Download Contain germ plasm, which is essential for germ cell development

Primordial germ cell specification
Objectives for this session
• 1. Understand the principle of primordial
germ cell formation.
• 2. Compare the primordial germ cell
specification in different species.
Inheritance takes place by means of
the germ cells
http://www.nbcnews.com/tech/tech-news/how-one-girls-search-brought-her-48-halfbrothers-sisters-n458091
Pole cells are the primordial
germ cell in Drosophlia
http://biology.kenyon.edu/courses/biol114/Ch
ap13/droslifecycle.jpg
Drosphila primordial germ cell
o The progenitor of germ cell, which appear in
early embryo developmental stage.
Function of pole plasm
Okada et al. 1974
Drosphila primordial germ cell
o The progenitor of germ cell, which appear in
early embryo developmental stage.
o Contain germ plasm, which is essential for
germ cell development
Drosophila germ cell determination
gcl
mtrRNA
oskar
Pole plasm
Pole cells
PGCs
pgc
Function of proteins in Drosophila germ plasm
Maternal deposit Nuclear
Function
genes?
localization
?
Germ cell-less
(gcl)
Y
Nuclear
envelope
Prevent gene transcription
Polar granule
component
(pgc)
Y
N
Prevent RNA polymerase II
phosphorylation
Oscar
Y
N
Localize the proteins and RNAs
necessary for germ cell
formation
Nanos
Y
N
Essential for inhibiting some
gene transltaion
Vasa
Y
N
Critical for initiating germ cell
differentiation and meiosis
In pgc mutant embryos, pole cells express the somatic cell marker
Curr Biol. 2004 Jan 20;14(2):159-65.
Drosophila primordial germ cell
o The progenitor of germ cell, which appear in
early embryo developmental stage.
o Contain germ plasm, which is essential for
germ cell development
o The components of germ plasm can inhibit
somatic gene expression in germ cell
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
Drosophila primordial germ cell determination
Stage 6 egg chamber
Vasa+
Oscar+
Polar granule visible
Stage 9-10 egg chamber
Nanos+, gcl+and
mtlrRNA+
Polar granule fragmented
Pole nucler cellulalization
precociously
Mature,
Stage 14 egg chamber
Cleavage stage embryo
Syncytial blastoderm
stage embryo
Anne Williamson and Ruth Lehmann 1996
Drosophila primordial germ cell
o The progenitor of germ cell, which appear in
early embryo developmental stage.
o Contain germ plasm, which is essential for
germ cell development
o The components of germ plasm can inhibit
somatic gene expression in germ cell
o The components of germ plasm entered the
zygote before 1st division
P-granules in C. elegans
P1
P2
P3
P4
Nuclear
P-granules
Developmental Biology
by Scott F. Gilbert
Conserved components in P-granule
and pole plasm
Vasa and
related
DEAD box
RNA
helicases
Argonau
te family
funtion
RNP
remodelin
g
Small RNA
(miRNA/pi
RNA)
regulation
Prevent
RNA
polymeras
e II
phosphory
lation
Repression of translation
Protein
Pgranule
GLH-1-4
PRG-1,
CSR-1
PIE1
CGH-1
CAR-1
Nanos
IFE-1
Protein
in pole
plasm
Vasa
Aubergin Pgc
e ,Piwi
Me31b
Trailer
Hitch
Nanos
eIF4A
Dhh1p/
Rck
Scd6p/R
ap55
Nanos
eIF4F
complex
Translati
onal
regulatio
n
Cold Spring Harb Perspect Biol. 2011 Dec;
3(12): a002774.
Post-Class assigment
• Please compare the primordial germ cell
specification process of Xenopus with
Drosophila and C. elegans. What are
conserved?
Reference:
http://www.ncbi.nlm.nih.gov/books/NBK10073/
Thank you!
Figure 2. Comparison of maternal germ plasm and zygotic germ granule components between two
organisms,...
Marlow F 2015 [version 1; referees: 3 approved] F1000Research 2015, 4:1462 (doi:
10.12688/f1000research.6995.1)
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.
https://en.wikipedia.org/wiki
August_Weismann
August Friedrich Leopold Weismann