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Differential Anatomical Expression of Ganglioside GM1 Species Containing d18:1 or d20:1 Sphingosine Detected by MALDI Imaging Mass Spectrometry in Mature Rat Brain.

Weishaupt N, Caughlin S, Yeung KK, Whitehead SN - Front Neuroanat (2015)

Bottom Line: Across layers of the sensory cortex, opposing expression gradients were found for GM1d18:1 and GM1d20:1.By far the highest GM1d18:1/d20:1 ratio was found in the amygdala.Differential expression of GM1 with d18:1- or d20:1-sphingosine bases in the adult rat brain suggests tight regulation of expression and points toward a distinct functional relevance for each of these GM1 species in neuronal processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London ON, Canada.

ABSTRACT
GM1 ganglioside plays a role in essential neuronal processes, including differentiation, survival, and signaling. Yet, little is known about GM1 species with different sphingosine bases, such as the most abundant species containing 18 carbon atoms in the sphingosine chain (GM1d18:1), and the less abundant containing 20 carbon atoms (GM1d20:1). While absent in the early fetal brain, GM1d20:1 continues to increase throughout pre- and postnatal development and into old age, raising questions about the functional relevance of the GM1d18:1 to GM1d20:1 ratio. Matrix-assisted laser desorption/ionization imaging mass spectrometry is a novel technology that allows differentiation between these two GM1 species and quantification of their expression within an anatomical context. Using this technology, we find GM1d18:1/d20:1 expression ratios are highly specific to defined anatomical brain regions in adult rats. Thus, the ratio was significantly different among different thalamic nuclei and between the corpus callosum and internal capsule. Differential GM1d18:1/GM1d20:1 ratios measured in hippocampal subregions in rat brain complement previous studies conducted in mice. Across layers of the sensory cortex, opposing expression gradients were found for GM1d18:1 and GM1d20:1. Superficial layers demonstrated lower GM1d18:1 and higher GM1d20:1 signal than other layers, while in deep layers GM1d18:1 expression was relatively high and GM1d20:1 expression low. By far the highest GM1d18:1/d20:1 ratio was found in the amygdala. Differential expression of GM1 with d18:1- or d20:1-sphingosine bases in the adult rat brain suggests tight regulation of expression and points toward a distinct functional relevance for each of these GM1 species in neuronal processes.

No MeSH data available.


Schematic shows the small sampling points within the hippocampus from which mass spectra were generated (A). While the cell layers across the CA1, CA3, and DG had a similar GM1d18:1/GM1d20:1 ratio, the ratio differed significantly among the molecular layer of the DG and the stratum radiatum in the CA1 and CA3 regions (Kruskal–Wallis test, DG vs. CA1 ∗∗p < 0.001, DG vs. CA3 ∗∗∗∗p < 0.0001, CA1 vs. CA3 ∗p < 0.05, B). CA1 pc, CA1 PC; CA1 rad, CA1 stratum radiatum; DG gc, dentate gyrus GC; DG ml, dentate gyrus molecular layer; CA3 rad, CA3 stratum radiatum; CA3 pc, CA3 PC. Molecular images of GM1d18:1 expression (green) and GM1d20:1 expression (red) showed high expression of the d20:1-species almost exclusively within the DG ml, while the d18:1-species was highest within the stratum radiatum (C). Scale bar = 2 mm.
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Figure 4: Schematic shows the small sampling points within the hippocampus from which mass spectra were generated (A). While the cell layers across the CA1, CA3, and DG had a similar GM1d18:1/GM1d20:1 ratio, the ratio differed significantly among the molecular layer of the DG and the stratum radiatum in the CA1 and CA3 regions (Kruskal–Wallis test, DG vs. CA1 ∗∗p < 0.001, DG vs. CA3 ∗∗∗∗p < 0.0001, CA1 vs. CA3 ∗p < 0.05, B). CA1 pc, CA1 PC; CA1 rad, CA1 stratum radiatum; DG gc, dentate gyrus GC; DG ml, dentate gyrus molecular layer; CA3 rad, CA3 stratum radiatum; CA3 pc, CA3 PC. Molecular images of GM1d18:1 expression (green) and GM1d20:1 expression (red) showed high expression of the d20:1-species almost exclusively within the DG ml, while the d18:1-species was highest within the stratum radiatum (C). Scale bar = 2 mm.

