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Fig. 1.7 Drosophila mechanosensory neuron morphology. a The neuron cell body is filled with
tubulin-GFP. The dendrite is lightly labeled by tubulin-GFP. At the dendrite tip, the cilium is
strongly labeled by tubulin-GFP. Red labels cuticle structures, including the bristle. Blue labels
the Transition zone vicinity. b Diagram of sensory cell dendrite and cilium. (The a panel is
modified from Fig.
7
c in (Avidor-Reiss et al.
2004
)
Fig. 1.8 Drosophila mutants with centriolar or cilia defects are mechanosensory defective.
Displacing a bristle 30 um for one second (a) generates a mechanoreceptor current in control flies
that adapts over the course of the stimulus (b). In contrast, mutations that affect centriole
formation (c and d) and thus cannot form mechanosensory cilia have no mechanoreceptor
current. (The a and b panels are modified from Fig.
1.4
c in (Avidor-Reiss et al.
2004
)
1.3 Centrosomes in Differentiated Cells
1.3.1 Sensory neuron differentiation
In Drosophila, the first cells that develop cilia are the type I sensory neurons
(Fig.
1.7
). These neurons mediate the reception of mechano- and chemo-sensory
information and are found in both larvae and the adult fly. One subtype of these
sensory neurons is found on the cuticle of the adult fly and mediate touch sensation
(Fig.
1.7
) (Keil
1997
). These neurons are bipolar sensory neurons that extend a
dendrite with sensory cilia at their tip in one direction. The sensory cilia are
attached to a cutaneous structure termed the bristle. When the bristle moves due to
mechanical stimuli, the mechanosensory transduction machinery found in the cilia
is activated and a mechanoreceptor current is generated (Fig.
1.8
). This current
produces an action potential that is delivered to the brain, transmitting information
regarding touch sensation or proprioception (Avidor-Reiss et al.
2004
; Kernan
et al.
1994
; Walker et al.
2000
).
