A chromosome from a frozen rat produced RNA again in a living mouse
Wakayama's group derived 17 ES cell lines from a rat frozen over a year; two retained rat chromosome 9, which showed 64 expression peaks matching rat heart tissue in chimeric mice, demonstrating that frozen genetic material can produce RNA again in a living interspecies system.
17 ES cell lines (embryonic stem cells) from a rat frozen for more than a year at -30°C. Only two retained a rat chromosome. Spectral karyotyping, a method that colors chromosomes by species of origin, identified the extra chromosome in both lines as rat chromosome 9. In the hearts of chimeric mice grown from those two lines, the group detected 64 expression peaks matching rat heart tissue. One traced to a specific gene, Hsp90ab1, on chromosome 9. Sayaka Wakayama and Teruhiko Wakayama published the paper June 1 in Scientific Reports. "Resurrection" in the title refers to a single chromosome.
What they did. Full cloning requires an intact donor cell nucleus, oocytes from a closely related species, and surrogate females. For an extinct or poorly preserved animal, that chain quickly breaks down: the cells are dead, the DNA is damaged, the related species may be rare, and obtaining hundreds of oocytes may be impossible. Sequencing gives you a DNA sequence but cannot tell you whether it functions in a living cell. The Wakayama group took an intermediate approach: they injected frozen rat blood cell nuclei into mouse oocytes whose own nuclei had been removed. Inside the oocyte, rat DNA condensed into separate chromosomes. They treated the oocyte with compounds that dismantle microtubules, pulled out a single chromosome with a glass micropipette, transferred it to a fresh mouse oocyte, and fertilized it with mouse sperm.
Only chromosome 9 proved workable. Other rat chromosomes may have disrupted early mouse embryo development or been lost in ES cells. Pig and cow cell nuclei also condensed into chromosomes inside mouse oocytes (the first step works), but the team has not yet carried that through to stable cell lines.
For cryobiology and de-extinction, this is a proof of concept: a single chromosome can be extracted from frozen biological material and tested to see whether its genes still function in a living cell. For rat chromosome 9, they do. But so far, one chromosome, one donor species, one host species.
George Church, #3 in the Eternal Search heroes rating (score 44.0).
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The paper's de-extinction keywords map directly to George Church (#3 in Eternal Search heroes, score 44.0), co-founder of Colossal Biosciences. The approved concept uses Church's bet as the frame: Wakayama's 2/17 chromosome-retention rate and one-year freezing window are the concrete baseline against which Colossal's multi-gene, multi-chromosome, multi-millennium task should be measured. Bob More is an investor tracked on Eternal Search; his profile is surfaced for readers interested in who is positioning financially around bets in this field.