossification in the hyoid and zygomatic arches, absent maxillary-premaxillary sutures, severely misshapen mandible, and what appears to be an additional tooth in the area of the mandibular foramina even though the teeth fail to erupt. As a result the head is misshapen. Whole body areal bone mineral density is significantly higher. Some homozygotes develop facial abscesses, and a few homozygotes have histologic signs of dystrophic muscle, with small muscle fibers and evidence of muscle fiber degeneration and regeneration. Tail length is proportionally shorter. Homozygous males have reduced fertility possibly due to decreased sperm motility, and pups born to homozygous females all die within a day of birth, likely due to failure of females to lactate, which is suggested by the absence of a milk spot. Heterozygotes are viable and fertile.
