A novel ITGA2B double cytosine frameshift variant (c.1986_1987insCC) leads to Glanzmann's thrombasthenia in a cat

BACKGROUND

Glanzmann's thrombasthenia (GT) is a congenital platelet disorder affecting approximately 1:1 000 000 people globally and characterized by impaired platelet aggregation and clot retraction. Autosomal recessive, loss-of-function, variants in ITGA2B or ITGB3 of the αIIbβ3 receptor cause the disease in humans. A cat affected by Glanzmann's and macrothrombocytopenia was presented to the UC Davis VMTH.

HYPOTHESIS/OBJECTIVES

Severe thrombopathia in this cat has an underlying genetic etiology.

ANIMALS

A single affected patient, 2 age-matched clinically healthy controls, and a geriatric population (n = 20) of normal cats.

METHODS

Physical examination and clinical pathology tests were performed on the patient. Flow cytometry and platelet aggregometry analyses for patient phenotyping were performed. Patient and validation cohort gDNA samples were extracted for Sanger sequencing of a previously identified ITGA2B (c.1986delC) variant. Reverse transcriptase PCR was performed on patient and healthy control PRP samples to verify ITGA2B variant consequence.

RESULTS

A novel c.1986_1987insCC autosomal recessive variant in ITGA2B was identified. This variant was absent in a population of 194 unrelated cats spanning 44 different breeds. Complete loss of ITGA2B transcript and protein expression was verified by RT-PCR and flow cytometry, explaining the underlying etiology of GT, and likely macrothrombocytopenia, in this cat.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study emphasizes the role of precision medicine in cardiovascular disease of cats and identified yet another variant that may be of utility for screening in the feline population. This study provides a small-volume, standardized, successful protocol for adequate platelet RNA isolation and subsequent molecular assessment of gene expression in cats.

A de novo nonsense variant in the DMD gene associated with X-linked dystrophin-deficient muscular dystrophy in a cat

BACKGROUND

X-linked dystrophin-deficient muscular dystrophy (MD) is a form of MD caused by variants in the DMD gene. It is a fatal disease characterized by progressive weakness and degeneration of skeletal muscles.

HYPOTHESIS/OBJECTIVES

Identify deleterious genetic variants in DMD by whole-genome sequencing (WGS) using a next-generation sequencer.

ANIMALS

One MD-affected cat, its parents, and 354 cats from a breeding colony.

METHODS

We compared the WGS data of the affected cat with data available in the National Center for Biotechnology Information database and searched for candidate high-impact variants by in silico analyses. Next, we confirmed the candidate variants by Sanger sequencing using samples from the parents and cats from the breeding colony. We used 2 genome assemblies, the standard felCat9 (from an Abyssinian cat) and the novel AnAms1.0 (from an American Shorthair cat), to evaluate genome assembly differences.

RESULTS

We found 2 novel high-impact variants: a 1-bp deletion in felCat9 and an identical nonsense variant in felCat9 and AnAms1.0. Whole genome and Sanger sequencing validation showed that the deletion in felCat9 was a false positive because of misassembly. Among the 357 cats, the nonsense variant was only found in the affected cat, which indicated it was a de novo variant.

CONCLUSION AND CLINICAL IMPORTANCE

We identified a de novo variant in the affected cat and next-generation sequencing-based genotyping of the whole DMD gene was determined to be necessary for affected cats because the parents of the affected cat did not have the risk variant.

First report of a novel 108 bp deletion and five novel SNPs in PRNP gene of stray cats and in silico analysis of their possible relation with feline spongiform encephalopathy

Prion diseases are fatal neurodegenerative diseases affecting humans and animals. A relationship between variations in the prion gene of some species and susceptibility to prion diseases has been detected. However, variations in the prion protein of cats that have close contact with humans and their effect on prion protein are not well-known. Therefore, this study aimed to investigate the variations of prion protein-encoding gene (PRNP gene) in stray cats and to evaluate variants detected in terms of genetic factors associated with susceptibility or resistance to feline spongiform encephalopathy using bioinformatics tools. For this, cat DNA samples were amplified by a PCR targeting PRNP gene and then sequenced to reveal the variations. Finally, the effects of variants on prion protein were predicted by bioinformatics tools. According to the obtained results, a novel 108 bp deletion and nine SNPs were detected. Among SNPs, five (c314A>G, c.454T>A, c.579G>C, c.642G>C and c.672G>C) were detected for the first time in this study. Bioinformatics findings showed that c.579G>C (Q193H), c.454T>A (Y152N) and c.457G>A (E153K) variants have deleterious effects on prion protein and c.579G>C (Q193H) has high amyloid propensities. This study demonstrates prion protein variants of stray cats and their deleterious effects on prion protein for the first time.

Association of a novel dystrophin (DMD) genetic nonsense variant in a cat with X-linked muscular dystrophy with a mild clinical course

X-linked muscular dystrophy in cats (FXMD) is an uncommon disease, with few reports describing its pathogenic genetic variants. A 9-year-old castrated male domestic shorthair cat was presented with persistent muscle swelling and breathing difficulty from 3 years of age. Serum activity of alanine aminotransferase, aspartate transaminase, and creatine kinase were abnormally high. Physical and neurological examinations showed muscle swelling in the neck and proximal limb, slow gait, and occasional breathing difficulties. Electromyography showed pseudomyotonic discharges and complex repetitive discharges with a "dive-bomber" sound. Histopathology revealed muscle necrosis and regeneration. Whole-genome sequencing identified a novel and unique hemizygous nonsense genetic variant, c.8333G > A in dystrophin (DMD), potentially causing a premature termination codon (p.Trp2778Ter). Based on a combination of clinical and histological findings and the presence of the DMD nonsense genetic variant, this case was considered FXMD, which showed mild clinical signs and long-term survival, even though immunohistochemical characterization was lacking.

Canine and Feline Models of Inherited Retinal Diseases

Naturally occurring inherited retinal diseases (IRDs) in cats and dogs provide a rich source of potential models for human IRDs. In many cases, the phenotypes between the species with mutations of the homologous genes are very similar. Both cats and dogs have a high-acuity retinal region, the area centralis, an equivalent to the human macula, with tightly packed photoreceptors and higher cone density. This and the similarity in globe size to that of humans means these large animal models provide information not obtainable from rodent models. The established cat and dog models include those for Leber congenital amaurosis, retinitis pigmentosa (including recessive, dominant, and X-linked forms), achromatopsia, Best disease, congenital stationary night blindness and other synaptic dysfunctions, RDH5-associated retinopathy, and Stargardt disease. Several of these models have proven to be important in the development of translational therapies such as gene-augmentation therapies. Advances have been made in editing the canine genome, which necessitated overcoming challenges presented by the specifics of canine reproduction. Feline genome editing presents fewer challenges. We can anticipate the generation of specific cat and dog IRD models by genome editing in the future.

Precision medicine using whole genome sequencing identifies a novel dystrophin (DMD) variant for X-linked muscular dystrophy in a cat

BACKGROUND

Muscular dystrophies (MDs) are a large, heterogeneous group of degenerative muscle diseases. X-linked dystrophin-deficient MD in cats is the first genetically characterized cat model for a human disease and a few novel forms have been identified.

HYPOTHESIS/OBJECTIVES

Muscular dystrophy was suspected in a young male domestic shorthair cat. Clinical, molecular, and genetic techniques could provide a definitive diagnosis.

ANIMALS

A 1-year-old male domestic shorthair cat presented for progressive difficulty walking, macroglossia and dysphagia beginning at 6 months of age. The tongue was thickened, protruded with constant ptyalism, and thickening and rigidity of the neck and shoulders were observed.

METHODS

A complete neurological examination, baseline laboratory evaluation and biopsies of the trapezius muscle were performed with owner consent. Indirect immunofluorescence staining of muscle cryosections was performed using several monoclonal and polyclonal antibodies against dystrophy-associated proteins. DNA was isolated for genomic analyses by whole genome sequencing and comparison to DNA variants in the 99 Lives Cat Genome Sequencing dataset.

RESULTS AND CLINICAL IMPORTANCE

Aspartate aminotransferase (687 IU/L) and creatine kinase (24 830 IU/L) activities were increased and mild hypokalemia (3.7 mmol/L) was present. Biopsy samples from the trapezius muscle confirmed a degenerative and regenerative myopathy and protein alterations identified by immunohistochemistry resulted in a diagnosis of a in dystrophin-deficient form of X-linked MD. A stop gain variant (c.4849C>T; p.Gln1617Ter) dystrophin was identified by genome sequencing. Precision/genomic medicine efforts for the domestic cat and in veterinary medicine support disease variant and animal model discovery and provide opportunities for targeted treatments for companion animals.

