DNA topoisomerase II beta and neural development

DNA topoisomerase II beta is shown to have an unsuspected and critical role in neural development. Neurogenesis was normal in II beta mutant mice, but motor axons failed to contact skeletal muscles, and sensory axons failed t o enter the spinal cord. Despite an absence of innervation, clusters of ace tylcholine receptors were concentrated in the central region of skeletal mu scles, thereby revealing patterning mechanisms that are autonomous to skele tal muscle. The defects in motor axon growth in II beta mutant mice resulte d in a breathing impairment and death of the pups shortly after birth.