One Health: Animal Models of Heritable Human Bleeding Diseases

Animal models of human and animal diseases have long been used as the lynchpin of experimental and clinical research. With the discovery and implementation of novel molecular and nano-technologies, cellular research now has advanced to assessing signal transduction pathways, gene editing, and gene therapies. The contribution of heritable animal models to human and animal health as related to hemostasis is reviewed and updated with the advent of gene editing, recombinant and gene therapies.

Genetic epidemiology of blood type, disease and trait variants, and genome-wide genetic diversity in over 11,000 domestic cats

In the largest DNA-based study of domestic cats to date, 11,036 individuals (10,419 pedigreed cats and 617 non-pedigreed cats) were genotyped via commercial panel testing elucidating the distribution and frequency of known disease, blood type, and physical trait associated genetic variants across cat breeds. This study provides allele frequencies for many disease-associated variants for the first time and provides updates on previously reported information with evidence suggesting that DNA testing has been effectively used to reduce disease associated variants within certain pedigreed cat populations over time. We identified 13 disease-associated variants in 47 breeds or breed types in which the variant had not previously been documented, highlighting the relevance of comprehensive genetic screening across breeds. Three disease-associated variants were discovered in non-pedigreed cats only. To investigate the causality of nine disease-associated variants in cats of different breed backgrounds our veterinarians conducted owner interviews, reviewed clinical records, and invited cats to have follow-up clinical examinations. Additionally, genetic variants determining blood types A, B and AB, which are relevant clinically and in cat breeding, were genotyped. Appearance-associated genetic variation in all cats is also discussed. Lastly, genome-wide SNP heterozygosity levels were calculated to obtain a comparable measure of the genetic diversity in different cat breeds. This study represents the first comprehensive exploration of informative Mendelian variants in felines by screening over 10,000 pedigreed cats. The results qualitatively contribute to the understanding of feline variant heritage and genetic diversity and demonstrate the clinical utility and importance of such information in supporting breeding programs and the research community. The work also highlights the crucial commitment of pedigreed cat breeders and registries in supporting the establishment of large genomic databases, that when combined with phenotype information can advance scientific understanding and provide insights that can be applied to improve the health and welfare of cats.

Domestic cats are one of the world’s most popular companion animals, of which pedigreed cats represent small unique subpopulations. Genetic research on pedigreed cats has facilitated discoveries of heritable conditions resulting in the availability of DNA testing for studying and managing inherited disorders and traits in specific cat breeds. We have explored an extensive study cohort of 11,036 domestic cat samples representing pedigreed cats of 90 breeds and breed types. This work provided insight into the heritage of feline disease and trait alleles. We gained knowledge on the most common and relevant genetic markers for inherited disorders and physical traits, and the genetic determinants of the clinically relevant AB blood group system. We also used a measure of genetic diversity to compare inbreeding levels within and between breeds. This information can help support sustainable breeding goals within the cat fancy. Direct-to-consumer genetic tests help to raise awareness of various inherited single gene conditions in cats and provide information that owners can share with their veterinarians. In due course, ventures of this type will enable the genetics of common complex feline disease to be deciphered, paving the way for precision healthcare with the potential to ultimately improve welfare for all cats.

Factor XII deficiency is common in domestic cats and associated with two high frequency F12 mutations

Factor XII (FXII) is a coagulation protein that initiates surface-activation of the coagulation cascade in vitro. The protein's in vivo role, however, remains poorly defined. Factor XII deficiency, or Hageman trait, is a rare hereditary disorder that is not associated with bleeding, and wide variations in FXII activity (FXII:C) exist among healthy people. While FXII-deficient knockout mice appear to be resistant to arterial thrombosis, human F12 polymorphisms that influence FXII:C have not been associated with thrombotic risk in population surveys. Factor XII deficiency is a naturally occurring hereditary trait in domestic cats. We undertook phenotypic and genotypic analyses of FXII-deficient cats for comparative studies with the human disease counterpart. A retrospective review of feline submissions to our laboratory revealed that FXII deficiency is common in domestic cats, and also present in many different breeds. The trait has a geographic bias toward the Midwestern United States. Clinical history, coagulation assays, and samples for F12 sequencing were obtained from 26 FXII deficient cats. None of the cats had experienced abnormal bleeding and their residual FXII:C was related to F12 mutation number and mutation-type. We found 2 high frequency F12 mutations: an exon 13 missense mutation (c.1631G > C) and an exon 11 deletion mutation (c.1321delC), and additional sequence variants throughout the gene. Factor XII deficiency in pet cat populations provides an animal model system to help clarify the biologic actions and clinical relevance of FXII protein.

A novel missense mutation in the factor XII gene in a litter of cats with factor XII deficiency

The feline F12 gene was examined to identify a mutation associated with coagulation factor XII (FXII) deficiency in a litter of 6 cats, including 2 cats with severely reduced FXII activity (7.1 and 9.3%, respectively) and 4 cats with moderately reduced FXII activity (range 36.0 to 46.3%). Cats with severely reduced FXII activity were homozygous for a G to C missense mutation in exon 13 of the F12 gene, resulting in an amino acid change (p.G544A). Cats with moderately reduced FXII activity were heterozygous for this mutation. Expression studies revealed reduced secretion of p.G544A mutant FXII protein from transfected HEK293 cells compared with wild type FXII. These results reveal a novel F12 mutation in FXII deficient cats and define the underlying mechanism for low FXII activity in homozygotes.

DNA mutations of the cat: the good, the bad and the ugly

PRACTICAL RELEVANCE

The health of the cat is a complex interaction between its environment (nurture) and its genetics (nature). Over 70 genetic mutations (variants) have been defined in the cat, many involving diseases, structural abnormalities and clinically relevant health concerns. As more of the cat's genome is deciphered, less commonly will the term 'idiopathic' be used regarding the diagnosis of diseases and unique health conditions. State-of-the-art health care will include DNA profiling of the individual cat, and perhaps its tumor, to establish the best treatment approaches. Genetic testing and eventually whole genome sequencing should become routine diagnostics for feline health care.

GLOBAL IMPORTANCE

Cat breeds have disseminated around the world. Thus, practitioners should be aware of the breeds common to their region and the mutations found in those regional populations. Specific random-bred populations can also have defined genetic characteristics and mutations.

AUDIENCE

This review of 'the good, the bad and the ugly' DNA variants provides the current state of knowledge for genetic testing and genetic health management for cats. It is aimed at feline and general practitioners wanting to update and review the basics of genetics, what tests are available for cats and sources for genetic testing. The tables are intended to be used as references in the clinic. Practitioners with a high proportion of cat breeder clientele will especially benefit from the review.

EVIDENCE BASE

The data presented is extracted from peer-reviewed publications pertaining to mutation identification, and relevant articles concerning the heritable trait and/or disease. The author also draws upon personal experience and expertise in feline genetics.