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A glial variant of the vesicular monoamine transporter is required to store histamine in the Drosophila visual system.

Romero-Calderón R, Uhlenbrock G, Borycz J, Simon AF, Grygoruk A, Yee SK, Shyer A, Ackerson LC, Maidment NT, Meinertzhagen IA, Hovemann BT, Krantz DE - PLoS Genet. (2008)

Bottom Line: In mammals, vesicular monoamine transporters (VMATs) are expressed exclusively in neurons and mediate the storage of histamine and other monoamines.We report here that a novel mRNA splice variant of Drosophila VMAT (DVMAT-B) is expressed not in neurons but rather in a small subset of glia in the lamina of the fly's optic lobe.Our results suggest a novel role for a monoamine transporter in glia that may be relevant to histamine homeostasis in other systems.

View Article: PubMed Central - PubMed

Affiliation: Gonda Goldschmied Center for Neuroscience and Genetics Research, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Unlike other monoamine neurotransmitters, the mechanism by which the brain's histamine content is regulated remains unclear. In mammals, vesicular monoamine transporters (VMATs) are expressed exclusively in neurons and mediate the storage of histamine and other monoamines. We have studied the visual system of Drosophila melanogaster in which histamine is the primary neurotransmitter released from photoreceptor cells. We report here that a novel mRNA splice variant of Drosophila VMAT (DVMAT-B) is expressed not in neurons but rather in a small subset of glia in the lamina of the fly's optic lobe. Histamine contents are reduced by mutation of dVMAT, but can be partially restored by specifically expressing DVMAT-B in glia. Our results suggest a novel role for a monoamine transporter in glia that may be relevant to histamine homeostasis in other systems.

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Antibodies raised against the C-terminus of DVMAT-B label the distal lamina.Confocal images of whole adult w and dVMATΔ14 mutant brains were labeled with the DVMAT-B antiserum anti-B1 (A,B). Labeling is visible in the distal lamina of the w control brain (A), but markedly reduced in the homozygous dVMATΔ14 mutant (B). Confocal images of wt and dVMATP1 homozygote head sections were labeled with anti-B2 (C,D) (magenta) and anti-Ebony (C,D) (green). In the wt, control sections, DVMAT-B labeling is visible in the distal lamina (C). In the dVMATP1 mutant, however, no DVMAT-B expression is detected (D). These results demonstrate the specificity of both anti-B1 and -B2. Re, retina; La, lamina; Me, medulla. Bars: 50 microns.
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pgen-1000245-g002: Antibodies raised against the C-terminus of DVMAT-B label the distal lamina.Confocal images of whole adult w and dVMATΔ14 mutant brains were labeled with the DVMAT-B antiserum anti-B1 (A,B). Labeling is visible in the distal lamina of the w control brain (A), but markedly reduced in the homozygous dVMATΔ14 mutant (B). Confocal images of wt and dVMATP1 homozygote head sections were labeled with anti-B2 (C,D) (magenta) and anti-Ebony (C,D) (green). In the wt, control sections, DVMAT-B labeling is visible in the distal lamina (C). In the dVMATP1 mutant, however, no DVMAT-B expression is detected (D). These results demonstrate the specificity of both anti-B1 and -B2. Re, retina; La, lamina; Me, medulla. Bars: 50 microns.

Mentions: We next characterized the two C-terminus directed antibodies that we generated to specifically detect DVMAT-B. Since only the C-termini of DVMAT-A and -B differ, a peptide representing the last 21 amino acids of DVMAT-B was used to develop a polyclonal antibody specific to the B form (anti-B1, see Methods). Immunoblots using anti-B1 did not show a detectable band on Western blots using adult head homogenates that gave robust signals when probed with either anti-DVMAT-A or anti-N (not shown). Therefore, to validate the specificity of the antibody and to determine the expression pattern of the DVMAT-B splice variant, we performed immunolabeling experiments using whole adult brains. In contrast to our previously described antibody to DVMAT-A (see [40],[47]), aminergic neurons in the adult brain were not labeled with anti-B1. Rather, anti-B1 specifically labeled a relatively thin layer between the retina and the optic lobe (Figure 2A). To confirm the specificity of labeling using anti-B1, we repeated this experiment using the dVMATΔ14 flies. Labeling using anti-B1 was dramatically reduced in the Δ14 mutants (Figure 2B), confirming the specificity of the anti-B1 antibody. Additional labeling experiments using anti-B1 indicate that DVMAT-B is not expressed elsewhere in the adult fly brain (data not shown). Despite the presence of dVMAT-B mRNA in the embryonic nervous system [47] we did not detect DVMAT-B protein in labeling experiments using anti-DVMAT-B in either whole embryos, the central nervous system of third-instar larvae (central brain plus optic lobes), or larval fillets that included Type II neuromuscular junctions, which are octopamine positive [58].


