Germ Cell Development Flashcards
What do we call a tumour which is able to give rise to multiple cell types?
A teratocarcinoma.
What occurs when you cross a teratocarcinoma mouse with a normal mouse? What does this imply?
Many cells in the offspring are derived from carcinoma cells. Therefore teratocarcinoma can give rise to germ cells!
What changes occur in teratocarcinoma cells which have differentiated?
They lose their tumour-like properties (undergo somatic differentiation).
What are teratocarcinoma cells derived from?
Germ cell tumours.
What differentiates a teratocarcinoma from a teratoma?
Teratocarcinoma: malignant
Teratoma: benign
Where in the female body is ovarian cancer likely to arise?
In the outer lining of the ovary. Very rare in the germ cells.
What differentiates germ cells and somatic cells, from a proliferation point of view?
Both derived from pluripotent cells, but somatic cells lose their link to multipotency while germ cells remain pluripotent.
Why did Theodor Boveri think that germ cells are able to retain pluripotency through repeated cell division?
A factor in the vegetal region of a blastomere prevents chromosome diminution/promotes germ cell formation
How would you identify a maternal effect gene which is necessary for germ cell formation?
Look for mutated females which don’t have grandchildren.
What is the importance of “germ cell less” gene in drosophila?
It is critical for germ cell formation. Without exposure to it cells can not retain pluripotency.
How are germ cells generated in mammals?
Induced in embryo during development.
At the epiblast stage of mammalian development, which cells are fated to become primordial germ cells?
The cells at the border between the extra-embryonic ectoderm and the visceral ectoderm.
Once primordial germ cells have been induced, where do they migrate to?
The posterior epiblast.
What factor induces border cells to become primordial germ cells?
BMP4 from the extra-embryonic ectoderm.
Later in development, where do primordial germ cells migrate to from the gut? What occurs if they fail to migrate?
The genital ridge. Cells which fail to migrate are usually destroyed, but can sometimes just remain inert in the tissue.
What factor helps guide primordial germ cells during their migration from the gut to the genital ridge?
Stromal cell-derived factor (SDF).
What is the developmental state of the gonads when the germs cells arrive (after migration)?
They are indifferent gonads and have not begun differentiating into male or female.
What duct is lost in the male gonads during development (+why)? What duct is retained?
Lost: mullerian duct (b/c of anti-mullerian hormone)
Retained: wolffian duct
What duct is lost in the female gonads during development? What duct is retained (+why)?
Lost: wolffian duct
Retained: mullerian duct (b/c of the presence of estrogen)
What is the master control gene for testis development?
Sex-determining region Y (Sry).
What does Sry control which is necessary for testis determination?
Sox9.
What happens if you insert a transgenic Sry gene into an XX mouse?
You get an intersex XX ma… jk you get a mouse with ballz.
What 5 transcription factors are importaint for maintaining pluripotency of germ cells?
- Oct3/4
- Sox2
- c-Myc
- Klf4
- Nanog
primordial germ cells can be identified by their expression of ____, ____, and ____.
Fragilis, Blimp1, and stella.
What happens to germ cell pluripotency if you knock out either fragilis or stella?
Nothing, there’s redundancy.
What 2 kinds of epigenetic modifications occur immediately after the specification of primordial germ cells? What enzymes do this
- Methylation by methyltransferases
2. Acetylation by acetyltransferases
How does Blimp1 act to maintain pluripotency in germ cells?
By repressing somatic differentiation via inhibition of Prmt5.
What effect does let-7 binding have on Blimp1 activity? How does this affect primordial germ cells?
Let-7 deactivates Blimp1, causing primordial germ cells to differentiate and lose pluripotency.
What effect does LIN-28 have on primordial germ cells? How does it act?
LIN-28 deactivates let-7, turning off Blimp1 inhibition and thereby maintaining primordial germ cell pluripotency.
