Читать книгу Human Developmental Biology - Danton Inc. O'Day - Страница 11

In humans the germ cell lineage is not established in the same way as it is in lower animals. For one thing as mentioned above, "germ plasm" does not appear to exist in humans and other mammals and the germ line is not predetermined. In the rat and mouse a similar material called "nuage" does appear in the cytoplasm of presumptive germ cells prior to gastrulation but it cannot be detected before this in the egg or during cleavage. More to the point, while PGCs are derived from the posterior epiblast transplantation experiments have shown that this material is not determined early. For example, in the mouse the germ cell lineage only becomes defined around the time of gastrulation not during oogenesis or early cleavage as it does in lower animals. Grafting experiments have shown that many regions of the mouse embryo are capable of forming germ cells when they are transplanted to the extraembryonic mesoderm region of the epiblast prior to gastrulation. Based upon this research, it can be assumed that the human germ cell population arises in a similar way.