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L2 Stem Cells > Postembryonic growth > Flashcards

Postembryonic growth Flashcards

1
Q

What are the 3 ways in which organisms can grow?

A
  • Cell proliferation
  • Cell enlargement
  • Accretion (bone)
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2
Q

What is accretion?

A

Depositing matrix between cells which causes growth

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3
Q

Which molecules drive the cell cycle? (2)

A
  • Cyclins
  • Cdks
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4
Q

What are the phases of the cell cycle? (4)

A
  • G1
  • S
  • G2
  • Mitosis
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5
Q

What does the G in G1/G2 etc. stand for?

A

Gap

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6
Q

What happens during S phase of the cell cycle?

A

DNA replication (synthesis)

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7
Q

Which molecules control G1 phase? (3)

A
  • Cdk 4/6
  • Cyclin D
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8
Q

Which molecules control S phase? (2)

A
  • Cdk2
  • Cyclin E
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9
Q

Which molecules control G2 phase? (2)

A
  • Cdk2
  • Cyclin A
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10
Q

Which molecules control mitosis? (3)

A
  • Cdk1
  • Cyclin A/B
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11
Q

How does cell proliferation occur in drosophila during early development? (4)

A
  • Egg is a syncytium
  • Nuclei undergo rapid division without G1/G2 phases (S to M repeats)
  • Division uses maternal String protein until cycle 14 where the zygotic genes kick in
  • At cycle 14 division slows, G2 is included, cellularisation occurs
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12
Q

What is String? (2)

A
  • A phosphatase which activates CDKs resulting in cell division
  • Controls mitotic domains
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13
Q

What is String expression controlled by? (2)

A
  • Patterning genes (Gap, Pair rule, segment polarity, Dorsal/Ventral genes)
  • This links patterning to proliferation
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14
Q

What is a mitotic domain?

A

Regions where cell division is occurring differently to form different tissues

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15
Q

Which gene controls mitotic domains?

A

String

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16
Q

Where is String action blocked in drosophila development? (2)

A
  • String is blocked by Tribbles in the mesoderm
  • Mesoderm needs to invaginate which requires cell migration not proliferation
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17
Q

Is the control of the growth programme for limbs intrinsic or extrinsic? (2)

A
  • Intrinsic control
  • If you transplant a limb from a large newt to a small newt, the limb will grow to its correct size which is too large for the recipient newt
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18
Q

Is control of organ size intrinsic or extrinsic? (4)

A
  • Depends on the organ
  • Thymus is intrinsic
  • Spleen is extrinsic/systemic
  • Growth programmes can be flexible e.g. liver regrowth
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19
Q

How is organ/animal size determined? (3)

A
  • Size is not determined by the number of cells in the organ/animal
  • The absolute dimensions matter more than the number of cells
  • Morphogens control the number of cells
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20
Q

What are 2 important growth control pathways?

A
  • TOR
  • Hippo
21
Q

What does the TOR pathway control?

A

Cell size

22
Q

What happens to cells when TOR signalling is active?

A

Cells increase in size

23
Q

What does the Hippo pathway do?

A

Limits organ size

24
Q

How does the Hippo pathway work? (3)

A
  • When Hippo is inactive, nuclear localisation of transcription factor Yki (drosophila)/Yap/Taz (mammals) which causes growth and survival of cells
  • When Hippo is active, Yki/Yap/Taz is excluded from the nucleus
  • Hippo signals to stop growth
25
Q

What is the equivalent of the Hippo pathway in vertebrates?

A

Mst1/2

26
Q

What activates Hippo? (2)

A
  • Cell-cell contact
  • Cell polarisation
27
Q

What inactivates Hippo? (3)

A
  • Mechanical stress
  • Stiff ECM
  • Signalling from GPCRs
28
Q

What happens to cells when Hippo signalling is active? (2)

A
  • Suppression of cell proliferation
  • Promotion of apoptosis
29
Q

What happens to cells when Hippo signalling is inactive? (2)

A
  • Promotion of cell proliferation
  • Suppression of apoptosis
30
Q

What determines overall size in drosophila?

A

Insulin signalling affects the duration and rate of larval growth

31
Q

Which hormones are involved in determining overall size in mammals? (2)

A
  • IGF1, 2
  • GH
32
Q

What is GH?

A

Growth Hormone

33
Q

How does GH signalling promote growth? (2)

A
  • Stimulates IGF1 synthesis in the liver which circulates
  • Stimulates local IGF1 synthesis in bone
34
Q

How is negative feedback involved in GH signalling? (3)

A
  • IGF1 inhibits GH production
  • GH stimulates production of somatostatin which inhibits GH production
  • GH blocks the production of GHRH
35
Q

Where is GH produced?

A

Pituitary gland

36
Q

What is GHRH?

A

Growth Hormone Releasing Hormone

37
Q

How does the maternal environment influence growth? (2)

A
  • Low birth weight is associated with coronary heart disease
  • Severe caloric restriction during pregnancy puts babies at higher risk for obesity and diabetes
38
Q

What is ecdysis?

A

The process of moulting

39
Q

What is an instar?

A

The developmental stage between each moult

40
Q

What is the process of ecdysis? (5)

A
  • Stretch receptors in the epidermis signal to the CNS
  • Prothoracicotropic hormone is released
  • Causes ecdysone release from the prothoracic gland
  • Activates enzymes which release the cuticle from the epidermis
  • Shedding
41
Q

What is the process of metamorphosis in insects? (2)

A
  • Environmental cues stimulate release of prothoracicotropic hormone (PTTH) which causes ecdysone release from the prothoracic gland
  • Ecdysone and juvenile hormone are balanced until an increase in ecdysone stimulates pupation
42
Q

What is the process of metamorphosis in tadpoles? (4)

A
  • Environmental cues act on the hypothalamus which releases corticotropin releasing hormone (CRH)
  • CRH stimulates thyroid stimulating hormone (TSH) release from the pituitary
  • TSH causes the thyroid to produce thyroxin (T4T3)
  • Thyroxin and prolactin are balanced until there is increased thyroxin which drives metamorphosis and does positive feedback on the hypothalamus and pituitary
43
Q

What are the tissue specific effects of thyroxin in frogs? (3)

A
  • Promotes limb growth
  • Promotes tail degeneration
  • Modulates tissue responsiveness to oestrogen
44
Q

Which tissues is cancer most common in?

A

Tissues that continue to divide throughout life e.g. epithelia and blood

45
Q

What is a proto-oncogene?

A

A gene which becomes an oncogene after a mutation causes it to be inappropriately activated

46
Q

What is a tumour suppressor gene?

A

A gene which normally suppresses cancer but can lead to cancer after inactivation

47
Q

What are examples of tumour suppressor genes? (2)

A
  • Retinoblastoma
  • p53
48
Q

What are examples of proto-oncogenes? (2)

A
  • Ras
  • Epidermal Growth Factor Receptor (EGFR)
49
Q

How are developmental signalling pathways involved in cancer? (2)

A
  • Proto-oncogenes/tumour suppressor genes are often involved in developmental signalling pathways
  • Aberrant developmental signals can drive cancer

L2 Stem Cells (12 decks)

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