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Feeding state, insulin and NPR-1 modulate chemoreceptor gene expression via integration of sensory and circuit inputs.

Gruner M, Nelson D, Winbush A, Hintz R, Ryu L, Chung SH, Kim K, Gabel CV, van der Linden AM - PLoS Genet. (2014)

Bottom Line: Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression.While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway.Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Feeding state and food availability can dramatically alter an animals' sensory response to chemicals in its environment. Dynamic changes in the expression of chemoreceptor genes may underlie some of these food and state-dependent changes in chemosensory behavior, but the mechanisms underlying these expression changes are unknown. Here, we identified a KIN-29 (SIK)-dependent chemoreceptor, srh-234, in C. elegans whose expression in the ADL sensory neuron type is regulated by integration of sensory and internal feeding state signals. We show that in addition to KIN-29, signaling is mediated by the DAF-2 insulin-like receptor, OCR-2 TRPV channel, and NPR-1 neuropeptide receptor. Cell-specific rescue experiments suggest that DAF-2 and OCR-2 act in ADL, while NPR-1 acts in the RMG interneurons. NPR-1-mediated regulation of srh-234 is dependent on gap-junctions, implying that circuit inputs regulate the expression of chemoreceptor genes in sensory neurons. Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression. While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway. Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

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Starvation downregulates the expression of srh-234 in ADL neurons.A) Expression of srh-234p::gfp in an ADL neuron of wild-type animals when well-fed in the presence of E. coli OP50 food (upper panel) and starved (lower panel) in the absence of food for 12 hours. The head of the animal is indicated with a white line. Arrow points to the ADL cell body. Images were acquired at the same exposure time. Lateral view: anterior is on the left. Scale, 100 µm. B) Levels of endogenous srh-234 messages are downregulated in starved animals compared to fed animals. Shown is the ratio of endogenous srh-234 message to endogenous odr-10[65] message as quantified by qRT–PCR in fed and starved animals. In hermaphrodite animals, expression of odr-10 is unaffected by starvation. The mean of the ratios from two independent experiments is shown. * indicates values that are different from fed wild-type animals at P<0.01 using a two-sample t-test. Error bars denote the SEM.
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pgen-1004707-g001: Starvation downregulates the expression of srh-234 in ADL neurons.A) Expression of srh-234p::gfp in an ADL neuron of wild-type animals when well-fed in the presence of E. coli OP50 food (upper panel) and starved (lower panel) in the absence of food for 12 hours. The head of the animal is indicated with a white line. Arrow points to the ADL cell body. Images were acquired at the same exposure time. Lateral view: anterior is on the left. Scale, 100 µm. B) Levels of endogenous srh-234 messages are downregulated in starved animals compared to fed animals. Shown is the ratio of endogenous srh-234 message to endogenous odr-10[65] message as quantified by qRT–PCR in fed and starved animals. In hermaphrodite animals, expression of odr-10 is unaffected by starvation. The mean of the ratios from two independent experiments is shown. * indicates values that are different from fed wild-type animals at P<0.01 using a two-sample t-test. Error bars denote the SEM.

Mentions: Since SIKs regulate feeding state-dependent gene expression, we investigated whether feeding and starvation regulates the expression of kin-29-dependent chemoreceptor genes. Expression of gfp driven under the regulatory sequences of candidate chemoreceptor genes, str-1, sra-6 and srh-234 is strongly downregulated in AWB, ASH and ADL neurons, respectively [15], [16]. We found that gfp expression driven under only 165 bp of the regulatory sequence of srh-234 (srh-234p::gfp) is strongly expressed in ADL in fed animals (Figure 1A, upper panel), but when animals were starved for long-periods of time (>6 hours), srh-234p::gfp was significantly downregulated (Figure 1A, lower panel). Similar results were found for another independent integrated transgenic array of srh-234p::gfp (oyIs57) (Table S2). The expression of str-1::gfp and sra-6::gfp was unaffected in starved animals. We further confirmed the starvation-induced change in expression by examining the endogenous levels of srh-234 with help of qRT-PCRs, and found that the transcript levels of srh-234 were similarly downregulated but not abolished in starved animals (Figure 1B). The effect of starvation on srh-234 expression is reversible as L1 larvae or adult animals starved for 12 hours and then re-fed with E. coli food restore expression to near wild-type levels within 6 hours (Figure S1A). Moreover, when starved L1 larvae were grown on a nutrient-rich minimal media for 24 hours that is axenic, i.e. in the absence of any bacterial food, allowing developmental growth albeit delayed {Szewczyk, 2003 #4559], no increase in srh-234 expression was observed (Figure S1B). As bacterial food can alter the production of pheromones in C. elegans[22], which in turn can regulate chemoreceptor gene expression [13], we examined srh-234 expression in the absence and presence of pheromones. However, no effect on srh-234 expression was found in daf-22(m130) mutants, which is required for pheromone biosynthesis [23], and in the presence of crude pheromone extracts (Table S2), suggesting that pheromones do not alter srh-234 expression. Thus, starvation reduces the expression of the kin-29-dependent chemoreceptor, srh-234, in ADL, and this modulation is reversible upon re-feeding with food.


Feeding state, insulin and NPR-1 modulate chemoreceptor gene expression via integration of sensory and circuit inputs.

