Scrambling the egg origin dogma

Evaluation of: Eggan K, Jurga S, Gosden R, Min IM, Wagers AJ. Ovulated oocytes in adult mice derive from non-circulating germ cells. Nature 441, 1109–1114 (2006) [1]. This interesting study investigates the hypothesis that stem cells in adult bone marrow and the circulatory system populate mouse ovaries and contribute to the germline. When pairs of GFP+ and GFP- parabiotic mice with joined circulatory systems were superovulated after 8 months of parabiosis, oocytes collected from the oviducts had the phenotype of the animal from which they had come. Follow-up experiments, in which oocytes were chemically destroyed before establishing parabiosis, yielded similar results. Injection of GFP+ or GFP- bone marrow cells into mice with ovaries ablated using ovotoxins or irradiation did not rescue production of ovulated oocytes. These data do not support the controversial hypothesis that bone marrow stem cells contribute to the germline of adult female mice.