For the first time, the College of Veterinary Medicine at the University of Missouri, under the direction of Leslie Lyons, PhD the Gilbreath-McLorn Endowed Professor of Comparative Medicine, now offers a test for Silver (Inhibitor) Color in cats. In just 5 steps, a test result will be emailed to you in a matter of weeks confirming if a cat is silver!
Leslie Lyons, PhD is renowned around the world for her tenacious and successful efforts to unravel the mysteries of the cat from within the feline genome. Years of efforts have allowed her to provide a test she’s been repeatedly asked for by feline enthusiasts around the world.
On behalf of TICA I asked Dr. Lyons, “How much effort has it taken to identify the inhibitor locus and create a test?” Dr. Lyons responded, “I am constantly asked for the Silver test, so, against the scientific standards and norms, we are releasing the test before we know how the DNA variant acts on a gene and reduces the pheomelanin. Until we know the function, we will not be releasing the test to other labs. I realize breeders are hoping to get the test for less money from the companies that offer large panel testing, but we really need to raise funds to continue the research aspects.”
Dr. Lyons went to point out, “many argue there is a recessive form of Silver. We may then ask other labs to help when we try to resolve potential recessive situations. However, we are hoping breeders will consider requesting the test as a contribution to our laboratory and to further the science on Silver (Inhibitor) and other projects. Since our lab has helped to identify nearly 30% of the DNA variants in cats, and we build resources for all scientists to use, I hope breeders will recognize the efforts and tell us job well done by requesting the test.”
Silver (Inhibitor) is called that because the fur of cats with this trait is prevented or inhibited from the expression of yellow, brown, tan, gray, and other colors that provide the visual background to tabby patterns. The lower portion of the hair shaft and the agouti bands have white hair instead of shades of brown/yellow/tan/gray, thus creating the visual silver coloration. Silver or Silver tabby, black smoke, chocolate, seal silver lynx tabby point, silver shaded are color patterns that can be confirmed through genetic testing.
A silver cat has one or two copies of the DNA variant causing silver. The test will determine if a cat has one or two copies. A cat with two copies of the silver (inhibitor) DNA variant will only produce silver offspring. Some have posited these cats, homozygous or having two copies of same DNA variant, demonstrate less rufousing, or golden/brown/yellow tones to their coloration, than those with just one copy.
No other laboratory in the world can offer silver (inhibitor) genetic testing in cats. The University of Missouri Veterinary School makes it clear they are testing for the inhibitor locus, a specific genetic position on a certain chromosome. Feline enthusiasts can help Dr. Lyons and her research colleagues identify the specific gene or genes by participating in the test, which requires photos of each cat.
Dr. Lyons described the importance of the breeder, enthusiast community, scientists, and researchers in helping further decipher the silver (inhibitor) genetic variant. Dr. Lyons noted, “Several laboratories have confirmed the genetic location of Silver using different cats and methods of analyses over the years. Our lab refined the ‘linkage’ location using microsatellite markers and an extended family of cats while back at UC Davis. Once getting to under a 1,000,000 basepair region (1 Mb), we did direct sequencing of every one of the genes in the region, but to no avail. Every person in the lab had a different gene with all the exons written out. We basically did a big tick-tack-toe board – eliminating all the coding regions of each gene.”
This left Silver as likely an intronic or intragenic mutation, like Spotting or Glitter, or exons that could be in the wrong order – a genetic inversion, like glycogen storage disease in Norwegian Forest cats. Genome-wide association studies using cases and controls and DNA arrays also re-located the candidate genomic region, but the causal variant remained unidentified. Once the lab transitioned to MU, whole genome sequencing techniques became available, as did a better cat genome assembly and better annotation of the genes. Only the most recent techniques have allowed the identification of the candidate mutation. Thus, the lab has spent years and lots of reagents, resources, and personnel, far beyond the funding that has been obtained specifically for Silver but benefitting from funding from Winn Feline/EveryCat Health Foundation that has supported the development of the 99 Lives project.
Read more and test a cat for Silver (Inhibitor) on the University of Missouri Veterinary School website.
Photo courtesy of Helmi Flick.
