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Selective Requirement for Maintenance of Synaptic Contacts onto Motoneurons by Target-Derived trkB Receptors.

Zhu X, Ward PJ, English AW - Neural Plast. (2016)

Bottom Line: Selective knockout of the trkB gene resulted in a marked reduction in contacts made by VGLUT2- and GAD67-immunoreactive structures in both sexes and a significant reduction in contacts containing only glycine in male mice.No reduction was found for glycinergic contacts in female mice or for VGLUT1 immunoreactive contacts in either sex.Signaling through postsynaptic trkB receptors is considered to be an essential part of a cellular mechanism for maintaining the contacts of some, but not all, synaptic contacts onto motoneurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
Synaptic contacts onto motoneurons were studied in mice in which the gene for the trkB neurotrophin receptor was knocked out selectively in a subset of spinal motoneurons. The extent of contacts by structures immunoreactive for either of two different vesicular glutamate transporters (VGLUT1 and VGLUT2), the vesicular GABA transporter, or glutamic acid decarboxylase 67 (GAD67) with the somata of motoneurons, was studied in wild type and trkB knockout cells in tamoxifen treated male and female SLICK-trkB(-/-) mice. Selective knockout of the trkB gene resulted in a marked reduction in contacts made by VGLUT2- and GAD67-immunoreactive structures in both sexes and a significant reduction in contacts containing only glycine in male mice. No reduction was found for glycinergic contacts in female mice or for VGLUT1 immunoreactive contacts in either sex. Signaling through postsynaptic trkB receptors is considered to be an essential part of a cellular mechanism for maintaining the contacts of some, but not all, synaptic contacts onto motoneurons.

No MeSH data available.


Related in: MedlinePlus

Immunoreactivity to different synapse-associated antigens surrounding the somata and proximal-most dendrites of large neurons in lamina IX of the L3–5 segments of the spinal cord of SLICK::trkB mice that had been treated with tamoxifen to knock out the trkB gene is shown. Cells expressing YPF (left column) are presumed to be  for the trkB gene and cells in the same histological sections that are YFP− are presumed to have normal expression of this gene. NeuN immunoreactivity (red) is shown to identify these cells as neurons. Because of their large size and laminar location they were considered motoneurons. Synaptic structures immediately adjacent to the perimeters of these cells (cyan) represent contacts made by structures immunoreactive to VGLUT1 (a), VGLUT2 (b), GAD67 (c), or VGAT (d). All cells are shown at the same magnification.
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fig1: Immunoreactivity to different synapse-associated antigens surrounding the somata and proximal-most dendrites of large neurons in lamina IX of the L3–5 segments of the spinal cord of SLICK::trkB mice that had been treated with tamoxifen to knock out the trkB gene is shown. Cells expressing YPF (left column) are presumed to be for the trkB gene and cells in the same histological sections that are YFP− are presumed to have normal expression of this gene. NeuN immunoreactivity (red) is shown to identify these cells as neurons. Because of their large size and laminar location they were considered motoneurons. Synaptic structures immediately adjacent to the perimeters of these cells (cyan) represent contacts made by structures immunoreactive to VGLUT1 (a), VGLUT2 (b), GAD67 (c), or VGAT (d). All cells are shown at the same magnification.

Mentions: Images of single 1 μm optical sections of cryostat sections were obtained using a Zeiss LSM510 confocal microscope at a magnification of 63x. Optical sections of presumed motoneurons were selected for study only if the location of the nucleus could be clearly visualized by the lack of immunoreactivity to either cholera toxin B or NeuN. Cell bodies of trkB knockout (KO) motoneurons innervating hind limb muscles were identified by the presence of both YFP (green) and either NeuN or cholera toxin B (red). In tamoxifen treated mice, these cells were assumed to be trkB (KO). Cell bodies of motoneurons that did not contain YFP but were adjacent to YFP+ cells on the same sections and were immunoreactive for either NeuN or cholera toxin B were assumed not to express Cre recombinase and were considered wild type (WT). Images of 10 KO motoneuron cell bodies and 10 WT cells were obtained from each side of the spinal cord in each mouse. Immunoreactivity to GAD67, VGAT, VGLUT1, or VGLUT2 was visualized with far red (647 nm) optics. Representative images of trkB-KO (YFP+) and WT (YFP−) neurons from sections reacted with antibodies to the different synapse-associated antigens are shown in Figure 1. In the control group (SLICK::trkBf/f mice not treated with tamoxifen), 20 YFP+ cells reacted with antibodies to each of the different synapse-associated proteins were selected from each side of the spinal cord for study. It was assumed that trkB expression in these cells was not affected.


