Germ cell differentiation

III. ROLE OF PROTEIN PHOSPHORYLATION IN GERM CELL DIFFERENTIATION... 

Observations from various systems, including yeast, suggest that phosphorylation and dephosphorylation of proteins play important roles in the mitotic and meiotic cell cycles and the differentiation of germ cells. Extracts from mitotic HeLa cells contained phosphoproteins also present in other mitotic and meiotic cell types, but not in interphase cells (Davis et al., 1983). Exposure of Xenopus oocytes to progesterone results in a burst of protein phosphorylation shortly before GVBD (Mailer et al.,... 

Determine whether guided differentiation toward one germ cell layer or differentiation phenotype is a better predictive model than the undirected differentiation culture protocol used currently. 

In the humans, the primordial germ cells are differentiated from about the sixth week of gestation and are consequently susceptible from then onward. In the female, production of the primary oocytes, which involves the first meiotic division, occurs in fetal life. These primary oocytes do not mature into ova until puberty, with the second meiotic division yielding one ovum from each primary oocyte (Fig. 6.48). 

A well-fed hydra (Fig. 1-13) appears immortal. Its body cells are sloughed off and replaced at a steady rate so that within a month or so its body has been completely renewed 35 The hydra contains only ten cell types. These include two kinds of stem cells that give rise to the ectodermal and endodermal cells of the body wall as well as small interstitial stem cells (Fig. 1-13) that differentiate nerve cells, germ cells, and the nematocytes or stinging cells. Of the 105 cells in a hydra about 3600 are interstitial stem cells. Each day they generate 400 nerve cells and 1800 nematocyte precursor cells as well as 3500 new interstitial cells. 

Kunz, W. (2001) Schistosome male-female interaction induction of germ-cell differentiation. Trends in Parasitology 1 7, 22 7-231. 

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