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GluRdelta2 expression in the mature cerebellum of hotfoot mice promotes parallel fiber synaptogenesis and axonal competition.

Mandolesi G, Autuori E, Cesa R, Premoselli F, Cesare P, Strata P - PLoS ONE (2009)

Bottom Line: In the proximal domain, we observed the formation of new spines that were innervated by PFs and a reduction in contact with the CF; ie, the pattern of innervation in the PC shifted to favor the PF input.Moreover, ectopic expression of GluRdelta2 in HEK293 cells that were cocultured with granule cells or in cerebellar Golgi cells in the mature brain induced the formation of new PF contacts.Collectively, our observations show that GluRdelta2 is an adhesion molecule that induces the formation of PF contacts independently of its cellular localization and promotes heterosynaptic competition in the PC proximal dendritic domain.

View Article: PubMed Central - PubMed

Affiliation: EBRI-Santa Lucia Foundation (IRCCS), Rome, Italy. g.mandolesi@hsantalucia.it

ABSTRACT
Glutamate receptor delta 2 (GluRdelta2) is selectively expressed in the cerebellum, exclusively in the spines of the Purkinje cells (PCs) that are in contact with parallel fibers (PFs). Although its structure is similar to ionotropic glutamate receptors, it has no channel function and its ligand is unknown. The GluRdelta2- mice, such as knockout and hotfoot have profoundly altered cerebellar circuitry, which causes ataxia and impaired motor learning. Notably, GluRdelta2 in PC-PF synapses regulates their maturation and strengthening and induces long term depression (LTD). In addition, GluRdelta2 participates in the highly territorial competition between the two excitatory inputs to the PC; the climbing fiber (CF), which innervates the proximal dendritic compartment, and the PF, which is connected to spiny distal branchlets. Recently, studies have suggested that GluRdelta2 acts as an adhesion molecule in PF synaptogenesis. Here, we provide in vivo and in vitro evidence that supports this hypothesis. Through lentiviral rescue in hotfoot mice, we noted a recovery of PC-PF contacts in the distal dendritic domain. In the proximal domain, we observed the formation of new spines that were innervated by PFs and a reduction in contact with the CF; ie, the pattern of innervation in the PC shifted to favor the PF input. Moreover, ectopic expression of GluRdelta2 in HEK293 cells that were cocultured with granule cells or in cerebellar Golgi cells in the mature brain induced the formation of new PF contacts. Collectively, our observations show that GluRdelta2 is an adhesion molecule that induces the formation of PF contacts independently of its cellular localization and promotes heterosynaptic competition in the PC proximal dendritic domain.

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GluRδ2 induces spinogenesis in the PC proximal dendritic compartment of δ2/GFP-ho mice.(A–D) Immunostaining of PC proximal dendrites in δ2/GFP-ho (A–C) and GFP-ho mice (D). In δ2/GFP-ho mice, many new spines, expressing the GluRδ2 subunit (red) (B and C), appears in the proximal dendrite relative to GFP-ho mice (D). (E) Histogram shows the mean spine density in the proximal dendritic domain. In the presence of GluRδ2, the number of spines significantly increases relative to control groups (GFP-wt; GFP-ho and δ2/GFP-ho CTR). *** p<0.001. Error bars indicate SE. Scale bars: A–E = 2 µm.
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pone-0005243-g004: GluRδ2 induces spinogenesis in the PC proximal dendritic compartment of δ2/GFP-ho mice.(A–D) Immunostaining of PC proximal dendrites in δ2/GFP-ho (A–C) and GFP-ho mice (D). In δ2/GFP-ho mice, many new spines, expressing the GluRδ2 subunit (red) (B and C), appears in the proximal dendrite relative to GFP-ho mice (D). (E) Histogram shows the mean spine density in the proximal dendritic domain. In the presence of GluRδ2, the number of spines significantly increases relative to control groups (GFP-wt; GFP-ho and δ2/GFP-ho CTR). *** p<0.001. Error bars indicate SE. Scale bars: A–E = 2 µm.

Mentions: In δ2/GFP-ho mice, we examined the proximal dendritic compartment of GluRδ2-positive PCs. Many new spines appeared in the proximal dendritic domain relative to control animals (Fig. 4A–D). Therefore, we measured spine density along the proximal dendrites whose diameters were greater than 2.5 µm. In the GFP-wt group, the spine density was 0.33 (±0.01 SE, n = 1434) per unit dendritic area and 0.42 in GFP-ho mice (±0.02 SE, n = 806) (Fig. 4E), with no significant difference (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p>0.05 versus GFP-ho). In the δ2/GFP-ho group, however, the mean density in GluRδ2-expressing PCs was 0.57 (±0.02 SE, n = 1575), 1.4-fold higher than in GFP-ho mice (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p<0.05). In the δ2/GFP-ho CTR sample, the spine density per unit area was 0.45 (±0.02 SE, n = 1198) but was not significantly different from the GFP-ho sample (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p>0.05 versus GFP-ho and p<0.05 versus δ2/GFP-ho).


