Primordial germ cells of the rabbit are specifically recognized by a monoclonal antibody labelling the perimitochondrial cytoplasm.

Instrumental for studies investigating the development of germ cells, and especially the separation of the germline in the early embryo, are molecular markers which reliably label germ cells and with which regulative factors of germ cell development may be analyzed. Here, we describe the monoclonal antibody PG-2, which is highly specific for the germ cells of the rabbit embryo and labels the perimitochondrial cytoplasm, as demonstrated by immunogold-silver staining. Identical expression patterns are found in germ cells of either sex from early organogenesis at 10 days post-conception (d.p.c.), when the germ cells leave the hindgut epithelium and settle in the gonadal anlage as primordial germ cells (PGCs), until the time immediately prior to birth (30 d.p.c.), when germ cells are either in their oogonial or prospermatogonial state. The antibody is the first to recognize specifically a cytoplasmic epitope in germ cells of a higher vertebrate and may well recognize the mammalian equivalent of the germ plasm found in invertebrates and lower vertebrates. The antibody can be used for early identification of PGCs and may be of help in the elucidation of mammalian germ cell development towards the gonial stages of spermatogenesis and oogenesis.