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The Drosophila homologue of Rootletin is required for mechanosensory function and ciliary rootlet formation in chordotonal sensory neurons.

Styczynska-Soczka K, Jarman AP - Cilia (2015)

Bottom Line: Knock-down of Rootletin results in loss of ciliary rootlet in these neurons and severe disruption of their sensory function.No evidence was found for a defect in cell division.Although our evidence is consistent with an anchoring role for the rootlet, severe loss of mechanosensory function of chordotonal (Ch) neurons upon Rootletin knock-down may suggest a direct role for the rootlet in the mechanotransduction mechanism itself.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD UK.

ABSTRACT

Background: In vertebrates, rootletin is the major structural component of the ciliary rootlet and is also part of the tether linking the centrioles of the centrosome. Various functions have been ascribed to the rootlet, including maintenance of ciliary integrity through anchoring and facilitation of transport to the cilium or at the base of the cilium. In Drosophila, Rootletin function has not been explored.

Results: In the Drosophila embryo, Rootletin is expressed exclusively in cell lineages of type I sensory neurons, the only somatic cells bearing a cilium. Expression is strongest in mechanosensory chordotonal neurons. Knock-down of Rootletin results in loss of ciliary rootlet in these neurons and severe disruption of their sensory function. However, the sensory cilium appears largely normal in structure and in localisation of proteins suggesting no strong defect in ciliogenesis. No evidence was found for a defect in cell division.

Conclusions: The role of Rootletin as a component of the ciliary rootlet is conserved in Drosophila. In contrast, lack of a general role in cell division is consistent with lack of centriole tethering during the centrosome cycle in Drosophila. Although our evidence is consistent with an anchoring role for the rootlet, severe loss of mechanosensory function of chordotonal (Ch) neurons upon Rootletin knock-down may suggest a direct role for the rootlet in the mechanotransduction mechanism itself.

No MeSH data available.


Related in: MedlinePlus

Rootletin knock-down results in loss of rootlet and proximal centriole. Transmission electron microscopy of Ch neuron dendrites in the adult antenna (Johnston’s organ). a–c Wild type. a Longitudinal section of cilium base showing the proximal centriole (black arrow, pc) and a robust ciliary rootlet structure (black arrow, cr). b Longitudinal section of cilium showing the axoneme (ax), distal centriole (dc), proximal centriole (pc), and ciliary rootlet (cr). c Transverse section of cilium at a level proximal to the ciliary dilation. Regular axonemal ninefold symmetry is visible. d–fRootletin knock-down. d, e Two examples of longitudinal sections labelled as before. Note the lack of ciliary rootlet structure and the proximal centriole. Instead, electron-dense aggregates are visible, possibly representing remains of the ciliary rootlet (*cr). f Transverse section at a level proximally to the ciliary dilation. Regular axonemal ninefold symmetry is apparent
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Fig3: Rootletin knock-down results in loss of rootlet and proximal centriole. Transmission electron microscopy of Ch neuron dendrites in the adult antenna (Johnston’s organ). a–c Wild type. a Longitudinal section of cilium base showing the proximal centriole (black arrow, pc) and a robust ciliary rootlet structure (black arrow, cr). b Longitudinal section of cilium showing the axoneme (ax), distal centriole (dc), proximal centriole (pc), and ciliary rootlet (cr). c Transverse section of cilium at a level proximal to the ciliary dilation. Regular axonemal ninefold symmetry is visible. d–fRootletin knock-down. d, e Two examples of longitudinal sections labelled as before. Note the lack of ciliary rootlet structure and the proximal centriole. Instead, electron-dense aggregates are visible, possibly representing remains of the ciliary rootlet (*cr). f Transverse section at a level proximally to the ciliary dilation. Regular axonemal ninefold symmetry is apparent

Mentions: To determine the effect of Rootletin knock-down on the cilium in more detail, we used transmission electron microscopy (TEM) to examine the large array of Ch neurons (Johnston’s organ) in the adult second antennal segment which is required for proprioception, gravitaxis and auditory sensation [24]. In longitudinal sections of the Ch organ units (scolopidia) of control antennae, the cilia of the sensory neurons and their prominent striated rootlets are readily visible (n = 27 cilia, Fig. 3a, b). In Rootletin knock-down antennae, the cilia themselves appeared generally normal and features such as the ciliary dilation were visible. In transverse sections, the 9 + 0 microtubular structure of the axoneme appeared normal (Fig. 3c, f). In contrast, the ciliary rootlet was completely disrupted and appeared to be absent in all cilia sectioned from knock-down flies (n = 23, Fig. 3d, e). In many instances, electron-dense ‘globules’ could be observed where the rootlet should be.Fig. 3


The Drosophila homologue of Rootletin is required for mechanosensory function and ciliary rootlet formation in chordotonal sensory neurons.

