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MM Development > Gastrulation and Asymmetry > Flashcards

Gastrulation and Asymmetry Flashcards

1
Q

sperm capacitated

A

made competent for fertilization by an unknown process (change in acrosome, sperm’s digestiv ezyme)

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2
Q

cumulus cells

A

also called follicle cells, surround egg.

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3
Q

sperm cross cumulus by

A

releasing acrosome

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4
Q

why one sperm only?

A

acrosome causes wave of Ca in oocyte, causes cortical granules in oocyte to fuse with zona pellucida

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5
Q

the first cleavage

A

combines the two pronuclei of egg and sperm

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6
Q

reductive cleavage

A

after first, cells get smaller after every split into many cells called blastomeres

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7
Q

blastomeres are totipotent up to

A

+/- 4 cell stage

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8
Q

compaction

A

occurs at 8 cell stage, determines inside and outside

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9
Q

only a few of the compancted cells become epiblastic, meaning

A

progenitors of the embryo

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10
Q

Trophectoderm

A

16 cell stage, outside cells, determined by Cdx

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11
Q

Cdx 2

A

turned on in edge cells via hippo pathway

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12
Q

Hippo pathway

A

inside cells have high cell-to-cell contact, so Yap is phosphorylated and does NOT enter the nucleus to turn on cdx

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13
Q

what TF determines inner cell mass?

A

Oct-4 (makes ES cells)

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14
Q

inner cell mass is the same as

A

ES cells

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15
Q

primitive endoderm (hypoblast) Tfs

A

gata6, gata4

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16
Q

primitive ectoderm Tf

A

nagog

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17
Q

apoptosis in first week

A

20% of cells. Why? Nobody knows!

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18
Q

by end of first week, trophectoderm becomes

A

placenta

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19
Q

by end of first week, inner cell mass becomes

A

epiblast making ectoderm, mesoderm, definitive endoderm AND parietal and visceral endoderm

20
Q

implantation: blastocele facing ____, epiblast facing ____

A

blastocele outward, epiblast inward toward uterine wall

21
Q

TGFbeta factor Nodal

A

binds TGFbeta s/t receptors and coreceptor Cripto, turns on SMAD2/3 and SMAD 4

22
Q

SMAD 2/3 and SMAD 4

A

bind foxh1 promotor, turns on Nodal and Lefty, a Nodal inhibitor

23
Q

How does Lefty inhibit Nodal?

A

binds to its TGFbeta receptor

24
Q

Nodal morphogen function

A

diffuses, elicits dose dependent response (ratio of nodal and lefty)

25
Q

Nodal /Cripto is expressed throughout

A

the epiblast

26
Q

distal visceral endoderm sets up oppositional field using

A

Lefty and Cerberus, both Nodal inhibitors

27
Q

Anterior cells express highest level of what where?

A

Lefty and Cerberus, anterior (head)

28
Q

Posterior cells express highest level of what where?

A

Nodal and Crypto, at the primitive streak in the posterior wall of the embryo

29
Q

Because lefty diffuses farther than nodal:

A

reduces range of Nodal to a discreet zone on the posterior (future caudal) side of embryo

30
Q

Wnt3 inhibitor

A

DKK1

31
Q

Wnt inhibitors are

A

posterior, like with Nodal

32
Q

gastrulation happens when?

A

third week

33
Q

gastrulatio nmeans what?

A

Epiblast cells migrate into streak and under epiblast.

34
Q

what do gastrulating epiblasts creat first?

A

definitive endoderm, then cells generating mesoderm

35
Q

epiblasts are what initially?

A

epithelial cells, but convert to mesenchyme during migration

36
Q

how do epithelial cells convert to mesenchyme?

A

downregulation of epithelial adhesion proteins, expression of SNAIL (inhibits e-cadherin expression) and CXCR4 (a receptor of SDF1, a “promigratory” pathway)

37
Q

cells moving to the anterior end of the cell in gastrulation

A

become axial-prechordal mesoderm & cardiac mesoderm

38
Q

what organizes the axis?

A

blastopore lip, through Wnt8 and Nodal

39
Q

head and neural tissue formation

A

anterior visceral endoderm signals to the epiblast, uses Lefty and Wnt to protect the head

40
Q

Dorsal-ventral patterning

A

signals between notochord and neural plate, via SHH.

41
Q

Left-right development disorders

A

situs inversus, isomerism (symmetrical), heterotaxia (random)

42
Q

symmetry broken by flow of fluid how?

A

cilia! (ciliary defects cause situ inversus, “Kartagener’s disease” in humans)

43
Q

assymetry propagates via what signal?

A

Nodal

44
Q

Nodal induced on which side?

A

Left, with lefty, who inhibits Nodal particularly on the right!

45
Q

Left side Nodal signal turns on

A

Pitx2 expression, Islet1, who maintain assymetry via magic.

46
Q

When Nodal coreceptor Criptic is inhibited

A

randomized postion of organs, e.g., right pulmonary isomerism, wrong-sided aorta

MM Development (9 decks)

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