Osteochondrodysplasia and the c.1024G>T variant of TRPV4 gene in Scottish Fold cats: genetic and radiographic evaluation

OBJECTIVES

The objectives of this study were to investigate the c.1024G>T SNP in the TRPV4 gene in Scottish Straight and Fold cats, and to evaluate the pattern of skeletal phenotype and the evolution of radiological signs of Scottish Fold osteochondrodysplasia (SFOCD) over time in heterozygous subjects.

METHODS

DNA was obtained from blood samples of 17 cats (Scottish Fold: n = 12; Scottish Straight: n = 5) and subsequently genotyped by sequencing in a 249 bp region of the TRPV4 gene (exon 6), including the known c.1024G>T causative mutation for osteochondrodysplasia. Orthopaedic and radiographic analyses were performed on animals carrying the mutant allele.

RESULTS

Genotyping by sequencing confirmed that all and only the Scottish Fold cats carried the mutant allele in a heterozygous asset. Furthermore, two other exon variants, already described in the literature as silent variants, were found in some of the sampled cats. Comparative orthogonal radiographic views of the shoulder, elbow, carpus, hip, stifle and tarsus were obtained. A mediolateral projection of the thoracic and lumbar column was also performed. Three out of four cats were clinically and radiographically examined again 1.5 years later.

CONCLUSIONS AND RELEVANCE

Although the presence of the mutant allele in all the tested Scottish Fold cats was confirmed, only 1/12 showed clinical signs of SFOCD. Furthermore, no cats in the 1.5-year follow-up showed skeletal changes. Although significant, the c.1024G>T mutation in the TRPV4 gene, supposedly, is not the only cause or risk of developing SFOCD.

How domestic cats wiped out the Scottish wildcat

After millennia of isolation, a few decades of interbreeding have rendered the animal "genomically extinct".

Optical detection using CRISPR-Cas12a of Helicobacter pylori for veterinary applications

Helicobacter pylori (H. pylori) is a zoonotic gastric microorganism capable of efficient interspecies transmission. Domesticated companion animals, particularly dogs and cats, serve as natural reservoirs for H. pylori. This phenomenon facilitates the extensive dissemination of H. pylori among households with pets. Hence, the prompt and precise identification of H. pylori in companion animals holds paramount importance for the well-being of both animals and their owners. With the assistance of Multienzyme Isothermal Rapid Amplification (MIRA) and CRISPR-Cas12a system, we successfully crafted a highly adaptable optical detection platform for H. pylori. Three sensor systems with corresponding visual interpretations were proposed. This study demonstrated a rapid turnaround time of approximately 45 min from DNA extraction to the result display. Moreover, this platform topped germiculture and real-time PCR in terms of sensitivity or efficiency in clinical diagnoses of 66 samples. This platform possesses significant potential as a versatile approach and represents the premiere application of CRISPR for the non-invasive detection of H. pylori in companion animals, thereby mitigating the dissemination of H. pylori among household members.

The Role of Personalized Medicine in Companion Animal Cardiology

Cardiomyopathies remain one of the most common inherited cardiac diseases in both human and veterinary patients. To date, well over 100 mutated genes are known to cause cardiomyopathies in humans with only a handful known in cats and dogs. This review highlights the need and use of personalized one-health approaches to cardiovascular case management and advancement in pharmacogenetic-based therapy in veterinary medicine. Personalized medicine holds promise in understanding the molecular basis of disease and ultimately will unlock the next generation of targeted novel pharmaceuticals and aid in the reversal of detrimental effects at a molecular level.

HCM-associated ALMS1 variant: Allele drop-out and frequency in Italian Sphynx cats

Hypertrophic cardiomyopathy (HCM) is the most common cardiomyopathy in domestic cats, and some inherited variants are available for genetic testing. A variant of the Alstrom syndrome protein 1 gene (ALMS1) was recently reported to be associated with HCM in the Sphynx cat breed (A3: g.92439157G>C). Genetic screening of the variant, promoted by the Osservatorio Veterinario Italiano Cardiopatie and Genefast Laboratory, was offered to Sphynx cat owners and breeders in Italy. Genotype data were initially obtained by Sanger sequencing. In one case where the samples of a trio were available, inconsistency in the vertical transmission of the variant suggested an allele dropout (ADO) of the wt allele. A new external primer pair was designed as an alternative to the original. The larger PCR product obtained was sanger sequenced, and five novel single nucleotide variants (SNVs) not yet annotated in open-access databases were detected. Three of these SNVs were within the original primer-binding regions and were assumed to have caused ADO. The haplotype, including the ADO SNVs, was detected in two cats belonging to different lineages. To accurately genotype ALMS1 g.92439157G>C in the samples, we set up a real-time TaqMan MGB assay while avoiding all surrounding SNVs. At g.92439157G>C, for 136 Sphynx cats, g.92439157 C variant was highly widespread (freq. >0.50). The present study reports five new variants surrounding ALMS1 g.92439157G>C that must be considered when designing the test. The study also indicates the need to verify the correspondence between the g.92439157 C variant frequency and the prevalence of HCM by increasing clinical visits and follow-ups and finally to promote genetic counselling for accurate management of mating plans in Italian Sphynx cats.

Cardiomyopathy associated 5 (CMYA5) implicated as a genetic risk factor for radial hemimelia in Siamese cats

OBJECTIVES

The present study aimed to determine the inheritance pattern and genetic cause of congenital radial hemimelia (RH) in cats.

METHODS

Clinical and genetic analyses were conducted on a Siamese cat family (n = 18), including two siblings with RH. Radiographs were obtained for the affected kittens and echocardiograms of an affected kitten and sire. Whole genome sequencing was completed on the two cases and the parents. Genomic data were compared with the 99 Lives Cat Genome data set of 420 additional domestic cats with whole genome and whole exome sequencing data. Variants were considered as homozygous in the two cases of the siblings with RH and heterozygous in the parents. Candidate variants were genotyped by Sanger sequencing in the extended pedigree.

RESULTS

Radiographs of the female kitten revealed bilateral absence of the radii and bowing of the humeri, while the male kitten showed a dysplastic right radius. Echocardiography suggested the female kitten had restrictive cardiomyopathy with a positive left atrial-to-aortic root ratio (LA:Ao = 1.83 cm), whereas hypertrophic cardiomyopathy was more likely in the sire, showing diastolic dysfunction using tissue Doppler imaging (59.06 cm/s). Twenty-two DNA variants were unique and homozygous in the affected kittens and heterozygous in the parents. Seven variants clustered in one chromosomal region, including two frameshift variants in cardiomyopathy associated 5 (CMYA5) and five variants in junction mediating and regulatory protein, P53 cofactor (JMY ), including a missense and an in-frame deletion.

CONCLUSIONS AND RELEVANCE

The present study suggested an autosomal recessive mode of inheritance with variable expression for RH in the Siamese cat family. Candidate variants for the phenotype were identified, implicating their roles in bone development. These genes should be considered as potentially causal for other cats with RH. Siamese cat breeders should consider genetically testing their cats for these variants to prevent further dissemination of the suspected variants within the breed.

Melanocortin-4 receptor and proopiomelanocortin: Candidate genes for obesity in domestic shorthair cats

Obesity is an escalating global health problem affecting both humans and companion animals. In cats it is associated with increased mortality and multiple diseases, including diabetes mellitus. Two genes coding for proteins known to play a critical role in energy homeostasis across species are the proopiomelanocortin (POMC) gene and the melanocortin-4 receptor (MC4R) gene. A missense variant in the coding sequence of the feline MC4R (MC4R:c.92C>T) has been reported to be associated with diabetes and overweight in domestic shorthair cats, and while variants in the POMC gene are known to cause obesity in humans and dogs, variants in POMC and their association with feline obesity and diabetes mellitus have not been investigated to date. The current study aimed to assess the association between the previously described MC4R variant and body condition score (BCS), as well as body fat content (%BF) in 89 non-diabetic domestic shorthair cats. Furthermore, we investigated the feline POMC gene as a potential candidate gene for obesity. Our results indicate that the MC4R:c.92C>T polymorphism is not associated with BCS or %BF in non-diabetic domestic shorthair cats. The mutation analysis of all POMC exons identified two missense variants, with a variant in exon 1 (c.28G>C; p.G10R) predicted to be damaging. The variant was subsequently assessed in all 89 cats, and cats heterozygous for the variant had a significantly increased body condition score (p = 0.03) compared with cats homozygous for the wild-type allele. Results from our study provide additional evidence that the previously described variant in MC4R is not associated with obesity in domestic shorthair cats. More importantly, we have identified a novel variant in the POMC gene, which might play a role in increased body condition score and body fat content in domestic shorthair cats.

