Fusion of unfertilized mouse eggs with somatic cells

The purpose of these investigations was to study optimal conditions for the maintenance and stimulation of division of unfertilized mouse eggs in culture after fusion with somatic cells of various species origin. When unfertilized eggs obtained from superovulated C57B1/6 virgin mice were maintained in culture in Brinster's medium for 72 hours, less than 6% of the eggs divided. Following fusion in the presence of inactivated Sendai virus with somatic cells of mouse, hamster, monkey or human origin, 10 to 60% of the eggs divided, often developing to the early morula stage (3–10 cells). Blastomeres observed at this stage of development did not differ morphologically from embryo cells dividing after fertilization. Examination of autoradiograms obtained after fusion of eggs with labeled somatic cells support the belief that fusion may be a factor which initiates egg cell division. Ultimately, nuclei of the somatic cells inside the cytoplasm undergo karyorrhexis. Mouse fibroblasts infected with Moloney sarcoma virus fused better with egg cells than did non‐infected fibroblasts.