Developmental motoneuron cell death and neurotrophic factors.
During the development of higher vertebrates, motoneurons are generated in excess. In the lumbar spinal cord of the developing rat, about 6000 motoneurons are present at embryonic day 14. These neurons grow out axons which make contact with their target tissue, the skeletal muscle, and about 50% of the motoneurons are lost during a critical period from embryonic day 14 until postnatal day 3. This process, which is called physiological motoneuron cell death, has been the focus of research aiming to identify neurotrophic factors which regulate motoneuron survival during this developmental period. Motoneuron cell death can also be observed in vitro when the motoneurons are isolated from the embryonic avian or rodent spinal cord. These isolated motoneurons and other types of primary neurons have been a useful tool for studying basic mechanisms underlying neuronal degeneration during development and under pathophysiological conditions in neurodegenerative disorders. Accumulating evidence from such studies suggests that some specific requirements of motoneurons for survival and proper function may change during development. The focus of this review is a synopsis of recent data on such specific mechanisms.
Sendtner
M
M
Klinische Forschergruppe Neuroregeneration, Neurologische Universitätsklinik Würzburg, Germany. sendtner@mail.uni-wuerzburg.de
Pei
G
G
Beck
M
M
Schweizer
U
U
Wiese
S
S
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002470:Cell Survival; D002642:Chick Embryo; D020934:Ciliary Neurotrophic Factor / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D005109:Extracellular Matrix / Q000502:physiology; D008159:Lumbar Vertebrae / Q000166:cytology / Q000196:embryology* / Q000502:physiology*; D051379:Mice; D009046:Motor Neurons / Q000502:physiology*; D009410:Nerve Degeneration; D009414:Nerve Growth Factors / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology; D011506:Proteins / Q000502:physiology; D051381:Rats; D020800:Receptor, Nerve Growth Factor / Q000502:physiology; D017475:Receptors, Nerve Growth Factor / Q000502:physiology; D015398:Signal Transduction; D051636:X-Linked Inhibitor of Apoptosis Protein; D019014:fas Receptor / Q000502:physiology
D020934:Ciliary Neurotrophic Factor; D009414:Nerve Growth Factors; D011506:Proteins; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D051636:X-Linked Inhibitor of Apoptosis Protein; D019014:fas Receptor; D000242:Cyclic AMP