F9 and hemophilia B: As an alternative animal model of hemophilia B, dogs with spontaneously acquired mutations that were further established during breeding are used: a Cairn terrier with a mutation leading to the amino acid substitution E379G and the absence of detectable factor IX; a Lhasa Apso with a 5 nt deletion 772–776 and a g.777C > T substitution, also without detectable factor IX and without development of inhibitors upon administration of canine factor IX; and a Labrador retriever with a complete F9 deletion that developed inhibitors [36].