Mentions: Sampling regions for spectral analysis were considerably smaller in hippocampal areas than in all other brain regions to limit accidental inclusion of neighboring regions, especially when sampling the narrow cellular layers (Figure 4A). Among the cell layers of the DG, (4.14 ± 0.25, n = 20), CA field 1 (CA1, 3.59 ± 0.18, n = 20) and CA field 3 (CA3, 3.72 ± 0.21, n = 17), there was no statistical difference in the GM1d18:1/GM1d20:1 expression (Figure 4B). However, the GC of the DG has a slightly higher ratio than the PCs of CA1 and CA3 (Figure 4B). In contrast, we found an extremely low GM1d18:1/GM1d20:1 ratio within the molecular layer of the DG (1.90 ± 0.06, n = 21, Figure 4C). This layer stood out as the area of greatest relative GM1d20:1 expression in a cross section of the hippocampus, while GM1d18:1 expression was visibly lower in this layer than in the neighboring stratum radiatum (Figure 4C). The GM1d18:1/GM1d20:1 ratio within the molecular layer of the DG is significantly lower than the ratio within the stratum radiatum of the CA1 (3.19 ± 0.15, n = 20) and CA3 region (4.03 ± 0.12, n = 21, Kruskal–Wallis test, DG vs. CA1 p < 0.001, DG vs. CA3 p < 0.0001, Figure 4B). Careful visual examination of the GM1d20:1 expression image (red, Figure 4C) indicated a change in expression between the stratum radiatum in the CA1 versus the CA3 region, which was reflected by a significantly lower GM1d18:1/GM1d20:1 ratio in the CA1 region (Kruskal–Wallis test, p < 0.05, Figure 4B).


Differential Anatomical Expression of Ganglioside GM1 Species Containing d18:1 or d20:1 Sphingosine Detected by MALDI Imaging Mass Spectrometry in Mature Rat Brain.

Weishaupt N, Caughlin S, Yeung KK, Whitehead SN - Front Neuroanat (2015)

Schematic shows the small sampling points within the hippocampus from which mass spectra were generated (A). While the cell layers across the CA1, CA3, and DG had a similar GM1d18:1/GM1d20:1 ratio, the ratio differed significantly among the molecular layer of the DG and the stratum radiatum in the CA1 and CA3 regions (Kruskal–Wallis test, DG vs. CA1 ∗∗p < 0.001, DG vs. CA3 ∗∗∗∗p < 0.0001, CA1 vs. CA3 ∗p < 0.05, B). CA1 pc, CA1 PC; CA1 rad, CA1 stratum radiatum; DG gc, dentate gyrus GC; DG ml, dentate gyrus molecular layer; CA3 rad, CA3 stratum radiatum; CA3 pc, CA3 PC. Molecular images of GM1d18:1 expression (green) and GM1d20:1 expression (red) showed high expression of the d20:1-species almost exclusively within the DG ml, while the d18:1-species was highest within the stratum radiatum (C). Scale bar = 2 mm.
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Related In: Results  -  Collection

