Lumbosacral transitional vertebra in 14 dog breeds in Norway: Occurrence, risk factors and association with hip dysplasia.

A lumbosacral transitional vertebra (LTV) is a congenital anomaly of the spine and has been suggested to predispose to canine hip dysplasia (CHD). This retrospective, cross-sectional study investigated the prevalence of LTV and CHD among 14 dog breeds in Norway, the possible associations with risk factors, and whether LTV was a risk factor for the development of hip dysplasia. The results were based on evaluation of ventrodorsal radiographs from the CHD screening program from the Norwegian Kennel Club from February 2014 to January 2022. A total of 13,950 dogs were included in the study. For statistical analysis, CHD grades were reclassified from the official Federation Cynologique Internationale (FCI) grades into three grades: CHD free (CHD=A, B), CHD mild (CHD=C), and CHD severe (CHD=D, E). In the study sample, the overall occurrence of LTV was 18.5%, of which 32.9% were type 1, 45.7% type 2% and 21.4% type 3. The occurrence of LTV varied significantly among the included breeds, ranging from 9.5% to 46.2%. There was no association between sex and LTV. The frequencies of CHD grades were A: 43.1%; B: 31.4%; C: 18.4%; D: 6.0%; E: 1.1%. There was a statistically significant association with mild and severe CHD in dogs with LTV type 2 and LTV type 3 (P< 0.001). In the population studied, the prevalence of LTV was different among breeds. This supports initial data on the heredity of LTV and the diverse occurrence of LTV among breeds. Our results indicate that LTV type 2 and type 3 are associated with mild and severe CHD development. Therefore, this study has potentially identified an additional risk factor for the development of hip dysplasia.

Breed distributions for diabetes mellitus and hypothyroidism in Norwegian dogs.

BACKGROUND: Diabetes mellitus (DM) and hypothyroidism are common canine endocrinopathies. Both canine DM and primary hypothyroidism are assumed to originate from autoimmune destruction of the respective endocrine glands and have been associated with the major histocompatibility complex (MHC) gene region. This study aims to investigate breed distributions for DM and hypothyroidism in the Norwegian canine population by calculating odds ratios (OR) from two different comparator groups. METHODS: Results from canine serum samples submitted from 2001 to 2018 to the Veterinary Clinical Pathology Laboratory (VCPL) at the Faculty of Veterinary Medicine, Norwegian University of Life Sciences for analysis of fructosamine and thyroid hormones in serum were used as cases in a retrospective bivariate analysis of canine breeds. The ORs were calculated as a measure of risk for the included breeds, where all the submitted blood samples to the VCPL and dogs registered in the Norwegian Kennel Club (NKK), the national organization for dog owners, were used as two comparator groups. RESULTS: Significant differences in disease prevalence between breeds were discovered using both comparator groups. Australian terrier, Swedish lapphund, Samoyed, and Schipperke were at highest risk for DM. German Shepherd, Golden retriever, German pointing dog, and Collie presented as the breeds with lowest risk for DM. For hypothyroidism, Schnauzer, Eurasier, Dunker, and English setter were at highest risk for developing the disease. The breeds at lowest risk of developing hypothyroidism were Rottweiler, Dachshund, German shepherd, and Border collie. The results from the different comparator groups gave different ORs and ranks, but the breeds with highest and lowest odds showed the same susceptibility using both comparators. CONCLUSIONS: These findings support that there are breeds more and less prone to develop DM and hypothyroidism. A strong genetic predisposition involved in the aetiology of these two diseases is therefore likely. Interestingly, there also appeared to be an inverse relationship of odds for the two diseases for some of the breeds since some breeds that had a high OR for DM or hypothyroidism had a lower OR for the other disease. This indicates that there may be different risk alleles/haplotypes for the two diseases. The possible aetiological relationship between canine DM and hypothyroidism should be further investigated.

Roan, ticked and clear coat patterns in the canine are associated with three haplotypes near usherin on CFA38.

