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Figure 1: A single subfamily of olfactory taar genes in Xenopus tropicalis. Phylogenetic tree of taar gene repertoires of mouse, zebrafish and frog (Xenopus tropicalis), using aminergic neurotransmitter receptors as outgroup (grey). Tree branches for the different species are color-coded, red for zebrafish, blue for mouse, and green for frog. The tree was constructed using a modified Maximum Likelihood method (PhyML-aLRT). Some nodes are shown collapsed (triangle), the number of genes in these nodes is given inside the respective triangle. Branch support of selected nodes is shown as p values (1 equals p > 0.995). Sequences were taken from10 (Danio rerio, zebrafish; Mus musculus, house mouse; Xenopus tropicalis, Western clawed-frog; aminergic receptors as outgroup) or newly identified in databank searches (2 additional Xenopus tropicalis genes, asterisks).
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Figure 2: TAAR4a, 4b expression and amine responses occur in sparsely distributed olfactory neurons. In situ hybridization was performed for TAAR4a and TAAR4b using horizontal sections of larval Xenopus laevis head tissue. Enlargements containing labeled cell(s) are shown to the right of each complete section. A ring of dark brown melanophores delineates the basal border of the epithelium; apical is toward the lumen. TAAR4a-expressing cells are found apically and laterally, whereas TAAR4b-expressing cells lie more basal and show no obvious enrichment in the medial-to-lateral dimension. Amine- and amino acid-responsive cells were identified by calcium imaging (green and red ovals, respectively). Traces for all cells depicted by colored ovals are shown to the right of the respective micrographs, with odor stimulus period indicated by the black bar (fluorescence intensity values are given as δF/F, see Materials and Methods). To be able to show several traces for amines, a slice with above average frequency of amine-responsive cells was chosen.
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Figure 3: Quantitative analysis of spatial patterns. Basal-to-apical distributions were quantified for olfactory receptor genes and odor responses. Top row, receptor gene (left panel) and odor response (right panel) distributions are shown as histogram of relative height (0, most basal; 1, most apical position; bin size 0.1, bin center is shown). Left panel, taar4a (brown) is centered apical; taar4b (green) shows a basal peak. Right panel, amine responses (blue) show a bimodal distribution. Second row, distributions are depicted as empirical cumulative distribution function (ECDF). Color code as above, for comparison to the amine responses the receptor distributions are shown in grey in the right panel. **p < 0.01. Third row, medial-to-lateral distribution is shown as bar graph for TAAR4a, TAAR4b, amine responses, and amino acid responses (values taken from2 for comparison). Bottom row, basal-to-apical distributions are shown independently for each segment of the medial-to-lateral distribution depicted above. Medial segment, blue; intermediate segment, red; lateral segment yellow. Note that for both taar genes and amine responses the height distribution is undistinguishable between segments, in contrast to the significant difference between lateral and non-lateral amino acid responses (right panel). **p < 0.01.
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Figure 4: Schematic representation of TAAR4a,4b expression and amine responses. The top panel shows a horizontal section of the MOE of Xenopus laevis as it appears both for measuring odor responses and receptor gene expression. The basalmost layer of the epithelium borders the basal lamina, and the apicalmost layer borders the lumen. The apicalmost layer consists of supporting cells, and the basalmost region of proliferating cells, sandwiching the neuronal region. Perpendicular to this basal-to-apical coordinate, cells in the MOE can also be distinguished by position in the lateral, intermediate, or medial compartment (lateral-to-medial coordinate). The bottom panel depicts a schematic representation of the different cellular distributions analysed. Note that only the neuronal region of the MOE is shown here. Distributions are shown along two axes, basal-to-apical and lateral-to-medial. OMP and TRPC2 distributions are taken from earlier work of our groups2,4, and are shown for comparison. We emphasize that TAAR4a and TAAR4b differ in both dimensions, and together comprise a large subset of the bimodal amine response region.
