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Initial characterization of a Syap1 knock-out mouse and distribution of Syap1 in mouse brain and cultured motoneurons

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ABSTRACT

Synapse-associated protein 1 (Syap1/BSTA) is the mammalian homologue of Sap47 (synapse-associated protein of 47 kDa) in Drosophila. Sap47 mutant larvae show reduced short-term synaptic plasticity and a defect in associative behavioral plasticity. In cultured adipocytes, Syap1 functions as part of a complex that phosphorylates protein kinase Bα/Akt1 (Akt1) at Ser473 and promotes differentiation. The role of Syap1 in the vertebrate nervous system is unknown. Here, we generated a Syap1 knock-out mouse and show that lack of Syap1 is compatible with viability and fertility. Adult knock-out mice show no overt defects in brain morphology. In wild-type brain, Syap1 is found widely distributed in synaptic neuropil, notably in regions rich in glutamatergic synapses, but also in perinuclear structures associated with the Golgi apparatus of specific groups of neuronal cell bodies. In cultured motoneurons, Syap1 is located in axons and growth cones and is enriched in a perinuclear region partially overlapping with Golgi markers. We studied in detail the influence of Syap1 knockdown and knockout on structure and development of these cells. Importantly, Syap1 knockout does not affect motoneuron survival or axon growth. Unexpectedly, neither knockdown nor knockout of Syap1 in cultured motoneurons is associated with reduced Ser473 or Thr308 phosphorylation of Akt. Our findings demonstrate a widespread expression of Syap1 in the mouse central nervous system with regionally specific distribution patterns as illustrated in particular for olfactory bulb, hippocampus, and cerebellum.

Electronic supplementary material: The online version of this article (doi:10.1007/s00418-016-1457-0) contains supplementary material, which is available to authorized users.

No MeSH data available.


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In the main olfactory bulb, intense Syap1-specific immunoreactivity is observed in olfactory nerve layer (asterisk) and glomeruli (x) of wild-type sections (a, c). Less intense Syap1 signals are found in the mitral layer (arrowheads in a). The Syap1 antiserum weakly cross-reacts with an unknown antigen in knock-out sections (b, d). Dual immunolabeling with anti-Syap1 antiserum (left) and anti-TH (middle) reveals Syap1 accumulation in glomerular neuropil. Nuclei are stained by DAPI [blue in the overlay (right)]. Scale bars 200 µm (upper half), 50 µm (lower half)
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Fig4: In the main olfactory bulb, intense Syap1-specific immunoreactivity is observed in olfactory nerve layer (asterisk) and glomeruli (x) of wild-type sections (a, c). Less intense Syap1 signals are found in the mitral layer (arrowheads in a). The Syap1 antiserum weakly cross-reacts with an unknown antigen in knock-out sections (b, d). Dual immunolabeling with anti-Syap1 antiserum (left) and anti-TH (middle) reveals Syap1 accumulation in glomerular neuropil. Nuclei are stained by DAPI [blue in the overlay (right)]. Scale bars 200 µm (upper half), 50 µm (lower half)

Mentions: At low magnification, most brain areas display diffuse Syap1-specific immunolabeling (Fig. 3a, e), and comparison with neuronal localization patterns visualized by DAPI nuclear counterstaining (Fig. 3b, f) indicates a preferential localization of the protein in gray matter neuropil. This is obvious in cortical regions and hippocampus, and is especially prominent in the cerebellum, where the molecular layer displays particularly intense diffuse fluorescence while the granular layer and the cerebellar medulla are significantly less strongly labeled (Fig. 3e, f, see below). In the olfactory bulb, Syap1 immunolabeling is strongest in the olfactory nerve layer and olfactory glomeruli (Fig. 4a, left column), which contain the glutamatergic terminals of the olfactory nerve axons and are surrounded and delineated by tyrosine hydroxylase (TH) immunoreactive dopaminergic periglomerular cells and their processes extending into the glomeruli (Fig. 4a, middle column). While there is light Syap1 immunoreactivity in the mitral layer (arrowheads in Fig. 4a), there is no conspicuous staining observed in the perikarya of dopaminergic periglomerular cells (arrows in Fig. 4c).Fig. 4