A glial variant of the vesicular monoamine transporter is required to store histamine in the Drosophila visual system.

Romero-Calderón R, Uhlenbrock G, Borycz J, Simon AF, Grygoruk A, Yee SK, Shyer A, Ackerson LC, Maidment NT, Meinertzhagen IA, Hovemann BT, Krantz DE - PLoS Genet. (2008)

Antibodies raised against the C-terminus of DVMAT-B label the distal lamina.Confocal images of whole adult w and dVMATΔ14 mutant brains were labeled with the DVMAT-B antiserum anti-B1 (A,B). Labeling is visible in the distal lamina of the w control brain (A), but markedly reduced in the homozygous dVMATΔ14 mutant (B). Confocal images of wt and dVMATP1 homozygote head sections were labeled with anti-B2 (C,D) (magenta) and anti-Ebony (C,D) (green). In the wt, control sections, DVMAT-B labeling is visible in the distal lamina (C). In the dVMATP1 mutant, however, no DVMAT-B expression is detected (D). These results demonstrate the specificity of both anti-B1 and -B2. Re, retina; La, lamina; Me, medulla. Bars: 50 microns.
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pgen-1000245-g002: Antibodies raised against the C-terminus of DVMAT-B label the distal lamina.Confocal images of whole adult w and dVMATΔ14 mutant brains were labeled with the DVMAT-B antiserum anti-B1 (A,B). Labeling is visible in the distal lamina of the w control brain (A), but markedly reduced in the homozygous dVMATΔ14 mutant (B). Confocal images of wt and dVMATP1 homozygote head sections were labeled with anti-B2 (C,D) (magenta) and anti-Ebony (C,D) (green). In the wt, control sections, DVMAT-B labeling is visible in the distal lamina (C). In the dVMATP1 mutant, however, no DVMAT-B expression is detected (D). These results demonstrate the specificity of both anti-B1 and -B2. Re, retina; La, lamina; Me, medulla. Bars: 50 microns.
Mentions: We next characterized the two C-terminus directed antibodies that we generated to specifically detect DVMAT-B. Since only the C-termini of DVMAT-A and -B differ, a peptide representing the last 21 amino acids of DVMAT-B was used to develop a polyclonal antibody specific to the B form (anti-B1, see Methods). Immunoblots using anti-B1 did not show a detectable band on Western blots using adult head homogenates that gave robust signals when probed with either anti-DVMAT-A or anti-N (not shown). Therefore, to validate the specificity of the antibody and to determine the expression pattern of the DVMAT-B splice variant, we performed immunolabeling experiments using whole adult brains. In contrast to our previously described antibody to DVMAT-A (see [40],[47]), aminergic neurons in the adult brain were not labeled with anti-B1. Rather, anti-B1 specifically labeled a relatively thin layer between the retina and the optic lobe (Figure 2A). To confirm the specificity of labeling using anti-B1, we repeated this experiment using the dVMATΔ14 flies. Labeling using anti-B1 was dramatically reduced in the Δ14 mutants (Figure 2B), confirming the specificity of the anti-B1 antibody. Additional labeling experiments using anti-B1 indicate that DVMAT-B is not expressed elsewhere in the adult fly brain (data not shown). Despite the presence of dVMAT-B mRNA in the embryonic nervous system [47] we did not detect DVMAT-B protein in labeling experiments using anti-DVMAT-B in either whole embryos, the central nervous system of third-instar larvae (central brain plus optic lobes), or larval fillets that included Type II neuromuscular junctions, which are octopamine positive [58].

Bottom Line: In mammals, vesicular monoamine transporters (VMATs) are expressed exclusively in neurons and mediate the storage of histamine and other monoamines.We report here that a novel mRNA splice variant of Drosophila VMAT (DVMAT-B) is expressed not in neurons but rather in a small subset of glia in the lamina of the fly's optic lobe.Our results suggest a novel role for a monoamine transporter in glia that may be relevant to histamine homeostasis in other systems.

View Article: PubMed Central - PubMed

Affiliation: Gonda Goldschmied Center for Neuroscience and Genetics Research, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Unlike other monoamine neurotransmitters, the mechanism by which the brain's histamine content is regulated remains unclear. In mammals, vesicular monoamine transporters (VMATs) are expressed exclusively in neurons and mediate the storage of histamine and other monoamines. We have studied the visual system of Drosophila melanogaster in which histamine is the primary neurotransmitter released from photoreceptor cells. We report here that a novel mRNA splice variant of Drosophila VMAT (DVMAT-B) is expressed not in neurons but rather in a small subset of glia in the lamina of the fly's optic lobe. Histamine contents are reduced by mutation of dVMAT, but can be partially restored by specifically expressing DVMAT-B in glia. Our results suggest a novel role for a monoamine transporter in glia that may be relevant to histamine homeostasis in other systems.

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