Induction of supernumerary primordial germ cells by injecting vegetal pole cytoplasm into Xenopus eggs

A fraction, precipitated at 20,000 xG, from vegetal pole cytoplasm of Xenopus laevis eggs was able to induce supernumerary primordial germ cells (PGCs) when injected into subcortical cytoplasm near the vegetal pole of the fertilized egg. The ability to induce supernumerary PGCs was not abolished by digesting the fraction with pronase (Pronase E, 200 μg/ml, at 37° C for 30 min). The possible nature of the “germinal determinant” is discussed.