Initial characterization of a Syap1 knock-out mouse and distribution of Syap1 in mouse brain and cultured motoneurons
In the main olfactory bulb, intense Syap1-specific immunoreactivity is observed in olfactory nerve layer (asterisk) and glomeruli (x) of wild-type sections (a, c). Less intense Syap1 signals are found in the mitral layer (arrowheads in a). The Syap1 antiserum weakly cross-reacts with an unknown antigen in knock-out sections (b, d). Dual immunolabeling with anti-Syap1 antiserum (left) and anti-TH (middle) reveals Syap1 accumulation in glomerular neuropil. Nuclei are stained by DAPI [blue in the overlay (right)]. Scale bars 200 µm (upper half), 50 µm (lower half)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: In the main olfactory bulb, intense Syap1-specific immunoreactivity is observed in olfactory nerve layer (asterisk) and glomeruli (x) of wild-type sections (a, c). Less intense Syap1 signals are found in the mitral layer (arrowheads in a). The Syap1 antiserum weakly cross-reacts with an unknown antigen in knock-out sections (b, d). Dual immunolabeling with anti-Syap1 antiserum (left) and anti-TH (middle) reveals Syap1 accumulation in glomerular neuropil. Nuclei are stained by DAPI [blue in the overlay (right)]. Scale bars 200 µm (upper half), 50 µm (lower half)
Mentions: At low magnification, most brain areas display diffuse Syap1-specific immunolabeling (Fig. 3a, e), and comparison with neuronal localization patterns visualized by DAPI nuclear counterstaining (Fig. 3b, f) indicates a preferential localization of the protein in gray matter neuropil. This is obvious in cortical regions and hippocampus, and is especially prominent in the cerebellum, where the molecular layer displays particularly intense diffuse fluorescence while the granular layer and the cerebellar medulla are significantly less strongly labeled (Fig. 3e, f, see below). In the olfactory bulb, Syap1 immunolabeling is strongest in the olfactory nerve layer and olfactory glomeruli (Fig. 4a, left column), which contain the glutamatergic terminals of the olfactory nerve axons and are surrounded and delineated by tyrosine hydroxylase (TH) immunoreactive dopaminergic periglomerular cells and their processes extending into the glomeruli (Fig. 4a, middle column). While there is light Syap1 immunoreactivity in the mitral layer (arrowheads in Fig. 4a), there is no conspicuous staining observed in the perikarya of dopaminergic periglomerular cells (arrows in Fig. 4c).Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Synapse-associated protein 1 (Syap1/BSTA) is the mammalian homologue of Sap47 (synapse-associated protein of 47 kDa) in Drosophila. Sap47 mutant larvae show reduced short-term synaptic plasticity and a defect in associative behavioral plasticity. In cultured adipocytes, Syap1 functions as part of a complex that phosphorylates protein kinase Bα/Akt1 (Akt1) at Ser473 and promotes differentiation. The role of Syap1 in the vertebrate nervous system is unknown. Here, we generated a Syap1 knock-out mouse and show that lack of Syap1 is compatible with viability and fertility. Adult knock-out mice show no overt defects in brain morphology. In wild-type brain, Syap1 is found widely distributed in synaptic neuropil, notably in regions rich in glutamatergic synapses, but also in perinuclear structures associated with the Golgi apparatus of specific groups of neuronal cell bodies. In cultured motoneurons, Syap1 is located in axons and growth cones and is enriched in a perinuclear region partially overlapping with Golgi markers. We studied in detail the influence of Syap1 knockdown and knockout on structure and development of these cells. Importantly, Syap1 knockout does not affect motoneuron survival or axon growth. Unexpectedly, neither knockdown nor knockout of Syap1 in cultured motoneurons is associated with reduced Ser473 or Thr308 phosphorylation of Akt. Our findings demonstrate a widespread expression of Syap1 in the mouse central nervous system with regionally specific distribution patterns as illustrated in particular for olfactory bulb, hippocampus, and cerebellum.

Electronic supplementary material: The online version of this article (doi:10.1007/s00418-016-1457-0) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus