[1] Univ Teramo, Fac Vet Med, Teramo, Italy
[2] Polish Acad Sci, Dept Expt Embryol, Inst Genet & Anim Breeding, Jastrzebiec, Poland
[3] Natl Inst Nat Sci, Ctr Genet Anal Behav, Natl Inst Physiol Sci, Okazaki, Aichi, Japan
[4] Univ Cambridge, Wellcome Trust, Canc Res UK Gurdon Inst, Cambridge CB2 1QN, England