Gruner M, Nelson D, Winbush A, Hintz R, Ryu L, Chung SH, Kim K, Gabel CV, van der Linden AM - PLoS Genet. (2014)

Starvation downregulates the expression of srh-234 in ADL neurons.A) Expression of srh-234p::gfp in an ADL neuron of wild-type animals when well-fed in the presence of E. coli OP50 food (upper panel) and starved (lower panel) in the absence of food for 12 hours. The head of the animal is indicated with a white line. Arrow points to the ADL cell body. Images were acquired at the same exposure time. Lateral view: anterior is on the left. Scale, 100 µm. B) Levels of endogenous srh-234 messages are downregulated in starved animals compared to fed animals. Shown is the ratio of endogenous srh-234 message to endogenous odr-10[65] message as quantified by qRT–PCR in fed and starved animals. In hermaphrodite animals, expression of odr-10 is unaffected by starvation. The mean of the ratios from two independent experiments is shown. * indicates values that are different from fed wild-type animals at P<0.01 using a two-sample t-test. Error bars denote the SEM.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4214617&req=5

pgen-1004707-g001: Starvation downregulates the expression of srh-234 in ADL neurons.A) Expression of srh-234p::gfp in an ADL neuron of wild-type animals when well-fed in the presence of E. coli OP50 food (upper panel) and starved (lower panel) in the absence of food for 12 hours. The head of the animal is indicated with a white line. Arrow points to the ADL cell body. Images were acquired at the same exposure time. Lateral view: anterior is on the left. Scale, 100 µm. B) Levels of endogenous srh-234 messages are downregulated in starved animals compared to fed animals. Shown is the ratio of endogenous srh-234 message to endogenous odr-10[65] message as quantified by qRT–PCR in fed and starved animals. In hermaphrodite animals, expression of odr-10 is unaffected by starvation. The mean of the ratios from two independent experiments is shown. * indicates values that are different from fed wild-type animals at P<0.01 using a two-sample t-test. Error bars denote the SEM.
Mentions: Since SIKs regulate feeding state-dependent gene expression, we investigated whether feeding and starvation regulates the expression of kin-29-dependent chemoreceptor genes. Expression of gfp driven under the regulatory sequences of candidate chemoreceptor genes, str-1, sra-6 and srh-234 is strongly downregulated in AWB, ASH and ADL neurons, respectively [15], [16]. We found that gfp expression driven under only 165 bp of the regulatory sequence of srh-234 (srh-234p::gfp) is strongly expressed in ADL in fed animals (Figure 1A, upper panel), but when animals were starved for long-periods of time (>6 hours), srh-234p::gfp was significantly downregulated (Figure 1A, lower panel). Similar results were found for another independent integrated transgenic array of srh-234p::gfp (oyIs57) (Table S2). The expression of str-1::gfp and sra-6::gfp was unaffected in starved animals. We further confirmed the starvation-induced change in expression by examining the endogenous levels of srh-234 with help of qRT-PCRs, and found that the transcript levels of srh-234 were similarly downregulated but not abolished in starved animals (Figure 1B). The effect of starvation on srh-234 expression is reversible as L1 larvae or adult animals starved for 12 hours and then re-fed with E. coli food restore expression to near wild-type levels within 6 hours (Figure S1A). Moreover, when starved L1 larvae were grown on a nutrient-rich minimal media for 24 hours that is axenic, i.e. in the absence of any bacterial food, allowing developmental growth albeit delayed {Szewczyk, 2003 #4559], no increase in srh-234 expression was observed (Figure S1B). As bacterial food can alter the production of pheromones in C. elegans[22], which in turn can regulate chemoreceptor gene expression [13], we examined srh-234 expression in the absence and presence of pheromones. However, no effect on srh-234 expression was found in daf-22(m130) mutants, which is required for pheromone biosynthesis [23], and in the presence of crude pheromone extracts (Table S2), suggesting that pheromones do not alter srh-234 expression. Thus, starvation reduces the expression of the kin-29-dependent chemoreceptor, srh-234, in ADL, and this modulation is reversible upon re-feeding with food.

Bottom Line: Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression.While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway.Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Nevada, Reno, Nevada, United States of America.

ABSTRACT
Feeding state and food availability can dramatically alter an animals' sensory response to chemicals in its environment. Dynamic changes in the expression of chemoreceptor genes may underlie some of these food and state-dependent changes in chemosensory behavior, but the mechanisms underlying these expression changes are unknown. Here, we identified a KIN-29 (SIK)-dependent chemoreceptor, srh-234, in C. elegans whose expression in the ADL sensory neuron type is regulated by integration of sensory and internal feeding state signals. We show that in addition to KIN-29, signaling is mediated by the DAF-2 insulin-like receptor, OCR-2 TRPV channel, and NPR-1 neuropeptide receptor. Cell-specific rescue experiments suggest that DAF-2 and OCR-2 act in ADL, while NPR-1 acts in the RMG interneurons. NPR-1-mediated regulation of srh-234 is dependent on gap-junctions, implying that circuit inputs regulate the expression of chemoreceptor genes in sensory neurons. Using physical and genetic manipulation of ADL neurons, we show that sensory inputs from food presence and ADL neural output regulate srh-234 expression. While KIN-29 and DAF-2 act primarily via the MEF-2 (MEF2) and DAF-16 (FOXO) transcription factors to regulate srh-234 expression in ADL neurons, OCR-2 and NPR-1 likely act via a calcium-dependent but MEF-2- and DAF-16-independent pathway. Together, our results suggest that sensory- and circuit-mediated regulation of chemoreceptor genes via multiple pathways may allow animals to precisely regulate and fine-tune their chemosensory responses as a function of internal and external conditions.

Show MeSH
Related in: MedlinePlus