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ANAT 381 > Making Eggs > Flashcards

Making Eggs Flashcards

1
Q

describe pre natal FEMALE GERM CELL DEVELOPMENT – OVERVIEW

A

generation of starting population of oocytes
all go through same prenatal

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2
Q

describe post natal FEMALE GERM CELL DEVELOPMENT – OVERVIEW

A

after birth
growth of the oocyte and its follicle
happens at different times - not all at once
meiotic maturation of fully grown oocyte - after oocytes grown

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3
Q

describe prenatal oocyte development - onwards

A

pcgs generate and migrate to genital ridge – proliferate- if become oogonia = meiosis, oocytes enter meiosis and assemble into primordial follicles - before birth - up to 6 months babygirl
starts cycle - after puberty - some before, after birth

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4
Q

what happens to oocyte population after birth

A

declines steadily after birth
~300,000 - make many oocytes but once 5 months old = steadily decrease
ends up ~1000 at 50 y/o
hard to get data from humans

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5
Q

what happens to oocyte population after birth - in mice

A

oocytes goes down before birth
what is reason to make so many then eliminate before birth = do not know theories = fetal ovary can sense unhealthy oocytes, do no know how they identify bad ones, also not all are actually individualized cells, some joined by cytoplasmic bridges * nurse cells, 1 oocyte –> 15 nurse cells that help oocyte, feed components to one winning oocyte, NO EVIDENCE THO
not super big decrease before birth in humans - could be true but not sure

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6
Q

describe the post natal ovarian follicles - histology components

A

preovulatory follicle - shortly before ovulation
much bigger - must become very large since all components
many oocytes of primordial follicles - begun meiosis (recomb) then arrest
surrounded by small molecules of follicle cells

concentric circles
oocyte = cells
zona pellucida = not cell, extracellular coat
granulosa cells = close to oocyte
antrum = space
theca = outside bm, more elongated -stretched nuclei
blood vessels run in interstitial space between follicle - not inside, always around

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7
Q

name stages of oocyte and follicle growth

A

primordial
primary
antral
pre ovulatory (graafian)

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8
Q

describe stages of oocyte and follicle growth- primordial

A

oocyte
small number granulosa cells enclose

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9
Q

describe stages of oocyte and follicle growth- primary

A

Granulosa cells activate and begins growth, enlarges
granulosa cell proliferation mitotically
Multiple layers to enclose oocyte which is grown

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10
Q

describe stages of oocyte and follicle growth-antral

A

theca cells outside
antrum = later in development, space between population of granulosa cells, filled with fluid (cavity), growth factors and steroids
antrum gets bigger - very big, before ovulation

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11
Q

describe stages of oocyte and follicle growth- pre ovulatory

A

antrum increase in size = more and more fluid
mural granulosa cells = close to theca cells
cumulus granulosa cells = around oocyte
these 2 categories = express diff genes and have diff functions

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12
Q

describe growth of oocyte and its follicle - length

A

very slow
3-4 months of oocyte and follicle to complete growth once it started
ex = begin to grow in jan, completed - ready to be ovulated in march/april
super slow growth (primordial to ready oocyte for fertilization)

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13
Q

describe how/when primordial follicles enter growth phase

A

cohorts of primordial follicles continuously enter growth phase
enter into growth phase at different times
like leaky sink

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14
Q

why is the continuous entry of primordial follicles into growth phase important

A

ensures all follicles not used up at once
regulation of entry into growth phase
so always follicles to ovulate, so do not use all at once
Follicles can continue to grow into menopause

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15
Q

where do all the oocytes go

A

1- oocytes grow and are ovulated (12x~40 =~500)
2- oocytes begin but do not complete growth, are not ovulated
3- oocytes do not grow and are eventually degraded
do not know where most of them go

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16
Q

describe initiation of growth - histologically

A

primordial = squamous granulosa cells, nuclei of granulosa elongated thin form
primary = cuboidal granulosa cells, spherical form, change shape now = more cuboidal
can recognize follicle has begun to grow by changed shape granulosa

