First published online February 2, 2004
doi: 10.1242/10.1242/dev.00959
Development 131, 819-828 (2004)
Published by The Company of Biologists 2004
The AHR-1 aryl hydrocarbon receptor and its co-factor the AHA-1 aryl hydrocarbon receptor nuclear translocator specify GABAergic neuron cell fate in C. elegans
Xun Huang1,*,
Jo Anne Powell-Coffman2 and
Yishi Jin1,
1 Department of Molecular, Cellular and Developmental Biology, Sinsheimer
Laboratories, Howard Hughes Medical Institute, University of California, Santa
Cruz, CA 95064, USA
2 Department of Genetics, Development, and Cell Biology, Iowa State University,
Ames, IA 50011-3260, USA
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Fig. 1. GABAergic RME neurons. (A) The cell lineage and morphology of RME cells. X,
dying cells. (B) Punc-25GFP expression. For wild type
(labeled as juIs76) and ju145, two focal planes are shown,
one on RMED/V, the other on RMEL. Schematic illustrations are shown on the
right. Asterisks denote the position of the processes from the RMED and RMEV
neurons; arrowheads point to the ectopic process from RMEL in ju145.
(C). Anti-GABA staining reveals defects in ahr-1 identical to those
shown in B. Two focal planes are shown, one on RMED/V, the other on RMEL.
Arrow points to the ectopic process from RMEL in ju145. Scale bar: 50
µm.
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Fig. 2. ju145 is a mutation in C41G7.5/AHR-1. (A,B) The genetic map
position and transformation rescue of ahr-1(ju145). The rescuing
activities are shown as number of rescued line/total number of lines. ND, not
determined. (C) AHR-1 domain structure and the molecular lesion of
ju145. HLH, helix-loop-helix; PAS, domain in Per, ARNT and Sim. The
PAS domain can be further divided to PAS A and PAS B subdomains.
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Fig. 3. ju145 affects RMEL/R cell fate. (A,B) RMEL/R form fewer synapses
(arrows) in ju145 animals compared with wild type; enlarged views are
shown below with arrows. (C-H) ju145 mutation affects cell-specific
marker expressions in RMEL/R neurons. Arrows point to the position of RMEL
neurons. (C,D) Pglr-1GFP is expressed in RMEL/R neurons in
wild type (C) but not in ju145 (D) animals. (E,F)
Plim-6rGFP is expressed in RMEL/R neurons in wild type (E)
but not ju145 (F) animals. (G,H) Punc-47sGFP is
expressed in RMEL/R neurons in wild type (G) but not ju145 animals.
(I) Pavr-15GFP expression in RMED/V cells (arrows) in
wild-type animals. (J-L) Pavr-15GFP is ectopically
expressed in RMEL/R cells (arrows in K and L) in ju145 animals;
arrows in J indicate RMED/V cells. Scale bar: 20 µm.
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Fig. 4. AHR-1 is expressed in RMEL/R cells. (A) Nomarski picture of the head of an
animal, with an enlarged view shown in B. (C) Fluorescence image of
Pahr-1GFP expression. Overlay is shown D. Arrows indicate
the RMEL neurons. Pahr-1GFP is also brightly expressed in
a pair of sensory neurons (arrowhead), likely to be ASKL/R. Scale bar: in
A,C,D, 50 µm; in B, 20 µm.
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Fig. 5. Ectopic AHR-1 expression in RMED/V cells can transform them into
RMEL/R-like cells. (A) juIs76 wild-type animals. (B) Ectopic AHR-1
expression (juEx467) in RMED/V cells inhibits the growth of dorsal
and ventral processes. Schematic illustrations are shown on the right.
Arrowheads in A and B indicate the processes from REMD/V neurons. (C-F)
Ectopic AHR-1 expression in RMED/V cells promotes
Plim-6GFP expression. (C) Plim-6rGFP
expression in a wild-type animal. Arrowhead indicates the RMEL neuron. (D-F)
juEx467 animals. Three focal planes are shown for
Plim-6rGFP expression in all four RME cells (arrowheads).
Scale bar: 50 µm.
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Fig. 6. aha-1 but not daf-21 is required for AHR-1 function in
RMEL/R cells. (A-D) Punc-25GFP expression in different
mutants. Left and middle panels show two focal planes focused on RMED/V and
RMEL neurons, respectively. Right panel shows the schematic illustration.
Asterisk indicates process from RMED/V neurons; arrowheads, the ectopic
processes from RMEL neurons. An aha-1 mutant has the same RMEL
phenotype (arrowheads) as an ahr-1 mutant (B,C). In a daf-21
mutant, RMEL and RMER neurons are normal (D). (EH) Mutations in aha-1
but not in daf-21 suppress the effect of ectopic ahr-1
expression in juEx467. Two focal planes are shown in G and H.
Arrowheads in E and F indicate the processes from RMED/V neurons, and in H
indicate the ectopic process from RMEL in aha-1 mutants. Asterisk in
G indicates the processes from RMED/V neurons. Scale bar: 50 µm.
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Fig. 7. ahr-1, ceh-10 and lim-4 function independently of each
other in RME neurons. (A) Expression of a functional AHR-1::GFP
(iaIs2) is unaltered in ceh-10 and lim-4 mutants.
Arrows indicate RMEL in the three panels. Not all AHR-1 expressing neurons are
in focus. (B) Double mutants of ahr-1, ceh-10 or lim-4 show
additive phenotypes. Genotypes are shown above the panels. The top panels show
RMEL/R neurons and the bottom panels show RMED/V neurons. Asterisks indicate
the ectopic nerve process of RMEL/R; arrows indicate RMEV; solid arrowhead
indicates RMED in ahr-1, lim-4 double mutants; empty triangles show
the presumed RMED position; and the fluorescence spots are from the distal
ends of RMEV. More than 100 animals were observed for each genotype.
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© The Company of Biologists Ltd 2004
