Effect of egg composition on the developmental capacity of androgenetic mouse embryos

Analysis of the developmental capacities of androgenetic and gynogenetic mouse embryos (bearing two paternal or two maternal pronuclei, respectively) revealed a defect in blastocyst formation of androgenetic, but not gynogenetic, embryos that was a function of the maternal genotype. Androgenetic embryos constructed using fertilized eggs from C57BL/6 or (B6D2)F1 mice developed to the blastocyst stage at frequencies similar to those previously reported, whereas androgenetic embryos constructed with fertilized eggs from DBA/2 mice developed poorly, the majority failing to progress beyond the 16-cell stage and unable to form a blastocoel-like cavity, regardless of whether the male pronuclei were of C57BL6 or DBA/2 origin. This impaired development was observed even in androgenetic embryos constructed by transplanting two male pronuclei from fertilized DBA/2 eggs to enucleated C57BL/6 eggs, indicating that the defect cannot be explained as the lack of some essential component in the DBA/2 cytoplasm that might otherwise compensate for androgeny. Rather, the DBA/2 egg cytoplasm apparently modifies the incoming male pronuclei differently than does C57BL/6 egg cytoplasm. Several specific alterations in the protein synthesis pattern of DBA/2 androgenones were observed that reflect a defect in the regulatory mechanisms that normally modulate the synthesis of these proteins between the 8-cell and blastocyst stages. These results are consistent with a model in which cytoplasmic factors present in the egg direct a strain-dependent modification of paternal genome function in response to epigenetic modifications (genomic imprinting) established during gametogenesis and indicate that preimplantation development can be affected by these modifications at both the morphological and biochemical levels.