Suppression of male pronuclear movement in frog eggs by hydrostatic pressure and deuterium oxide yields androgenetic haploids.

The disruptive effects of microtubule-specific agents on pronuclear movement illustrate the requirement of an intact cytoskeletal system for movement. In this study, we investigated the effects of high hydrostatic pressure and deuterium oxide (D2O) on fertilized Rana pipiens eggs during the time of pronuclear migration. The eggs were either pulsed for six min with 3000, 5000, or 7000 psi or placed for ten min in 80% D2O between the time of second polar body emission and first cleavage. Both treatments disrupted male pronuclear migration as shown by eccentric first cleavage furrows. Treatment of eggs prior to pronuclear association resulted in haploid production. The androgenetic origin of the haploid embryos was demonstrated using morphological and isozymal markers produced by the cross Rana pipiens female x Rana utricularia male. Eggs treated with D2O also yielded embryos with neural defects identical to those following ultraviolet irradiation. This study complements the recent reports on pressure-suppression of the second polar body and of first cleavage by showing that the selective suppression of microtubular function between these two events produces an entirely different set of genetic and developmental consequences.