Styczynska-Soczka K, Jarman AP - Cilia (2015)

Rootletin knock-down results in loss of rootlet and proximal centriole. Transmission electron microscopy of Ch neuron dendrites in the adult antenna (Johnston’s organ). a–c Wild type. a Longitudinal section of cilium base showing the proximal centriole (black arrow, pc) and a robust ciliary rootlet structure (black arrow, cr). b Longitudinal section of cilium showing the axoneme (ax), distal centriole (dc), proximal centriole (pc), and ciliary rootlet (cr). c Transverse section of cilium at a level proximal to the ciliary dilation. Regular axonemal ninefold symmetry is visible. d–fRootletin knock-down. d, e Two examples of longitudinal sections labelled as before. Note the lack of ciliary rootlet structure and the proximal centriole. Instead, electron-dense aggregates are visible, possibly representing remains of the ciliary rootlet (*cr). f Transverse section at a level proximally to the ciliary dilation. Regular axonemal ninefold symmetry is apparent
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4489026&req=5

Fig3: Rootletin knock-down results in loss of rootlet and proximal centriole. Transmission electron microscopy of Ch neuron dendrites in the adult antenna (Johnston’s organ). a–c Wild type. a Longitudinal section of cilium base showing the proximal centriole (black arrow, pc) and a robust ciliary rootlet structure (black arrow, cr). b Longitudinal section of cilium showing the axoneme (ax), distal centriole (dc), proximal centriole (pc), and ciliary rootlet (cr). c Transverse section of cilium at a level proximal to the ciliary dilation. Regular axonemal ninefold symmetry is visible. d–fRootletin knock-down. d, e Two examples of longitudinal sections labelled as before. Note the lack of ciliary rootlet structure and the proximal centriole. Instead, electron-dense aggregates are visible, possibly representing remains of the ciliary rootlet (*cr). f Transverse section at a level proximally to the ciliary dilation. Regular axonemal ninefold symmetry is apparent
Mentions: To determine the effect of Rootletin knock-down on the cilium in more detail, we used transmission electron microscopy (TEM) to examine the large array of Ch neurons (Johnston’s organ) in the adult second antennal segment which is required for proprioception, gravitaxis and auditory sensation [24]. In longitudinal sections of the Ch organ units (scolopidia) of control antennae, the cilia of the sensory neurons and their prominent striated rootlets are readily visible (n = 27 cilia, Fig. 3a, b). In Rootletin knock-down antennae, the cilia themselves appeared generally normal and features such as the ciliary dilation were visible. In transverse sections, the 9 + 0 microtubular structure of the axoneme appeared normal (Fig. 3c, f). In contrast, the ciliary rootlet was completely disrupted and appeared to be absent in all cilia sectioned from knock-down flies (n = 23, Fig. 3d, e). In many instances, electron-dense ‘globules’ could be observed where the rootlet should be.Fig. 3

Bottom Line: Knock-down of Rootletin results in loss of ciliary rootlet in these neurons and severe disruption of their sensory function.No evidence was found for a defect in cell division.Although our evidence is consistent with an anchoring role for the rootlet, severe loss of mechanosensory function of chordotonal (Ch) neurons upon Rootletin knock-down may suggest a direct role for the rootlet in the mechanotransduction mechanism itself.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD UK.

ABSTRACT

Background: In vertebrates, rootletin is the major structural component of the ciliary rootlet and is also part of the tether linking the centrioles of the centrosome. Various functions have been ascribed to the rootlet, including maintenance of ciliary integrity through anchoring and facilitation of transport to the cilium or at the base of the cilium. In Drosophila, Rootletin function has not been explored.

Results: In the Drosophila embryo, Rootletin is expressed exclusively in cell lineages of type I sensory neurons, the only somatic cells bearing a cilium. Expression is strongest in mechanosensory chordotonal neurons. Knock-down of Rootletin results in loss of ciliary rootlet in these neurons and severe disruption of their sensory function. However, the sensory cilium appears largely normal in structure and in localisation of proteins suggesting no strong defect in ciliogenesis. No evidence was found for a defect in cell division.

Conclusions: The role of Rootletin as a component of the ciliary rootlet is conserved in Drosophila. In contrast, lack of a general role in cell division is consistent with lack of centriole tethering during the centrosome cycle in Drosophila. Although our evidence is consistent with an anchoring role for the rootlet, severe loss of mechanosensory function of chordotonal (Ch) neurons upon Rootletin knock-down may suggest a direct role for the rootlet in the mechanotransduction mechanism itself.

No MeSH data available.


Related in: MedlinePlus