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Constitutively expressed Protocadherin-α regulates the coalescence and elimination of homotypic olfactory axons through its cytoplasmic region.

Hasegawa S, Hirabayashi T, Kondo T, Inoue K, Esumi S, Okayama A, Hamada S, Yagi T - Front Mol Neurosci (2012)

Bottom Line: Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α's cytoplasmic region, but not OR specificity or neural activity.These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity.The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

View Article: PubMed Central - PubMed

Affiliation: KOKORO-Biology Group and CREST-JST, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University Osaka, Japan.

ABSTRACT
Olfactory sensory neuron (OSN) axons coalesce into specific glomeruli in the olfactory bulb (OB) according to their odorant receptor (OR) expression. Several guidance molecules enhance the coalescence of homotypic OSN projections, in an OR-specific- and neural-activity-dependent manner. However, the mechanism by which homotypic OSN axons are organized into glomeruli is unsolved. We previously reported that the clustered protocadherin-α (Pcdh-α) family of diverse cadherin-related molecules plays roles in the coalescence and elimination of homotypic OSN axons throughout development. Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α's cytoplasmic region, but not OR specificity or neural activity. These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity. The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

No MeSH data available.


Related in: MedlinePlus

Expression of Pcdh-α and the number of M71 and MOR23 glomeruli after naris occlusion of WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. (A) A WT mouse was subjected to unilateral naris closure at P21 and analyzed after 1 week. The expression of tyrosine hydroxylase (TH) (a) and αCR transcripts (b) of the closed (X) and open (O) sides in the OB were examined by in situ hybridization histochemistry. The expression of α11 and αCR transcripts in the OE were also examined (c, d). Scale bar, 100 μm. (B) A WT mouse was subjected to naris occlusion at P5 and analyzed at P30. Pcdh-α immunoreactivity with the anti-Pcdhα CR antibody was strong in OSN axons and glomeruli in both the closed (X) and open (O) sides at similar levels (e), in contrast to the change in TH signals (f). Scale bar, 100 μm. (C) The number of M71 and MOR23 glomeruli per lateral and medial half-bulb of the open (white bars) and closed (black bars) sides after naris occlusion in WT (+/+) and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice at P30. Although ectopic glomeruli were further increased in PcdhaΔCR/ΔCR (ΔCR/ΔCR) and PcdhaΔCR2/ΔCR2 (ΔCR2/ΔCR2) mice by the treatment, the total number of glomeruli after treatment was almost the same in the WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. The number of MOR23 glomeruli in PcdhaΔCR2/ΔCR2 mice are shown in Table 1. Significant differences at *P < 0.05, **P < 0.01, and ***P < 0.001 calculated by the Mann–Whitney U-test.
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Figure 9: Expression of Pcdh-α and the number of M71 and MOR23 glomeruli after naris occlusion of WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. (A) A WT mouse was subjected to unilateral naris closure at P21 and analyzed after 1 week. The expression of tyrosine hydroxylase (TH) (a) and αCR transcripts (b) of the closed (X) and open (O) sides in the OB were examined by in situ hybridization histochemistry. The expression of α11 and αCR transcripts in the OE were also examined (c, d). Scale bar, 100 μm. (B) A WT mouse was subjected to naris occlusion at P5 and analyzed at P30. Pcdh-α immunoreactivity with the anti-Pcdhα CR antibody was strong in OSN axons and glomeruli in both the closed (X) and open (O) sides at similar levels (e), in contrast to the change in TH signals (f). Scale bar, 100 μm. (C) The number of M71 and MOR23 glomeruli per lateral and medial half-bulb of the open (white bars) and closed (black bars) sides after naris occlusion in WT (+/+) and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice at P30. Although ectopic glomeruli were further increased in PcdhaΔCR/ΔCR (ΔCR/ΔCR) and PcdhaΔCR2/ΔCR2 (ΔCR2/ΔCR2) mice by the treatment, the total number of glomeruli after treatment was almost the same in the WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. The number of MOR23 glomeruli in PcdhaΔCR2/ΔCR2 mice are shown in Table 1. Significant differences at *P < 0.05, **P < 0.01, and ***P < 0.001 calculated by the Mann–Whitney U-test.

Mentions: Axon guidance molecules showing OR-specific expression are often regulated by the neural activity of OSNs (Serizawa et al., 2006; Kaneko-Goto et al., 2008); therefore, we examined whether a reduction in OSN neural activity would affect the Pcdh-α expression. WT mice were subjected to unilateral naris occlusion at 3 weeks and analyzed by in situ hybridization histochemistry after 1 week. Efficiency of the naris occlusion was validated by the loss of tyrosine hydroxylase (TH) signals from the glomerular layer on the closed side of the OB (Figure 9A a) (Stone et al., 1990). In contrast, mRNA signals of the isoform common αCR probe in the OE were quite similar between the open and closed sides (Figure 9A b). In the OE, the expression levels with the α11 and αCR probes were quite similar between the open and closed sides (Figure 9A c, d). Furthermore, immunohistochemistry of the P30 WT mouse after naris occlusion showed that the distribution and intensity of Pcdh-α immunoreactivity in the OB were almost the same between the closed and open sides (Figure 9B). These results indicated that the Pcdh-α expression in the OSNs and OB was not altered by the OSN neural activity.


Constitutively expressed Protocadherin-α regulates the coalescence and elimination of homotypic olfactory axons through its cytoplasmic region.

