Triple knock-out of CNTF, LIF, and CT-1 defines cooperative and distinct roles of these neurotrophic factors for motoneuron maintenance and function.
Members of the ciliary neurotrophic factor (CNTF)-leukemia inhibitory factor (LIF) gene family play an essential role for survival of developing and postnatal motoneurons. When subunits of the shared receptor complex are inactivated by homologous recombination, the mice die at approximately birth and exhibit reduced numbers of motoneurons in the spinal cord and brainstem nuclei. However, mice in which cntf, lif, or cardiotrophin-1 (ct-1) are inactivated can survive and show less motoneuron cell loss. This suggests cooperative and redundant roles of these ligands. However, their cooperative functions are not well understood. We generated cntf/lif/ct-1 triple-knock-out and combinations of double-knock-out mice to study the individual and combined roles of CNTF, LIF and CT-1 on postnatal motoneuron survival and function. Triple-knock-out mice exhibit increased motoneuron cell loss in the lumbar spinal cord that correlates with muscle weakness during early postnatal development. LIF deficiency leads to pronounced loss of distal axons and motor endplate alterations, whereas CNTF-and/or CT-1-deficient mice do not show significant changes in morphology of these structures. In cntf/lif/ct-1 triple-knock-out mice, various degrees of muscle fiber type grouping are found, indicating that denervation and reinnervation had occurred. We conclude from these findings that CNTF, LIF, and CT-1 have distinct functions for motoneuron survival and function and that LIF plays a more important role for postnatal maintenance of distal axons and motor endplates than CNTF or CT-1.
Holtmann
Bettina
B
The Institute for Clinical Neurobiology, Department of Neurology, D-97080 Wuerzburg, Germany.
Wiese
Stefan
S
Samsam
Mohtashem
M
Grohmann
Katja
K
Pennica
Diane
D
Martini
Rudolf
R
Sendtner
Michael
M
D000818:Animals; D020934:Ciliary Neurotrophic Factor / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016207:Cytokines / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D018737:Hand Strength; D015850:Interleukin-6 / Q000235:genetics / Q000502:physiology*; D053605:Leukemia Inhibitory Factor; D051379:Mice; D018345:Mice, Knockout; D009045:Motor Endplate / Q000648:ultrastructure; D009046:Motor Neurons / Q000502:physiology*; D009121:Muscle Denervation; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D018908:Muscle Weakness / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D009410:Nerve Degeneration; D010525:Peripheral Nerves / Q000473:pathology; D013116:Spinal Cord / Q000473:pathology
D020934:Ciliary Neurotrophic Factor; D016207:Cytokines; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; C092073:cardiotrophin 1
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