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17
Q

describe initiation of growth - signals from granulosa cells - gen

A

maybe signal comes from granulosa cells
known to be a ligand receptor pair active in follicles

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18
Q

describe initiation of growth - signals from granulosa cells - ligand and receptor

A

granulosa = produces kit ligand
oocyte = expresses kit receptor
also play roles in other cells too

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19
Q

what is kit receptor - describe initiation of growth - signals from granulosa cells

A

receptor tyrosine kinase
growth factor binds = signalling pathway = end result is increase in protein synthesis, triggers initiation into oocyte growth
cancer when pathways deregulated

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20
Q

what happens if increase kit ligand

A

growth

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21
Q

what happens if inhibit kit ligand

A

no growth

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22
Q

what activates primordial follicles

A

local relaxation of ovarian stroma

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23
Q

describe experiment - for activation of primordial follicles- generally

A

exp 1 = made cuts in ct of ovary = stimulated to grow
other = eggs and granulosa only, cells reconstructed, ended up growing and no ct there

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24
Q

describe experiment 1 - for activation of primordial follicles- A B C D

A

A= regular, starting situation
B = partial digest small pieces with enzyme = partially degrade ct
C= that was enough to trigger growth, but if increase pressure = growth stops
D= cell in mitosis
made cuts in ct, stimulated eggs to grow, something about ct between follicles = prevents from growing unless activated = appropriate signal

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25
Q

what prevents growth of follicle - fully explain

A

dense matrix of ct between follicles - exerts pressure and flattens granulosa cells = prevent growth of follicle
local degradation of ct = oocyte can growth, so pressure released
change in ct sends signal to granulosa which then sends signal to oocyte to start growing
do not know what degrades ct, could be blood vessels - release factors that degrade matrix
TIGHTLY REGULATED SO SUPPLY LASTS THROUGHOUT REPRODUCTIVE LIFE

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26
Q

what happens when oocyte grows - vol/accumulate

A

volume increases by factor of 100 10x diameter
by end = almost 100 microns - by time finished growth = one of biggest cells in body

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27
Q

what does oocyte while growing store

A

Translated mrna, stored mrna and mitochondria
mrna, proteins, ribosome, standard cell components
accumulates factors needed for growth and for embryo (for few days after fertilization)

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28
Q

how many kinds of messages does oocytes store

A

2 kinds = translated and untranslated
very transcriptionally active when growing

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29
Q

describe the translated messages oocyte stores

A

acquire poly a tail in nucleus, 3’ end
long poly a tail = associated with high translational activity
sent to cytoplasm and then translated
makes all proteins oocyte needs to survive and grow

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30
Q

describe the untranslated messages oocyte stores

A

some undergo deadenylation = enzymes chew up poly a tail
no translation
stored in ribonuclear protein particles, stored to be translated later = final stage oocyte development or after fertilization
cpe = cytoplasmic polyadenylation element, message has this UUUUUAAU element in 3’ utr = deadenylation element, so shut down = translationally silent and stored, must have this sequence

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31
Q

as oocytes get bigger…

A

= more mitochondria
larger oocytes make more and more mito and generate more and more ribosomes

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32
Q

what is essential for embryonic development

A

large oocytes
vol increase ~100 fold
need big oocyte

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33
Q

why do oocytes need to be large

A

after fertilization = embryo undergoes cleavage division for first few days = cell division without increase in size, number of cells increase but total amount of cellular material the same
Produces a large cell that will be divided into many small cells by cleavage after fertilization
divides into 50-100 cells
NEED HUGE OOCYTE SO IT CAN GO THROUGH CLEAVAGE DIVISIONS (also accumulate nutrients and organelles embryo needs)

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34
Q

what is role of granulosa cells in oocyte growth?