Selective Requirement for Maintenance of Synaptic Contacts onto Motoneurons by Target-Derived trkB Receptors.

Zhu X, Ward PJ, English AW - Neural Plast. (2016)

Immunoreactivity to different synapse-associated antigens surrounding the somata and proximal-most dendrites of large neurons in lamina IX of the L3–5 segments of the spinal cord of SLICK::trkB mice that had been treated with tamoxifen to knock out the trkB gene is shown. Cells expressing YPF (left column) are presumed to be  for the trkB gene and cells in the same histological sections that are YFP− are presumed to have normal expression of this gene. NeuN immunoreactivity (red) is shown to identify these cells as neurons. Because of their large size and laminar location they were considered motoneurons. Synaptic structures immediately adjacent to the perimeters of these cells (cyan) represent contacts made by structures immunoreactive to VGLUT1 (a), VGLUT2 (b), GAD67 (c), or VGAT (d). All cells are shown at the same magnification.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4940568&req=5

fig1: Immunoreactivity to different synapse-associated antigens surrounding the somata and proximal-most dendrites of large neurons in lamina IX of the L3–5 segments of the spinal cord of SLICK::trkB mice that had been treated with tamoxifen to knock out the trkB gene is shown. Cells expressing YPF (left column) are presumed to be for the trkB gene and cells in the same histological sections that are YFP− are presumed to have normal expression of this gene. NeuN immunoreactivity (red) is shown to identify these cells as neurons. Because of their large size and laminar location they were considered motoneurons. Synaptic structures immediately adjacent to the perimeters of these cells (cyan) represent contacts made by structures immunoreactive to VGLUT1 (a), VGLUT2 (b), GAD67 (c), or VGAT (d). All cells are shown at the same magnification.
Mentions: Images of single 1 μm optical sections of cryostat sections were obtained using a Zeiss LSM510 confocal microscope at a magnification of 63x. Optical sections of presumed motoneurons were selected for study only if the location of the nucleus could be clearly visualized by the lack of immunoreactivity to either cholera toxin B or NeuN. Cell bodies of trkB knockout (KO) motoneurons innervating hind limb muscles were identified by the presence of both YFP (green) and either NeuN or cholera toxin B (red). In tamoxifen treated mice, these cells were assumed to be trkB (KO). Cell bodies of motoneurons that did not contain YFP but were adjacent to YFP+ cells on the same sections and were immunoreactive for either NeuN or cholera toxin B were assumed not to express Cre recombinase and were considered wild type (WT). Images of 10 KO motoneuron cell bodies and 10 WT cells were obtained from each side of the spinal cord in each mouse. Immunoreactivity to GAD67, VGAT, VGLUT1, or VGLUT2 was visualized with far red (647 nm) optics. Representative images of trkB-KO (YFP+) and WT (YFP−) neurons from sections reacted with antibodies to the different synapse-associated antigens are shown in Figure 1. In the control group (SLICK::trkBf/f mice not treated with tamoxifen), 20 YFP+ cells reacted with antibodies to each of the different synapse-associated proteins were selected from each side of the spinal cord for study. It was assumed that trkB expression in these cells was not affected.

Bottom Line: Selective knockout of the trkB gene resulted in a marked reduction in contacts made by VGLUT2- and GAD67-immunoreactive structures in both sexes and a significant reduction in contacts containing only glycine in male mice.No reduction was found for glycinergic contacts in female mice or for VGLUT1 immunoreactive contacts in either sex.Signaling through postsynaptic trkB receptors is considered to be an essential part of a cellular mechanism for maintaining the contacts of some, but not all, synaptic contacts onto motoneurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.

ABSTRACT
Synaptic contacts onto motoneurons were studied in mice in which the gene for the trkB neurotrophin receptor was knocked out selectively in a subset of spinal motoneurons. The extent of contacts by structures immunoreactive for either of two different vesicular glutamate transporters (VGLUT1 and VGLUT2), the vesicular GABA transporter, or glutamic acid decarboxylase 67 (GAD67) with the somata of motoneurons, was studied in wild type and trkB knockout cells in tamoxifen treated male and female SLICK-trkB(-/-) mice. Selective knockout of the trkB gene resulted in a marked reduction in contacts made by VGLUT2- and GAD67-immunoreactive structures in both sexes and a significant reduction in contacts containing only glycine in male mice. No reduction was found for glycinergic contacts in female mice or for VGLUT1 immunoreactive contacts in either sex. Signaling through postsynaptic trkB receptors is considered to be an essential part of a cellular mechanism for maintaining the contacts of some, but not all, synaptic contacts onto motoneurons.

No MeSH data available.


Related in: MedlinePlus