Abstract
We have tested the role of glial cell line-derived neurotrophic factor (GDNF) in regulating a group of putatively nociceptive dorsal root ganglion (DRG) neurons that do not express calcitonin gene-related peptide (CGRP) and that downregulate the nerve growth factor (NGF) receptor tyrosine kinase, TrkA, after birth. We show that mRNA and protein for the GDNF receptor tyrosine kinase, Ret, are expressed in the DRG in patterns that differ markedly from those of any of the neurotrophin receptors. Most strikingly, a population of small neurons initiates expression of Ret between embryonic day 15.5 and postnatal day 7.5 and maintains Ret expression into adulthood. These Ret-expressing small neurons are selectively labeled by the lectin IB4 and project to lamina IIi of the dorsal horn. Ret-expressing neurons also express the glycosyl-phosphatidyl inositol-linked (GPI-linked) GDNF binding component GDNFR-alpha and retrogradely transport 125I-GDNF, indicating the presence of a biologically active GDNF receptor complex. In vitro, GDNF supports the survival of small neurons that express Ret and bind IB4 while failing to support the survival of neurons expressing TrkA and CGRP. Together, our findings suggest that IB4-binding neurons switch from dependence on NGF in embryonic life to dependence on GDNF in postnatal life and are likely regulated by GDNF in maturity.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Aging / physiology*
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Animals
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Axonal Transport
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Binding Sites
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Carrier Proteins / pharmacology
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Cholera Toxin / metabolism*
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Drosophila Proteins*
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Embryonic and Fetal Development
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Ganglia, Spinal / embryology
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Ganglia, Spinal / growth & development
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Ganglia, Spinal / physiology*
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Gene Expression Regulation, Developmental*
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Glial Cell Line-Derived Neurotrophic Factor
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Glial Cell Line-Derived Neurotrophic Factor Receptors
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In Situ Hybridization
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Intermediate Filament Proteins
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Male
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Mice
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Mice, Inbred Strains
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Nerve Growth Factors / metabolism*
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Nerve Tissue Proteins / metabolism*
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Neurons / drug effects
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Neurons / physiology*
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Polymerase Chain Reaction
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Proto-Oncogene Proteins / biosynthesis*
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Proto-Oncogene Proteins c-ret
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Rats
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Rats, Sprague-Dawley
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Receptor Protein-Tyrosine Kinases / biosynthesis*
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Receptor, trkA
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Receptors, Nerve Growth Factor / biosynthesis*
Substances
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Carrier Proteins
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Drosophila Proteins
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Gdnf protein, mouse
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Gdnf protein, rat
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Glial Cell Line-Derived Neurotrophic Factor
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Glial Cell Line-Derived Neurotrophic Factor Receptors
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Intermediate Filament Proteins
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Nerve Growth Factors
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Nerve Tissue Proteins
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Proto-Oncogene Proteins
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Receptors, Nerve Growth Factor
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alpha-internexin
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Cholera Toxin
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Proto-Oncogene Proteins c-ret
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Receptor Protein-Tyrosine Kinases
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Receptor, trkA
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Ret protein, Drosophila
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Ret protein, mouse
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Ret protein, rat