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Biology 467 > Retinal Development > Flashcards

Retinal Development Flashcards

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1
Q

Which area of the developing CNS gives rise to the retina?

A

The diencephalon

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2
Q

The extension of the CNS which forms the retina begins to form right after…

A

Neural tube formation

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3
Q

The first sign of the developing retina in a human embryo occurs on this day, usually

A

22

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4
Q

Invagination of the lens placode and evagination of the optic vesicle forms this structure

A

Optic cup

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5
Q

The mutation which results in small eyes is called…

A

Micropthalmia

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6
Q

The mutation causing micropthalmia is called…

A

Ocular retardation: mutant gene is orJ

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7
Q

Another name for Chx10 is…

A

Vsx2

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8
Q

The orJ mutation is a mutation affecting this protein…

A

Chx10

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9
Q

Describe the mouse orJ mutation: how does it result in micropthalmia?

A

There is a tyrosine (Y) at 176, which results in a stop codon, resulting in a truncated Chx10 protein

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10
Q

Define the human micropthalmia mutation

A

R200Q (arginine to glutamine) - same as mouse results in a truncated protein

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11
Q

Chx10 is exclusively expressed in this area of the eye…

A

The retina

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12
Q

If Chx10 is only expressed in the retina, why are there mutations to the lens and the cornea in micropthalmia?

A

The retina secretes different signaling factors: a lack of signals could result in structural defects

Key: secondary, cell non-autonomous effects

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13
Q

When in retinal development is Chx10 expressed?

A

Early, when the retina is mostly comprised of progenitor cells

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14
Q

What are the 7 primary cell types of the retina?

A

Rods, cones, bipolar cells, horizontal cells, amacrine cells, muller glia, ganglion cells

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15
Q

Rods are good for detecting…

A

Low light at night

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16
Q

Cones are good for detecting…

A

Colour, good for daytime vision

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17
Q

What are the 3 types of cone?

A

Each type expresses a different opsin, for R G or B light

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18
Q

In what layer of the retina do photoreceptors synapse to bipolar cells?

A

In the inner nuclear layer

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19
Q

Where are the cell bodies of muller glia located?

A

Inner nuclear layer

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20
Q

What is the proposed purpose of muller glia?

A

Form a scaffolding for other retinal cell types and scavenge ions

21
Q

Which cells are responsible for lateral inhibition?

A

Horizontal cells

22
Q

Bipolar cells form circuits with these two cell types

A

Amacrine and Ganglion cells

23
Q

What is the output cell of the retina which projects towards the brain?

A

Ganglion cells

24
Q

Thinking about the interactions of Chx10 with other proteins, why do people with the micropthalmia mutation have small eyes?

A

Chx10 normally inhibits Kip1 which is a cdk inhibitor. With kip1 active, cdk and cyclin D1 will be inactive and the cell will not progress to S phase, cells will exit the cell cycle (G0) and will differentiate prematurely into retinal cells

decreased proliferation because progenitor pool is depleted

25
Q

What happens to a Chx10-Kip1 double mutant? Is the retina larger? What does this mean?

A

The phenotype is actually more similar to wild type, don’t get enlarged retina

There must be another factor acting redundantly with Kip1 to regulate cell cycle exit

26
Q

What is unusual about the bipolar cells of Chx10 mutants?

A

They don’t have bipolar cells

27
Q

What molecule is required for bipolar cell specification?

A

Chx10

28
Q

What are 2 roles for Chx10 in retinal development?

A
  1. regulate cell cycle exit
  2. specification of bipolar cells
29
Q

Describe this experiment (not the results, just the methodology)

A

Authors were interested in learning about retinal progenitor divisions and engineered a retrovirus which would stain progenitors, but injected such a low amount such that it would affect only one cell. Then, the authors visualized the divisions of that cell because they were stained with beta-galactosidase

30
Q

What were the key results of this experiment?

A

Progenitors gave rise to the following cell types:
Rods
Bipolar cells
Amacrine cells
Muller glia

31
Q

Why did the authors of this experiment not observe any cones or ganglion cells which arose from progenitors?

A

There is temporal ordering of retinal cells during development - those cells are born earlier than the cells they observed

32
Q

A single retinal progenitor cell can give rise to (a single/multiple) type(s) of retinal cell

A

Multiple

33
Q

What is a key factor which regulates retinal progenitor multipotency (ability to give rise to multiple cell types)

A

Pax6

34
Q

What kind of protein is Pax6?

A

Homeodomain transcription factor

35
Q

What does it mean to say that retinal progenitors are thought to progress through multiple states of “competence”

A

At different times depending on the factors present (and the concentration of these factors), retinal progenitors may choose to differentiate into different retinal cell types. These windows are overlapping

36
Q

What cell types are born “early”

A

Ganglion cells, cones, horizontal cells, amacrine cells

37
Q

What cell types are born “late”

A

Rods, muller, bipolar cells

38
Q

A loss of function of Pax6 leads to…

A

Anopthalmia (being born with no eyes)

39
Q

Define conditional gene targeting

A

Making constructs where genes can be temporarily or conditionally knocked out so that loss of a gene does not adversely affect other aspects of development in a model

40
Q

What are the 2 requirements for cre-lox site specific recombination?

A

DNA that you want to remove must be flanked by loxP sites (“floxed”)

Need tissue-specific or cell-specific cre recombinase expression

41
Q

How does cre remove DNA?

A

Cleaves DNA at the loxP sites so that floxed region of DNA will be excised

42
Q

What are P0 and alpha of the Pax6 gene?

A

P0 = promoter
alpha = enhancer

43
Q

In a transgene construct of P0 and alpha (Pax6 gene) where they are combined upstream of the LacZ marker, where do these regulatory regions direct transcription to?

A

The distal retina

44
Q

How was the alpha region of Pax6 identified?

A

Among several species, this intron region was highly conserved: must have important regulatory role

45
Q

In conditional knockouts of Pax6, which retinal cell types are severely downregulated? Which are not affected?

A

Loss: bipolar, ganglion, muller, PRs

Unaffected: Amacrine

46
Q

If all retinal cells express Pax6, and Pax6 is required for differentiation into different retinal cell types, how are these different types specified?

A

Pax6 works in concert with other downstream TFs at different times to create all the different cell fates

47
Q

What are the 2 categories of downstream TFs that Pax6 (and other related molecules) activate to induce different retinal cell fates?

A

Basic helix loop helix
Homeodomain TFs

48
Q

What does crispr stand for?

A

Clustered regularly-interspaced short palindromic repeats

49
Q

Where does crispr come from?

A

Bacterial adaptive immunity system

Biology 467 (20 decks)

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