A

essential role in growth process
sends signal to oocyte to grow
kit ligand activates kit receptor

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35
Q

do the oocytes need to be in contact with granulosa cells for growth

A

yes experiment = take oocyte in early stage of growth, if remove granulosa cells= strip off cells and incubate in vitro = oocyte does not grow
need granulosa cells for growth, and must be in physical contact with oocyte
cannot just have granulosa cells in same area - needs contacts

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36
Q

what connects oocytes and granulosa cells

A

gap junctions
channel between cells - permits passage of molecules between cells

37
Q

describe what happens when inactivate gap junctions

A

no gap junctional communication between oocytes and granulosa cells
oocytes grow to only ~75% of normal sized
oocytes cannot undergo final stage of development = meiotic maturation. Cannot complete it
COMMUNICATION ESSENTIAL FOR GROWTH

38
Q

what cant oocytes do themselves

A

oocytes can take up some amino acids by itself but does not have receptors for some so granulosa cells = pick up aas and transfer to oocyte
glucose too

39
Q

explain how granulosa feeds oocyte

A

for some aas
glucose made inot pyruvate, transfers pyruvate to oocyte since oocyte not good at taking up glucose or pyruvate so depends on granulosa cells
provide cholesterol synthesis too
granulosa cells feed building blocks to oocyte to help it grow

40
Q

where is zona pellucida

A

structure between granulosa and zona pellucida
very thick
around oocyte of egg of mammals (other species have something similar)

41
Q

what is zona composed of

A

zp 1-4 (zona pellucida proteins)
mesh like network

42
Q

how do granulosa and oocyte cells communicate since zona in the way

A

filopodia termed transzonal projections (TZPs) extend from granulosa cells to oocyte
tzps come from granulosa cells to oocyte, mediate contact and communication between oocyte and granulosa
Extension of cytoplasm

43
Q

what happens if mutation in actin

A

tzps made of actin
no tzps then but also huge problem for many other tissues

44
Q

WHAT ABOUT THE SOMATIC COMPARTMENT OF THE FOLLICLE? - 5

A

proliferation of granulosa cells
Recruitment of thecal cells
production of estrogen- by growing follicle, major source of estradiol in females
differentiation of mural and cumulus granulosa cells = cavity is huge, biggest = ripest
growth of antrum

45
Q

WHAT ABOUT THE SOMATIC COMPARTMENT OF THE FOLLICLE? - explain recruitment of thecal cells

A

before = around outside= just float around ovarian stroma- have no purpose
present once oocyte and follicle grow
= get called in
not in primordial or early primary stage

46
Q

which cells produce estradiol

A

granulosa and thecal

47
Q

explain synthesis of estradiol - from cholesterol

A

cholesterol to progesterone to testosterone to estradiol
women make both testosterone and estradiol, most testosterone concerted to estradiol

48
Q

describe role of thecal cells - estradiol

A

synthesize testosterone from cholesterol (like leydig cells), 1st part of reaction
convert cholesterol to testosterone

49
Q

describe role of granulosa cells - estradiol

A

2nd part = picks up testosterone
converts testosterone to estradiol

50
Q

what do gonadotropins do

A

regulate follicle development
peak of lh triggers ovulation

51
Q

Compare fsh and lh

A

fsh and lh closely related, both produced by piutary
have alpha and beta subunits
both have same alpha subunit
beta subunit = diff, gives them different unique activities
role in male and female - diff levels obviously

52
Q

when is fsh required

A

for most of growth = fsh not required
women who have mutation in fsh or in receptor = follicles can grow to pre antral stage (or early antral) but final stage cannot happen (prior 2 weeks to ovulation)
fsh needed 2 weeks prior to ovulation (antral, preovulatory stage)

53
Q

why do most pre antral follicles die

A

due to insufficient fsh
lots of follicles get to late pre antral/early antral phases
but only enough fsh to get one or 2 to grow, dominant follicle gets enough fsh and others die

54
Q

what does estrogen produced by growing follicles do

A

inhibits fsh production

55
Q

describe entire diabolical cycle of estrogen

A

FSH SYNTHESIS AND RELEASE (PITUITARY) = causes granulosa cells to proliferate, helps final stage of dev
GRANULOSA PROLIFERATE = takes up testosterone from theca cells and coverts to estrogen, high estradiol
INCREASED PRODUCTION OF ESTROGEN = negative feeback, inhibits fsh synthesis and release from pituitary
DOMINANT FOLLICLE Suppresses GROWTH OF OTHER FOLLICLES

