Thyroid hormone controls the development of connections between the spinal cord and limbs during Xenopus laevis metamorphosis.
During premetamorphic stages, Xenopus laevis tadpoles expressing either a dominant-negative thyroid hormone (TH) receptor or a type-III iodothyronine deiodinase transgene in the nervous system have reduced TH-induced proliferation in the spinal cord and produce fewer hindlimb-innervating motorneurons. During prometamorphic stages, innervation of the hindlimbs is reduced, and few functional neuromuscular connections are formed. By metamorphic climax, limb movement is impaired, ranging from uncoordinated leg swimming to complete quadriplegia. This phenotype is due to transgene action in the tadpole spinal cord. The requirement of TH for neurogenesis during premetamorphosis is the earliest TH-regulated process reported to date in the sequence of metamorphic changes in anurans. The muscle formed during limb growth was previously shown to be a direct target of TH control. Here, we show that the same is true of the development of spinal cord cells that innervate the limbs.
Marsh-Armstrong
Nicholas
N
Department of Neuroscience, Johns Hopkins University School of Medicine, and Kennedy Krieger Institute, 707 North Broadway Street, Baltimore, MD 21205, USA. marsh-armstrong@kennedykrieger.org
Cai
Liquan
L
Brown
Donald D
DD
D000818:Animals; D030801:Animals, Genetically Modified; D005121:Extremities / Q000254:growth & development* / Q000294:innervation*; D008675:Metamorphosis, Biological; D009046:Motor Neurons / Q000166:cytology / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects; D010243:Paralysis / Q000209:etiology; D010641:Phenotype; D013116:Spinal Cord / Q000187:drug effects* / Q000254:growth & development*; D013550:Swimming; D013963:Thyroid Hormones / Q000494:pharmacology*; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
D013963:Thyroid Hormones