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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

Generation of the PcdhaΔ(2–c2) and Pcdhadup(2–c2) alleles in mice. (A)PcdhaΔ(2–c2) and Pcdhadup(2–c2) mice were generated by mating G16Neo mice, G1 loxP mice, and Sycp-Cre transgenic mice created by synaptosomal-Cre (TAMERE) system in the testis. This Cre is expressed during meiotic crossing-over. (B) Partial genomic structures of the WT and PcdhaΔ(2–c2) allele. (C,D) Genotyping of WT (+/+), Pcdha+/Δ(2–c2) [+/Δ (2–c2)], and PcdhaΔ(2–c2)/Δ(2–c2) [Δ 2–c2/Δ(2–c2)] by Southern blot and PCR analyses (see “Materials and Methods”).
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Figure 5: Generation of the PcdhaΔ(2–c2) and Pcdhadup(2–c2) alleles in mice. (A)PcdhaΔ(2–c2) and Pcdhadup(2–c2) mice were generated by mating G16Neo mice, G1 loxP mice, and Sycp-Cre transgenic mice created by synaptosomal-Cre (TAMERE) system in the testis. This Cre is expressed during meiotic crossing-over. (B) Partial genomic structures of the WT and PcdhaΔ(2–c2) allele. (C,D) Genotyping of WT (+/+), Pcdha+/Δ(2–c2) [+/Δ (2–c2)], and PcdhaΔ(2–c2)/Δ(2–c2) [Δ 2–c2/Δ(2–c2)] by Southern blot and PCR analyses (see “Materials and Methods”).

Mentions: By mating G16Neo mutant mice, in which two loxP sites were inserted between exons α1 and α2 (Noguchi et al., 2009), G1loxP mice in which a loxP site was inserted between exons αc2 and αCR1 (Hasegawa et al., 2008), and synaptosomal complex protein1 (Sycp)-Cre transgenic mice (Noguchi et al., 2009), male mice carrying the G16Neo allele, G1loxP allele, and Sycp-Cre transgene were generated. These mice were crossed with C57BL/6 females, and the genotypes of pups were determined by Southern blotting using probes amplified by PCR with Probe-G16-F (5′-GGAGGACATGCACAAGTCATG-3′) and Probe-G16-R (5′-TTGTGGTGTACAGCGACACC-3′) primers, and by PCR using G16 primer (5′-GGCTATCCTGTGCTACAGAAC-3′), G16-GTP-R2 primer (5′-CCAATTAATATTTGAGATTCATCCCC-3′), and G1-GTP-R primer (5′- GCCCAGGATGGCTCAAATTC-3′). Some pups carried the PcdhaΔ(2–c2) or the Pcdhadup(2–c2) allele generated by trans-allelic targeted meiotic recombination (TAMERE) in the testis (Herault et al., 1998) (Figure 5). PcdhaΔA/ΔA mutant mice with a truncated Pcdh-α protein were described previously (Katori et al., 2009).


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)

Generation of the PcdhaΔ(2–c2) and Pcdhadup(2–c2) alleles in mice. (A)PcdhaΔ(2–c2) and Pcdhadup(2–c2) mice were generated by mating G16Neo mice, G1 loxP mice, and Sycp-Cre transgenic mice created by synaptosomal-Cre (TAMERE) system in the testis. This Cre is expressed during meiotic crossing-over. (B) Partial genomic structures of the WT and PcdhaΔ(2–c2) allele. (C,D) Genotyping of WT (+/+), Pcdha+/Δ(2–c2) [+/Δ (2–c2)], and PcdhaΔ(2–c2)/Δ(2–c2) [Δ 2–c2/Δ(2–c2)] by Southern blot and PCR analyses (see “Materials and Methods”).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472330&req=5

Figure 5: Generation of the PcdhaΔ(2–c2) and Pcdhadup(2–c2) alleles in mice. (A)PcdhaΔ(2–c2) and Pcdhadup(2–c2) mice were generated by mating G16Neo mice, G1 loxP mice, and Sycp-Cre transgenic mice created by synaptosomal-Cre (TAMERE) system in the testis. This Cre is expressed during meiotic crossing-over. (B) Partial genomic structures of the WT and PcdhaΔ(2–c2) allele. (C,D) Genotyping of WT (+/+), Pcdha+/Δ(2–c2) [+/Δ (2–c2)], and PcdhaΔ(2–c2)/Δ(2–c2) [Δ 2–c2/Δ(2–c2)] by Southern blot and PCR analyses (see “Materials and Methods”).
Mentions: By mating G16Neo mutant mice, in which two loxP sites were inserted between exons α1 and α2 (Noguchi et al., 2009), G1loxP mice in which a loxP site was inserted between exons αc2 and αCR1 (Hasegawa et al., 2008), and synaptosomal complex protein1 (Sycp)-Cre transgenic mice (Noguchi et al., 2009), male mice carrying the G16Neo allele, G1loxP allele, and Sycp-Cre transgene were generated. These mice were crossed with C57BL/6 females, and the genotypes of pups were determined by Southern blotting using probes amplified by PCR with Probe-G16-F (5′-GGAGGACATGCACAAGTCATG-3′) and Probe-G16-R (5′-TTGTGGTGTACAGCGACACC-3′) primers, and by PCR using G16 primer (5′-GGCTATCCTGTGCTACAGAAC-3′), G16-GTP-R2 primer (5′-CCAATTAATATTTGAGATTCATCCCC-3′), and G1-GTP-R primer (5′- GCCCAGGATGGCTCAAATTC-3′). Some pups carried the PcdhaΔ(2–c2) or the Pcdhadup(2–c2) allele generated by trans-allelic targeted meiotic recombination (TAMERE) in the testis (Herault et al., 1998) (Figure 5). PcdhaΔA/ΔA mutant mice with a truncated Pcdh-α protein were described previously (Katori et al., 2009).

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