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Figure 4: Schematic shows the small sampling points within the hippocampus from which mass spectra were generated (A). While the cell layers across the CA1, CA3, and DG had a similar GM1d18:1/GM1d20:1 ratio, the ratio differed significantly among the molecular layer of the DG and the stratum radiatum in the CA1 and CA3 regions (Kruskal–Wallis test, DG vs. CA1 ∗∗p < 0.001, DG vs. CA3 ∗∗∗∗p < 0.0001, CA1 vs. CA3 ∗p < 0.05, B). CA1 pc, CA1 PC; CA1 rad, CA1 stratum radiatum; DG gc, dentate gyrus GC; DG ml, dentate gyrus molecular layer; CA3 rad, CA3 stratum radiatum; CA3 pc, CA3 PC. Molecular images of GM1d18:1 expression (green) and GM1d20:1 expression (red) showed high expression of the d20:1-species almost exclusively within the DG ml, while the d18:1-species was highest within the stratum radiatum (C). Scale bar = 2 mm.
Mentions: Sampling regions for spectral analysis were considerably smaller in hippocampal areas than in all other brain regions to limit accidental inclusion of neighboring regions, especially when sampling the narrow cellular layers (Figure 4A). Among the cell layers of the DG, (4.14 ± 0.25, n = 20), CA field 1 (CA1, 3.59 ± 0.18, n = 20) and CA field 3 (CA3, 3.72 ± 0.21, n = 17), there was no statistical difference in the GM1d18:1/GM1d20:1 expression (Figure 4B). However, the GC of the DG has a slightly higher ratio than the PCs of CA1 and CA3 (Figure 4B). In contrast, we found an extremely low GM1d18:1/GM1d20:1 ratio within the molecular layer of the DG (1.90 ± 0.06, n = 21, Figure 4C). This layer stood out as the area of greatest relative GM1d20:1 expression in a cross section of the hippocampus, while GM1d18:1 expression was visibly lower in this layer than in the neighboring stratum radiatum (Figure 4C). The GM1d18:1/GM1d20:1 ratio within the molecular layer of the DG is significantly lower than the ratio within the stratum radiatum of the CA1 (3.19 ± 0.15, n = 20) and CA3 region (4.03 ± 0.12, n = 21, Kruskal–Wallis test, DG vs. CA1 p < 0.001, DG vs. CA3 p < 0.0001, Figure 4B). Careful visual examination of the GM1d20:1 expression image (red, Figure 4C) indicated a change in expression between the stratum radiatum in the CA1 versus the CA3 region, which was reflected by a significantly lower GM1d18:1/GM1d20:1 ratio in the CA1 region (Kruskal–Wallis test, p < 0.05, Figure 4B).

Bottom Line: Across layers of the sensory cortex, opposing expression gradients were found for GM1d18:1 and GM1d20:1.By far the highest GM1d18:1/d20:1 ratio was found in the amygdala.Differential expression of GM1 with d18:1- or d20:1-sphingosine bases in the adult rat brain suggests tight regulation of expression and points toward a distinct functional relevance for each of these GM1 species in neuronal processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London ON, Canada.

ABSTRACT
GM1 ganglioside plays a role in essential neuronal processes, including differentiation, survival, and signaling. Yet, little is known about GM1 species with different sphingosine bases, such as the most abundant species containing 18 carbon atoms in the sphingosine chain (GM1d18:1), and the less abundant containing 20 carbon atoms (GM1d20:1). While absent in the early fetal brain, GM1d20:1 continues to increase throughout pre- and postnatal development and into old age, raising questions about the functional relevance of the GM1d18:1 to GM1d20:1 ratio. Matrix-assisted laser desorption/ionization imaging mass spectrometry is a novel technology that allows differentiation between these two GM1 species and quantification of their expression within an anatomical context. Using this technology, we find GM1d18:1/d20:1 expression ratios are highly specific to defined anatomical brain regions in adult rats. Thus, the ratio was significantly different among different thalamic nuclei and between the corpus callosum and internal capsule. Differential GM1d18:1/GM1d20:1 ratios measured in hippocampal subregions in rat brain complement previous studies conducted in mice. Across layers of the sensory cortex, opposing expression gradients were found for GM1d18:1 and GM1d20:1. Superficial layers demonstrated lower GM1d18:1 and higher GM1d20:1 signal than other layers, while in deep layers GM1d18:1 expression was relatively high and GM1d20:1 expression low. By far the highest GM1d18:1/d20:1 ratio was found in the amygdala. Differential expression of GM1 with d18:1- or d20:1-sphingosine bases in the adult rat brain suggests tight regulation of expression and points toward a distinct functional relevance for each of these GM1 species in neuronal processes.

No MeSH data available.