56
Q

does treatment with fsh help increase number of oocytes for assisted repro - explain

A

to increase chance of getting pregnant = can provide fsh directly or give drug to antagonist inhibitory effects of estradiol
raise fsh so then can make more cells grow
do not know if all the follicles are of the same quality tho

57
Q

explain ivf fsh treatments

A

fsh treatments = rescued dev of follicles

58
Q

describe lh - what it does

A

Triggers ovulation by acting on somatic cells of follicle and also triggers maturation of oocyte

59
Q

describe meiotic maturation - length in humans and micce

A

place where things can get messed up = trisomies
in humans = 36 hrs, short
12hrs in mice

60
Q

what happens during meiotic maturation - gen

A

1st meiotic division
asymmetric cytokinetic division

61
Q

describe meiosis 1 and 2 - oogenesis

A

meiosis 1 during meiotic maturation
meiosis 2 after fert
oocyte frozen in late diplotene stage - undergone recomb, from before birth until meiotic maturation

62
Q

describe meiosis 1 and 2 - spermatogenesis

A

Meiosis 1 and 2 during spermatogenesis = both happen at same time, time frame shorter
might affect frequencies of aneuploidies

63
Q

what exactly happens during meiotic maturation

A

1st meiotic division and preparation for 2nd meiotic division

64
Q

describe meiotic maturation - gv stage oocyte and gvbd

A

chroms underwent recomb
nucleus, zona, and oocyte
germinal vesicle
then germinal vesicle breakdown = nuclear envelop and chroms condense

65
Q

describe meiotic maturation - spindle formation

A

chroms condensed and arranged on spindle then spindle migrates to periphery - one spindle pole becomes attached to cortex of oocyte
1st meiotic division

66
Q

describe meiotic maturation - first polar body extrusion

A

first meiotic division = chrom segregate into 2 groups then cytokinesis= divides cells into big oocyte and small polar body
need spindle migration to get big oocyte and small polar body
polar body can be used for chromosome abnormality analysis

67
Q

describe what we should see visually - meiotic maturation

A

polar body contains 1/2 chroms from 1st meiotic division
once 1st meiotic done = chroms in oocyte arrange in new spindle = metaphase 2 spindle but then arrest till after fert

68
Q

what does lh bind to

A

mural granulosa cells located far from oocyte
have receptors on theca and mural but relevant binding for oocyte = lh on mural cells
lh acts then signal must be transmitted to oocyte

69
Q

describe experiment - involving lh

A

take ovary and remove oocyte from big antral follicle
and put in culture dish = went to maturation w/o lh
= something repressing (inhibits follicle, blocks maturation, lh relieves blocking effect)

70
Q

what is the hormonal regulation of maturation

A

release from repression - lh

71
Q

what is cgmp

A

cyclic guanosine monophosphate
made by mural granulosa cells - main source
also made by cumulus cells

72
Q

describe when maturation inhibited

A

recall = all cells (oocyte, mural, cumulus) connected by gap junctions (allows small molecules through)
HIGH LEVELS OF CGMP IN OOCYTE = BLOCKS MATURATION

73
Q

describe when maturation initiated

A

lh can directly inhibit cgmp (also by egfr acted on by egfr ligands)
lh binds receptor and activates signalling pathways on mural cells activate egfr signalling pathway, and egfr recptor on mural and cumulus cells
levels of cgmp in granulosa fall so cgmp levels in oocyte also fall bc of gap junctions = initiate maturation = when CGMP LOW

74
Q

describe whole pathway of cgmp

A

cgmp = if high blocks pde3A (phosphodiesterase pde3a) –> inhibits camp, if high camp (so pde3a low) –> much activate protein kinase a –> inhibits = blocks cdc25b, so cdk1 in active = highly phosphorylated
but if cdc25b (phosphatase) active = cdk1 active with one phosphorus and cyclin b1 active = drive into metaphase of cell cycle for all cells

