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Making Eggs Flashcards

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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
what prevents growth of follicle - fully explain
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
26
what happens when oocyte grows - vol/accumulate
volume increases by factor of 100 10x diameter by end = almost 100 microns - by time finished growth = one of biggest cells in body
27
what does oocyte while growing store
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)
28
how many kinds of messages does oocytes store
2 kinds = translated and untranslated very transcriptionally active when growing
29
describe the translated messages oocyte stores
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
30
describe the untranslated messages oocyte stores
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
31
as oocytes get bigger...
= more mitochondria larger oocytes make more and more mito and generate more and more ribosomes
32
what is essential for embryonic development
large oocytes vol increase ~100 fold need big oocyte
33
why do oocytes need to be large
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)
34
what is role of granulosa cells in oocyte growth?
essential role in growth process sends signal to oocyte to grow kit ligand activates kit receptor
35
do the oocytes need to be in contact with granulosa cells for growth
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
36
what connects oocytes and granulosa cells
gap junctions channel between cells - permits passage of molecules between cells
37
describe what happens when inactivate gap junctions
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
what cant oocytes do themselves
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
explain how granulosa feeds oocyte
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
where is zona pellucida
structure between granulosa and zona pellucida very thick around oocyte of egg of mammals (other species have something similar)
41
what is zona composed of
zp 1-4 (zona pellucida proteins) mesh like network
42
how do granulosa and oocyte cells communicate since zona in the way
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
what happens if mutation in actin
tzps made of actin no tzps then but also huge problem for many other tissues
44
WHAT ABOUT THE SOMATIC COMPARTMENT OF THE FOLLICLE? - 5
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
WHAT ABOUT THE SOMATIC COMPARTMENT OF THE FOLLICLE? - explain recruitment of thecal cells
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
which cells produce estradiol
granulosa and thecal
47
explain synthesis of estradiol - from cholesterol
cholesterol to progesterone to testosterone to estradiol women make both testosterone and estradiol, most testosterone concerted to estradiol
48
describe role of thecal cells - estradiol
synthesize testosterone from cholesterol (like leydig cells), 1st part of reaction convert cholesterol to testosterone
49
describe role of granulosa cells - estradiol
2nd part = picks up testosterone converts testosterone to estradiol
50
what do gonadotropins do
regulate follicle development peak of lh triggers ovulation
51
Compare fsh and lh
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
when is fsh required
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
why do most pre antral follicles die
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
what does estrogen produced by growing follicles do
inhibits fsh production
55
describe entire diabolical cycle of estrogen
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
does treatment with fsh help increase number of oocytes for assisted repro - explain
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
explain ivf fsh treatments
fsh treatments = rescued dev of follicles
58
describe lh - what it does
Triggers ovulation by acting on somatic cells of follicle and also triggers maturation of oocyte
59
describe meiotic maturation - length in humans and micce
place where things can get messed up = trisomies in humans = 36 hrs, short 12hrs in mice
60
what happens during meiotic maturation - gen
1st meiotic division asymmetric cytokinetic division
61
describe meiosis 1 and 2 - oogenesis
meiosis 1 during meiotic maturation meiosis 2 after fert oocyte frozen in late diplotene stage - undergone recomb, from before birth until meiotic maturation
62
describe meiosis 1 and 2 - spermatogenesis
Meiosis 1 and 2 during spermatogenesis = both happen at same time, time frame shorter might affect frequencies of aneuploidies
63
what exactly happens during meiotic maturation
1st meiotic division and preparation for 2nd meiotic division
64
describe meiotic maturation - gv stage oocyte and gvbd
chroms underwent recomb nucleus, zona, and oocyte germinal vesicle then germinal vesicle breakdown = nuclear envelop and chroms condense
65
describe meiotic maturation - spindle formation
chroms condensed and arranged on spindle then spindle migrates to periphery - one spindle pole becomes attached to cortex of oocyte 1st meiotic division
66
describe meiotic maturation - first polar body extrusion
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
describe what we should see visually - meiotic maturation
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
what does lh bind to
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
describe experiment - involving lh
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
what is the hormonal regulation of maturation
release from repression - lh
71
what is cgmp
cyclic guanosine monophosphate made by mural granulosa cells - main source also made by cumulus cells
72
describe when maturation inhibited
recall = all cells (oocyte, mural, cumulus) connected by gap junctions (allows small molecules through) HIGH LEVELS OF CGMP IN OOCYTE = BLOCKS MATURATION
73
describe when maturation initiated
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
describe whole pathway of cgmp
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
describe age dependent decline of fertility in women
Probability of success decreases as age older = harder to get pregnant must turn to art
76
what happens if give young donor oocytes to older woman
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
describe meiotic errors - what do they depend on
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
describe meiotic errors - what do they depend on - TRISOMY 21
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
DESCRIBE TIming of meiotic progression
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
describe roles of cohesion in chrom segregation
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
describe roles of cohesion in chrom segregation - connection with mistakes in meiosis
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
EXOGENOUS COHESINS TO RESCUE AGE-RELATED ANEUPLOIDY?- describe experiment
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
what is cytoplasmic maturation
changes that happen in cytoplasm as same time as oocyte goes through meiotic divisions
84
describe key events of cytoplasmic maturation - 5
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
why translation regulation
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
what is a key event of cytoplasmic maturation
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
describe TRANSLATIONAL ACTIVATION OF CPE-BEARING MRNAS
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
what can pass through gap junctions
sugars, nucleotides, atp, amino acids NO proteins or mrna, bigger proteins, too large
89
xxy - klinefelter - is it from mom or dad
equally frequently from male or female

ANAT 381 (24 decks)

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