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Diverse Roles of Axonemal Dyneins in Drosophila Auditory Neuron Function and Mechanical Amplification in Hearing.

Karak S, Jacobs JS, Kittelmann M, Spalthoff C, Katana R, Sivan-Loukianova E, Schon MA, Kernan MJ, Eberl DF, Göpfert MC - Sci Rep (2015)

Bottom Line: Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2.This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins.Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Neurobiology, University of Göttingen, 37077 Göttingen, Germany.

ABSTRACT
Much like vertebrate hair cells, the chordotonal sensory neurons that mediate hearing in Drosophila are motile and amplify the mechanical input of the ear. Because the neurons bear mechanosensory primary cilia whose microtubule axonemes display dynein arms, we hypothesized that their motility is powered by dyneins. Here, we describe two axonemal dynein proteins that are required for Drosophila auditory neuron function, localize to their primary cilia, and differently contribute to mechanical amplification in hearing. Promoter fusions revealed that the two axonemal dynein genes Dmdnah3 (=CG17150) and Dmdnai2 (=CG6053) are expressed in chordotonal neurons, including the auditory ones in the fly's ear. Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2. Epistasis analysis revealed that Dmdnah3 acts downstream of Nan-Iav channels in controlling the amplificatory gain. Dmdnai2, in addition to being required for amplification, was essential for outer dynein arms in auditory neuron cilia. This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins. Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

No MeSH data available.


Related in: MedlinePlus

Axonemal dynein expression and localization in chordotonal neurons.(A,B) Expression of Dmdnah3-GAL4 and Dmdnai2-GAL4 in Johnston’s organ neurons (A) and in chordotonal neurons of the larval pentascolopidial organ (lch5) and the adult femoral chordotonal organ (FCO) (B). Expression was assessed by driving an UAS-GFP reporter via Dmdnah3-GAL4 or Dmdnai2-GAL4. GFP signals were enhanced with an anti-GFP antibody. Johnston’s organ neurons were counterstained with the neuronal antibody 22C10 (A). (C) DmDNAI2 protein localization in Johnston’s organ neurons, revealed by expressing UAS-Dmdnai2-YFP under the control of Dmdnai2-Gal4. YFP signals were enhanced with an anti-GFP antibody and counterstained with an anti-Iav antibody, which recognizes Iav protein in the proximal region of the cilia. Within the cilia, DmDNAI2-YFP signals superimpose with Iav in the proximal ciliary region but do not extend distally in the ciliary tips.
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f1: Axonemal dynein expression and localization in chordotonal neurons.(A,B) Expression of Dmdnah3-GAL4 and Dmdnai2-GAL4 in Johnston’s organ neurons (A) and in chordotonal neurons of the larval pentascolopidial organ (lch5) and the adult femoral chordotonal organ (FCO) (B). Expression was assessed by driving an UAS-GFP reporter via Dmdnah3-GAL4 or Dmdnai2-GAL4. GFP signals were enhanced with an anti-GFP antibody. Johnston’s organ neurons were counterstained with the neuronal antibody 22C10 (A). (C) DmDNAI2 protein localization in Johnston’s organ neurons, revealed by expressing UAS-Dmdnai2-YFP under the control of Dmdnai2-Gal4. YFP signals were enhanced with an anti-GFP antibody and counterstained with an anti-Iav antibody, which recognizes Iav protein in the proximal region of the cilia. Within the cilia, DmDNAI2-YFP signals superimpose with Iav in the proximal ciliary region but do not extend distally in the ciliary tips.

Mentions: To characterize the cellular expression patterns of Dmdnah3 and Dmdnai2, we generated fusions between the Dmdnah3 or Dmdnai2 enhancer/promoter regions and the yeast transcription activator GAL4 (see Supplementary Methods). To visualize GAL4 expression, transgenic flies expressing Dmdnah3-GAL4 and Dmdnai2-GAL4 were crossed to flies expressing a green fluorescent protein (GFP) under the control of upstream activating sequence (UAS) elements (UAS-GFP). GFP signals were enhanced with an anti-GFP antibody, and neurons were counterstained with the monoclonal anti-Futsch antibody 22c10 (Ref. 36). Labelling induced by the Dmdnah3 and Dmdnai2 enhancer/promoter regions was observed in Johnston’s organ, the chordotonal auditory sensory organ in the fly’s antenna (Fig. 1A). Within this organ, anti-GFP and 22c10 staining superimposed, documenting that virtually all its 500 sensory neurons express Dmdnah3 and Dmdnai2 (Fig. 1A). Apart from Johnston’s organ neurons, expression of Dmdnah3 and Dmdnai2 was also observed in other chordotonal neurons, including those of the femoral chordotonal organ (FCO) in the fly’s leg and those of the larval pentascolopidial organ (lch5) (Fig. 1B). No expression was seen in the central nervous system or ciliated chemoreceptors and mechanosensory bristle neurons whose cilia reportedly lack dynein arms7. Chordotonal sensory neurons thus seem to be the only Drosophila neurons that express Dmdnah3 and Dmdnai2.


