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I. Ocular Physiology > Lens Development and Differentiation (F) > Flashcards

Lens Development and Differentiation (F) Flashcards

1
Q

What is the first morphological sign of lens development?

A

lens placode

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2
Q

What is the process of secreted, signaling molecules derived from the optic vesicle crossing the extracellular matrix between the surface ectoderm and optic vesicle to trigger the formation of the lens placode and lens development?

A

lens induction

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3
Q

What are BMP proteins important for? 1. Where are they located? 2

A
  1. lens development

2. neural retina and lens ectoderm

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4
Q

What are BMP proteins important for? 1. Where are they located? 2

A
  1. lens development

2. neural retina and lens ectoderm

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5
Q

What molecules derived from the lens placode (future lens), cross the extracellular matrix between the surface ectoderm (future retina) and optic vesicle and facilitates neural retinal development?

A

FGF

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6
Q

What transcription factor triggers expression of a number of additional known transcription factors important for eye development?

A

PAX6

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7
Q

What processes require PAX6?

A
  1. Lens induction
  2. Lens fiber differentiation
  3. Corneal development
  4. Iris formation
  5. Retinal development
  6. Ciliary body
  7. Lacrimal gland
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8
Q

What is the molecule that, if not present, can lead to a lack of an eye?

A

PAX6

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9
Q

What direction does signaling for lens fiber differentiation come from?

A

posterior direction

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10
Q

What is required for lens fiber development?

A

Fgf: fibroblast growth factor

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11
Q

What is required for lens fiber development and differentiation embryonically and after maturation?

A

Fgf: fibroblast growth factor

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12
Q

What do secondary lens fibers differentiate from?

A

lens epithelial cells of the transitional zone

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13
Q

Where does mitosis of the epithelial lens cells take place?

A

the germinative zone

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14
Q

Where does the anterior meshwork of capillaries that surrounds the lens during embryonic development come from? 1. The posterior meshwork? 2

A
  1. iris stroma

2. hyaloid artery

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15
Q

When do the capillaries surrounding the lens during embryonic development regress? 1. What is this regression due to? 2

A
  1. second trimester

2. macrophage-derived signals triggering apoptosis of vessels

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16
Q

What are the three zones of epithelial cells?

A
  1. pregerminative zone
  2. germinative zone
  3. transition zone
17
Q

What are the three zones of epithelial cells?

A
  1. pregerminative zone
  2. germinative zone
  3. transition zone
18
Q

What cell cycle phase does a cell exit in order to be differentiated?

A

G1

19
Q

What are required for cell cycle progression?

A

Cyclin dependent kinase (Cdks) and cyclin

20
Q

What are the proteins that inhibit Cdk proteins and trigger G0 in the lens? 1. What zone do they then enter? 2

A
  1. p27 and p57

2. transition zone

21
Q

What factors lead to more differentiated lens cells?

A
  1. increase age

2. closer relative distance to lens nucleus

22
Q

Where is the index of refraction greater within the lens?

A

higher in center than periphery

23
Q

Where does denucleation occur in the body?

A
  1. erythrocytes
  2. keratinocytes
  3. lens fibers
24
Q

Where does denucleation occur in the body?

A
  1. erythrocytes
  2. keratinocytes
  3. lens fibers
25
Q

What are the events that occur during lens cell denucleation?

A

1) Transcriptional activity ends
2) Gradual nuclear lamina break down
3) fusion of lysosomes with nuclear envelope
4) Dnase IIβ in nuclear compartment
5) chromatin condensation and breakdown

26
Q

What are the intermediate filaments that become phosphorylated triggering disassembly of the nuclear envelope during denuleation?

A

lamins

27
Q

What is the enzyme that breaks down DNA during denuleation?

A

Dnase IIβ

28
Q

What are calcium dependent non-lysosomal proteases (breaks up organelle specific proteins) that mediate organelle breakdown?

A

Calpain

29
Q

What target mitochondrial membrane proteins and facilitates mitochondrial degradation to mediate organelle breakdown?

A

Ubiquitin-proteasomes

30
Q

What target mitochondrial membrane proteins and facilitates mitochondrial degradation to mediate organelle breakdown?

A

Ubiquitin-proteasomes

31
Q

What are the functions of α-crystallin? 1. What triggers its expression? 2

A
  1. Contributes to refractive power and bind up proteins that have a tendancy to unfold (“chaperone” function)
  2. PAX6 and FGF
32
Q

What makes up 50% of total protein in lens cells?

A

aquaporins

33
Q

How are lens fibers held together?

A
  1. adherin junctional proteins (N-cadherin, catenins)

2. ball-and-socket junctions

34
Q

What is required for some proteins to penetrate deeper layers within the lens with fiber cell fusions?

A

Lim2

35
Q

What is required for some proteins to penetrate deeper layers within the lens with fiber cell fusions?

A

Lim2

36
Q

What re the highly organized cytoskeletal structures that mediate the ordered arrangement of lens fibers?

A
  1. Actin filaments

2. Actin filament orgainizers (Tropomodulin and Spectrin)

37
Q

What is required for some proteins to penetrate deeper layers within the lens with fiber cell fusions?

A

Lim1

I. Ocular Physiology (20 decks)

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