Retina Development

Question 1

When does eye development begin?

Answer 1

week 4 –> 8 years post natal

Question 2

neural tissues (forebrain) forms

Answer 2

retina, RPE, iris, ciliary body

Question 3

surface ectoderm forms

Answer 3

lens, eyelids, cornea

Question 4

neural crest forms

Answer 4

cornea, ciliary body

Question 5

mesenchyme forms

Answer 5

sclera, blood vessels

Question 6

5 parts of neural tube

Answer 6

telencephalon 
diencephalon 
mesencephalon 
metencephalon 
myelencephalon

Question 7

Eyes are outgrowings of?

Answer 7

the diencephalon - optic vesicles

Question 8

optic vesicles reach what and what happens?

Answer 8

surface ecoderm - induces lens placode

optic cup folds - bilayer optic cup

Question 9

posterior region of optic cup

Answer 9

optic stalk - blood vessels and axons

Question 10

lens placode invaginates to form what?

Answer 10

lens vesicle

Question 11

what does lens placode lose contact with?

Answer 11

surface epithelium

Question 12

2 parts of optic cup

Answer 12

retina and RPE

Question 13

what does lens vesicle make?

Answer 13

lens

Question 14

what induces formation of cornea?

Answer 14

signals from lens

Question 15

spemann and Lewis, 1900

Answer 15

amphibians - contact of optic nesicle with surface ectoderm - form lens
remove optic vesicle = no lens placode

Question 16

Later optic vesicle/lens induction experiments

Answer 16

lens like structure can form

differences in timing of inductive events between species

Question 17

Can all ectoderm form a lens? why?

Answer 17

no - at gastrulation head ectoderm bias towards lens fate

Question 18

optic vesicle transplanted to trunk

Answer 18

no lens

Question 19

lens signalling back to optic vesicle

Answer 19

lens induce expression in distal optic cup of genes - Chx10, Lhx2 for neural retina development

Question 20

dissect of epithelium or rotate optic vesicle - retina genes

Answer 20

no expression as no lens

retina genes where normally RPE

Question 21

signals from where pattern optic cup?

Answer 21

lens and extraocular mesenchyme

Question 22

extraocular mesenchyme - RPE genes

Answer 22

upregulate

Question 23

where is pax 6 expressed?

Answer 23

widely in developing eye - optic cup and lens vesicle

Question 24

master regulator of eye development

Answer 24

pax6

Question 25

mouse - pax 6

Answer 25

``` +/- = microphthalmia - small eyes -/- = no eyes ```

Question 26

Pax 6 +/- humans

Answer 26

no iris, cataract, glaucoma

Question 27

other genes essential for eye development

Answer 27

Rx - retinal homeobox | six3

Question 28

genes eye development - early distribution

Answer 28

pax 6, rx and six 3 continuous across early neural plate | single eye field

Question 29

What splits eyefield in two?

Answer 29

shh in midline of neural tube

Question 30

what does shh activate?

Answer 30

expression of genes required for optic stalk development eg pax 2

Question 31

what does shh repress?

Answer 31

expression of genes required for optic vesicle development eg pax 6

Question 32

pax 6 and pax 2

Answer 32

mutual repressors

Question 33

cyc -/- or shh -/-

Answer 33

pax 6 not repressed at midline - no activation of pax2 | form single large optic cup

Question 34

increased shh in midline

Answer 34

increased repression pax 6 and increased activation pax 2 | smaller eye field

Question 35

cyclopia in humans

Answer 35

rare disrupt shh signalling associated with cranial defects lose midline structures

Question 36

what is nasal/temporal and dorsal/ventral patterning of retina needed for?

Answer 36

visual function - green cones in dorsal and blue cones ventral mapping retina onto visual targets - positional identity

Question 37

what cells relay visual info from eye to brain?

Answer 37

RGC

Question 38

primary target of RGC

Answer 38

amphibians = tectum | humans - LGN, some to superior colliculus

Question 39

dorsal and ventral RGC axons to tectum

Answer 39

dorsal - lateral | ventral - medial

Question 40

nasal and temporal RGC axons to tectum

Answer 40

nasal posterior | temporal - anterior

Question 41

transcription factors imposing n/t and d/v specificty of optic cup

Answer 41

nasal - Foxg1 and SOHO1 temporal - Foxd1 dorsal - Tbx5 ventral - Vax2

Question 42

What does vax 2 in ventral retina induce expression of?

Answer 42

EPHBs

Question 43

Express EPHB in dorsal retina also or KO

Answer 43

``` dorsal = ventral and dorsal RGC map medially KO = both map laterally ```

Question 44

retina cell types

Answer 44

6 neuronal cell types and muller glia | rods, cones, horizontal, bipolar, amacrine, RGC

Question 45

Retinal progenitor cell fate

Answer 45

became all major types but biased

Question 46

generation of retinal cell types

Answer 46

stereotypical sequence | ganglion cells first, amacrine, horizontal, cones, rods, bipolar, muller glia

Question 47

waves of retinal neurogenesis

Answer 47

central - peripheral

Question 48

ciliary margin

Answer 48

far peripheral retina | neurogenesis continues here in lower vertebrates throughout life - stem cells?

Question 49

asymmetric and symmetric division of progenitor cells

Answer 49

``` symmetric = 2 progenitor or undifferentiated cell asymmetric = 1 of each ```

Question 50

where are RGC found?

Answer 50

inner most surface of retina

Question 51

where do progenitor cells divide?

Answer 51

adjacent to RPE

Question 52

what happens to progenitors that differentiate as RGC?

Answer 52

basal process to vitreal surface nucleus migrates axon extends into OFL break attachment of apical surface

Question 53

what triggers the initial central patch of differentiated RGCs?

Answer 53

FGFs

Question 54

evidence for FGF - central RGC

Answer 54

FGF expressed in central retina/optic stalk before neuogenesis block FGF inhibits neurogenesis

Question 55

what drives RGC differentitation in fish?

Answer 55

shh

Question 56

RGC differentiation in fish

Answer 56

wave of shh - self propagating | disrupt shh signal = neurogenesis initiates but fails to spread normally

Question 57

commitment to RGC fate - important

Answer 57

notch/delta signalling - premature differentiation, overproduction RGC Atho7 - no RGC Islet2 - born but fail to differentiate and die

Question 58

retinal cell types - bias

Answer 58

eg VC1.1 -ve = cones +ve = amacrine/horz +ve then -ve = rods

Question 59

generation of retinal cell types

Answer 59

cannot go back or skip a step controlled by transcription factors environment