Читать книгу Human Developmental Biology - Danton Inc. O'Day - Страница 5

Primordial germ cells (PGCs) are the precursors of the sex cells. As such they are considered to be a type of stem cell. In lower animals, PGCs are determined by a specialized region of the cytoplasm called “germ plasm”. However there is no solid evidence that true germ plasm exist in humans or other mammals. In contrast, research has shown that similar genes to those found in lower animals are involved in the formation of human PGCs. Alkaline phosphatase is a classic germ cell "marker enzyme" for PGCs and can be used to determine when they first appear. Evidence indicates that human PGCs arise in a special region just prior to gastrulation appearing in the epiblast in the area that will become the extraembryonic mesoderm. Since they arise extra-gonadally (i.e., outside of the gonads), PGCs must migrate through different tissues to reach the genital ridges where the gonads will form.