Since the late 1990s, when Ian Wilmut and Keith Campbell cloned Dolly, the now-famous Finn-Dorset sheep, the pantheon of mammals cloned by somatic cell nuclear transfer (SCNT) has expanded to include cows, mice, goats, pigs, rabbits, cats, mules, rats, horses, and dogs. Now, researchers report a new addition to the cloned mammal club: Mustela putorius furos, the domestic ferret.

Ferrets have great potential for research because of the striking similarity between human and ferret pulmonary physiology, which makes ferrets good models for studies of influenza and other respiratory diseases. John F. Engelhardt and Li Ziyi, researchers at the University of Iowa (Iowa City), and their research team became interested in ferrets as an outgrowth of their interest in cystic fibrosis (CF), a common inherited disease characterized by the accumulation of thick, sticky mucus in the lungs that blocks the airways and causes premature death. The striking physiological similarity between the ferret and human lung would make ferrets ideal candidates for the study of CF, for which at present there is no appropriate animal model. To use a ferret in this capacity, however, a CF ferret would be necessary. Unfortunately, no such ferret has yet been found.

That lack has not discouraged Engelhardt and his fellow researchers; they have proposed to create a CF ferret. As a first step Engelhardt's team set out to clone wild-type ferrets using SCNT. Although Engelhardt and Li had other cloning models to follow, they had to tailor cloning protocols specifically to ferrets. After failed cloning attempts using superovulated eggs, Engelhardt's team decided to try the procedure using naturally ovulated oocytes. Once they had harvested the oocytes, Engelhardt and his colleagues enucleated them and placed ferret somatic cells into the perivitelline space. They then fused the cells via an electric pulse.

The result was two viable female ferrets that have since been successfully bred (Dev. Biol., May). The next step toward the greater goal of this research is to insert a defective copy of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which causes CF, into somatic ferret cells cultured in vitro. The nuclei from those cells can then be removed for use in cloning, eventually giving rise to a supply of ferrets that would be used for CF research.

How soon can we expect cloned ferrets for CF research? “Putting a time on getting a CF ferret is difficult,” Engelhardt told Lab Animal, “we hope within 2 years, but the major variable involves the health and numbers of CFTR-targeted fibroblast cells we can obtain.”