White coat patterning is a feature of many dog breeds and is known to be coded primarily by the gene micropthalmia-associated transcription factor (MITF). This patterning in the coat can be modified by other factors to produce the attractive phenotypes termed 'ticked' and 'roan' that describe the presence of flecks of color that vary in distribution and intensity within otherwise 'clear' white markings. The appearance of the pigment in the white patterning caused by ticking and roaning intensifies in the weeks after birth. We applied genome-wide association to compare English Cocker Spaniels of roan phenotype (N = 34) with parti-color (non-roan) English Cocker Spaniels (N = 9) and identified an associated locus on CFA 38, CFA38:11 057 040 (Praw  = 8.9 × 10-10 , Pgenome  = 2.7 × 10-5 ). A local case-control association in English Springer Spaniels comparing 11 ticked and six clear dogs identified indicative association with a different haplotype, CFA38:11 122 467G>T (Praw  = 1.7 × 10-5 ) and CFA38:11 124 294A>C (Praw  = 1.7 × 10-5 ). We characterize three haplotypes in Spaniels according to their putative functional variant profiles at CFA38:11 111 286C>T (missense), CFA38:11 131 841-11 143 239DUP.insTTAA (using strongly linked marker CFA38:11 143 243C>T) and CFA38:11 156 425T>C (splice site). In Spaniels, the haplotypes work as an allelic series including alleles (t, recessive clear; T, dominant ticked/parti-color; and TR , incomplete dominant roan) to control the appearance of pigmented spots or flecks in otherwise white areas of the canine coat. In Spaniels the associated haplotypes are t (CCT), T (TCC) and TR (TTT) for SNP markers on CFA38 at 11 111 286C>T, 11 143 243C>T and 11 156 425T>C respectively. It is likely that other alleles exist in this series and together the haplotypes result in a complex range of patterning that is only visible when dogs have white patterning resulting from the epistatic gene Micropthalmia-associated transcription factor (the S-locus).

Neuronal ceroid lipofuscinosis in Salukis is caused by a single base pair insertion in CLN8.

Neuronal ceroid lipofuscinoses (NCLs) are heterogenic inherited lysosomal storage diseases that have been described in a number of species including humans, sheep, cattle, cats and a number of different dog breeds, including Salukis. Here we present a novel genetic variant associated with the disease in this particular breed of dog. In a clinical case, a Saluki developed progressive neurological signs, including disorientation, anxiety, difficulties in eating, seizures and loss of vision, and for welfare reasons, was euthanized at 22 months of age. Microscopy showed aggregation of autofluorescent storage material in the neurons of several brain regions and also in the retina. The aggregates showed positive staining with Sudan black B and periodic acid Schiff, all features consistent with NCL. Whole genome sequencing of the case and both its parents, followed by variant calling in candidate genes, identified a new variant in the CLN8 gene: a single bp insertion (c.349dupT) in exon 2, introducing an immediate stop codon (p.Glu117*). The case was homozygous for the insertion, and both parents were heterozygous. A retrospective study of a Saluki from Australia diagnosed with NCL identified this case as being homozygous for the same mutation. This is the fourth variant identified in CLN8 that causes NCL in dogs.

A statistical assessment of the biological relationship between simultaneous canine mammary tumours.

Simultaneous canine mammary tumours (CMTs) are frequently reported in the literature, but few studies have addressed their biological relationship in detail or performed statistical assessments. In this study, 269 canine mammary gland tumours from 216 dogs were categorized using an extended histopathological classification, where semiquantitative and binomial scales enumerated morphological parameters of the tumours. The classification facilitated a statistical study of the biological relationship between simultaneous within-dog tumours. Seventy-seven percent of the dogs had single tumours and 23% had simultaneous tumours. Sixty-one percent of the neoplasias were benign, with complex adenoma as the most frequent diagnosis and 39% were malignant, with complex carcinoma as the most common malignancy. Simultaneous tumours within dogs more often had equal diagnoses and neoplastic level (benign or malignant) than would be expected by chance alone, as compared with random pairs of single tumours from different dogs. This statistically supported finding indicated the presence of a biological relationship between simultaneous tumours.

A genome-wide association study identifies a region strongly associated with symmetrical onychomadesis on chromosome 12 in dogs.