Pyruvate kinase deficiency mutant gene carriage in stray cats and rescued cats from animal hoarding in Hokkaido, Japan

The mutant allele frequency of the Pyruvate kinase (PK) gene has been investigated mostly in pure breed cats. We investigated the PK mutant gene in stray and animal hoarding mongrel cats in Hokkaido, Japan. We also investigated the kinship of individuals carrying the mutant gene. Genotyping was conducted using the previously reported real-time PCR method. Fourteen microsatellite markers were used to identify the parents and offspring of cats carrying the PK mutant gene, and some kinship such as parent-offspring and siblings was observed. Some stray and animal hoarding cats carried the PK mutation gene and that consanguinity was confirmed among these cats indicated that the PK mutation gene was spread by unregulated interbreeding.

Obesity-induced changes in gene expression in feline adipose and skeletal muscle tissue

Indoor-confined cats are prone to developing obesity due to a sedentary life and an energy intake exceeding energy requirements. As in humans, feline obesity decreases insulin sensitivity and increases the risk of developing feline diabetes mellitus, but the pathophysiological mechanisms are currently poorly understood. Human obesity-related metabolic alterations seem to relate to changes in the expression of genes involved in glucose metabolism, insulin action and inflammation. The objective of the current study was to investigate changes in the expression of genes relating to obesity, glucose metabolism and inflammation in cats with non-experimentally induced obesity. Biopsies from the sartorius muscle and subcutaneous adipose tissue were obtained from 73 healthy, neutered, indoor-confined domestic shorthaired cats ranging from lean to obese. Quantification of obesity-related gene expression levels relative to glyceraldehyde-3-phosphate dehydrogenase was performed by quantitative real-time polymerase chain reaction. A negative association between obesity and adiponectin expression was observed in the adipose tissue (mean ± SD; normal weight, 27.30 × 10-3  ± 77.14 × 10-3 ; overweight, 2.89 × 10-3  ± 0.38 × 10-3 and obese, 2.93 × 10-3  ± 4.20 × 10-3 , p < 0.05). In muscle, the expression of peroxisome proliferative activated receptor-γ2 and plasminogen activator inhibitor-1 was increased in the obese compared to the normal-weight cats, and resistin was increased in the normal-weight compared to the overweight cats. There were no detectable obesity-related changes in the messenger RNA levels of inflammatory cytokines. In conclusion, a possible obesity-related low-grade inflammation caused by increased expression of key proinflammatory regulators was not observed. This could imply that the development of feline obesity and ensuing insulin resistance may not be based on tissue-derived inflammation, but caused by several determining factors, many of which still need further investigation.

Use of cutting-edge RNA-sequencing technology to identify biomarkers and potential therapeutic targets in canine and feline cancers and other diseases

With the growing interest in companion animals and the rapidly expanding animal healthcare and pharmaceuticals market worldwide. With the advancements in RNA-sequencing (RNA-seq) technology, it has become a valuable tool for understanding biological processes in companion animals and has multiple applications in animal healthcare. Historically, veterinary diagnoses and treatments relied solely on clinical symptoms and drugs used in human diseases. However, RNA-seq has emerged as an effective technology for studying companion animals, providing insights into their genetic information. The sequencing technology has revealed that not only messenger RNAs (mRNAs) but also non-coding RNAs (ncRNAs) such as long ncRNAs and microRNAs can serve as biomarkers. Based on the examination of RNA-seq applications in veterinary medicine, particularly in dogs and cats, this review concludes that RNA-seq has significant potential as a diagnostic and research tool. It has enabled the identification of potential biomarkers for cancer and other diseases in companion animals. Further research and development are required to maximize the utilization of RNA-seq for improved disease diagnosis and therapeutic targeting in companion animals.

Precision medicine using whole genome sequencing in a cat identifies a novel COL5A1 variant for classical Ehlers-Danlos syndrome

BACKGROUND

Ehlers-Danlos syndromes (EDS) are a heterogeneous group of heritable connective tissue disorders occurring in both human and veterinary patients. The genetics of these disorders are poorly described in small animal patients.

HYPOTHESIS/OBJECTIVES

Define the clinical manifestations and genetic cause of a suspected form of EDS in a cat.

ANIMALS

A 14-week-old male domestic medium hair cat was presented with skin hyperextensibility and fragility. The classic tragic facial expression was observed as well as chronic pruritus and mild hyperesthesia.

METHODS

Blood samples and a skin biopsy sample were collected from the affected cat. Clinical examinations, histology, electron microscopy and whole genome sequencing were conducted to characterize the clinical presentation and identify possible pathogenic DNA variants to support a diagnosis. Criteria defining variant pathogenicity were examined including human disease variant databases.

RESULTS

Histology showed sparse, disorganized collagen and an increase in cutaneous mast cells. Electron microscopy identified ultrastructural defects commonly seen in collagen type V alpha 1 chain (COL5A1) variants including flower-like collagen fibrils in cross-section. Whole genome sequencing and comparison with 413 cats in the 99 Lives Cat Genome Sequencing Consortium database identified a novel splice acceptor site variant at exon 4 in COL5A1 (c.501-2A>C).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our report broadens the current understanding of EDS in veterinary patients and supports the use of precision medicine techniques in clinical veterinary practice. The classification of variants for pathogenicity should be considered in companion animals.

Identification of an ADAMTS2 frameshift variant in a cat family with Ehlers-Danlos syndrome

We investigated 4 European domestic shorthair kittens with skin lesions consistent with the dermatosparaxis type of the Ehlers-Danlos syndrome, a connective tissue disorder. The kittens were sired by the same tomcat but were born by 3 different mothers. The kittens had easily torn skin resulting in nonhealing skin wounds. Both clinically and histologically, the skin showed thin epidermis in addition to inflammatory changes. Changes in collagen fibers were visible in electron micrographs. The complete genome of an affected kitten was sequenced. A one base pair duplication leading to a frameshift in the candidate gene ADAMTS2 was identified, p.(Ser235fs*3). All 4 affected cats carried the frameshift duplication in a homozygous state. Genotypes at this variant showed perfect cosegregation with the autosomal recessive Ehlers-Danlos syndrome phenotype in the available family. The mutant allele did not occur in 48 unrelated control cats. ADAMTS2 loss-of-function variants cause autosomal recessive forms of Ehlers-Danlos syndrome in humans, mice, dogs, cattle, and sheep. The available evidence from our investigation together with the functional knowledge on ADAMTS2 in other species allows to classify the identified ADAMTS2 variant as pathogenic and most likely causative variant for the observed Ehlers-Danlos syndrome.

The MARS PETCARE BIOBANK protocol: establishing a longitudinal study of health and disease in dogs and cats

BACKGROUND

The veterinary care of cats and dogs is increasingly embracing innovations first applied to human health, including an increased emphasis on preventative care and precision medicine. Large scale human population biobanks have advanced research in these areas; however, few have been established in veterinary medicine. The MARS PETCARE BIOBANK™ (MPB) is a prospective study that aims to build a longitudinal bank of biological samples, with paired medical and lifestyle data, from 20,000 initially healthy cats and dogs (10,000 / species), recruited through veterinary hospitals over a ten-year period. Here, we describe the MPB protocol and discuss its potential as a platform to increase understanding of why and how diseases develop and how to advance personalised veterinary healthcare.

METHODS

At regular intervals, extensive diet, health and lifestyle information, electronic medical records, clinicopathology and activity data are collected, genotypes, whole genome sequences and faecal metagenomes analysed, and blood, plasma, serum, and faecal samples stored for future research.

DISCUSSION

Proposed areas for research include the early detection and progression of age-related disease, risk factors for common conditions, the influence of the microbiome on health and disease and, through genome wide association studies, the identification of candidate loci for disease associated genetic variants. Genomic data will be open access and research proposals for access to data and samples will be considered. Over the coming years, the MPB will provide the longitudinal data and systematically collected biological samples required to generate important insights into companion animal health, identifying biomarkers of disease, supporting earlier identification of risk, and enabling individually tailored interventions to manage disease.

Large-scale epidemiological study on feline autosomal dominant polycystic kidney disease and identification of novel PKD1 gene variants

OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disease in cats. In most cases, the responsible abnormality is a nonsense single nucleotide polymorphism in exon 29 of the PKD1 gene (chrE3:g.42858112C>A, the conventional PKD1 variant). The aim of this study was to conduct a large-scale epidemiological study of ADPKD caused by the conventional PKD1 variant in Japan and to search for novel polymorphisms by targeted resequencing of the PKD1 using a next-generation sequencer.

