Radiographic and histological characterization of Tc/tw5 mice: an animal model of lumbosacral agenesis/myelomeningocele.

Twenty-five Tc/tw5 and 12 control mice were killed at different ages and radiographically and histologically examined. In addition, histochemical analysis was performed on muscles from four mutant and one control mouse. All Tc/tw5 mice were tailless and had a fluid-filled lumbar myelomeningocele. Radiographically, most animals had six instead of 10 lumbosacral vertebrae. Vertebral anomalies were common. The spinal cord was grossly abnormal: at the level of the plaque, it was replaced by patches of neural tissue intermingled with connective tissue and muscle. Affected skeletal muscles had small myofibers with centrally placed nuclei consistent with arrest of development at the myotubular stage secondary to denervation in early embryonic life. Abnormal nerves were smaller and had fewer axons. Tc/tw5 mice show features of neural tube and notochord dysplasia. These mutant mice may be useful as animal models of lumbosacral agenesis and myelomeningocele.