Oocyte Development in Hydra Involves Selection from Competent Precursor Cells

Abstract

We have investigated oocyte development in Hydra vulgaris, a member of one of the oldest metazoan phyla. We show that oocyte determination involves a mechanism that establishes a subset of precursor interstitial cells competent to differentiate into oocytes. The oocyte is singled out from this subset and the competence of the remaining cells to become oocytes dramatically decreases as they adopt the alternative nurse cell fate. Progression through the nurse cell differentiation program requires the presence of the oocyte. When the oocyte is removed from the egg field, nurse cells abort their differentiation program, undergo apoptosis, and are phagocytosed and degraded by somatic epithelial cells. However, in the presence of the oocyte, nurse cells differentiate and enter an unusual apoptosis program where they are phagocytosed by the oocyte, but are not degraded. We show that the oocyte is able to induce this unusual apoptosis program in immature nurse cells that have not completed differentiation. A new model for oocyte development in Hydra is discussed.

Naturally occurring tumours in the basal metazoan Hydra

“…Conversely, the tumour cells resemble in size and morphology large germ cells, described as 'germ cell II' (GCII) 20 , which can be observed in early stages of oogenesis (stage 1-3 (ref. 21), Supplementary Figs 1a-d and 2). In normal polyps, GCII cells appear in the ectoderm of female polyps only after oogenesis is initiated by environmental stimulus.…”

Evolutionary history of the mammalian synaptonemal complex

“…One of the centrally lying cells in the aggregate becomes the oocyte while the rest of the numerous cells turn into nutrient rich nurse cells. These will undergo apoptosis later and will be phagocytosed by the oocyte (Miller et al 2000). Because there is only a small amount of oocytes per animal at a time, the female oogenesis is less convenient for meiosis research.…”

In an early branching metazoan, bacterial colonization of the embryo is controlled by maternal antimicrobial peptides

“…In the oocyte (Fig. 2 I and J), which has engulfed thousands of surrounding interstitial "nurse" cells (17), granules containing periculin1a are localized within the ooplasm. Male polyps do not express the gene (Fig.…”