METHODS

A total of 1281 cats visiting the Veterinary Medical Center of the University of Tokyo were included in this study. DNA was extracted from the blood of each cat. We established a novel TaqMan real-time PCR genotyping assay for the conventional PKD1 variant, and all cases were examined for the presence of this variant. Targeted resequencing of all exons of the PKD1 was performed on the DNA of 23 cats with the conventional PKD1 variant, six cats diagnosed with cystic kidneys but without this variant, and 61 wild-type normal cats.

RESULTS

Among the 1281 cats examined in this study, 23 (1.8%) harboured the conventional PKD1 variant. The odds of having the conventional PKD1 variant were significantly higher in Persian cats, Scottish Folds and Exotic Shorthairs than in the other breeds, although the number of cases in each breed was small. Furthermore, we identified four variants unique to cats with cystic kidneys that were not found in wild-type normal cats, all of which were in exon 15. In particular, two (chrE:g.42848725delC, pGly1641fs and chrE:g.42850283C>T, pArg2162Trp) were candidate variants.

CONCLUSIONS AND RELEVANCE

This study revealed that the conventional PKD1 variant was prevalent in Scottish Fold, Persian and Exotic Shorthair breeds in Japan, and variants in exon 15 of PKD1, in addition to the conventional variant in exon 29, would be key factors in the pathogenesis of ADPKD in cats.

Morbidity of insured Swedish cats between 2011 and 2016: Comparing disease risk in domestic crosses and purebreds

BACKGROUND

Sources of population-based cat health information are scarce. The objective of this study was to determine disease frequency in cats using pet insurance data to inform health promotion efforts.

METHODS

A descriptive analysis of cats insured with Agria Pet Insurance in Sweden (2011-2016) was performed. Incidence rates of broad disease categories were calculated based on veterinary care events and an exact denominator consisting of cat-years-at-risk. Rate ratios were calculated, comparing domestic crosses to all purebreds and specific purebreds to all other purebreds combined.

RESULTS

The study included over 1.6 million cat-years-at-risk (78.5% were domestic crosses), 18 breeds and 24 disease categories. The most common disease categories causing morbidity in purebreds were digestive, whole body, injury, urinary lower, skin and female reproduction. Purebreds had the highest relative risk (compared to domestics crosses) in the female reproduction, heart, operation complication, respiratory lower and immunological disease categories.

LIMITATIONS

There are typical limitations of secondary data, but they do not negate the overall value of such a large dataset.

CONCLUSION

This study demonstrates how pet insurance data can be used to find breed-specific differences in the incidence of various disease categories in cats. This may be of importance for breeders, cat owners, veterinarians and researchers.

Feline precision medicine using whole-exome sequencing identifies a novel frameshift mutation for vitamin D-dependent rickets type 2

OBJECTIVES

A 14-week-old female domestic longhair kitten presented with shifting lameness and disproportionately smaller size compared with a co-housed littermate.

METHODS

Hematology and serum biochemical testing were conducted to investigate causes for delayed growth, and radiographs of the appendicular skeleton were obtained.

RESULTS

The afflicted kitten had marked hypocalcemia, mild hypophosphatemia and substantial elevations in alkaline phosphatase activity, as well as pathognomonic radiographic findings consistent with rickets. Skeletal changes and hypocalcemia prompted testing of concentrations of parathyroid hormone (PTH) and vitamin D metabolites. Endocrine testing demonstrated significant increases in serum concentrations of PTH and 1,25-dihydroxycholecalciferol (calcitriol), supporting a diagnosis of vitamin D-dependent rickets type 2. Provision of analgesia, supraphysiologic doses of calcitriol and calcium carbonate supplementation achieved normalization of the serum calcium concentration and restoration of normal growth, although some skeletal abnormalities persisted. Once skeletally mature, ongoing calcitriol supplementation was not required. Whole-exome sequencing (WES) was conducted to identify the underlying DNA variant. A cytosine deletion at cat chromosome position B4:76777621 in VDR (ENSFCAT00000029466:c.106delC) was identified and predicted to cause a stop codon in exon 2 (p.Arg36Glufs*18), disrupting >90% of the receptor. The variant was unique and homozygous in this patient and absent in the sibling and approximately 400 other cats for which whole-genome and whole-exome data were available.

CONCLUSIONS AND RELEVANCE

A unique, heritable form of rickets was diagnosed in a domestic longhair cat. WES identified a novel frameshift mutation affecting the gene coding for the vitamin D3 receptor, determining the likely causal genetic variant. Precision medicine techniques, including whole-exome and whole-genome sequencing, can be a standard of care in cats to identify disease etiologies, and to target therapeutics and personalize treatment.

Genomic integration and expression of Felis catus papillomavirus type 2 oncogenes in feline Merkel cell carcinoma

The involvement of Felis catus papillomavirus type 2 (FcaPV2) in feline Merkel cell carcinoma (MCC) has been previously hypothesized. In this study, the expression and localization of FcaPV2 oncogene mRNA, the integration of FcaPV2 genes, and p53 mutations in feline MCC were examined by RNAscope in situ hybridization (ISH), whole genome sequencing (WGS), and Sanger DNA sequencing, respectively. Furthermore, the morphological and molecular characteristics of FcaPV2-positive (FMX-MCC01) and FcaPV2-negative (AS-MCC01) MCC cell lines were compared in vitro and in vivo using immunofluorescence, ISH, xenotransplantation into mice, and immunohistochemistry. ISH for FcaPV2 E6/E7 detected viral RNA in 18/21 FcaPV2-positive MCC and not in 1/1 FcaPV2-negative MCC. WGS of 2 FcaPV2-positive cases revealed the integration of FcaPV2 genes in both cases. In cultured cells and xenograft tissues of FMX-MCC01, most cells were positive for E6/E7 by ISH and p16CDKN2A, a few cells were positive for the retinoblastoma protein (pRb), and all cells were negative for p53. In cultured cells and xenograft tissues of AS-MCC01, all cells were negative for p16CDKN2A, most cells were positive for pRb, and some cells were positive for p53. Missense mutations in p53 were identified in 8/10 FcaPV2-positive and 1/1 FcaPV2-negative MCC. These results suggest that the expression of integrated FcaPV2 oncogenes might be associated with reduced expression of the tumor suppressor proteins pRb and p53 and might contribute to the development of feline MCC. On the other hand, p53 mutations may be involved in both FcaPV2-positive and FcaPV2-negative MCC tumorigenesis.

Prevalence of polycystic kidney disease in Persian and Persian-related cats in western Mexico

OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD), the most frequently diagnosed hereditary disease affecting Persian cats, is caused by a cytosine-to-adenine transversion (10063C>A) in PKD1, the gene that codes for polycystin-1. The objective of this study was to provide a preliminary estimate of the frequency of the pathogenic 10063C>A single nucleotide polymorphism (SNP) of PKD1 in Persian and Persian-related cat breeds in western Mexico.

METHODS

Blood samples were collected from 104 cats (89 Persian, seven Persian crossbreed, five Siamese and three Himalayan cats). Genotyping was performed with our proposed PCR restriction fragment length polymorphism (RFLP) assay, as well as a previously established PCR-RFLP method for validation. The genotypes of control cats were corroborated by a commercial veterinary genetics laboratory.

RESULTS

Our proposed PCR-RFLP assay and the validated PCR-RFLP methodology indicated that 24/104 (23.1%) cats in this study were heterozygous carriers of the 10063C>A SNP, including 23/89 Persian cats (25.8%) and 1/7 Persian crossbreed cats (14.3%). No Siamese or Himalayan cats were carriers. There were no discrepancies between the results obtained with our proposed assay and those obtained with the validation method or with commercial laboratory results.

CONCLUSIONS AND RELEVANCE

The carrier frequency of the PKD1 10063C>A SNP in Persian and Persian-related cat breeds in western Mexico was found to be 23.1%. ADPKD frequencies among cat populations in Mexico have not been published previously. Genotyping assays can be used to facilitate the selection of breeding stocks by local breeders and veterinarians to avoid propagation of ADPKD.

Epidemiology and clinical presentation of feline presumed hereditary or breed-related ocular diseases in France: retrospective study of 129 cats

OBJECTIVES

This study aimed to describe the epidemiology and clinical presentation of presumed hereditary or presumed breed-related ocular diseases in a population of cats in France.

METHODS

Medical records from between September 2013 and August 2017 were reviewed to identify cats with at least one presumed hereditary or breed-related ocular disease. Cats with concurrent, or a history of, ocular or systemic infectious diseases were excluded. Signalment, history and clinical findings were recorded.

