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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

Axonal coalescence of OSN projections in PcdhaΔ(2–c2)/Δ(2–c2) mice. (A) X-gal-stained dorsal M71 glomeruli in WT (+/+) and PcdhaΔ(2–c2)/Δ(2–c2) (Δ(2–c2)/Δ(2–c2)) mice at P30. Glomeruli appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Scale bars, 1 mm for panels (a, d), and 500 μm for panels (b, c, e, and f). (B) Analysis of M71 (b) and MOR23 (f) glomeruli in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Sections of OBs were double-labeled with β-galactosidase (β-gal; green) and NCAM (red) (a, e) antibodies. Each adjacent section (c, d and g, h) was stained with anti-Pcdha CR antibody and 4′,6-diamidino-2-phenylindole (DAPI; blue). Scale bars, 50 μm for panels (a–d) and 100 μm for panels (e–h).
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Figure 7: Axonal coalescence of OSN projections in PcdhaΔ(2–c2)/Δ(2–c2) mice. (A) X-gal-stained dorsal M71 glomeruli in WT (+/+) and PcdhaΔ(2–c2)/Δ(2–c2) (Δ(2–c2)/Δ(2–c2)) mice at P30. Glomeruli appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Scale bars, 1 mm for panels (a, d), and 500 μm for panels (b, c, e, and f). (B) Analysis of M71 (b) and MOR23 (f) glomeruli in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Sections of OBs were double-labeled with β-galactosidase (β-gal; green) and NCAM (red) (a, e) antibodies. Each adjacent section (c, d and g, h) was stained with anti-Pcdha CR antibody and 4′,6-diamidino-2-phenylindole (DAPI; blue). Scale bars, 50 μm for panels (a–d) and 100 μm for panels (e–h).

Mentions: We next examined the axonal coalescence of homotypic OSNs of the PcdhaΔ(2–c2)/Δ(2–c2) mice. We crossed the PcdhaΔ(2–c2)/Δ(2–c2) mice with M71-IRES-taulacZ or MOR23-IRES-taulacZ mice. In whole-mount OB preparations of M71-IRES-taulacZ or MOR23-IRES-taulacZ mice at P30, there was typically one labeled glomerulus per half-bulb at the lateral and medial side in both WT and PcdhaΔ(2–c2)/Δ(2–c2) mice (Table 2) (Figure 7A). Sectional analyses of the MOR23 glomeruli showed that the average number of glomeruli in both the lateral and medial sides of the half-bulbs were not significantly different between the WT and PcdhaΔ(2–c2)/Δ(2–c2) mice (Table 2). Whole-mount analyses of the M71 glomeruli also showed no significant difference between the WT and PcdhaΔ(2–c2)/Δ(2–c2) mice in the average number of glomeluli in both the lateral and medial sides of the half-bulbs (Table 2). The coalescence of M71 and MOR23 axons appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice, in which the α1 protein was extensively enriched in all the OSN axons and glomeruli (Figure 7B). In addition, immunostaining of adjacent sections with the anti-Pcdhα CR antibody revealed that the α1 protein was distributed in both the lateral M71 and medial MOR23 glomeruli of the OB in the PcdhaΔ(2–c2)/Δ(2–c2) mice (Figure 7B). These results indicated that a diversity of Pcdh-α isoforms in OSNs is not always required for the axonal coalescence of M71 and MOR23 homotypic OSNs into glomeruli. Instead, constitutive expression of the α1 isoform in neurons including OSNs was sufficient for the normal coalescence and elimination of OSN projections.


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)

Axonal coalescence of OSN projections in PcdhaΔ(2–c2)/Δ(2–c2) mice. (A) X-gal-stained dorsal M71 glomeruli in WT (+/+) and PcdhaΔ(2–c2)/Δ(2–c2) (Δ(2–c2)/Δ(2–c2)) mice at P30. Glomeruli appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Scale bars, 1 mm for panels (a, d), and 500 μm for panels (b, c, e, and f). (B) Analysis of M71 (b) and MOR23 (f) glomeruli in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Sections of OBs were double-labeled with β-galactosidase (β-gal; green) and NCAM (red) (a, e) antibodies. Each adjacent section (c, d and g, h) was stained with anti-Pcdha CR antibody and 4′,6-diamidino-2-phenylindole (DAPI; blue). Scale bars, 50 μm for panels (a–d) and 100 μm for panels (e–h).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 7: Axonal coalescence of OSN projections in PcdhaΔ(2–c2)/Δ(2–c2) mice. (A) X-gal-stained dorsal M71 glomeruli in WT (+/+) and PcdhaΔ(2–c2)/Δ(2–c2) (Δ(2–c2)/Δ(2–c2)) mice at P30. Glomeruli appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Scale bars, 1 mm for panels (a, d), and 500 μm for panels (b, c, e, and f). (B) Analysis of M71 (b) and MOR23 (f) glomeruli in the PcdhaΔ(2–c2)/Δ(2–c2) mice. Sections of OBs were double-labeled with β-galactosidase (β-gal; green) and NCAM (red) (a, e) antibodies. Each adjacent section (c, d and g, h) was stained with anti-Pcdha CR antibody and 4′,6-diamidino-2-phenylindole (DAPI; blue). Scale bars, 50 μm for panels (a–d) and 100 μm for panels (e–h).
Mentions: We next examined the axonal coalescence of homotypic OSNs of the PcdhaΔ(2–c2)/Δ(2–c2) mice. We crossed the PcdhaΔ(2–c2)/Δ(2–c2) mice with M71-IRES-taulacZ or MOR23-IRES-taulacZ mice. In whole-mount OB preparations of M71-IRES-taulacZ or MOR23-IRES-taulacZ mice at P30, there was typically one labeled glomerulus per half-bulb at the lateral and medial side in both WT and PcdhaΔ(2–c2)/Δ(2–c2) mice (Table 2) (Figure 7A). Sectional analyses of the MOR23 glomeruli showed that the average number of glomeruli in both the lateral and medial sides of the half-bulbs were not significantly different between the WT and PcdhaΔ(2–c2)/Δ(2–c2) mice (Table 2). Whole-mount analyses of the M71 glomeruli also showed no significant difference between the WT and PcdhaΔ(2–c2)/Δ(2–c2) mice in the average number of glomeluli in both the lateral and medial sides of the half-bulbs (Table 2). The coalescence of M71 and MOR23 axons appeared normal in the PcdhaΔ(2–c2)/Δ(2–c2) mice, in which the α1 protein was extensively enriched in all the OSN axons and glomeruli (Figure 7B). In addition, immunostaining of adjacent sections with the anti-Pcdhα CR antibody revealed that the α1 protein was distributed in both the lateral M71 and medial MOR23 glomeruli of the OB in the PcdhaΔ(2–c2)/Δ(2–c2) mice (Figure 7B). These results indicated that a diversity of Pcdh-α isoforms in OSNs is not always required for the axonal coalescence of M71 and MOR23 homotypic OSNs into glomeruli. Instead, constitutive expression of the α1 isoform in neurons including OSNs was sufficient for the normal coalescence and elimination of OSN projections.

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