75
Q

describe age dependent decline of fertility in women

A

Probability of success decreases as age
older = harder to get pregnant
must turn to art

76
Q

what happens if give young donor oocytes to older woman

A

probability does not change much so can still get pregnant with young oocytes
Conclusion = egg quality declines, nothing else wrong (not blood supply, uterus, hormones etc)

77
Q

describe meiotic errors - what do they depend on

A

mainly maternal - oocyte and age
probability of aneuploidy increases with maternal age
Origin = during 1st and second meiotic divisions
not much difference from men

78
Q

describe meiotic errors - what do they depend on - TRISOMY 21

A

Down syndrome = mild case of triploidy, they usually survive and we can se where extra chrom comes from
usually associated with high maternal age
incorrect function of meiotic spindle
mostly 1st division, then 2nd, not usually paternal or mitotic error

79
Q

DESCRIBE TIming of meiotic progression

A

all oocytes get to diplotene/diakinesis before birth then meiotic division resume after like maybe 40 years,

1 month, no arrest = meiotic process for sperms

could difference in timing of meiosis underly the difference in how frequently errors of meiosis originate on oocyte side

80
Q

describe roles of cohesion in chrom segregation

A

rec8 - cohesin holds chroms together
degradation of some of cohesin molecules located in certain regions of chromosomes away from centromeres = permits 1st meiotic division
2nd meiotic= more degradation around centromeres of sister chromatids
regulated disassembly important for meiosis to occur properly

81
Q

describe roles of cohesion in chrom segregation - connection with mistakes in meiosis

A

no turnover of cohesin in molecule = put on before birth so maybe not acting well so increased mistakes
cohesin that is so important in regulating chromosome separation is getting messed up

82
Q

EXOGENOUS COHESINS TO RESCUE AGE-RELATED ANEUPLOIDY?- describe experiment

A

remove cumulus oocyte complex from preovulatory follicle = ones that are ready to mature, and put in petri dish and will mature in vitro spontaneously
inject cohesin into oocyte = before maturation, will replenish supply - will stick together as they should
permit meiotic maturation
fertilize egg = see if fewer meiotic errors in oocyte of old mic, compared to ones that did not get new cohesin
DO NOT ACTUALLY KNOW IF WORKS

83
Q

what is cytoplasmic maturation

A

changes that happen in cytoplasm as same time as oocyte goes through meiotic divisions

84
Q

describe key events of cytoplasmic maturation - 5

A

changes in protein synthesis
Beginning of degradation of oocyte (maternal) mRNA
Redistribution of mitochondria
Redistribution of endoplasmic reticulum Accumulation of cortical granules at the cortex

85
Q

why translation regulation

A

when oocytes grow = v transcriptionally active, make many mrnas
once reach full size = transcriptional activity drops
some mrnas that have accumulated are now degraded
after fertilization = remain silent during most until 4 cell stage (until stage specific activation of transcription)
after fertilization = do not need these genes that were for making oocyte = so maybe messages for embryo development will only be left - not mixture of embryo dev and oocyte dev

86
Q

what is a key event of cytoplasmic maturation

A

TRANSLATIONAL ACTIVATION OF CPE-BEARING MRNAS
messages made during growth have to sustain development throughout maturation and during first couple of cleavages after fertilization = translational activation of previously silent message= proteins at right time of dev

87
Q

describe TRANSLATIONAL ACTIVATION OF CPE-BEARING MRNAS

A

during maturation = many repressed rnas become translationally activated
poly a tail becomes long bc cytoplasmic conditions of maturing oocyte change = increase translation of messages
very important part of maturation = helps oocyte complete maturation and undergo embryonic development after fert
if translation activation does not occur properly = oocytes do not develop into embryo

88
Q

what can pass through gap junctions

A

sugars, nucleotides, atp, amino acids
NO proteins or mrna, bigger proteins, too large

89
Q

xxy - klinefelter - is it from mom or dad

A

equally frequently from male or female

ANAT 381 (24 decks)

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