Tyrosinase Mutations
So, you all remember the foolish floof that runs this blog and my life, right?
About a year ago, he colicked, we went to get some pain meds and subcutaneous fluids since he was free of an obstruction. Coriander then had some fatty infiltration in the area where he got his SC fluids over his right shoulder. We shaved his hair to collect a sterile sample with needles to observe this under the microscope.
About a month later, when his hair began growing back in it was black. Over the course of a year, it has grayed out, but my initial thought was: what the fuck?
Below are before and progress photos over the course of 10 months. (An auricular artery appreciation pic provided as well!)
Now that I am on my dermatology rotation, I finally have the answer. My attending did not know what a Lionhead is, so I had to show her my bunny. She asked me what I knew about his coat coloring and I had to admit that I did not know the mechanism for pointed hair coats (like Siamese cats have).
Tyrosinase is an enzyme that is involved in the synthesis of melanin, the brown-black pigment. Pointed animals have a mutation in their tyrosinase gene, resulting in it being temperature sensitive. In areas where it is cool, the extremities like the nose, ear, feet, and tail, the enzyme is increasingly active. These areas of the animal are then darker due to the increased amount of melanin production in the hair.
So, when I shaved Coriander’s shoulder, I made it very cold and so then his tyrosinase was activated during hair regrowth, making the hair much darker than it was before. This was probably more dramatic due to the time of year and his surface area:volume resulting in heat loss. I was confused for nothing and no one seemed to know what was up, but I now know when you shave pointed animals that coat color change is possible.