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CORE II Block 4 > Development/differentiation > Flashcards

Development/differentiation Flashcards

1
Q

when is the morula formed?

A

day 4, 8 cells

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2
Q

what are the two parts of the blastocyst?

A

Day 5:

  1. inner cell mass (becomes organism)
  2. outer cell mass (becomes placenta)
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3
Q

Layers of the inner cell mass?

A
  1. epiblast (high in nanog)
  2. hypoblast (high in GATA6)
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4
Q

What layer forms placenta?

A

trophoblast

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5
Q

What layer forms yolk sac?

A

hypoblast of the ICM

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6
Q

What layer forms the organism’s body?

A

epiblast of the ICM

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7
Q

What are the 3 germ layers formed from the epiblast?

A
  1. mesoderm
  2. endoderm
  3. ectoderm
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8
Q

Describe formation of the three germ layers.

A

gastrulation:

  1. epiblast starts as a disc shape
  2. epithelial to mesenchymal transition (ETM)
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9
Q

describe the epithelial to mesenchymal transition (ETM).

A

starting as epithelium:

  1. dissociation of tight junction markers. loss of microvilli
  2. adherent junction and desmosome dissociation. loss of apical-basal polarity
  3. alpha-SMA exprssion. cytoskeletal reorganization. front-back polarity. migration
  4. MMPs upregulation. basement membrane degradation and invasion.
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10
Q

what are the epithelial markers

A
  • e-cadherins (anchoring junctions)
  • claudins (tight junctions)
  • occludins (tight junctions)
  • ZO-1 (tight junctions)
  • desmoplakin (cell-cell anchoring junctions)
  • cytokeratins
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11
Q

What are the mesenchymal cell markers?

A
  • N-cadherin
  • fibronectin
  • collagen I/III
  • Snail
  • alpha-SMA
  • vimentin
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12
Q

What are the key molecules involved in heart organogenesis?

A
  • GATA
  • BMPs
  • Wnt inhibitors
  • Nks2.5
  • Fgf
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13
Q

Describe the development of the heart.

A

Start with cardiac crescent

  1. at 21 days, two endocardial tubes fuse into the primitive heart tube
  2. 22 days, primitive chambers of the heart form
  3. 35 days, aortic arch forms
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14
Q

What is the role of miRNA in heart development?

A

there are many microRNAs that bind mRNAs involved in heart development and affect gene expression.

txn factors and cell cycle factors are also tightly regulated to regulate timing and location of heart development

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15
Q

what does the cardiac mesoderm become?

A

the heart

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16
Q

what does the cardiac neural crest become?

A

these cells migrate to the heart area to become smooth muscle and nervous system cells

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17
Q

what does the proepicardium become?

A

this is below the heart area and becomes the smooth muscle and coronary artery the gives the heart beat

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18
Q

Describe the early development of the lungs.

A
  1. beginning of 4th week, lung buds form from laryngotrachael tube. Splanchnic mesoderm becomes the esophagus
  2. lung buds (trachael buds) turn into trachae and bronchial buds at the end of the 4th week.
  3. more and more branching takes place to increase surface area. respiratory bronchioles form, alveolar ducts form, alveolar sacs, and right before birth surfactin
19
Q

What are the five stages of lung development?

A
  1. embryonic
  2. pseudoglandular
  3. canalicular
  4. saccular
  5. alveolar
20
Q

What are the key molecules and proteins involved in lung development?

A
  1. lung-trachae specification: Tbx5, Wnt2, Wnt2b
  2. lung bud formation: Tbx5
  3. trachae formation: Tbx5, Bmp
21
Q

Describe the mechanism of lung branching.

A
  1. FGF made from mesenchyme cells is bound by FGFR on bud epithelium cells, allowing for growth
  2. Shh protein is released at the tip of the growing epithelial bud, which inhibits FGF production from mesenchyme cells
  3. two new centers of FGF production are formed
  4. two new buds are formed and the whole process repeats
22
Q

What is the result of disruption of apoptosis in interdigital tissues?