RESULTS

Of the 1161 cats that presented to our institution during the study period, 129 were diagnosed with at least one presumed hereditary or presumed breed-related ocular disease (11.1%, 95% confidence interval [CI] 9.3-12.9). Five ocular abnormalities had a prevalence of >1%: entropion, corneal sequestration, persistent pupillary membrane, cataract and retinal dysplasia. The prevalence of entropion was 2.2% (95% CI 1.3-3.0), with Persians (P = 0.03), Maine Coons (P <0.01) and male cats (P <0.01) being over-represented. The prevalence of corneal sequestration was 2.4% (95% CI 1.5-3.3), with Persians (P <0.01) and Exotic Shorthairs (P = 0.02) being over-represented. Persistent pupillary membranes and cataracts had the same prevalence of 2.3% (95% CI 1.5-3.2), with no particular sex or breed significantly over-represented. Retinal dysplasia had a prevalence of 1.6% (95% CI 0.8-2.3) and Persian cats were over-represented (P = 0.04). Anterior segment dysgenesis had a low prevalence (0.9%, 95% CI 0.4-1.5), with all affected cats being domestic shorthairs and this breed therefore was over-represented (P = 0.04).

CONCLUSIONS AND RELEVANCE

In a French population of cats, presumed hereditary or breed-related ocular diseases accounted for 11.1% of all ocular diseases. Cataracts, corneal sequestration, persistent pupillary membrane, entropion and retinal dysplasia were the most common conditions. Statistical breed over-representation was observed for entropion, corneal sequestration and retinal dysplasia. We recommend that more systematic screening of feline species is conducted.

Cardiac gene activation varies between young and adult cats and in the presence of hypertrophic cardiomyopathy

Little is known about the difference of myocardial gene transcription in young and adult cats and how transcription is further modified in cats with hypertrophic cardiomyopathy (HCM) and with left atrial (LA) thrombus formation. We hypothesized that selected factors for coagulation, endothelial activation, inflammation, and remodelling are modified with age and are activated in the hearts of cats with HCM. Left atrial and ventricular (LV) samples from 12 cats with HCM (seven without (HCMwoAT] and five with LA thrombi [HCMwAT]), and six young (YC) and six adult (AC) control cats without cardiac disease were investigated for relative expression of the following genes using quantitative polymerase chain reaction: von Willebrand factor, a disintegrin and metalloproteinase with a thrombospondin type 1 motif member 13, platelet activating factor, E- and P-selectin, intercellular and vascular adhesion molecules-1, ß2-integrin, vascular endothelial growth factor, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), heat shock protein-70, and myocyte-specific enhancer factor 2C. Significant differences in gene activation were found between YC and AC, and YC and cats with HCM. Compared to AC, MCP-1 and IL-6 were significantly higher in cats with HCM. The presence of an LA thrombus was associated with higher IL-6 expression. These results illustrate the relevance of age and/or lifestyle on gene expression in the feline heart. The gene transcription pattern found in AC hearts might predispose cats to their characteristic cardiac remodelling processes and thrombus formation if disease occurs. It further supports the involvement of inflammation, but not coagulation and endothelial activation, in HCM.

Novel clonality assays for T cell lymphoma in cats targeting the T cell receptor beta, T cell receptor delta, and T cell receptor gamma loci

BACKGROUND

T cell clonality assays in veterinary medicine currently target only the T cell receptor gamma (TRG) locus. Existing assays have suboptimal sensitivity because of insufficient primer coverage of all possible rearrangements.

OBJECTIVE

Develop higher sensitivity clonality assays targeting the TRG, delta (TRD), and beta (TRB) loci in cats.

ANIMALS

Cats with histopathologically confirmed lymphoma (n = 89), non-lymphoma (n = 35), and possible hepatic small cell lymphoma (n = 31).

METHODS

Molecular clonality assay development utilizing our recently reported topology and expressed repertoire data of the T cell receptor loci in cats. Determination of clonality status of lymphoma, non lymphoma, and possible hepatic small cell lymphoma samples, and calculation of assay sensitivity and specificity.

RESULTS

The new multiplex TRG assay yielded the highest sensitivity (95.5%). All assays yielded 100% specificity except for the new multiplex TRG assay (97.3%). The combination of the new TRG and TRB assays yielded sensitivity of 98.9% and specificity of 97.0%. The new TRG assay detected clonality in 17/31 possible small cell lymphoma livers, whereas an existing TRG assay detected clonality in 6/31 livers.

CONCLUSIONS AND CLINICAL IMPORTANCE

The assessment of multiple T cell loci compensates for the potential shortcomings of individual assays. Using a combination of molecular clonality assays will increase the overall sensitivity for the diagnosis of T-cell lymphoma in cats, especially intestinal, and hepatic small cell lymphoma. Hepatic small cell lymphomas detected by the new TRG assay utilized rarely expressed V and J genes not recognized by previous assays, likely indicating unique biology of hepatic small cell lymphoma in cats.

Genome-wide DNA methylation profile in feline haematological tumours: A preliminary study

Although DNA methylation has been analysed in few studies for a limited number of loci in cats with diseases, genome-wide profile of DNA methylation has never been addressed. The hypothesis for this study is that next-generation sequencing with sequential digestion of genomic DNA with SmaI and XmaI enzymes could provide highly quantitative information on methylation levels in cats. Using blood from four healthy control cats and two disease cats as well as three feline lymphoma/leukemia cell lines, approximately 74-94 thousand CpG sites across the cat genome could be analysed. CpG sites in CpG island (CGI) were broadly either methylated or unmethylated in normal blood, while CpG sites in non-CpG islands (NCGI) are largely methylated. Lymphoma cell lines showed thousands of CpG sites with gain of methylation at normally unmethylated CGI sites and loss of methylation at normally methylated NCGI sites. Hypermethylated CpG sites located at promoter regions included genes annotated with 'developmental process' and 'anatomical structure morphogenesis' such as HOXD10. This highly quantitative method would be suitable for studies of DNA methylation changes not only in cancer but also in other common diseases in cats.

Radiographical Survey of Osteochondrodysplasia in Scottish Fold Cats caused by the TRPV4 gene variant

The unique appearance of Scottish Fold cats is caused by a single gene variant in TRPV4, which impacts the development of cartilage. This results in the ears folding forward and variable effects on articular cartilage and bone. While some find this appearance desirable, early work demonstrated that homozygous cats with two copies of this variant develop severe radiographic consequences. Subsequent breeding programs have mated heterozygous cats with straight-eared cats to ensure an equal mix of heterozygous (fold) and wild-type (nonfolded) offspring, in the hope of raising healthy cats. More recent radiological surveys suggest that these heterozygous cats may also have medical problems consisting of deformed distal extremities in the worst cases and accelerated onset of osteoarthritis. However, these previous studies were undermined by selection biases, lack of controls, unblinded assessment and lack of known genotypes. Our aim was to determine if heterozygous cats exhibit radiological abnormalities when controlling for these limitations. Specifically, DNA and radiographs were acquired for 22 Scottish Fold cats. Four reviewers, blinded to the ear phenotype, assessed the lateral radiographs. Genotyping showed that all 10 folded-ear cats were heterozygous, and none of the straight-ear cats (n = 12) had the abnormal TRPV4 variant. Although each reviewer, on average, gave a numerically worse 'severity score' to folded-ear cats relative to straight-ear cats, the images in heterozygous cats showed much milder radiological signs than previously published. This study provides additional information to be considered in the complicated debate as to whether cats with the TRPV4 variant should be bred for folded ears given the potential comorbidities.

Role of an ABCB11930_1931del TC gene mutation in a temporal cluster of macrocyclic lactone-induced neurologic toxicosis in cats associated with products labeled for companion animal use

OBJECTIVE

To determine whether ABCB11930_1931del TC predisposed cats to macrocyclic-lactone toxicosis and the frequency of the ABCB11930_1931del TC gene mutation in banked feline DNA samples.

SAMPLE

DNA samples from 5 cats presented for neurologic clinical signs presumed to be caused by exposure to macrocyclic lactones and 1,006 banked feline DNA samples.

PROCEDURES

The medical history pertaining to 5 cats was obtained from veterinarians who examined, treated, or performed necropsies on them. The DNA from these 5 cats and 1,006 banked feline samples were analyzed for the presence of the ABCB11930_1931del TC genotype.

RESULTS

4 of the 5 cats with neurologic signs presumed to be associated with macrocyclic-lactone exposure were homozygous for ABCB11930_1931del TC. The other cat had unilateral vestibular signs not typical of macrocyclic-lactone toxicosis. The distribution of genotypes from the banked feline DNA samples was as follows: 0 homozygous for ABCB11930_1931del TC, 47 heterozygous for ABCB11930_1931del TC, and 959 homozygous for the wild-type ABCB1 allele. Among the 47 cats with the mutant ABCB1 allele, only 3 were purebred (Ragdoll, Russian Blue, and Siamese).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested a strong relationship between homozygosity for ABCB11930_1931del TC and neurologic toxicosis after topical application with eprinomectin-containing antiparasitic products labeled for use in cats. Although this genotype is likely rare in the general cat population, veterinarians should be aware of this genetic mutation in cats and its potential for enhancing susceptibility to adverse drug reactions.

