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stem cells > L2 - Germ cells > Flashcards

L2 - Germ cells Flashcards

1
Q

what do germ cells give rise to

A

eggs and sperm

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2
Q

what is a stem cell niche

A

microenvironment which protects stem cells

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3
Q

when are the key organs developed

A

period of embryonic organogenesis - 3 weeks post fertilisation

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4
Q

when is the fatal period

A

week 8 onward

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5
Q

what is a gonadal germ stem cell

A

specialised totipotent cells set aside in the gonads

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6
Q

what does sexual reproduction require

A

the fusion of gametes to form the fertilised egg (zygote)

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7
Q

where to the primordial germ cells that give rise to the gametes arise

A

arise outside of the gonads and migrate into them

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8
Q

how are the primordial germ cells specialised

A

through a combination of cell non-autonomous signals, cell autonomous cytoplasmic determinants

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9
Q

outline w step process of germ cell determination

A
  1. primordial germ cells are determined in a specific location just on edge or outside of the developing embryo
  2. PGCs migrate to the gonad and become the progenitor population for eggs and sperm
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10
Q

what is needed for germ cell. determination

A

a plastic cell type (totipotent - zygote)

a cell capable of undergoing meiosis

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11
Q

what does division along the meridian line generate

A

2 identical daughter cells

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12
Q

what does division along the equator generate

A

2 different daughter cells

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13
Q

what do p cells inherit

A

P-granules (mix of proteins and RNAs) that are in cytoplasm but can get into nucleus

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14
Q

what do P-granules do

A
  1. bind to DNA of P-cell and block all transcription
  2. in cytoplasm they block translation
  3. promote stem cell fate, cause cells. to undergo meiosis rather than mitosis
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15
Q

where do P cell equivalents lie in vertebrates

A

Germ cells - lies at posterior part of developing embryo

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16
Q

what do Germ cells express

A

Nanos (transcriptional blocker)

17
Q

mechanisms involved in wide spread shut down

A

epigenetic silencing mechanisms

  • DNA methylation, represses gene activity
  • Histone modification, histone proteins govern accessibility of gene promoters
18
Q

what do primordial germ cells arise from

A

extra embryonic mesodendodermal cells just beyond the posterior part of the embryo

19
Q

where are the PGCs determined

A

at the junction of the epiblast/hypoblast

20
Q

what does position of where the PGCs are determined mean ?

A

that they are protected from the signals that are specifying the axes and controlling cell/tissue/organ differentiation

21
Q

what type of divisions can PGCs undergo

A

meiotic NOT mitotic

22
Q

when can PGCs go into the embryo

A

once rapid differentiation and early embryogenesis begins to decrease

23
Q

what are PGCs in drosophila

A

pole cells

24
Q

what to germ cells transcribe in drosophila

A

gene called Vasa

25
Q

how can we follow pole cells

A

by following the expression of vasa

26
Q

describe movement of the pole cells

A

attach to the endoderm and migrate through the midgut

after this they attach to the mesoderm

27
Q

once they leave the midgut where do germ cells go

A

move sideways into future somites, where they are protected in the gonadal niche

28
Q

where do PGCs cell attach in ovaries and testes

A

ovaries - stromal cap

testes - hub cells

29
Q

outline genital ridges

A

provide specialised microenvironment that protects the PGCs in their pluripotent state, then supports their meiotic divisions and formation of either eggs or sperm cells

30
Q

outline the travelling stem cell niche idea

A

supports cells travel with PGCs to maintain the stem cell phenotype
they secrete stem cell factor (SCF)

31
Q

what happens if primordial germ cells fail to migrate out of the gut . fail to be protected in the gonads

A

teratoma is produced

stem cells (4 decks)

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