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Figure 1. A single subfamily of olfactory taar genes in Xenopus tropicalis.Phylogenetic tree of taar gene repertoires of mouse, zebrafish and frog (Xenopus tropicalis), using aminergic neurotransmitter receptors as outgroup (grey). Tree branches for the different species are color-coded, red for zebrafish, blue for mouse, and green for frog. The tree was constructed using a modified Maximum Likelihood method (PhyML-aLRT). Some nodes are shown collapsed (triangle), the number of genes in these nodes is given inside the respective triangle. Branch support of selected nodes is shown as p values (1 equals p > 0.995). Sequences were taken from10 (Danio rerio, zebrafish; Mus musculus, house mouse; Xenopus tropicalis, Western clawed-frog; aminergic receptors as outgroup) or newly identified in databank searches (2 additional Xenopus tropicalis genes, asterisks).
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Figure 2. TAAR4a, 4b expression and amine responses occur in sparsely distributed olfactory neurons.In situ hybridization was performed for TAAR4a and TAAR4b using horizontal sections of larval Xenopus laevis head tissue. Enlargements containing labeled cell(s) are shown to the right of each complete section. A ring of dark brown melanophores delineates the basal border of the epithelium; apical is toward the lumen. TAAR4a-expressing cells are found apically and laterally, whereas TAAR4b-expressing cells lie more basal and show no obvious enrichment in the medial-to-lateral dimension. Amine- and amino acid-responsive cells were identified by calcium imaging (green and red ovals, respectively). Traces for all cells depicted by colored ovals are shown to the right of the respective micrographs, with odor stimulus period indicated by the black bar (fluorescence intensity values are given as ΔF/F, see Materials and Methods). To be able to show several traces for amines, a slice with above average frequency of amine-responsive cells was chosen.
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Figure 3. Quantitative analysis of spatial patterns.Basal-to-apical distributions were quantified for olfactory receptor genes and odor responses. Top row, receptor gene (left panel) and odor response (right panel) distributions are shown as histogram of relative height (0, most basal; 1, most apical position; bin size 0.1, bin center is shown). Left panel, taar4a (brown) is centered apical; taar4b (green) shows a basal peak. Right panel, amine responses (blue) show a bimodal distribution. Second row, distributions are depicted as empirical cumulative distribution function (ECDF). Color code as above, for comparison to the amine responses the receptor distributions are shown in grey in the right panel. **p < 0.01. Third row, medial-to-lateral distribution is shown as bar graph for TAAR4a, TAAR4b, amine responses, and amino acid responses (values taken from2 for comparison). Bottom row, basal-to-apical distributions are shown independently for each segment of the medial-to-lateral distribution depicted above. Medial segment, blue; intermediate segment, red; lateral segment yellow. Note that for both taar genes and amine responses the height distribution is undistinguishable between segments, in contrast to the significant difference between lateral and non-lateral amino acid responses (right panel). **p < 0.01.
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Figure 4. Schematic representation of TAAR4a,4b expression and amine responses.The top panel shows a horizontal section of the MOE of Xenopus laevis as it appears both for measuring odor responses and receptor gene expression. The basalmost layer of the epithelium borders the basal lamina, and the apicalmost layer borders the lumen. The apicalmost layer consists of supporting cells, and the basalmost region of proliferating cells, sandwiching the neuronal region. Perpendicular to this basal-to-apical coordinate, cells in the MOE can also be distinguished by position in the lateral, intermediate, or medial compartment (lateral-to-medial coordinate). The bottom panel depicts a schematic representation of the different cellular distributions analysed. Note that only the neuronal region of the MOE is shown here. Distributions are shown along two axes, basal-to-apical and lateral-to-medial. OMP and TRPC2 distributions are taken from earlier work of our groups24, and are shown for comparison. We emphasize that TAAR4a and TAAR4b differ in both dimensions, and together comprise a large subset of the bimodal amine response region.
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