Hasegawa S, Hirabayashi T, Kondo T, Inoue K, Esumi S, Okayama A, Hamada S, Yagi T - Front Mol Neurosci (2012)

Expression of Pcdh-α and the number of M71 and MOR23 glomeruli after naris occlusion of WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. (A) A WT mouse was subjected to unilateral naris closure at P21 and analyzed after 1 week. The expression of tyrosine hydroxylase (TH) (a) and αCR transcripts (b) of the closed (X) and open (O) sides in the OB were examined by in situ hybridization histochemistry. The expression of α11 and αCR transcripts in the OE were also examined (c, d). Scale bar, 100 μm. (B) A WT mouse was subjected to naris occlusion at P5 and analyzed at P30. Pcdh-α immunoreactivity with the anti-Pcdhα CR antibody was strong in OSN axons and glomeruli in both the closed (X) and open (O) sides at similar levels (e), in contrast to the change in TH signals (f). Scale bar, 100 μm. (C) The number of M71 and MOR23 glomeruli per lateral and medial half-bulb of the open (white bars) and closed (black bars) sides after naris occlusion in WT (+/+) and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice at P30. Although ectopic glomeruli were further increased in PcdhaΔCR/ΔCR (ΔCR/ΔCR) and PcdhaΔCR2/ΔCR2 (ΔCR2/ΔCR2) mice by the treatment, the total number of glomeruli after treatment was almost the same in the WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. The number of MOR23 glomeruli in PcdhaΔCR2/ΔCR2 mice are shown in Table 1. Significant differences at *P < 0.05, **P < 0.01, and ***P < 0.001 calculated by the Mann–Whitney U-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 9: Expression of Pcdh-α and the number of M71 and MOR23 glomeruli after naris occlusion of WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. (A) A WT mouse was subjected to unilateral naris closure at P21 and analyzed after 1 week. The expression of tyrosine hydroxylase (TH) (a) and αCR transcripts (b) of the closed (X) and open (O) sides in the OB were examined by in situ hybridization histochemistry. The expression of α11 and αCR transcripts in the OE were also examined (c, d). Scale bar, 100 μm. (B) A WT mouse was subjected to naris occlusion at P5 and analyzed at P30. Pcdh-α immunoreactivity with the anti-Pcdhα CR antibody was strong in OSN axons and glomeruli in both the closed (X) and open (O) sides at similar levels (e), in contrast to the change in TH signals (f). Scale bar, 100 μm. (C) The number of M71 and MOR23 glomeruli per lateral and medial half-bulb of the open (white bars) and closed (black bars) sides after naris occlusion in WT (+/+) and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice at P30. Although ectopic glomeruli were further increased in PcdhaΔCR/ΔCR (ΔCR/ΔCR) and PcdhaΔCR2/ΔCR2 (ΔCR2/ΔCR2) mice by the treatment, the total number of glomeruli after treatment was almost the same in the WT and Pcdh-α-deficient (PcdhaΔCR/ΔCR and PcdhaΔCR2/ΔCR2) mice. The number of MOR23 glomeruli in PcdhaΔCR2/ΔCR2 mice are shown in Table 1. Significant differences at *P < 0.05, **P < 0.01, and ***P < 0.001 calculated by the Mann–Whitney U-test.
Mentions: Axon guidance molecules showing OR-specific expression are often regulated by the neural activity of OSNs (Serizawa et al., 2006; Kaneko-Goto et al., 2008); therefore, we examined whether a reduction in OSN neural activity would affect the Pcdh-α expression. WT mice were subjected to unilateral naris occlusion at 3 weeks and analyzed by in situ hybridization histochemistry after 1 week. Efficiency of the naris occlusion was validated by the loss of tyrosine hydroxylase (TH) signals from the glomerular layer on the closed side of the OB (Figure 9A a) (Stone et al., 1990). In contrast, mRNA signals of the isoform common αCR probe in the OE were quite similar between the open and closed sides (Figure 9A b). In the OE, the expression levels with the α11 and αCR probes were quite similar between the open and closed sides (Figure 9A c, d). Furthermore, immunohistochemistry of the P30 WT mouse after naris occlusion showed that the distribution and intensity of Pcdh-α immunoreactivity in the OB were almost the same between the closed and open sides (Figure 9B). These results indicated that the Pcdh-α expression in the OSNs and OB was not altered by the OSN neural activity.

Bottom Line: Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α's cytoplasmic region, but not OR specificity or neural activity.These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity.The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

View Article: PubMed Central - PubMed

Affiliation: KOKORO-Biology Group and CREST-JST, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University Osaka, Japan.

ABSTRACT
Olfactory sensory neuron (OSN) axons coalesce into specific glomeruli in the olfactory bulb (OB) according to their odorant receptor (OR) expression. Several guidance molecules enhance the coalescence of homotypic OSN projections, in an OR-specific- and neural-activity-dependent manner. However, the mechanism by which homotypic OSN axons are organized into glomeruli is unsolved. We previously reported that the clustered protocadherin-α (Pcdh-α) family of diverse cadherin-related molecules plays roles in the coalescence and elimination of homotypic OSN axons throughout development. Here we showed that the elimination of small ectopic homotypic glomeruli required the constitutive expression of a Pcdh-α isoform and Pcdh-α's cytoplasmic region, but not OR specificity or neural activity. These results suggest that Pcdh-α proteins provide a cytoplasmic signal to regulate repulsive activity for homotypic OSN axons independently of OR expression and neural activity. The counterbalancing effect of Pcdh-α proteins for the axonal coalescence mechanisms mediated by other olfactory guidance molecules indicate a possible mechanism for the organization of homotypic OSN axons into glomeruli during development.

No MeSH data available.


Related in: MedlinePlus