F3 is an old gene, originally developed in fish over 450 million years ago pubmed.ncbi.nlm.nih.gov/12871284/ so cats certainly have it. Association with spontaneous nose bleeds perhaps, or covid-19 severity?

Now I can see my reply….

Hmm. I just replied but can’t see it now. Another try: I haven’t read the paper but would guess it is F3 which codes for tissue factor and together with FVII initiates blood coagulation.

Without looking at the paper my guess is F3, which codes for tissue factor and together with FVII initiates blood coagulation.