Production of viable adult trisomy 17 reversible diploid mouse chimeras.

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Abstract
Aneuploid mouse embryos and fetuses are an important system for investigating the pathogenesis of the developmental and functional consequences of chromosome imbalance in mammals. The fact that almost all mouse aneuploids die in embryonic or fetal life restricts their usefulness for studies of loci and functions that are expressed only after birth. As an approach to rescuing aneuploid cells, chimeras were prepared by aggregating aneuploid embryos with diploid embryos at the 8-16 cell stage. This technique produced trisomy 17 .tautm. diploid (Ts17 .tautm. 2n) chimeras containing cells of a trisomic state, which is ordinarily lethal at 10-12 days of gestation. All of the analyzed organs from the chimeras, including brain, liver, kidney, lung, muscle, heart thymus, spleen, bone marrow, blood and skin, contained both Ts17 and 2n cells. The proportion of Ts17 cells in each organ as estimate dfrom coat color, enzyme markers (glucosephosphate isomerase), and karyotypes ranged from 5% to 85%, most commonly 20-40%. This is in contrast to the control 2n .tautm. 2n chimeras in which the 2n component on the same genetic background as the Ts17 generally comprised 60-90% of the cell population. The growth rates of the living Ts17 .tautm. 2n chimeras were in the lower half of the normal range, and the oldest animals are now age 14 mo. No progeny were obtained from Ts17 germ cells in the 2 fertile Ts17 .tautm. 2n chimeras. In comparison with analogous human situations, it is striking that, except for a kink in the tail of one living animal, none of the Ts17 .tautm. 2n chimeras had any discernible structural abnormalities. It seems feasible to rescue cells from autosomal aneuploidies that otherwise result in early fetal death.