Symmetrical onychomadesis causes periodic loss of claws in otherwise healthy dogs. Genome-wide association analysis in 225 Gordon Setters identified a single region associated with symmetrical onychomadesis on chromosome 12 (spanning about 3.3 mb). A meta-analysis including also English Setters indicated that this genomic region predisposes for symmetrical onychomadesis in English Setters as well. The associated region spans most of the major histocompatibility complex and nearly 1 Mb downstream. Like many other autoimmune diseases, associations of symmetrical onychomadesis with DLA class II alleles have been reported. In this study, no associated markers were revealed within any of the DLA-DRB1, -DQA1 or -DQB1 genes, and the odds for symmetrical onychomadesis in the Gordon Setters were much higher, carrying significant single nucleotide polymorphisms compared to the odds of any of the recorded DLA-DRB1/DQA1/DQB1 haplotypes. We noticed that some of the associated DLA haplotypes were different between the English Setters and the Gordon Setters. Interestingly, associated SNP chip markers showed a more consistent pattern of allelic variants related to cases or controls regardless of breed. In conclusion, the associated genetic markers identified in this study hold the potential to aid in selection of breeding animals to reduce the frequency of symmetrical onychomadesis in the dog.

Progressive retinal atrophy in Shetland sheepdog is associated with a mutation in the CNGA1 gene.

Progressive retinal atrophy (PRA) is the collective name of a class of hereditary retinal dystrophies in the dog and is often described as the equivalent of retinitis pigmentosa in humans. PRA is characterized by visual impairment due to degeneration of the photoreceptors in the retina, usually leading to blindness. PRA has been reported in dogs from more than 100 breeds and can be genetically heterogeneous both between and within breeds. The disease can be subdivided by age at onset and rate of progression. Using genome-wide association with 15 Shetland Sheepdog (Sheltie) cases and 14 controls, we identified a novel PRA locus on CFA13 (Praw  = 8.55 × 10(-7) , Pgenome  = 1.7 × 10(-4) ). CNGA1, which is known to be involved in human cases of retinitis pigmentosa, was located within the associated region and was considered a likely candidate gene. Sequencing of this gene identified a 4-bp deletion in exon 9 (c.1752_1755delAACT), leading to a frameshift and a premature stop codon. The study indicated genetic heterogeneity as the mutation was present in all PRA-affected individuals in one large family of Shelties, whereas some other cases in the studied Sheltie population were not associated with this CNGA1 mutation. To our knowledge, this is the first report of a mutation in CNGA1 causing PRA in dogs.

Glomerular Collagen V Codeposition and Hepatic Perisinusoidal Collagen III Accumulation in Canine Collagen Type III Glomerulopathy.

Collagen type III glomerulopathy, also known as collagenofibrotic glomerulopathy, is a rare renal disease of unknown pathogenesis. The disease occurs in humans and animals and is characterized by massive glomerular accumulations of collagen type III. In the present study, we describe a Drever dog litter affected by an early onset variant of this glomerular disease, where 4 of 9 puppies developed renal failure within 50 days of age. Necropsy specimens of kidney from the 4 affected cases were studied by light microscopy, electron microscopy, and immunohistochemistry, and characteristic lesions compatible with a diagnosis of collagen type III glomerulopathy were found. In addition, 2 cases showed atypical epithelium in the collecting ducts of the medulla, so-called adenomatoid change. Immunohistochemistry of renal specimens from collagen type III glomerulopathy-affected dogs (n = 10) originating from two different dog strains, the Drever dogs and a mixed-breed strain, demonstrated that the deposited glomerular collagen is composed of a mixture of collagen III and collagen V. The distribution of the collagen V corresponded to the localization of collagen III; however, differences in staining intensity showed that collagen type III is the dominating component. Immunohistochemistry for collagen III (n = 9) and a transmission electron microscopic study (n = 1) showed hepatic perisinusoidal collagen type III deposition in affected cases from both dog strains. This is the first report documenting glomerular accumulations of collagen type V and perisinusoidal liver collagen III deposition in canine collagen type III glomerulopathy.

Identification of genetic variation in 11 candidate genes of canine mammary tumour.