Comparison of the oncogenomic landscape of canine and feline hemangiosarcoma shows novel parallels with human angiosarcoma

Angiosarcoma (AS) is a highly aggressive tumor of blood and lymphatic vessels in humans that shares many similarities with spontaneously occurring hemangiosarcoma (HSA) in dogs and cats. To investigate the genetic suitability of HSA as a model for AS, we sequenced ∼1000 cancer genes in 41 cases of HSA and matched germline tissue: 15 canine visceral HSAs, 13 canine skin HSAs and 13 feline skin HSAs. Analysis of visceral HSAs from dogs presenting with concurrent splenic and cardiac neoplasms showed that the tumors were not independent primaries, consistent with the highly metastatic nature of HSA. Comparison of HSA to AS revealed that several driver genes were recurrently mutated in both species, such as TP53, PIK3CA, ATRX, GRIN2A and LRP1B. Similar to AS, a UV mutational signature was found in a subset of canine cutaneous HSAs and both species show differing mutational profiles between tissue sites. Our characterization of canine and feline HSA demonstrates many important parallels to AS and provides hope that future studies on these cancers will benefit of all three species.

Sudden cardiac death: A comparative review of humans, dogs and cats

Sudden death is one of the most common causes of death in humans in Western countries. Approximately 85% of these cases are of cardiac origin. In dogs and cats, sudden cardiac death (SCD) also commonly occurs, but fewer pathophysiological and prevalence data are available. Both structural, primarily 'electrical' and ischemic heart diseases are known to cause SCD, many of which share similar underlying arrhythmogenic mechanisms between humans and companion animals. As for underlying genetics, numerous mutations on multiple loci have been related to SCD in humans, but only a few mutations associated with dilated cardiomyopathy and SCD have been identified in dogs, e.g. in the phospholamban and titin genes. Information published from human medicine can therefore inform future veterinary studies, but also dogs and cats could act as spontaneous models of SCD in humans. Further research in both fields is therefore warranted to better understand the pathophysiology, genetics, and prevention of SCD.

Web resource on available DNA variant tests for hereditary diseases and genetic predispositions in dogs and cats: An Update

Vast progress has been made in the clinical diagnosis and molecular basis of hereditary diseases and genetic predisposition in companion animals. The purpose of this report is to provide an update on the availability of DNA testing for hereditary diseases and genetic predispositions in dogs and cats utilizing the WSAVA-PennGen DNA Testing Database web resource (URL: http://research.vet.upenn.edu/WSAVA-LabSearch ). Information on hereditary diseases, DNA tests, genetic testing laboratories and afflicted breeds added to the web-based WSAVA-PennGen DNA Testing Database was gathered. Following verification through original research and clinical studies, searching various databases on hereditary diseases in dogs and cats, and contacting laboratories offering DNA tests, the data were compared to the resource reported on in 2013. The number of molecularly defined Mendelian inherited diseases and variants in companion animals listed in the WSAVA-PennGen DNA Testing Database in 2020 drastically increased by 112% and 141%, respectively. The number of DNA variant tests offered by each laboratory has also doubled for dogs and cats. While the overall number of laboratories has only slightly increased from 43 to 47, the number of larger corporate laboratories increased, while academic laboratories have declined. In addition, there are now several laboratories that are offering breed-specific or all-breed panel tests rather than single-DNA tests for dogs and cats. This unique regularly updated searchable web-based database allows veterinary clinicians, breeders and pet owners to readily find available DNA tests, laboratories performing these DNA tests worldwide, and canine and feline breeds afflicted and also serves as a valuable resource for comparative geneticists.

The Genetic Basis of Obesity and Related Metabolic Diseases in Humans and Companion Animals

Obesity is one of the most prevalent health conditions in humans and companion animals globally. It is associated with premature mortality, metabolic dysfunction, and multiple health conditions across species. Obesity is, therefore, of importance in the fields of medicine and veterinary medicine. The regulation of adiposity is a homeostatic process vulnerable to disruption by a multitude of genetic and environmental factors. It is well established that the heritability of obesity is high in humans and laboratory animals, with ample evidence that the same is true in companion animals. In this review, we provide an overview of how genes link to obesity in humans, drawing on a wealth of information from laboratory animal models, and summarise the mechanisms by which obesity causes related disease. Throughout, we focus on how large-scale human studies and niche investigations of rare mutations in severely affected patients have improved our understanding of obesity biology and can inform our ability to interpret results of animal studies. For dogs, cats, and horses, we compare the similarities in obesity pathophysiology to humans and review the genetic studies that have been previously reported in those species. Finally, we discuss how veterinary genetics may learn from humans about studying precise, nuanced phenotypes and implementing large-scale studies, but also how veterinary studies may be able to look past clinical findings to mechanistic ones and demonstrate translational benefits to human research.

Profibrotic gene transcription in renal tissues from cats with ischemia-induced chronic kidney disease

OBJECTIVE

To characterize transcription of profibrotic mediators in renal tissues of cats with ischemia-induced chronic kidney disease (CKD).

SAMPLE

Banked renal tissues from 6 cats with experimentally induced CKD (RI group) and 8 healthy control cats.

PROCEDURES

For cats of the RI group, both kidneys were harvested 6 months after ischemia was induced for 90 minutes in 1 kidney. For control cats, the right kidney was evaluated. All kidney specimens were histologically examined for fibrosis, inflammation, and tubular atrophy. Renal tissue homogenates underwent reverse transcription quantitative PCR assay evaluation to characterize gene transcription of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase (MMP)-2, MMP-7, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), transforming growth factor-β1, and vascular endothelial growth factor A. Gene transcription and histologic lesions were compared among ischemic and contralateral kidneys of the RI group and control kidneys.

RESULTS

Ischemic kidneys had greater transcript levels of MMP-7, MMP-9, and transforming growth factor-β1 relative to control kidneys and of MMP-2 relative to contralateral kidneys. Transcription of TIMP-1 was upregulated and that of vascular endothelial growth factor A was downregulated in ischemic and contralateral kidneys relative to control kidneys. Transcription of HIF-1α did not differ among kidney groups. For ischemic kidneys, there were strong positive correlations between transcription of HIF-1α, MMP-2, MMP-7, and TIMP-1 and severity of fibrosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Transcription of genes involved in profibrotic pathways remained altered in both kidneys 6 months after transient renal ischemia. This suggested that a single unilateral renal insult can have lasting effects on both kidneys.

Analysis of Copy-Number Variations and Feline Mammary Carcinoma Survival

Feline mammary carcinomas (FMCs) are highly malignant. As the disease-free survival (DFS) and overall survival (OS) are short, prognostication is crucial. Copy-number variations (CNVs) analysis by next-generation sequencing serves to identify critical cancer-related genomic regions. Thirty-three female cats with FMCs were followed during two years after surgery. Tumours represented tubulopapillary and solid carcinomas encompassing six molecular subtypes. Regardless of the histopathological diagnosis, molecular subtypes showed important differences in survival. Luminal A tumours exhibited the highest DFS (p = 0.002) and cancer-specific OS (p = 0.001), and the lowest amount of CNVs (p = 0.0001). In contrast, basal-like triple-negative FMCs had the worst outcome (DFS, p < 0.0001; and OS, p < 0.00001) and were the most aberrant (p = 0.05). In the multivariate analysis, copy-number losses (CNLs) in chromosome B1 (1-23 Mb) harbouring several tumour-repressors (e.g. CSMD1, MTUS1, MSR1, DBC2, and TUSC3) negatively influenced DFS. Whereas, copy-number gains (CNGs) in B4 (1-29 Mb) and F2 (64-82.3 Mb) comprising epithelial to mesenchymal transition genes and metastasis-promoting transcription factors (e.g. GATA3, VIM, ZEB1, and MYC) negatively influenced DFS and cancer-specific OS. These data evidence an association between specific CNVs in chromosomes B1, B4 and F2, and poor prognosis in FMCs.

miR-26a Inhibits Feline Herpesvirus 1 Replication by Targeting SOCS5 and Promoting Type I Interferon Signaling

In response to viral infection, host cells activate various antiviral responses to inhibit virus replication. While feline herpesvirus 1 (FHV-1) manipulates the host early innate immune response in many different ways, the host could activate the antiviral response to counteract it through some unknown mechanisms. MicroRNAs (miRNAs) which serve as a class of regulatory factors in the host, participate in the regulation of the host innate immune response against virus infection. In this study, we found that the expression levels of miR-26a were significantly upregulated upon FHV-1 infection. Furthermore, FHV-1 infection induced the expression of miR-26a via a cGAS-dependent pathway, and knockdown of cellular cGAS significantly blocked the expression of miR-26a induced by poly (dA:dT) or FHV-1 infection. Next, we investigated the biological function of miR-26a during viral infection. miR-26a was able to increase the phosphorylation of STAT1 and promote type I IFN signaling, thus inhibiting viral replication. The mechanism study showed that miR-26a directly targeted host SOCS5. Knockdown of SOCS5 increased the phosphorylation of STAT1 and enhanced the type I IFN-mediated antiviral response, and overexpression of suppressor of the cytokine signalling 5 (SOCS5) decreased the phosphorylation of STAT1 and inhibited the type I IFN-mediated antiviral response. Meanwhile, with the knockdown of SOCS5, the upregulated expression of phosphorylated STAT1 and the anti-virus effect induced by miR-26a were significantly inhibited. Taken together, our data demonstrated a new strategy of host miRNAs against FHV-1 infection by enhancing IFN antiviral signaling.