GluRdelta2 expression in the mature cerebellum of hotfoot mice promotes parallel fiber synaptogenesis and axonal competition.

Mandolesi G, Autuori E, Cesa R, Premoselli F, Cesare P, Strata P - PLoS ONE (2009)

GluRδ2 induces spinogenesis in the PC proximal dendritic compartment of δ2/GFP-ho mice.(A–D) Immunostaining of PC proximal dendrites in δ2/GFP-ho (A–C) and GFP-ho mice (D). In δ2/GFP-ho mice, many new spines, expressing the GluRδ2 subunit (red) (B and C), appears in the proximal dendrite relative to GFP-ho mice (D). (E) Histogram shows the mean spine density in the proximal dendritic domain. In the presence of GluRδ2, the number of spines significantly increases relative to control groups (GFP-wt; GFP-ho and δ2/GFP-ho CTR). *** p<0.001. Error bars indicate SE. Scale bars: A–E = 2 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2666267&req=5

pone-0005243-g004: GluRδ2 induces spinogenesis in the PC proximal dendritic compartment of δ2/GFP-ho mice.(A–D) Immunostaining of PC proximal dendrites in δ2/GFP-ho (A–C) and GFP-ho mice (D). In δ2/GFP-ho mice, many new spines, expressing the GluRδ2 subunit (red) (B and C), appears in the proximal dendrite relative to GFP-ho mice (D). (E) Histogram shows the mean spine density in the proximal dendritic domain. In the presence of GluRδ2, the number of spines significantly increases relative to control groups (GFP-wt; GFP-ho and δ2/GFP-ho CTR). *** p<0.001. Error bars indicate SE. Scale bars: A–E = 2 µm.
Mentions: In δ2/GFP-ho mice, we examined the proximal dendritic compartment of GluRδ2-positive PCs. Many new spines appeared in the proximal dendritic domain relative to control animals (Fig. 4A–D). Therefore, we measured spine density along the proximal dendrites whose diameters were greater than 2.5 µm. In the GFP-wt group, the spine density was 0.33 (±0.01 SE, n = 1434) per unit dendritic area and 0.42 in GFP-ho mice (±0.02 SE, n = 806) (Fig. 4E), with no significant difference (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p>0.05 versus GFP-ho). In the δ2/GFP-ho group, however, the mean density in GluRδ2-expressing PCs was 0.57 (±0.02 SE, n = 1575), 1.4-fold higher than in GFP-ho mice (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p<0.05). In the δ2/GFP-ho CTR sample, the spine density per unit area was 0.45 (±0.02 SE, n = 1198) but was not significantly different from the GFP-ho sample (one-way ANOVA, p<0.001; post hoc Holm-Sidack test, p>0.05 versus GFP-ho and p<0.05 versus δ2/GFP-ho).

Bottom Line: In the proximal domain, we observed the formation of new spines that were innervated by PFs and a reduction in contact with the CF; ie, the pattern of innervation in the PC shifted to favor the PF input.Moreover, ectopic expression of GluRdelta2 in HEK293 cells that were cocultured with granule cells or in cerebellar Golgi cells in the mature brain induced the formation of new PF contacts.Collectively, our observations show that GluRdelta2 is an adhesion molecule that induces the formation of PF contacts independently of its cellular localization and promotes heterosynaptic competition in the PC proximal dendritic domain.

View Article: PubMed Central - PubMed

Affiliation: EBRI-Santa Lucia Foundation (IRCCS), Rome, Italy. g.mandolesi@hsantalucia.it

ABSTRACT
Glutamate receptor delta 2 (GluRdelta2) is selectively expressed in the cerebellum, exclusively in the spines of the Purkinje cells (PCs) that are in contact with parallel fibers (PFs). Although its structure is similar to ionotropic glutamate receptors, it has no channel function and its ligand is unknown. The GluRdelta2- mice, such as knockout and hotfoot have profoundly altered cerebellar circuitry, which causes ataxia and impaired motor learning. Notably, GluRdelta2 in PC-PF synapses regulates their maturation and strengthening and induces long term depression (LTD). In addition, GluRdelta2 participates in the highly territorial competition between the two excitatory inputs to the PC; the climbing fiber (CF), which innervates the proximal dendritic compartment, and the PF, which is connected to spiny distal branchlets. Recently, studies have suggested that GluRdelta2 acts as an adhesion molecule in PF synaptogenesis. Here, we provide in vivo and in vitro evidence that supports this hypothesis. Through lentiviral rescue in hotfoot mice, we noted a recovery of PC-PF contacts in the distal dendritic domain. In the proximal domain, we observed the formation of new spines that were innervated by PFs and a reduction in contact with the CF; ie, the pattern of innervation in the PC shifted to favor the PF input. Moreover, ectopic expression of GluRdelta2 in HEK293 cells that were cocultured with granule cells or in cerebellar Golgi cells in the mature brain induced the formation of new PF contacts. Collectively, our observations show that GluRdelta2 is an adhesion molecule that induces the formation of PF contacts independently of its cellular localization and promotes heterosynaptic competition in the PC proximal dendritic domain.

Show MeSH
Related in: MedlinePlus