The incidence of canine mammary tumours (CMTs) differs significantly between breeds, strongly supporting an influence of genetic risk factors. We aimed at identifying germline genetic variations in mammary tumour-associated genes in dogs and survey whether these might alter the encoded proteins. We sequenced 11 genes (BRCA1, BRCA2, BRIP1, CDH1, CHEK2, EGFR, ESR1, HER2, PTEN, STK11 and TP53) and screened for genetic variations. Sixty-four single nucleotide polymorphisms (SNPs) were identified. Nine of the coding SNPs were non-synonymous, of which four were located in gene regions conserved across four species. Three of the non-synonymous SNPs might be damaging according to PolyPhen predictions. One of the indels identified has previously been associated with CMTs. Because of the founder effects, genetic drift and inbreeding in many dog breeds the allele frequencies of the genes studied are likely to vary significantly between breeds and contribute to the considerable difference in genetic risk associated with cancer.

Association of dopamine- and serotonin-related genes with canine aggression.

Human-directed canine aggression was studied using 50 aggressive and 81 non-aggressive dogs. We examined 62 single nucleotide polymorphisms (SNPs) occurring in or in the close vicinity of 16 neurotransmitter-related genes. Allelic associations with aggression were identified for DRD1, HTR1D, HTR2C and SLC6A1. Risk or protective haplotypes for aggressive behaviour based on 2-5 SNPs were identified. The frequency of aggressive dogs varied significantly between the haplotypes within loci and the odds ratios of aggression in dogs with risk haplotypes compared with protective haplotypes varied from 4.4 (HTR2C) to 9.0 (SLC6A1). A risk haplotype across the neurotransmitter receptor gene HTR1D harboured a non-synonymous SNP with a potential effect on protein function. We identified no haplotypes in complete association with the recorded phenotypes, supporting a complex inheritance of aggression.

A population study of a mutation allele associated with cone-rod dystrophy in the standard wire-haired dachshund.

Cone-rod dystrophy in the standard wire-haired dachshund (SWHD) is inherited as a simple autosomal recessive trait and the recently discovered mutation is widespread within the SWHD population in Norway and other Scandinavian countries. The gene frequency was estimated to be 4.8%. On the basis of the assumption that the size of the ancestral haplotype around a mutation is inversely correlated with the number of generations since the mutation arose, we have found that the mutation is of a relatively recent origin. The conserved haplotype was found to be 8 Mb in size and therefore we estimate that the mutation arose roughly eight generations (approximately 37 years) ago. This indicates that the mutation arose after breed separation.

A study of inherited short tail and taillessness in Pembroke Welsh corgi.

OBJECTIVES: To study whether natural short tail in adult Pembroke Welsh corgi is associated with congenital spinal defects. To report anatomical defects in two newborn tailless puppies from short-tailed parents, and to check whether they were homozygous for the dominant mutation in the T-gene (C295G). METHODS: The vertebral column of 19 adult dogs with natural short tail, from short-tail x long-tail crossings, was radiographically examined. Two tailless puppies were radiographed and submitted for necropsy. Samples from the puppies, their parents and five siblings were analysed for the mutation of the T-gene. RESULTS: No congenital spinal defects were diagnosed in any of the short-tailed dogs. The tailless puppies had anorectal atresia, had multiple spinal defects and were homozygous for the mutation in the T-gene. CLINICAL SIGNIFICANCE: As tail docking is forbidden in many countries, breeding Pembroke Welsh corgis with natural short tail is becoming increasingly common. Previous studies indicated that the mutation in homozygotes is lethal in early fetal life. It is of clinical significance that natural short tail is probably not associated with congenital spinal defects, as is known from studies of other species, and that homozygotes for this mutation with serious anatomical defects may be born.

Mapping of the bovine genes of the de novo AMP synthesis pathway.