Diverse Roles of Axonemal Dyneins in Drosophila Auditory Neuron Function and Mechanical Amplification in Hearing.

Karak S, Jacobs JS, Kittelmann M, Spalthoff C, Katana R, Sivan-Loukianova E, Schon MA, Kernan MJ, Eberl DF, Göpfert MC - Sci Rep (2015)

Axonemal dynein expression and localization in chordotonal neurons.(A,B) Expression of Dmdnah3-GAL4 and Dmdnai2-GAL4 in Johnston’s organ neurons (A) and in chordotonal neurons of the larval pentascolopidial organ (lch5) and the adult femoral chordotonal organ (FCO) (B). Expression was assessed by driving an UAS-GFP reporter via Dmdnah3-GAL4 or Dmdnai2-GAL4. GFP signals were enhanced with an anti-GFP antibody. Johnston’s organ neurons were counterstained with the neuronal antibody 22C10 (A). (C) DmDNAI2 protein localization in Johnston’s organ neurons, revealed by expressing UAS-Dmdnai2-YFP under the control of Dmdnai2-Gal4. YFP signals were enhanced with an anti-GFP antibody and counterstained with an anti-Iav antibody, which recognizes Iav protein in the proximal region of the cilia. Within the cilia, DmDNAI2-YFP signals superimpose with Iav in the proximal ciliary region but do not extend distally in the ciliary tips.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660584&req=5

f1: Axonemal dynein expression and localization in chordotonal neurons.(A,B) Expression of Dmdnah3-GAL4 and Dmdnai2-GAL4 in Johnston’s organ neurons (A) and in chordotonal neurons of the larval pentascolopidial organ (lch5) and the adult femoral chordotonal organ (FCO) (B). Expression was assessed by driving an UAS-GFP reporter via Dmdnah3-GAL4 or Dmdnai2-GAL4. GFP signals were enhanced with an anti-GFP antibody. Johnston’s organ neurons were counterstained with the neuronal antibody 22C10 (A). (C) DmDNAI2 protein localization in Johnston’s organ neurons, revealed by expressing UAS-Dmdnai2-YFP under the control of Dmdnai2-Gal4. YFP signals were enhanced with an anti-GFP antibody and counterstained with an anti-Iav antibody, which recognizes Iav protein in the proximal region of the cilia. Within the cilia, DmDNAI2-YFP signals superimpose with Iav in the proximal ciliary region but do not extend distally in the ciliary tips.
Mentions: To characterize the cellular expression patterns of Dmdnah3 and Dmdnai2, we generated fusions between the Dmdnah3 or Dmdnai2 enhancer/promoter regions and the yeast transcription activator GAL4 (see Supplementary Methods). To visualize GAL4 expression, transgenic flies expressing Dmdnah3-GAL4 and Dmdnai2-GAL4 were crossed to flies expressing a green fluorescent protein (GFP) under the control of upstream activating sequence (UAS) elements (UAS-GFP). GFP signals were enhanced with an anti-GFP antibody, and neurons were counterstained with the monoclonal anti-Futsch antibody 22c10 (Ref. 36). Labelling induced by the Dmdnah3 and Dmdnai2 enhancer/promoter regions was observed in Johnston’s organ, the chordotonal auditory sensory organ in the fly’s antenna (Fig. 1A). Within this organ, anti-GFP and 22c10 staining superimposed, documenting that virtually all its 500 sensory neurons express Dmdnah3 and Dmdnai2 (Fig. 1A). Apart from Johnston’s organ neurons, expression of Dmdnah3 and Dmdnai2 was also observed in other chordotonal neurons, including those of the femoral chordotonal organ (FCO) in the fly’s leg and those of the larval pentascolopidial organ (lch5) (Fig. 1B). No expression was seen in the central nervous system or ciliated chemoreceptors and mechanosensory bristle neurons whose cilia reportedly lack dynein arms7. Chordotonal sensory neurons thus seem to be the only Drosophila neurons that express Dmdnah3 and Dmdnai2.

Bottom Line: Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2.This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins.Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Neurobiology, University of Göttingen, 37077 Göttingen, Germany.

ABSTRACT
Much like vertebrate hair cells, the chordotonal sensory neurons that mediate hearing in Drosophila are motile and amplify the mechanical input of the ear. Because the neurons bear mechanosensory primary cilia whose microtubule axonemes display dynein arms, we hypothesized that their motility is powered by dyneins. Here, we describe two axonemal dynein proteins that are required for Drosophila auditory neuron function, localize to their primary cilia, and differently contribute to mechanical amplification in hearing. Promoter fusions revealed that the two axonemal dynein genes Dmdnah3 (=CG17150) and Dmdnai2 (=CG6053) are expressed in chordotonal neurons, including the auditory ones in the fly's ear. Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2. Epistasis analysis revealed that Dmdnah3 acts downstream of Nan-Iav channels in controlling the amplificatory gain. Dmdnai2, in addition to being required for amplification, was essential for outer dynein arms in auditory neuron cilia. This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins. Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

No MeSH data available.


Related in: MedlinePlus