The cloning of “Dolly” from adult sheep tissue was widely hailed as a breakthrough 10 years ago this week, when it was published in Nature. David Wells of AgResearch, New Zealand, says “it is still remarkable that NT [nuclear transfer] using differentiated donor cells can produce physiologically normal cloned animals.”
However, as he points out in CAB Reviews, “the process is very inefficient, poorly understood and appears highly prone to epigenetic errors. With the present technology, only up to 6% of the embryos transferred to the reproductive tracts of recipient females typically result in long-term surviving clones. Not only are there high losses throughout gestation, during birth and in the immediate post-natal period, but also throughout adulthood.”
So will cloning have an impact in agriculture? “Considerably more efficient cloning methods will be required for large-scale dissemination of whole genotypes of elite livestock from nucleus herds directly to commercial producers,” says Wells. However, the genomics revolution may help cloning be more effective. “The continual advances in animal genomics towards the identification of genes that influence livestock production traits and human health serve to increase the ability to genetically modify cultured cells, prior to NT, to generate livestock with increased productivity or that produce superior quality food and biomedical products for niche markets.”
However, Wells is realistic about the practicalities beyond achieving successful cloning. “The potential opportunities for animal agriculture are more challenging because of the greater demands on cost, efficiency, consumer acceptance and relative value of the product to be viable in contrast to biomedical applications. Hence, the integration of this technology into practical farming systems remains some time in the future.”
The original Nature paper: Viable offspring derived from fetal and adult mammalian cells. Wilmut, I., Schnieke, A.E., McWhir, J., Kind, A.J. & Campbell K.H.S, Nature 385, 810–813 (27 Feb 1997).