1. Primordial germ cell specification

2. Objectives for this session
1. Understand the principle of primordial germ cell formation.
2. Compare the primordial germ cell specification in different species.

3. Inheritance takes place by means of the germ cells

4. Pole cells are the primordial germ cell in Drosophlia

5. Drosphila primordial germ cell
The progenitor of germ cell, which appear in early embryo developmental stage.

6. Function of pole plasm
Okada et al. 1974

7. Drosphila primordial germ cell
The progenitor of germ cell, which appear in early embryo developmental stage.
Contain germ plasm, which is essential for germ cell development
pole plasm, a complexcollection of mitochondria, fibrils, and polar granules

8. Drosophila germ cell determination
gcl
pgc
oskar
mtrRNA
Pole plasm
Pole cells
PGCs

9. Function of proteins in Drosophila germ plasm
Maternal deposit genes?
Nuclear localization?
Function
Germ cell-less (gcl) Y
Nuclear envelope
Prevent gene transcription
Polar granule component (pgc) N
Prevent RNA polymerase II phosphorylation
Oscar
Localize the proteins and RNAs necessary for germ cell formation
Nanos
Essential for inhibiting some gene transltaion
Vasa
Critical for initiating germ cell differentiation and meiosis

10. In pgc mutant embryos, pole cells express the somatic cell marker
Curr Biol Jan 20;14(2):

11. Drosophila primordial germ cell
The progenitor of germ cell, which appear in early embryo developmental stage.
Contain germ plasm, which is essential for germ cell development
The components of germ plasm can inhibit somatic gene expression in germ cell

12. Among the following events, which occurs first during Drosophila development?
A. Zygote division 7 B. Germ plasm form C. Germ plasm related RNA can be detected in the embryo D. Primordial germ cell nuclear migrate to the posterior region of the embryo

13. Drosophila primordial germ cell determination
Stage 6 egg chamber
Vasa+
Oscar+
Polar granule visible
Stage 9-10 egg chamber
Mature,
Stage 14 egg chamber
Nanos+, gcl+and
mtlrRNA+
Cleavage stage embryo
Polar granule fragmented
Pole nucler cellulalization
precociously
Syncytial blastoderm
stage embryo
Anne Williamson and Ruth Lehmann 1996

14. Drosophila primordial germ cell
The progenitor of germ cell, which appear in early embryo developmental stage.
Contain germ plasm, which is essential for germ cell development
The components of germ plasm can inhibit somatic gene expression in germ cell
The components of germ plasm entered the zygote before 1st division

15. P-granules in C. elegans
Developmental Biology
by Scott F. Gilbert
Nuclear
P-granules

16. Conserved components in P-granule and pole plasm
Vasa and related DEAD box RNA helicases
Argonaute family
Dhh1p/Rck
Scd6p/Rap55
Nanos
eIF4F complex
funtion
RNP remodeling
Small RNA (miRNA/piRNA) regulation
Prevent RNA polymerase II phosphorylation
Repression of translation
Translational regulation
Protein P-granule
GLH-1-4
PRG-1, CSR-1
PIE1
CGH-1
CAR-1
IFE-1
Protein in pole plasm
Vasa
Aubergine ,Piwi
Pgc
Me31b
Trailer Hitch
eIF4A
Cold Spring Harb Perspect Biol Dec; 3(12): a

17. Post-Class assigment
Please compare the primordial germ cell specification process of Xenopus with Drosophila and C. elegans. What are conserved?
Reference:

18. Thank you!

19. Figure 2. Comparison of maternal germ plasm and zygotic germ granule components between two organisms,...
Figure 2. Comparison of maternal germ plasm and zygotic germ granule components between two organisms, Drosophila and zebrafish, that use maternal inheritance to specify their primordial germ cells (PGCs). The first column depicts the localization of germ plasm components (listed beneath the cartoon) at the posterior pole of mid-stage oocytes of Drosophila (top) and in the Balbiani body of early-stage oocytes of zebrafish. After fertilization, maternal germ plasm components (listed beneath the schematic) localize to specific membranes within the syncitial blastoderm of Drosophila and meroblastic cleavage (cells are incompletely separated and connected to the yolk) stage zebrafish embryos. The cells that receive these membranes develop as the PGCs. White rectangles depict maternal germ plasm components. The last column (grey rectangle) depicts PGCs of Drosophila and zebrafish after their migration to the gonad and indicates components of embryonic PGCs and germ granules. Dazap2, deleted in azoospermia-associated protein 2; Dazl, deleted in azoospermia-like; Elav, HuC; gcl, germ cell-less; Rbpms2, ribonuclear-binding protein with multiple splice isoforms 2.
How to cite: Marlow F 2015 Primordial Germ Cell Specification and Migration [version 1; referees: 3 approved] F1000Research 2015, 4:1462 (doi: /f1000research )
Marlow F 2015 [version 1; referees: 3 approved] F1000Research 2015, 4:1462 (doi: /f1000research )

20. Weismannism Inheritance only takes place by means of the germ cells
The effect is one-way: germ cells produce
somatic cells and are not affected by
anything the somatic cells learn or therefore
any ability an individual acquires during its
life.
Genetic information cannot pass from soma to germ plasm and on to the next generation.
August_Weismann
August Friedrich Leopold Weismann