Abstract
Diploid gynogenetic mouse eggs were produced by the following micromanipulation procedures. Fertilized eggs were obtained 15 hrs after hCG injection from superovulated C57BL/6 (GPI type: bb) and Fl (C57BL/6 × CBA, GPI type: bb) females mated with males of CD-1 strain (GPI type: aa). The eggs were incubated with the culture medium (M16) including cytochalasin B (5μg/m1) for 4 hrs to suppress the second polar body extrusion. The eggs which had 3 pronuclei were used in the present study. Male pronucleus was microsurgically removed from the eggs following the method of BORSUK3) (Experiment 1) or of SURANI and BARTON4) (Experiment 2). The treated eggs were cultured for 1 to 5 days in vitro, then transferred to recipients. In some eggs, one of 2 female pronuclei was removed by the same method to restore the normal diploid state. The results obtained are as follows.
Experiment 1. Thirty-one of 44 eggs (70%) from C57BL/6 and 39 of 51 eggs (76%) from F1 fe-males were morphologically normal after micromanipulation, respectively. Sixteen of 39 eggs (41%) from the F1 females developed to blastocysts in vitro. Five of 15 blastocysts (33%) implanted after transfer, and one of them developed to a live fetus with 25 somites, GPI type of which was not deter-mined.
Experiment 2. The eggs from the F1 females were used through out. Out of 69 eggs manipulated 57 (83%) had morphologically normal appearance. Twenty-eight of them (49%) developed to morula or blastocyst stage. Out of 28 eggs transferred, 16 (57%) implanted and one of them developed to alive fetus with 27 somites, GPI type of which was ab, indicating the mistake in the enucleation pro-cedure. After removal of one of two female pronuclei, 39 outof 43 eggs (91%) were morphologically normal. The proportion of morulae or blastocysts developed in vitro from these eggs was 67% (26/ 39), being significantly P (<0. 05) higher than those for the gynogenetic eggs in Experiments 1 and 2.After transfer to recipients, 7 of 26 eggs developed to live fetuses on Day 18 of pregnancy, GPI type of which was all ab as expected. These results support the assertion by McGrath and Soter (1984) that both female and male genomes are necessary for normal development.
