-
Mammary epithelium cells from a 6-year-old Finn Dorset ewe in the last
trimester of pregnancy, were used as donors of nuclei.
- The donor cells were made quiescent by reducing the concentration
of serum
in the culture medium
from 10 to 0.5% for 5 days, causing them to exit the growth cycle
and arrest in G0.
- Electrical pulses were used to fuse nuclei from the donor cells
to oocytes from a Scottish Blackface ewe and to activate the oocytes.
- Most of the resulting embryos were cultur in ligated oviducts of
sheep, but some of those that had been derived from
embryonic or fetal cells were cultured in a chemically
defined medium.
- Embryos that had developed to the morula or blastocyst stage after 6
days in culture
were transferred to recipients
(1-3 embryos per recipient).
- DNA microsatellite analysis of the donor cell populations
and lambs for 4 polymorphic loci confirmed that each lamb was derived from
the nucleus donor.
- The lamb born after nuclear transfer from a mammary epithelium
cell is the first mammal known to be derived from an adult tissue.
- The fact that a lamb was derived from an adult cell confirms that
differentiation of that cell did not involve the irreversible modification
of the genetic material required for
development to term.