Determination of Sex of Teratomas Derived From Early Mouse Embryos23

Abstract

Teratomas have been experimentally produced in mice from segmenting ova grafted to adult testes. These tumors might have originated in either of two ways. 1) The grafts give rise to cells with characteristics of primordial germ cells which in turn produce the tumors. 2) Since the embryonic cells are disorganized in the grafts, lack of normal intercellular relationships results in the retention of the proliferative embryonic state. The sex of 8 transplantable teratomas derived from intratesticular grafts of 6-day mouse embryos was determined by a count of the number of smallest chromosomes in metaphase figures. Female mouse cells contain 2 short chromosomes of equal size, which are significantly shorter than the second smallest autosomes. Male cells contain 3 small chromosomes, 2 of which are the smallest autosomes and 1 the Y chromosome. Four tumors sexed by this method were determined as male, and four as female. Since female primordial germ cells never produce teratomas experimentally, the presence of female tumors indicates that the neoplastic change occurred in undifferentiated cells. This supports the theory of spontaneous teratocarcinogenesis; i.e., diploid primordial germ cells give rise to a disorganized population of undifferentiated embryonic cells and these cells, in turn, undergo a neoplastic change.