A TAC3 Missense Variant in a Domestic Shorthair Cat with Testicular Hypoplasia and Persistent Primary Dentition

A single male domestic shorthair cat that did not complete puberty was reported. At four years of age, it still had primary dentition, testicular hypoplasia, and was relatively small for its age. We hypothesized that the phenotype might have been due to an inherited form of hypogonadotropic hypogonadism (HH). We sequenced the genome of the affected cat and compared the data to 38 genomes from control cats. A search for private variants in 40 candidate genes associated with human HH revealed a single protein-changing variant in the affected cat. It was located in the TAC3 gene encoding tachykinin 3, a precursor protein of the signaling molecule neurokinin B, which is known to play a role in sexual development. TAC3 variants have been reported in human patients with HH. The identified feline variant, TAC3:c.220G>A or p.(Val74Met), affects a moderately conserved region of the precursor protein, 11 residues away from the mature neurokinin B sequence. The affected cat was homozygous for the mutant allele. In a cohort of 171 randomly sampled cats, 169 were homozygous for the wildtype allele and 2 were heterozygous. These data tentatively suggest that the identified TAC3 variant might have caused the suppression of puberty in the affected cat.

Prevalence of p53 dysregulations in feline oral squamous cell carcinoma and non-neoplastic oral mucosa

Squamous cell carcinoma is the most common malignant oral tumor in cats. The late presentation is one of the factors contributing to the detrimental prognosis of this disease. The immunohistochemical expression of the p53 tumor suppressor protein has been reported in 24% to 65% of feline oral squamous cell carcinomas, but no study has systematically evaluated in this tumor the presence of p53 encoding gene (TP53) mutations. The aim of this retrospective study was to determine whether p53 immunohistochemistry accurately reflects the mutational status of the TP53 gene in feline oral squamous cell carcinoma. Additionally, the prevalence of p53 dysregulation in feline oral squamous cell carcinoma was compared with that of feline non-neoplastic oral mucosa, in order to investigate the relevance of these dysregulations in cancer development. The association between p53 dysregulations and exposure to environmental tobacco smoke and tumor characteristics was further assessed. Twenty-six incisional biopsies of oral squamous cell carcinomas and 10 cases each of lingual eosinophilic granuloma, chronic gingivostomatitis and normal oral mucosa were included in the study. Eighteen squamous cell carcinomas (69%) expressed p53 and 18 had mutations in exons 5-8 of TP53. The agreement between immunohistochemistry and mutation analysis was 77%. None of non-neoplastic oral mucosa samples had a positive immunohistochemical staining, while one case each of eosinophilic granuloma and chronic gingivostomatitis harbored TP53 mutations. Unlike previously hypothesized, p53 dysregulations were not associated with exposure to environmental tobacco smoke. These results suggest an important role of p53 in feline oral tumorigenesis. Additionally, the immunohistochemical detection of p53 expression appears to reflect the presence of TP53 mutations in the majority of cases. It remains to be determined if the screening for p53 dysregulations, alone or in association with other markers, can eventually contribute to the early detection of this devastating disease.

Pre-existing antibodies to candidate gene therapy vectors (adeno-associated vector serotypes) in domestic cats

Adeno-associated virus (AAV) vectors represent promising candidates for gene therapy; however, pre-existing neutralizing antibodies (NAb) may reduce AAV vector delivery efficiency. In this study, the presence of AAV NAb was investigated in cats, which serve as a larger and outbred animal model for the prediction of gene therapy outcomes in humans but also in cats.Serum/plasma samples from 230 client-owned Swiss cats and 20 specified pathogen-free cats were investigated for NAb to AAV1, AAV2, AAV5, AAV6, AAV7, AAV8 and AAV9 using in vitro transduction inhibition and a beta-galactosidase assay. NAb to all tested AAV serotypes were found. Of the client-owned cats, 53% had NAb to one or more of the AAV serotypes. NAb (≥1:10) were found at frequencies of 5% (AAV6) to 28% (AAV7). The highest titers were found against AAV7 (≥1:160). The NAb prevalence to AAV2, AAV7 and AAV9 differed geographically. Regarding titers ≥1:10 against single AAV serotypes, age, breed and sex of the cats were not associated with the NAb prevalence. Cats with titers ≥1:20 against AAV2 and titers ≥1:40 against AAV7 were significantly younger than cats with low/no titers, and purebred cats were significantly more likely than non-purebred cats to have NAb to AAV2 (≥1:40). Additionally, regarding NAb to all AAV combined, female cats were significantly more likely than male cats to have NAb titers ≥1:40. Preliminary data using AAV-DJ indicated that less pre-existing NAb to the hybrid AAV-DJ can be expected compared to the wild-type AAV serotypes. AAV NAb will need to be taken into account for future in vivo gene therapy studies in cats.

Use of slide scrape lysates for polymerase chain reaction confirmation of disseminated Mycobacterium avium infection in a cat

Disseminated mycobacteriosis in a 3-year-old domestic medium-haired cat was diagnosed on lymph node cytology. Slide scrape lysates from the cytology submission were used to confirm Mycobacterium avium by polymerase chain reaction (PCR) and sequencing and proved a simple technique that could be a valuable tool in veterinary diagnostics and research.

Characterization of gene expression in naturally occurring feline degenerative joint disease-associated pain

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Nervous system tissue from cats with painful degenerative joint disease (DJD) was analyzed.

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Gene expression was determined to investigate the neurobiological signature of DJD pain.

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There was decreased NGF and increased CX3CL1 expression in the spinal cord in DJD-affected cats compared to healthy controls.

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There was increased expression of ATF3 and CX3CL1 in dorsal root ganglia, in DJD-affected cats compared to healthy controls.

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Such studies have the potential to inform about relevant targets for the control of chronic feline pain.

Degenerative joint disease (DJD) associated-pain is a clinically relevant and common condition affecting domesticated cats and other species including humans. Identification of the neurobiological signature of pain is well developed in rodent pain models, however such information is lacking from animals or humans with naturally occurring painful conditions. In this study, identification of housekeeping genes (HKG) for neuronal tissue and expression levels of genes considered associated with chronic pain in rodent models were explored in cats with naturally occurring osteoarthritic pain. Fourteen adult cats were evaluated — seven without clinical signs of osteoarthritic pain, and seven with hind limb radiographic DJD and pain. Expression of an investigator-selected set of pain signaling genes (including ASIC3, ATF3, COX2, CX3CL1, NAV1.7, NAV1.8, NAV1.9, NGF, NK1R, TNFα, TRKA) in lumbar spinal cord dorsal horn and lumbar dorsal root ganglia tissues from clinically healthy cats and cats with DJD were studied using quantitative RT-PCR (qPCR).

HKG identified as the most stable across all tissue samples were many of the ribosomal protein genes, such as RPL30 and RPS19. qPCR results showed ATF3 and CX3CL1 up-regulated in DJD-affected dorsal root ganglia compared to clinically healthy controls. In spinal cord, CX3CL1 was up-regulated and NGF was down-regulated when DJD-affected samples were compared to healthy samples. Further work is needed to understand the neurobiology of pain in naturally occurring disease and what rodent models are predictive of these changes in more heterogeneous populations such as domestic cats.

