Hybrid vigor, fetal overgrowth, and viability of mice derived by nuclear cloning and tetraploid embryo complementation
- Kevin Eggan*,†,
- Hidenori Akutsu‡,
- Janet Loring*,
- Laurie Jackson-Grusby*,
- Martina Klemm*,
- William M. Rideout3rd*,
- Ryuzo Yanagimachi‡, and
- Rudolf Jaenisch*,†,§
- *Whitehead Institute for Biomedical Research and †Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, MA 02142; and ‡Institute for Biogenesis Research and Department of Anatomy and Reproductive Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96822
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Communicated by Robert A. Weinberg, Whitehead Institute for Biomedical Research, Cambridge, MA (received for review February 12, 2001)
Abstract
To assess whether heterozygosity of the donor cell genome was a general parameter crucial for long-term survival of cloned animals, we tested the ability of embryonic stem (ES) cells with either an inbred or F1 genetic background to generate cloned mice by nuclear transfer. Most clones derived from five F1 ES cell lines survived to adulthood. In contrast, clones from three inbred ES cell lines invariably died shortly after birth due to respiratory failure. Comparison of mice derived from nuclear cloning, in which a complete blastocyst is derived from a single ES cell, and tetraploid blastocyst complementation, in which only the inner cell mass is formed from a few injected ES cells, allows us to determine which phenotypes depend on the technique or on the characteristics of the ES cell line. Neonatal lethality also has been reported in mice entirely derived from inbred ES cells that had been injected into tetraploid blastocysts (ES cell-tetraploids). Like inbred clones, ES cell-tetraploid pups derived from inbred ES cell lines died shortly after delivery with signs of respiratory distress. In contrast, most ES cell-tetraploid neonates, derived from six F1 ES cell lines, developed into fertile adults. Cloned pups obtained from both inbred and F1 ES cell nuclei frequently displayed increased placental and birth weights whereas ES cell-tetraploid pups were of normal weight. The potency of F1 ES cells to generate live, fertile adults was not lost after either long-term in vitro culture or serial gene targeting events. We conclude that genetic heterozygosity is a crucial parameter for postnatal survival of mice that are entirely derived from ES cells by either nuclear cloning or tetraploid embryo complementation. In addition, our results demonstrate that tetraploid embryo complementation using F1 ES cells represents a simple, efficient procedure for deriving animals with complex genetic alterations without the need for a chimeric intermediate.
