Stability of transferred human chromosome fragments in cultured cells and in mice

Chromosome fragments represent feasible gene delivery vectors with the use of microcell-mediated chromosome transfer. To test a prerequisite for a gen e delivery vector, we examined the stability of human chromosome fragments (hCFs) in cultured cells and in trans-chromosomic (Tc) mice. Fragments of h uman chromosomes 2 (hCF(2-W23)), 11 (hCF-11) and 14 (hCF(SC20)) tagged with neo were introduced into the TT2F mouse ES cells, and retention of the hCF s was examined by FISH during long-term culture without selection. In contr ast to the gradual loss of hCF(2-W23) and hCF-11, hCF(SC20) remained stable over 70 population doublings in the ES cells. The hCF(SC20) was also stabl e in cultured human tumor cells and chicken DT40 cells. We have previously generated chimeric mice using the ES cells harboring the hCF(2-W23) or hCF( SC20), followed by production of Tc mice. Although both the hCF(2-W23) and hCF(SC20) persisted in cells of Tc mice as an additional chromosome and wer e transmitted to offspring, the hCF(SC20) was more stable than the hCF(2-W2 3) in F1 and F2 mice. The present study shows that the stability of hCFs in Tc mice differs with tissue types and with genetic background used for suc cessive breedings. Thus, the hCF(SC20), which was relatively stable in both mouse and human cells, may be a promising candidate for development as a g ene delivery vector.