Zusammenfassung der Ressource
Development of sense organs
Anmerkungen:
- Key points
Lineage-dependent vs competitive development
What regulates sensory / accessory cell differentiation in sensory apparatuses?
- Senses
- General
and special
senses
- Sensory neuron origins
- Neural crest e.g. DRG
- Neural tube e.g. retina
- Placodes, e.g. olfactory epithelium, some cranial nerves (e.g.V)
- C. elegans
- Range of mechanoreceptors
- e.g. gentle body touch, harsh body touch
- Numerous touch-insensitive mutants screened
- Touch cell lineage
- Q cell lineage
- Q cell – Q1a and Q1p
- Q1p gives rise to GBT cell and an interneuron
- Control of Q cell division
- Loss of MEC-3 transforms touch cell
- UNC-86 induces MEC-3
- UNC-86 and MEC-3 combine to
induce touch cell-specific genes
- E.g. involved in
- 15 protofilament
microtubules
- specialised ECM
- A form of lineage-dependent
differentiation – an intrinsic blueprint
- UNC-86 turned on in Q1p
- Loss UNC-86 gives loss of touch cell
- Drosophila
- Mechanoreceptors
- Numerous types of sensory structures
- e.g. mechanosensory
- Derived from sensory organ precursors (SOP)
- SOPs for chordotonal organs express atonal
- SOPs for external receptors express ct
- Single innervated sensilla
- NUMB is
asymmetrically
distributed between
SPIIb and SPIIa
- NUMB inhibits NOTCH pathway
- Low NOTCH activity required for neural fate
- To some extent
lineage-dependent
development
- The drosophila eye
- consists of
~800 ommatidia
- 8 photoreceptors
R1-8
- 12 accessory cells
- Atonal
- During OM development,
atonal expression is ↑ in
R8 by posterior tip Hh
- Atonal and R8 (Hh+)
required for OM formation
- Activates Notch and Delta
producing spaced R8 cells
- Interaction cascade
- Subsequent OM development
depends on cell-cell interaction
- e.g. Bride of Sevenless
on R8 causes R7 to
become a photoreceptor
and not a cone cell
- Development of stereotypy by competition and
rules rather than strict predetermination
- Vertebrate
- vertebrate eye
- Retina - laminar structure
- Derived from neural and non-neural ectoderm
- Requires expression of Pax-6 (eyeless)
- Ventricular progenitors produce types in sequence
- Not separate progenitors
- Neurogenesis of ganglion cells first
- Cell production influenced by environment
- The ear
- develops from the otic placode
- Forms into otic pit then otic vesicle (otocyst)
- VIII ganglion is placodal
- Hair cell development
- Hair cell development regulated by cell- cell interactions
- High notch activation = supporting cells. Low
notch activation = hair cells.
- Retinoic acid and thyroid hormone involved later
- Hair bundle formation
- Poorly understood
- In human deaf/blindness Usher Ib myosin VII a altered
- Ushers Id and If involve cadherins
- Olfactory neurons
- Olfactory receptor cells and secretory cells from basal cells
- Form throughout life
- Olfactory bulb neurons generated (at least in part) from SVZ
- Rostral migratory stream
- Lateral line
- The lateral line
detects water motion
in fish
- Like inner
ear sensory
systems
- Contain sensory
neurons
-neuromasts
- Develops from placodes
- Primordial region of placode
migrates towards the tail
- Deposits neuromasts as it moves