GROWTH OF MOUSE PUPS DERIVED FROM BIOPSIED BLASTOCYSTS

Objective: To test the hypothesis that removal of cells from the pre-e mbryo affects intrauterine growth, as reflected in birth weight or gro wth to weaning. Methods: ICR Swiss albino and C57Bl/6 mice served as e mbryo donors to provide two strains of distinct coat colors. Alternate strains were assigned to control treatment or blastocyst biopsy of tr ophectoderm. Embryos from both treatments were transferred to a differ ent uterine horn within each pseudopregnant recipient. A total of 412 embryos (206 controls and 206 biopsied blastocysts) were transferred t o 26 recipients, which resulted in the birth of 122 pups. Results: The re was no significant difference (P > .1) in birth weight or growth to weaning, defined as [[(weaning weight - birth weight)/birth weight)] x 100], between male and female pups. There was a significant differen ce (P < .01) between pups derived from ICR (birth weight 1.9 +/- 0.02 g; growth to weaning 544 +/- 14%; n = 72) versus C57Bl/6 (birth weight 1.43 +/- 0.03 g; growth to weaning 460 +/- 14%; n = 50) embryos. Howe ver, there was no significant difference (P > .1) in birth weight or g rowth to weaning for pups derived from biopsied embryos (birth weight 1.70 +/- 0.03 g; growth to weaning 502 +/- 14%; ($) over bar X +/- sta ndard error of the mean; n = 67) or control embryos (birth weight 1.71 +/- 0.05 g; growth to weaning 520 +/- 17%; n = 55). Conclusion: These data support the null hypothesis that embryo biopsy does not result i n reduced birth weight or altered subsequent growth to weaning.