A large case-control study indicates a breed-specific predisposition to feline tooth resorption.

Tooth resorption (TR) is one of the most common dental diseases of cats. It is a painful condition leading to tooth loss. The etiology of TR remains unclear, but old age, breed, other oral and dental diseases, and environmental factors are suspected predisposing factors. In our study, we used part of the data from the extensive feline health online survey of 8115 Finnish cats. As TR is difficult to detect and as the feline health survey included diagnoses defined by both veterinarians and the owners, we limited our study to a subpopulation of cats diagnosed with oral or dental disease by a veterinarian and had dental examination or surgery under sedation (n=944). We utilized case-control study analysed by multivariable logistic regression to determine the risk factors and breed variation of feline TR. The 202 cats diagnosed with TR were defined as TR cases and the remaining 742 cats as controls. The frequency of veterinarian-diagnosed TR was 3.9% in the health survey data (316/8115) and 21% in the subpopulation (202/944). The risk of TR increased with age (14.7% in youngest and 25.3% in oldest age group). Our finding that TR was significantly associated with gingivitis or periodontitis in cats that had also calculus (OR: 2.49 and 3.70, respectively) suggests that inflammatory changes caused by calculus increase the risk of TR. We found that Cornish Rex, European, and Ragdoll are at higher risk for TR (OR: 2.44, 2.98 and 2.90, respectively). Exotic-Persians breed group had lower risk (OR: 0.28). TR was not observed in Turkish van or Devon Rex. The differences between breeds highlight a genetic contribution. In addition, female cats that had food available constantly had significantly less TR than female cats that had feeding times (OR: 0.44). The underlying reasons for this remain unexplained in our study.

Ventricular arrhythmia and sudden cardiac death in young Leonbergers.

INTRODUCTION: To describe unexpected sudden cardiac death (SCD) in young Leonbergers (<3 years) and to review the circumstances before death and necropsy findings; to prospectively evaluate the presence of possible arrhythmias in young Leonbergers; and to examine pedigrees for determining potential modes of inheritance. ANIMALS: Postmortem evaluations included 21 Leonbergers. Clinical evaluation consisted of 46 apparently healthy Leonbergers with and without a close family history of SCD. MATERIALS AND METHODS: Necropsy reports were reviewed retrospectively. Prospective clinical evaluation included physical examination, 5-min electrocardiogram, 24-h Holter, echocardiography, and laboratory tests. Pedigree data were examined for mode of inheritance. RESULTS: Based on necropsy reports, SCD occurred at a median age of 12 months (range, 2.0-32.0 months) without any previous clinical signs and usually in rest. No evidence of structural cardiac disease was found; arrhythmia-related death was suspected. Clinical evaluation and 24-h Holter showed ventricular arrhythmia (VA) in 14 apparently healthy Leonbergers (median age, 18 months; range, 12-42 months). Severity of VA varied from infrequent couplets/triplets to frequent complexity (couplets, triplets, nonsustained ventricular tachycardias,VTs) characterized by polymorphology. During follow-up, two dogs with polymorphic VT died. Although breed specificity and high prevalence indicate a heritable disease, based on available pedigree data, the mode of inheritance could not be determined. CONCLUSIONS: Sudden cardiac death in young Leonbergers is associated with malignant VA characterized by complexity and polymorphic nature. Diagnosis is based on 24-h Holter monitoring. Pedigree analysis suggests that the arrhythmia is familial.

Interbreed variation in serum serotonin (5-hydroxytryptamine) concentration in healthy dogs.

INTRODUCTION: Serotonin (5-hydroxytryptamine [5-HT]) has several biological functions. In different species, excessive 5-HT has been linked to valvular lesions, similar to those seen in dogs with myxomatous mitral valve disease. Previous studies suggest higher 5-HT in healthy Cavalier King Charles Spaniels (CKCSs), a breed highly affected by myxomatous mitral valve disease, compared to other breeds. OBJECTIVE: To investigate potential interbreed variation in serum 5-HT in healthy dogs. ANIMALS: 483 healthy dogs of nine breeds aged 1-7 years. METHODS: Dogs were examined at five European centers. Absence of cardiovascular, organ-related, or systemic diseases was ensured by thorough clinical investigations including echocardiography. Serum was frozen and later analyzed by enzyme-linked immunosorbent assay (ELISA). RESULTS: Median 5-HT concentration was 252.5 (interquartile range = 145.5-390.6) ng/mL. Overall breed difference was found (p<0.0001), and 42% of pairwise breed comparisons were significant. Univariate regression analysis showed association between serum 5-HT concentration and breed, center of examination, storage time, and sex, with higher 5-HT in females. In multiple regression analysis, the final model had an adjusted R2 of 0.27 with breed (p<0.0001), center (p<0.0001), and storage time (p=0.014) remaining significant. Within centers, overall breed differences were found at 3/5 centers (p≤0.028), and pairwise comparisons within those centers showed breed differences in 42% of comparisons. Among the included breeds, Newfoundlands, Belgian Shepherds and CKCSs had highest 5-HT concentrations. CONCLUSIONS: Interbreed variation in serum 5-HT concentration was found in healthy dogs aged 1-7 years. These differences should be taken into account when designing clinical studies.

