Patterning of dopaminergic neurotransmitter identity among Caenorhabditis elegans ray sensory neurons by a TGFbeta family signaling pathway and a Hox gene.
We have investigated the mechanism that patterns dopamine expression among Caenorhabditis elegans male ray sensory neurons. Dopamine is expressed by the A-type sensory neurons in three out of the nine pairs of rays. We used expression of a tyrosine hydroxylase reporter transgene as well as direct assays for dopamine to study the genetic requirements for adoption of the dopaminergic cell fate. In loss-of-function mutants affecting a TGFbeta family signaling pathway, the DBL-1 pathway, dopaminergic identity is adopted irregularly by a wider subset of the rays. Ectopic expression of the pathway ligand, DBL-1, from a heat-shock-driven transgene results in adoption of dopaminergic identity by rays 3-9; rays 1 and 2 are refractory. The rays are therefore prepatterned with respect to their competence to be induced by a DBL-1 pathway signal. Temperature-shift experiments with a temperature-sensitive type II receptor mutant, as well as heat-shock induction experiments, show that the DBL-1 pathway acts during an interval that extends from two to one cell generation before ray neurons are born and begin to differentiate. In a mutant of the AbdominalB class Hox gene egl-5, rays that normally express EGL-5 do not adopt dopaminergic fate and cannot be induced to express DA when DBL-1 is provided by a heat-shock-driven dbl-1 transgene. Therefore, egl-5 is required for making a subset of rays capable of adopting dopaminergic identity, while the function of the DBL-1 pathway signal is to pattern the realization of this capability.
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Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Emmons
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SW
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C117509:Dbl-1 protein, C elegans; D020690:GTPase-Activating Proteins; C120767:Git2 protein, mouse; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D009479:Neuropeptides; D010750:Phosphoproteins; D016212:Transforming Growth Factor beta; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine