Development of sense organs

Question 1

what are three sensory neuron origins? give examples for each.

Answer 1

neural crest - DRG
neural tube - Retina
placodes - olfactory epithelium and some cranial nerves e.g V

Question 2

in c.elegans what do the mechonoreceptors respond to?

Answer 2

ranges from gentle body touch to harsh body touch.

Question 3

what happens to the Q-cell?

Answer 3

• Q-cell divides to produce Q1a and Q1p

- these then divide and one of the daughter cells disappear

Question 4

what does Q1p give rise to? what does Q1a give rise to?

Answer 4

Q1p gives rise to gentle body touch cell and an interneuron

g1a gives rise to another sensory cell

Question 5

where is UNC-86 turned on in? what does loss of UNC-86 lead to?

Answer 5

UNC-86 turned on only in Q1p
loss of UNC-86 gives loss of touch cell
the cell that should have been Q1p just turns into the mother cell again, this repeats.

Question 6

what happens when the MEC-3 protein is lost?

Answer 6

the touch cell is transformed

Question 7

what induces MEC-3 what does this lead to?

Answer 7

UNC-86 protein induces MEC-3, these then combine to induce a touch cell specific genes that are involved

Question 8

what kind of differentiation does this UNC-86 and MEC-3 form?

Answer 8

lineage-dependant differentiation, like an intrinsic blueprint

Question 9

where are drosophila mechonoreceptors derived from?

Answer 9

sensory organ precursers

Question 10

what gene does SOPs for chordotonal organs express?

Answer 10

atonal

Question 11

what gene does SOPs for external receptors express?

Answer 11

ct

Question 12

what happens to numb distribution?

Answer 12

it is asymettrically distributed between sp11b and sp11a which are the first division daughter cells.

Question 13

what does numb do? what is this required for?

Answer 13

inhibits the Notch pathway, low NOTCH activity is required for neural fate.

Question 14

what does one daughter cell that’s going down the neural fate do to the other daughter cell?

Answer 14

it inhibits the other daughter cell from going down the neural fate.

Question 15

what kind of development is the pathway that includes notch and numb?

Answer 15

to some extent is can be seen as lineage independant however not completely as there’s ability for plasticity due to cell-cell interactions

Question 16

what does the drosophilla eye consist of?

Answer 16

around 800 ommatidia
8 photoreceptors, R1- R8
and 12 accessory cells

Question 17

what is required for ommadidia formation?
how is this activated?
what does this then activate?

Answer 17

Atonal, R8 and Hh are required
atonal is activated in R8 by posterior tip Hh
this activates Notch and delta pathways which produce spaced R8 cells

Question 18

what does subsequent ommatidia development depend on?

Answer 18

it depends on cell -cell interactions

Question 19

where is the bridge of sevenless and what does this cause?

Answer 19

bridge of sevenless is on R8 and causes R7 to become a photoreceptor and not a cone cell

Question 20

what is development of stereotypy by? whatis this rather than?

Answer 20

by competition and rules rather than strict predeterminations

Question 21

in the vertebrate eye:

• what kind of structure is the retina?
• what is it derived from?
• what does is require expression of?

Answer 21

it’s a laminar structure
derived from neural and non-neural ectoderm
it requires the expression of Pax-6 (eyeless)

Question 22

how do ventricular progenitors produce types?

Answer 22

in sequence

Question 23

are there seperate proginators?

Answer 23

no, they can shift their production of one type of neuron to another.

Question 24

what cell types come first in neurogenesis?

Answer 24

ganglion cells.

Question 25

what is cell production by the proginator influenced by?

Answer 25

the environment?

Question 26

when progenita cells are labelled the 3H-thymadine what can be seen at embryonic 14?
what’s seen postnatally?

Answer 26

E14, there’s both rods and RGC however there’s mainly RGCs

postnatally there’s noth Rods and RGCs however there’s more rods

Question 27

if these are mixed together what is seen?

Answer 27

have to wait until lecture slide to answer this

Question 28

where does the ear develop from?

Answer 28

the otic placode

Question 29

what does the otic placode form into? then?

Answer 29

forms into the otic pit and then the otic vesicle (otocyst)

Question 30

where does the VIII ganglion come from?

Answer 30

it is placodal, it comes from the otic placode

Question 31

what is hair cell development regulated by?
what cell form with high NOTCH activation?
what cell is formed from low NOTCH activation?
what two things are involved later on in hair cell development?

Answer 31

it is regulated by hair-hair interactions
high NOTCH = becomes a supporting cell
low NOTCH = becomes a hair cell
retonoic acid and thyroid hormone are involved later

Question 32

what is altered in human deaf/blindness?

Answer 32

Usher Ib myosin VIIa

Question 33

what do Usher Id and If involve?

Answer 33

cadherins

Question 34

why are olfactory cells lost regularly? why isn’t this a problem.

Answer 34

due to exposure

isn’t a problem because rthere’s progenitor cells in the epithelium ready to make new ones.