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-half-brothers-sisters-n458091

Pole cells are the primordial germ cell in Drosophlia http://biology.kenyon.edu/courses/biol114/Chap13/droslifecycle.jpg

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

Function of pole plasm Okada et al. 1974

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

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

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

In pgc mutant embryos, pole cells express the somatic cell marker Curr Biol. 2004 Jan 20;14(2):159-65.

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

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 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

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

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

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. 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,... 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: 10.12688/f1000research.6995.1) 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