Aug30 M1-Oocyte Development Flashcards
2 phases of oocyte growth and maturation
- growth (3 months): primordial to fully grown with GCs and ZP. (primordial to pre-antral follicle)
- meiotic maturation, pre-ovulatory (36 hours = between LH surge and ovulation). FSH and LH (LH also responsible for the surge and the ovulation) are the hormones that triggers step 2 (antral follicle to ovulation)
primordial follicle charact
oocyte + surrounding GCs (somatic ovarian cells)
primary follicle charact
GCs increase in number to keep enclosing oocyte as it grows. give it molecules
secondary follicle charact
inside to outside
- oocyte
- GCs
- basement membrane
- theca cells
function of GCs and theca in secondary follicle
make estrogen
- theca makes androstenedione bc of LH infl
- GCs make estradiol (from androstenedione) using aromatase enzyme bc of FSH infl
early antral follicle is what
follicle with an antrum (cavity filled with fluid produced by GCs in between layers of GCs)
last step of growth phase
early antral follicle layers
inside to outside
- oocyte
- cumulus granulosa
- antrum
- mural granulosa
- BM
- theca cells
late antral follicle charact
- like early but more GC layers
- is the Graafian follicle
- is the dominant follicle that will be ovulated
- beginning of maturation, ovulation phase*
reserve oocytes in the ovary means what
oocytes that didn’t enter the growth phase yet
when did an ovulated oocyte start its growth phase
3-4 months before ovulation
when do oocytes enter the growth phase
constantly have oocytes entering growth phase
general concept of growth signaling between cells
-GF secreted by cell
1 interacts with an RTK on cell 2
-cell 2 activates a signaling pathway
-cell 2 increases prot synth
how GCs tell oocyte to grow
- GCs produce the KIT ligand (KITL)
- KITL binds Rs on oocyte
- oocyte increases prot synthesis and gets bigger
why not all follicles grow because of signals from granulosa cells
because of ovary architecture, not all follicles and oocytes can grow simultaneously
2 reasons why oocyte has to grow a lot
- after fertilization, will undergo many divisions without preceding cell growth, to form a blastomere
- during growth, accumulate factors (prot, RNA) needed for embryo to feed itself in week 1 (before implantation)
other role of GCs in growth of oocytes than telling them to grow
transfer to them the nutrients necessary for growth via gap junctions (adjacent channels forming holes in memb)
molecules passing in gap junctions from GC to oocyte
- aa
- small molecules
- pyruvate
- cholesterol
- nts (during meiotic maturation, triggered by EGF-like molecules of mural GCs binding EGF-Rs on mural and cumulus GCs)
gene of gap junctions between GCs and oocyte + KO consequence
- GJA4
- KO = oocyte 75% of normal size + can’t undergo meiotic maturation
zona pellucida is what
coat of glycoproteins made by oocyte surrounding it
2 fcts of ZP
- block 2nd sperm from fertilizing oocyte (chemically modified after fert)
- protect embryo before implant
how GCs reach oocyte and make gap junctions through the ZP
send transzonal projections (tube, foot with actin)
what triggers the transfer of nutrients from GCs to oocytes
oocytes themselves, have to tell GCs to do it
-secrete 3 molecules (GDF9, BMP15, FGF8B) that go on GC Rs.
what happens in the follicular phase of the menstrual cycle
many follicles complete the last two weeks of the growth phase to reach the early antral stage. many will die after that
pre-ovulatory phase (meiotic maturation) depends on what hormone
FSH (without it = only reach early antral stage)