Urinary shedding of pathogenic Leptospira in stray dogs and cats, Algiers: A prospective study

Background

Leptospirosis is an important worldwide zoonosis. This disease is caused by pathogenic species of the genus Leptospira which are maintained in the environment via chronic renal infection of carrier animals which can be asymptomatic excretors of the organisms in their urines and become a source of infection for humans and other hosts. The prevalence of animal leptospirosis in Algiers, Algeria, is unknown.

Methodology/principal findings

Real-time PCR and standard PCR and sequencing were used to detect pathogenic Leptospira organisms in the urines of stray dogs and cats in Algiers. In the presence of appropriate controls, none of the 107 cat urine samples were positive while 5/104 (4.8%) canine urine samples (asymptomatic mixed-breed dogs, three females and two males) were positive in two real-time PCR assays targeting the rrs and hsp genes. The positivity of these samples was confirmed by partial PCR-sequencing of the rpoB gene which yielded 100% sequence similarity with Leptospira interrogans reference sequence. In this study, L. interrogans prevalence was significantly higher in dogs aged < one year (16.46% - 29.41%) than in adults (0%) (P value = 0.0001) and then in the overall dog population (2.68% - 4.8%) (P = 0.0007).

Conclusions/significance

These results suggest that dogs are maintenance hosts for zoonotic leptospirosis in Algiers, Algeria. To face this situation, effective canine vaccination strategies and raising public health awareness are mandatory. Further investigations incorporating a larger sample in more localities will be undertaken to document the epidemiology of urban animal leptospirosis in Algeria at large.

Tracking the Continuous Evolutionary Processes of an Endogenous Retrovirus of the Domestic Cat: ERV-DC

An endogenous retrovirus (ERV) is a remnant of an ancient retroviral infection in the host genome. Although most ERVs have lost their viral productivity, a few ERVs retain their replication capacity. In addition, partially inactivated ERVs can present a potential risk to the host via their encoded virulence factors or the generation of novel viruses by viral recombination. ERVs can also eventually acquire a biological function, and this ability has been a driving force of host evolution. Therefore, the presence of an ERV can be harmful or beneficial to the host. Various reports about paleovirology have revealed each event in ERV evolution, but the continuous processes of ERV evolution over millions of years are mainly unknown. A unique ERV family, ERV-DC, is present in the domestic cat (Felis silvestriscatus) genome. ERV-DC proviruses are phylogenetically classified into three genotypes, and the specific characteristics of each genotype have been clarified: their capacity to produce infectious viruses; their recombination with other retroviruses, such as feline leukemia virus or RD-114; and their biological functions as host antiviral factors. In this review, we describe ERV-DC-related phenomena and discuss the continuous changes in the evolution of this ERV in the domestic cat.

Feline hypersomatotropism and acromegaly tumorigenesis: a potential role for the AIP gene

Acromegaly in humans is usually sporadic, however up to 20% of familial isolated pituitary adenomas are caused by germline sequence variants of the aryl-hydrocarbon-receptor interacting protein (AIP) gene. Feline acromegaly has similarities to human acromegalic families with AIP mutations. The aim of this study was to sequence the feline AIP gene, identify sequence variants and compare the AIP gene sequence between feline acromegalic and control cats, and in acromegalic siblings. The feline AIP gene was amplified through PCR using whole blood genomic DNA from 10 acromegalic and 10 control cats, and 3 sibling pairs affected by acromegaly. PCR products were sequenced and compared with the published predicted feline AIP gene. A single nonsynonymous SNP was identified in exon 1 (AIP:c.9T > G) of two acromegalic cats and none of the control cats, as well as both members of one sibling pair. The region of this SNP is considered essential for the interaction of the AIP protein with its receptor. This sequence variant has not previously been reported in humans. Two additional synonymous sequence variants were identified (AIP:c.481C > T and AIP:c.826C > T). This is the first molecular study to investigate a potential genetic cause of feline acromegaly and identified a nonsynonymous AIP single nucleotide polymorphism in 20% of the acromegalic cat population evaluated, as well as in one of the sibling pairs evaluated.

Assessment of regional left ventricular systolic function by strain imaging echocardiography in phenotypically normal and abnormal Maine coon cats tested for the A31P mutation in the MYBPC3 gene

Myocardial dysfunction occurs in cats with hypertrophic cardiomyopathy (HCM), but little is known about the early stages of the disease. Strain imaging echocardiography is a method that enables the quantitative assessment of myocardial function and deformity, allowing the characterization of systolic dysfunction. The objective of this study was to assess systolic function using strain imaging echocardiography in Maine coon cats genetically tested for the A31P mutation in the MYBPC3 gene, with and without ventricular hypertrophy. For this purpose, 57 Maine coon cats of both genders, with an unknown status regarding the mutation at inclusion, were included prospectively and evaluated by conventional and strain imaging echocardiography. Comparisons were made among cats without hypertrophy (n = 45), suspect cats (n = 7), and cats with hypertrophic cardiomyopathy (n = 5), and also between the heterozygous for the mutation group (n = 26) and the negative for the mutation group (n = 28). Finally, in the group of phenotypically normal cats, heterozygous cats carrying the mutation were compared to cats without the mutation. Strain values were compared among the groups (blinded prospective study). While echocardiography demonstrated normal contractility, strain values (middle of the septum) were lower in HCM cats. Strain values (base of anterior wall of the left ventricle) were lower in heterozygous than in negative cats, even before hypertrophy. Negative correlation was observed between some values of myocardial strain and thickness. While strain imaging echocardiography was able to detect systolic abnormalities, despite apparent normality on conventional echocardiography, it was not able to identify cats that carry the A31P mutation in the MYBPC3 gene. Strain imaging echocardiography could be a useful tool, however, for detecting systolic alterations in HCM cats with an apparently normal systolic function or for detecting alterations in normal carriers of the MYBPC3 gene mutation.

Early-Onset Progressive Retinal Atrophy Associated with an IQCB1 Variant in African Black-Footed Cats (Felis nigripes)

African black-footed cats (Felis nigripes) are endangered wild felids. One male and full-sibling female African black-footed cat developed vision deficits and mydriasis as early as 3 months of age. The diagnosis of early-onset progressive retinal atrophy (PRA) was supported by reduced direct and consensual pupillary light reflexes, phenotypic presence of retinal degeneration, and a non-recordable electroretinogram with negligible amplitudes in both eyes. Whole genome sequencing, conducted on two unaffected parents and one affected offspring was compared to a variant database from 51 domestic cats and a Pallas cat, revealed 50 candidate variants that segregated concordantly with the PRA phenotype. Testing in additional affected cats confirmed that cats homozygous for a 2 base pair (bp) deletion within IQ calmodulin-binding motif-containing protein-1 (IQCB1), the gene that encodes for nephrocystin-5 (NPHP5), had vision loss. The variant segregated concordantly in other related individuals within the pedigree supporting the identification of a recessively inherited early-onset feline PRA. Analysis of the black-footed cat studbook suggests additional captive cats are at risk. Genetic testing for IQCB1 and avoidance of matings between carriers should be added to the species survival plan for captive management.

ProANP as a screening biomarker for hypertrophic cardiomyopathy in Maine coon cats

The aim of this study was to determine if atrial natriuretic peptide can be used as an early screening tool for hypertrophic cardiomyopathy in Maine coon cats.

ANIMALS

The study was performed in 43 Maine coon cats of both sexes, aged 11 to 92 months. Clinical and echocardiographic examinations were done and proANP serum concentrations were measured every three months over a period of one year (each cat had a total of five examinations). Cats were divided into 3 groups based on echocardiographic results: group 1 - healthy cats, group 2 - cats with unequivocal hypertrophic cardiomyopathy results, group 3 - cats with HCM. The study showed that the concentration of atrial natriuretic peptide correlates with the severity of HCM. A significant increase in serum concentration of this peptide was observed in cats from group 3, but it did not differ significantly between cats from group 2 and the healthy animals (p>0.05). A correlation was also found between proANP and age of the cats (p<0.01, r=0.5578) as well as between the ejection fraction (p=0.0285, r=0.5305) and end-systolic left ventricular diameter (p=0.05, r=0.48) in the affected animals. Atrial natriuretic peptide may be used to help in the diagnosis of advanced stages of HCM in Maine coon cats. Cats with high levels of proANP should be assigned to echocardiographic studies to confirm the disease.

Screening for hypertrophic cardiomyopathy in cats

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats, and it can lead to increased morbidity and mortality. Cats are often screened for HCM because of the presence of a heart murmur, but screening for breeding purposes has also become common. These cats are usually purebred cats of breeding age, and generally do not present with severe disease or with any clinical signs. This type of screening is particularly challenging because mild disease may be difficult to differentiate from a normal phenotype, and the margin for error is small, with potentially major consequences for the breeder. This article reviews HCM screening methods, with particular emphasis on echocardiography.