A

syndactyly

23
Q

What are the two different axes of polarity for limb development?

A
  1. anterior-posterior
  2. proximal-distal
24
Q

Describe the signaling pathways of limb development.

A
  1. at initiation, the pre-limb is a disc. posterior end is high in e-Wnt, Hoxd and Hand2 (will become zone of polarizing activity, ZPA, which will produce Shh)
  2. distal end is high in FGF and Wnt. Will become the apical ectodermal ridge
25
Q

Define teratology.

A

study of birth defects/congenital malformations

26
Q

What is developmental toxicology?

A

study of environmental chemicals that cause birth defects

27
Q

How frequent are birth defects in total? Heart defects?

A

5% in total

1% for heart defects

28
Q

What are the known causes of birth defects?

A
  • genetic abnormalities
  • infection (rubella, CMV(
  • X-rays
  • smoking
  • alcohol
  • poor nutrition
  • diabetes
  • chemicals/drugs
29
Q

What are the common animal models to study teratology?

A
  • because the embryo stage is the same as humans, we can study
  • fruit flies
  • frog
  • fish
  • chicken
  • mammals (mouse)
30
Q

How can permanent collections of ES cells be made?

A
  1. in vitro fertilization
  2. remove inner cell mass from blastocyst
  3. culture undifferentiated stem cells
  4. grow, freeze, and thaw the ES cell line
31
Q

Pros and cons of making knockout mice?

A

pro: can determine gene function in vivo
con: takes a long time, expensive, viability not guarenteed

32
Q

Describe the process of generating knockout mice.

A
  1. genetically engineered ES stem cells are injected into inner cell mass of recipient blastocyst
  2. injected cells become incorporated into embryo of recipient
  3. blastocyst develops in foster mother into chimeric mouse, because ES cells can contribute to any tissue
33
Q

pros and cons of CRISPR genome editing?

A

pros: can make any time of KO directly to fertilized egg, don’t need ES cells for human therapy
cons: off target effects, because gRNA is not very long

34
Q

Define specification.

A

programming of stem cells to develop along a particular pathway

35
Q

Define differentiation.

A

process by which an unspecialized cell matures to possess a distinct function

36
Q

what are the types of stem cell specification?

A
  1. autonomous specification
  2. syncytial specification
  3. conditional specification
37
Q

Describe autonomous stem cell specification.

A
  • development along a pathway in absence of external influences
  • cells develop according to original fate when removed from embryo
  • remaining cells of embryo cannot replace those that were removed
38
Q

What is the mechanism of autonomouse specification?

A

asymmetric cell division:

unequal distribution of molecules during division

39
Q

Describe syncytial specification.

A
  • nucleus divides without cytoplasmic division
  • different genes are expressed in different nuclei
40
Q

What is an example of syncytial specification?

A

In D. melanogaster, mature egg undergoes nuclear development without cytoplasmic development. bicoid protein and nanos protein are differentially expressed in the nuclei on either pole of the egg.

41
Q

Describe conditional specification.

A
  • fate of cell depends on environment
  • interactions with other cells restrict fate of one or both cells
  • when removed from the embryo, remaining cells alter fate to assume role of missing cels
42
Q

Describe the mechanisms of induction of conditional specification in stem cells.

A
  1. paracrine factors – indirect induction by diffusion of factors from one cell to another
  2. matrix of one cell influences that of another (integrins) – indirect induction
  3. juxtacrine – direct contact between two cells using cadherins and notch.
43
Q

Describe role of indirect induction in limb development.

A

relies on gradient of sonic hedgehog (Shh).

  • formation of each digit has a certain threshold of Shh protein that must be reached for the digit to be formed.
  • as Shh concentration increases, more digits are formed

CORE II Block 4 (6 decks)

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