Abstract
Primordial germ cells represent the founder population for establishing the germ line providing the continuity of life between generations. PG2, a germ cell-specific antigen, is one of the few continuously detectable epitopes in mammalian primordial germ cells and it is dynamically expressed during early post-fertilization development and during postnatal germ cell maturation. Immunoelectron microscopy shows a localization of PG2 in the peri-mitochondrial cytoplasm but its further subcellular or biochemical nature remains elusive. For further characterization of the PG2 epitope we used regular and semi-thin cryosection of ovulated and isolated follicular rabbit oocytes and localized all mitochondria with the help of the constitutive mitochondrial antigen MTC02 in double immunofluorescence stainings. Semi-thin cryosections of ovulated oocytes revealed a general close co-localization of both antibody reactions at the level of single mitochondria. In centrifuged follicular oocytes both antigens co-sedimented almost completely indicating a topographical association of the epitopes on the basis of a strong interaction of PG2 with mitochondria. To begin to characterize the germ cell epitope biochemically we treated oocyte cryosections either with acetone to reduce lipids or with N-glycosidase F to remove N-linked glycosylations before the immuoreaction. Neither treatment affected the antibody characteristics, which suggests that the PG2 epitope is most probably a protein. Because of the close interaction of PG2 with the mitochondria we speculate that PG2 is involved in the change of the mitochondrial morphology typically observed during differentiation of germ cells.
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Acknowledgements
The authors like to thank Elke Bernhard for her outstanding technical assistance and Rosemarie Rappold for her practical support.This work was supported by the Deutsche Forschungsgemeinschaft (grant vi 151/6-1) and by the Deutsche Akademische Austauschdienst (grant D/0205773).
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Püschel, B., Demus, U. & Viebahn, C. Subcellular characterization of the primordial germ cell antigen PG2 in adult oocytes. Histochem Cell Biol 124, 275–284 (2005). https://doi.org/10.1007/s00418-005-0041-9
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DOI: https://doi.org/10.1007/s00418-005-0041-9