science
Scientists Create Limited Chimeric Mice With One Added Rat Chromosome From Frozen Tissue, Fail With Others
Researchers at the University of Yamanashi transferred a chromosome from a rat frozen for over a year into mouse cells, producing chimeric mice. The team now plans to test the method on elephant tissue and mammoth chromosomes.
Jun 7, 4:58 AM·2m read1 source
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Scientists at the University of Yamanashi created chimeric mice containing some cells with an added rat chromosome taken from tissue frozen for more than a year. The work demonstrates a method for introducing chromosomes from preserved samples into living cells. Teruhiko Wakayama at Yamanashi University led the project.
He was the first researcher to clone mice using nuclear transfer. The team extracted blood cells from the tail of a genetically modified rat engineered to fluoresce green, then used the cells to generate mouse embryonic stem cells carrying the extra rat chromosome. The process begins by extracting the nucleus of a donor cell and injecting it into an egg to trigger chromosome condensation.
Enzymes are added to help separate the chromosomes. A single chromosome is then removed with a microscopic hollow needle and injected into a second egg. If the egg develops into an embryo, the resulting embryonic stem cells contain the added chromosome.
These stem cells were injected into normal mouse embryos, which were implanted into female mice. The resulting chimeric mice appear normal but show green fluorescence under UV light in some cells, matching the original rat. The technique currently works only with rat chromosome 9.
When other chromosomes are added, the eggs do not develop into embryos. The team has not yet produced mice in which every cell contains the extra rat chromosome. Wakayama said the group is testing various methods to improve the success rate.
The immediate goal is to study gene activity from extinct animals inside living cells rather than relying solely on genetic sequences. The team has already obtained frozen elephant tissue from a zoo. Wakayama is also in contact with researchers who extracted and studied cell nuclei from a 28,000-year-old mammoth named Yuka.
