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Cis-regulatory mechanisms for robust olfactory sensory neuron class-restricted odorant receptor gene expression in Drosophila.

Jafari S, Alenius M - PLoS Genet. (2015)

Bottom Line: Our results demonstrate that the spatial restriction of expression to a single OSN class is directed by clusters of transcription-factor DNA binding motifs.We further demonstrate that changes in metabolism or temperature perturb the function of complex clusters.We show that the cooperative regulation between motifs around and within the cluster generates robust, class-specific OR expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.

ABSTRACT
Odor perception requires that each olfactory sensory neuron (OSN) class continuously express a single odorant receptor (OR) regardless of changes in the environment. However, little is known about the control of the robust, class-specific OR expression involved. Here, we investigate the cis-regulatory mechanisms and components that generate robust and OSN class-specific OR expression in Drosophila. Our results demonstrate that the spatial restriction of expression to a single OSN class is directed by clusters of transcription-factor DNA binding motifs. Our dissection of motif clusters of differing complexity demonstrates that structural components such as motif overlap and motif order integrate transcription factor combinations and chromatin status to form a spatially restricted pattern. We further demonstrate that changes in metabolism or temperature perturb the function of complex clusters. We show that the cooperative regulation between motifs around and within the cluster generates robust, class-specific OR expression.

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Spatial expression pattern is dictated by the structure of the Or59b cluster.GFP expression (green) produced by (A) the Or59b cluster, (B) the cluster with the E-box displaced 125bps, (C) with the E-box 10bps upstream the cluster, (D-E) the Ebox 5 or 10 bp downstream the cluster. Synaptic neuropil regions are labeled with the presynaptic marker nc82 (magenta). A schematic representation of different rearrangements is shown under each figure. Schematic interpretations of the results are presented in S5 Fig.
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pgen.1005051.g004: Spatial expression pattern is dictated by the structure of the Or59b cluster.GFP expression (green) produced by (A) the Or59b cluster, (B) the cluster with the E-box displaced 125bps, (C) with the E-box 10bps upstream the cluster, (D-E) the Ebox 5 or 10 bp downstream the cluster. Synaptic neuropil regions are labeled with the presynaptic marker nc82 (magenta). A schematic representation of different rearrangements is shown under each figure. Schematic interpretations of the results are presented in S5 Fig.

Mentions: To investigate whether cluster structure regulates expression, we rearranged the order of the motifs in the Or59b cluster. First, we moved the E-box 125 bp downstream the cluster, which disrupted expression (Figs. 4B and S4A), demonstrating that the combinatorial clustering of the motifs was required for expression. Next, we addressed the regulatory function of the overlap between the Pou motif and the E-box. Moving the E-box upstream of the cluster caused ectopic expression in seven OSN classes, Ab1a, Ab2a, Ab3a, Ab5b, Ab7b, Ab8a, Ab8b and Ab10b (Figs. 4C and S4A), indicating that the precise location of the E-box dictates a repressive function necessary for class-specific OR expression. To further address how TFs binding at the E-box and Pou motifs interact, we moved the E-box either one-half or a full DNA turn (5 or 10 bp, respectively, S1C Fig.) that placed the TFs at different phases and sides of the DNA. Both constructs resulted in stereotyped ectopic expression in the seven OSN classes (Figs. 4D, E and S4A). As both the Ebox and the Pou motifs were shown to be required for cluster function (Fig. 3A), the above results indicate that occupancy of either of the two motifs interferes with the other and causes the repression of expression. Further genetic analyses placed Fer1 downstream of the Hox/Pou factors (S4B–S4C Fig.). Together, these results demonstrate that the composition and relative positions of motifs within the cluster define and restrict the expression of Or59b.


Cis-regulatory mechanisms for robust olfactory sensory neuron class-restricted odorant receptor gene expression in Drosophila.

Jafari S, Alenius M - PLoS Genet. (2015)

Spatial expression pattern is dictated by the structure of the Or59b cluster.GFP expression (green) produced by (A) the Or59b cluster, (B) the cluster with the E-box displaced 125bps, (C) with the E-box 10bps upstream the cluster, (D-E) the Ebox 5 or 10 bp downstream the cluster. Synaptic neuropil regions are labeled with the presynaptic marker nc82 (magenta). A schematic representation of different rearrangements is shown under each figure. Schematic interpretations of the results are presented in S5 Fig.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4356613&req=5

pgen.1005051.g004: Spatial expression pattern is dictated by the structure of the Or59b cluster.GFP expression (green) produced by (A) the Or59b cluster, (B) the cluster with the E-box displaced 125bps, (C) with the E-box 10bps upstream the cluster, (D-E) the Ebox 5 or 10 bp downstream the cluster. Synaptic neuropil regions are labeled with the presynaptic marker nc82 (magenta). A schematic representation of different rearrangements is shown under each figure. Schematic interpretations of the results are presented in S5 Fig.
Mentions: To investigate whether cluster structure regulates expression, we rearranged the order of the motifs in the Or59b cluster. First, we moved the E-box 125 bp downstream the cluster, which disrupted expression (Figs. 4B and S4A), demonstrating that the combinatorial clustering of the motifs was required for expression. Next, we addressed the regulatory function of the overlap between the Pou motif and the E-box. Moving the E-box upstream of the cluster caused ectopic expression in seven OSN classes, Ab1a, Ab2a, Ab3a, Ab5b, Ab7b, Ab8a, Ab8b and Ab10b (Figs. 4C and S4A), indicating that the precise location of the E-box dictates a repressive function necessary for class-specific OR expression. To further address how TFs binding at the E-box and Pou motifs interact, we moved the E-box either one-half or a full DNA turn (5 or 10 bp, respectively, S1C Fig.) that placed the TFs at different phases and sides of the DNA. Both constructs resulted in stereotyped ectopic expression in the seven OSN classes (Figs. 4D, E and S4A). As both the Ebox and the Pou motifs were shown to be required for cluster function (Fig. 3A), the above results indicate that occupancy of either of the two motifs interferes with the other and causes the repression of expression. Further genetic analyses placed Fer1 downstream of the Hox/Pou factors (S4B–S4C Fig.). Together, these results demonstrate that the composition and relative positions of motifs within the cluster define and restrict the expression of Or59b.

Bottom Line: Our results demonstrate that the spatial restriction of expression to a single OSN class is directed by clusters of transcription-factor DNA binding motifs.We further demonstrate that changes in metabolism or temperature perturb the function of complex clusters.We show that the cooperative regulation between motifs around and within the cluster generates robust, class-specific OR expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.

ABSTRACT
Odor perception requires that each olfactory sensory neuron (OSN) class continuously express a single odorant receptor (OR) regardless of changes in the environment. However, little is known about the control of the robust, class-specific OR expression involved. Here, we investigate the cis-regulatory mechanisms and components that generate robust and OSN class-specific OR expression in Drosophila. Our results demonstrate that the spatial restriction of expression to a single OSN class is directed by clusters of transcription-factor DNA binding motifs. Our dissection of motif clusters of differing complexity demonstrates that structural components such as motif overlap and motif order integrate transcription factor combinations and chromatin status to form a spatially restricted pattern. We further demonstrate that changes in metabolism or temperature perturb the function of complex clusters. We show that the cooperative regulation between motifs around and within the cluster generates robust, class-specific OR expression.

Show MeSH