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35 Cards in this Set
- Front
- Back
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what type of germ cell specification occurs in frogs, nematodes and flies?
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autonomous (germ plasm)- a cell can be removed and will produce the same types of cells that it would if it were still part of the embryo, mosaic development, morphogenetic determinants in different regions of egg cytoplasm
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what type of germ cell specification occurs in salamanders and mammals?
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conditional- each cell has the ability to become any of the cell types, interactions between cells determine fate,
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In Parascaris zygotic cleavage, how was the germ cell derived?
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from the vegetalmost pole, the chromosomes remain normal (w/o chromosome diminution)
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In C. elegans how is the germ line preserved?
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germline precursor cell is P4, containes P-granules (transcriptional inhibitors, RNA binding proteins), nuclei are silenced- POLE CELLS
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In Drosphila what is needed at the posterior end to give rise to germcell line?
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pole cells and the pole plasm
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what is the role of the germ plasm?
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responsible for specifying the cells to become germ cells and for inhibitin somatic gene expression
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how is the gcl (germ cell-less) gene related to the induction of germ cells?
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The mothers gcl RNA resides in the germ plasm and there in cells is trancribed into a protein that mediates the production of germ cells, essential to give rise to germ cells
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what does the gcl gene encode for?
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a nuclear envelope protein that prevents gene transcription and is critical for specifying pole cells
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what is Pgc, polar granule component?
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pole plasm: noncoding RNA that prevents phosphorlyation of RNA polymerase III
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what is oskar?
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pole plasm: functions to localize proteins and RNAs required for
germ cell formation to the posterior pole |
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what is nanos?
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pole plasm: an mRNA localized by Oskar to the posterior end,
and it is essential for posterior segmentation and germ cell specification |
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why is it so important for transcription to be repressed?
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so the cells to dont under go somatic cell differentiation and lose their puripotency.
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how is frog germ cell determination like that of drosphila?
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also a special cytoplasmic localization, contains RNAs and proteins that inhibit transcription and translation
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how is frog germ cell determination different that that of drosphila?
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occurs at the vegetal pole, germinal granules, germ plasm consists of "islands" in yolk mass at veg, aggregate, may direct germ plasm movement
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what are 2 mRNAs involved in zebrafish germ cell development? how are they supplied? where to they localize?
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Vasa and Nanos
maternally supplied localize in only 1 of the cells at asymetrical cleavages in development, |
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how is germ cell determination different in mammals?
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conditional
the germ cells are determined by material in the egg cytoplasm no obv. germ plasm they are "induced" in the embryo |
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how are PGCs migrated and to where in Zebrafish?
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migration is motivated by chemorepulsion of germ cell precursors, they arrive to the gonads via chemoattraction
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ZEBRAFISH: what protein is secreted by a developming gonad to attract the PGCs? what receptor is on PGCs?
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Sdf1 protein
CXCR4 receptor |
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describe the route of Zebrafish PGCs?
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clusters @ boarder of trunk mesoderm-->
then go to developing gonad |
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Describe the path of the germ plasm/PGC in Xenopus (frog)? (6)
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1. collects at vegetal pole
2. during cleavage travels up through yolky cytoplasm 3. become associated with the endodermal cells lining the floor of the blatocoel 4. PGCs at posterior gut as abd. cavity forms 5. dorsal side of gut 6. abd. wall to the genital ridge, finally at tissue of dev. gonads |
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How are PGCs in mammals specified? And where are they for early gastulation?
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BMP signals from the neighboring extraembryonic ectoderm induce epiblast cells to become PGC precursors.
localized in posterior epiblast |
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what are some genes expressed in mammalian PGC precursor cells.
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fragilis
stella blimp1 |
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what is the migration path of PGCs in mammals?
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1. posterior epiblast
2. endoderm 3. through the gut and go dorsal to genital ridges |
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what are 2 adhesive related proteins that germ cells need to migrate?
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fibronectin
integrin receptor |
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what are some paracrine factors involved in ushering PGCs in mammals?
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Fgf7
SCF (stem cell factor) |
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where can SCF be found?
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in cells lining the migration pathway and is membrane bound.
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what transcription factors are associated with maintaining toti/pluripotency in mammals (b/c no germ plasm)?
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Oct4
Stat3 Nanog |
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what are PGC
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primodial germ cells- cells that migrate to the gonads and give rise to the germ line (totipotent)
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what are ES
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embryonic stem cells- form the inner cell mass blastomers that can give rise a embryo, but not extraembryonic tissues (pluripotent) except in humans
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what can give rise to more stuff:
totipotency or pluripotency? |
totipotent
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Oct4 in mammals is found where?
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inner cell mass, posterior epiblast and in migrating PGCs
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how do you get embryonic germ cells (EG) from PGCs? and how can they be used?
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FgF2
produce pluripotent cells- used to make nerual or hematopoetic stem cells regenerate |
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how do PGCs migrate in Drosphila
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1. passivly move fom posterior pole to the midgut by gastrulation movements
2. endoderm triggers diapedasis to the posterior mid gut 3. to mesoderm 4. split to gonad primordium |
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what migration promoting genes are important in drosophila
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wunen
columbus hedgehog need E cadherin to go gonad |
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describe the steps of x chromosome inactivation
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1. at fertalization, paternal X is initially inactived
2. placenta remains paternal X inactived, the inner cell mass returns to no inact 3. then there is random inactivation selection 4. the germ cell line remains uncommited to a X 5. germ line imprint is then established |
