Feline genetics: clinical applications and genetic testing

Abstract

DNA testing for domestic cat diseases and appearance traits is a rapidly growing asset for veterinary medicine. Approximately 33 genes contain 50 mutations that cause feline health problems or alterations in the cat's appearance. A variety of commercial laboratories can now perform cat genetic diagnostics, allowing both the veterinary clinician and the private owner to obtain DNA test results. DNA is easily obtained from a cat via a buccal swab with a standard cotton bud or cytological brush, allowing DNA samples to be easily sent to any laboratory in the world. The DNA test results identify carriers of the traits, predict the incidence of traits from breeding programs, and influence medical prognoses and treatments. An overall goal of identifying these genetic mutations is the correction of the defect via gene therapies and designer drug therapies. Thus, genetic testing is an effective preventative medicine and a potential ultimate cure. However, genetic diagnostic tests may still be novel for many veterinary practitioners and their application in the clinical setting needs to have the same scrutiny as any other diagnostic procedure. This article will review the genetic tests for the domestic cat, potential sources of error for genetic testing, and the pros and cons of DNA results in veterinary medicine. Highlighted are genetic tests specific to the individual cat, which are a part of the cat's internal genome.

Figure 1. Genetic sequence for the cat “points” mutation

a) Protein sequence, b) DNA sequence. The letters on the top line are the single letter codes for amino acids, for example, a P is proline, an N is asparagine, an R is arginine, and a G is glycine. The top line is the sequence for a normal, non-pointed cat. The second line is the sequence in humans, the third is the Siamese-pointed cat, and the bottom line is the sequence for the domestic dog. c) A Dominant white Siberian cat with yellow eyes had one allele for points but the other allele had a normal DNA variant. This variant did not change the amino acid, this is silent. A genetic test that incorporates this sequence surrounding the mutation for points may fail in some cats, producing allelic drop-out. The cat would have a result of homozygous for points. All pointed cats must have blue eyes, thus, this variant was identified and the genetic assay changed to account for this possibility in the flanking genetic sequencing.