Two-Faced Cats: How Do They Get That Way? (via National Geographic)

Last weekend, during the charity event of one of the cat sanctuaries in Malta, we were talking about the Janus Cat and investigated about this genetic mutation. Here's a nice article on National Geographic from 2 years ago about the subject:

"The famous two-faced cat, Frank and Louie (sometimes called Frankenlouie), passed away this week at the ripe old age of 15. The Massachusetts feline held the Guinness Book of World Records title for the longest lived Janus cat.

Named for the Roman god Janus, who was usually portrayed as having two faces, domestic cats with two faces are extremely rare, noted Leslie Lyons of the University of Missouri's Department of Veterinary Medicine and Surgery, who specializes in feline genetics. (Related: "R.I.P. Duecy: The Kitten With Two Faces.")

The animals also generally don't live very long due to health problems related to their deformity—making Frank and Louie's 15-year run that much more impressive, Lyons said.

The cause of Janus cats isn't completely understood, but "we know there's a variety of genetic mechanisms that could cause it," Lyons said. Only DNA testing can pinpoint the exact cause..." read on.