Absence Seizures as a Feature of Juvenile Myoclonic Epilepsy in Rhodesian Ridgeback Dogs.

Myoclonic epilepsy in Rhodesian Ridgeback (RR) dogs is characterized by myoclonic seizures occurring mainly during relaxation periods, a juvenile age of onset and generalized tonic-clonic seizures in one-third of patients. An 8-month-old female intact RR was presented for myoclonic seizures and staring episodes that both started at 10 weeks of age. Testing for the DIRAS1 variant indicated a homozygous mutant genotype. Unsedated wireless video-electroencephalography (EEG) identified frequent, bilaterally synchronous, generalized 4 Hz spike-and-wave complexes (SWC) during the staring episodes in addition to the characteristic myoclonic seizures with generalized 4-5 Hz SWC or 4-5 Hz slowing. Photic stimulation did not evoke a photoparoxysmal response. Repeat video-EEG 2 months after initiation of levetiracetam treatment disclosed a >95% decrease in frequency of myoclonic seizures, and absence seizures were no longer evident. Absence seizures represent another seizure type in juvenile myoclonic epilepsy (JME) in RR dogs, which reinforces its parallels to JME in humans.

Exploration of known stereotypic behaviour-related candidate genes in equine crib-biting.

Crib-biting in horses is a stereotypic oral behaviour. Genetic susceptibility has been suggested on a causal basis, together with environmental factors such as stress, gastric discomfort and frustration caused by stall restrictions. This study aimed to test the associations of known or suspected stereotypic genes with equine crib-biting, including Ghrelin, Ghrelin receptor, Leptin, Dopamine receptor, µ-opioid receptor, N-cadherin, Serotonin receptor and Semaphorin. We conducted a candidate gene study with a case-control design, including 98 crib-biting and 135 control horses of two breeds, Finnhorses and half-breds. Detailed phenotypic information on crib-biting behaviour was surveyed through an owner-completed questionnaire. Control horses were more than 10 years old and without a history of crib-biting. Single nucleotide polymorphisms flanking the candidate genes were genotyped using either Sanger sequencing or Taqman assays. According to the survey, the affected horses started crib-biting at a young age, had exhibited crib-biting for more than a year, and expressed the behaviour after feeding or when stressed. Comparison of allele frequencies between the cases and controls for each breed separately did not provide evidence of an association at any of the tested loci. These results suggest that the previously known stereotypic genes are not major risk factors for crib-biting in horses, and further genome-wide studies are warranted on larger sample cohorts.

Assessment of the functionality of genome-wide canine SNP arrays and implications for canine disease association studies.

Domestic dogs share a wide range of important disease conditions with humans, including cancers, diabetes and epilepsy. Many of these conditions have similar or identical underlying pathologies to their human counterparts and thus dogs represent physiologically relevant natural models of human disorders. Comparative genomic approaches whereby disease genes can be identified in dog diseases and then mapped onto the human genome are now recognized as a valid method and are increasing in popularity. The majority of dog breeds have been created over the past few hundred years and, as a consequence, the dog genome is characterized by extensive linkage disequilibrium (LD), extending usually from hundreds of kilobases to several megabases within a breed, rather than tens of kilobases observed in the human genome. Genome-wide canine SNP arrays have been developed, and increasing success of using these arrays to map disease loci in dogs is emerging. No equivalent of the human HapMap currently exists for different canine breeds, and the LD structure for such breeds is far less understood than for humans. This study is a dedicated large-scale assessment of the functionalities (LD and SNP tagging performance) of canine genome-wide SNP arrays in multiple domestic dog breeds. We have used genotype data from 18 breeds as well as wolves and coyotes genotyped by the Illumina 22K canine SNP array and Affymetrix 50K canine SNP array. As expected, high tagging performance was observed with most of the breeds using both Illumina and Affymetrix arrays when multi-marker tagging was applied. In contrast, however, large differences in population structure, LD coverage and pairwise tagging performance were found between breeds, suggesting that study designs should be carefully assessed for individual breeds before undertaking genome-wide association studies (GWAS).

Genetic diagnosis in Lafora disease: genotype-phenotype correlations and diagnostic pitfalls.

Lafora disease (LD) can be diagnosed by skin biopsy, but this approach has both false negatives and false positives. Biopsies of other organs can also be diagnostic but are more invasive. Genetic diagnosis is also possible but can be inconclusive, for example, in patients with only one heterozygous EPM2A mutation and patients with apparently homozygous EPM2B mutations where one parent is not a carrier of the mutation. We sought to identify occult mutations and clarify the genotypes and confirm the diagnosis of LD in patients with apparent nonrecessive disease inheritance. We used single nucleotide polymorphism, quantitative PCR, and fluorescent in situ hybridization analyses. We identified large EPM2A and EPM2B deletions undetectable by PCR in the heterozygous state and describe simple methods for their routine detection. We report a coding sequence change in several patients and describe why the pathogenic role of this change remains unclear. We confirm that adult-onset LD is due to EPM2B mutations. Finally, we report major intrafamilial heterogeneity in age at onset in LD.

Upregulation of CFTR expression but not SLC26A3 and SLC9A3 in ulcerative colitis.

In inflamed colonic mucosa, the equilibrium between absorptive and secretory functions for electrolyte and salt transport is disturbed. We compared the expression of three major mediators of the intestinal salt transport between healthy and inflamed colonic mucosa to understand the pathophysiology of diarrhea in inflammatory bowel disease. Expression levels of the cystic fibrosis transmembrane regulator (CFTR) (Cl- channel), SLC26A3 (Cl-/HCO exchanger) and SLC9A3 (Na+/H+ exchanger) mRNAs were measured by real-time quantitative RT-PCR in peroperative colonic samples from controls (n = 4) and patients with ulcerative colitis (n = 10). Several samples were obtained from each individual. Tissue samples were divided into three subgroups according to their histological degree of inflammation. Expression of CFTR and SLC26A3 proteins were determined by immunohistochemistry and Western blotting from the same samples, respectively. Increased expression of CFTR mRNA was observed in all three groups of affected tissue samples, most pronounced in mildly inflamed colonic mucosa (5-fold increase in expression; P < 0.001). The expression of the CFTR protein was detected from health and inflamed colon tissue. Although the expression of the SLC26A3 mRNA was significantly decreased in severe ulcerative colitis (P < 0.05), the SLC26A3 protein levels remained unchanged in all groups. The expression of SLC9A3 mRNA was significantly changed between the mild and severe groups. Intestinal inflammation modulates the expression of three major mediators of intestinal salt transport and may contribute to diarrhea in ulcerative colitis both by increasing transepithelial Cl- secretion and by inhibiting the epithelial NaCl absorption.

The congenital chloride diarrhea gene is expressed in seminal vesicle, sweat gland, inflammatory colon epithelium, and in some dysplastic colon cells.

Congenital chloride diarrhea (CLD) is an autosomal recessive disorder of intestinal electrolyte transportation caused by mutations in the anion transporter protein encoded by the down-regulated in adenoma (DRA), or CLD, gene. In this study, in situ hybridization and immunohistochemistry were performed to investigate the expression of CLD in extraintestinal normal epithelia and in intestinal inflammatory and neoplastic epithelia. The expression of the closely related anion transporter diastrophic dysplasia sulfate transporter, DTDST, was also examined and compared with that of CLD in colon. The only extraintestinal tissues showing CLD expression were eccrine sweat glands and seminal vesicles. In inflammatory bowel disease and ischemic colitis, expression of CLD mRNA in colon epithelium was similar to histologically normal colon epithelium, but the protein was found deeper in crypts, including proliferative epithelial cells. In intestinal tumors, the expression pattern of CLD was dependent on the differentiation status of the tissue studied: epithelial polyps with no or minor dysplasia showed abundant expression, whereas adenocarcinomas were negative. The DTDST gene was abundantly expressed in the upper crypt epithelium of colonic mucosa.

Genetic Disorders of Membrane Transport III. Congenital chloride diarrhea.

Congenital chloride diarrhea (CLD) is a recessively inherited disorder of intestinal electrolyte absorption that involves, specifically, Cl-/HCO-3 exchange. CLD is caused by mutations in a chromosome 7 gene, first known as DRA (for downregulated in adenoma). The disease occurs in all parts of the world but is more common in some populations with genetic founder effects. More than 20 mutations in the gene are known to date. The CLD (or DRA) gene encodes a transmembrane protein belonging to the sulfate transporter family with three known members in humans, all associated with a distinct genetic disease. Members of the gene family can transport other anions as well that may turn out to be physiologically more important than sulfate transport. The gene family is well conserved in many prokaryotic and eukaryotic species and is expected to be much larger than presently known.