Summary The purine nucleotides adenosine monophosphate (AMP) and guanosine monophosphate (GMP) are critical for energy metabolism, cell signalling and cell reproduction. Despite their essential function, little is known about the regulation and in vivo expression pattern of the genes involved in the de novo purine synthesis pathway. The complete coding region of the bovine phosphoribosylaminoimidazole carboxylase gene (PAICS), which catalyses steps 6 and 7 of the de novo purine biosynthesis pathway, as well as bovine genomic sequences of the six other genes in the pathway producing inosine monophosphate (IMP) and AMP [phosphoribosyl pyrophosphate amidotransferase (PPAT), phosphoribosylglycinamide formyltransferase (GART), phosphoribosylformylglycinamidine synthase (PFAS), adenylosuccinate lyase (ADSL), 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) and adenylosuccinate synthase (ADSS)], were identified. The genes were mapped to segments of six different bovine chromosomes using a radiation hybrid (RH) cell panel. The gene PPAT, coding for the presumed rate-limiting enzyme of the purine de novo pathway was closely linked to PAICS on BTA6. These, and the other bovine locations i.e. GART at BTA1, PFAS at BTA19, ADSL at BTA5, ATIC at BTA2 and ADSS at BTA16, are in agreement with published comparative maps of cattle and man. PAICS and PPAT genes are known to be closely linked in human, rat and chicken. Previously, an expressed sequence fragment of PAICS (Bos taurus corpus luteum, BTCL9) was mapped to BTA13. By isolation and characterization of a BAC clone, we have now identified a PAICS processed pseudogene sequence (psiPAICS) on BTA13. Processed pseudogene sequences of PAICS and other genes of the purine biosynthesis pathway were identified in several mammalian species, indicating that the genes of this pathway have been susceptible to retrotransposition. The seven bovine genes are expressed at a higher level in testicular and ovary tissues compared with skeletal muscle.

Identification and physical mapping of genes expressed in the corpus luteum in cattle.

A representational difference analysis was performed to identify genes expressed in the corpus luteum of cattle. The corpus luteum is an ovarian structure that is essential for the establishment and maintenance of pregnancy. Knowledge of gene expression and function of corpus luteum will be important to improve fertility in humans and domestic animals. Housekeeping genes were removed from the corpus luteum representation (tester) using skeletal muscle as the subtracting agent (driver). A total of 80 clones of the final subtraction product were analysed by sequencing and 11 new bovine gene sequences were identified (pBTCL1-11). The sequences were mapped to segments of 10 different chromosomes using a somatic cell hybrid panel and a radiation hybrid panel. With one exception the locations are in agreement with published comparative maps of cattle and man. Expression in corpus luteum was verified by RT-PCR for all the 11 clones.

Canine homolog of the T-box transcription factor T; failure of the protein to bind to its DNA target leads to a short-tail phenotype.

Domestic dog breeds show a wide variety of morphologies and offer excellent opportunities to study the molecular genetics of phenotypic traits. We are interested in exploring this potential and have begun by investigating the genetic basis of a short-tail trait. Our focus has been on the T gene, which encodes a T-box transcription factor important for normal posterior mesoderm development. Haploinsufficiency of T protein underlies a short-tail phenotype in mice that is inherited in an autosomal dominant fashion. We have cloned the dog homolog of T and mapped the locus to canine Chromosome (Chr) 1q23. Full sequence analysis of the T gene from a number of different dog breeds identified several polymorphisms and a unique missense mutation in a bob-tailed dog and its bob-tailed descendants. This mutation is situated in a highly conserved region of the T-box domain and alters the ability of the T protein to bind to its consensus DNA target. Analysis of offspring from several independent bobtail x bobtail crosses indicates that the homozygous phenotype is embryonic lethal.

Renal microcystic tubular lesions in two 1Year-old dogs - an early sign of hereditary renal cystadenocarcinoma?

As a part of a study of early renal changes in renal cystadenocarcinoma (RC), a 5-year-old German shepherd dog and two 1-year-old German shepherd mixed-breed dogs were examined. All three animals had bilateral, microscopic renal cysts, and the 5-year-old dog also had RC. Microscopical examination showed papillary hyperplastic tubular epithelial cells lining the inner wall of the renal cysts in all dogs. These cells showed strong reactivity with a monoclonal antibody against a broad-spectrum type of cytokeratin. The dam of the young dogs had suffered from autosomal dominant inherited RC and nodular dermatofibrosis (ND) syndrome. It is likely that the microscopic renal cystic lesions seen in the young dogs represented an early renal change in the RC/ND syndrome. This suggests that the diagnosis of RC can be made on suspected carriers by microscopical examination of renal biopsies as early as 1 year of age, i.e., before the dogs are used for breeding.

Genetic mapping of a naturally occurring hereditary renal cancer syndrome in dogs.

Canine hereditary multifocal renal cystadenocarcinoma and nodular dermatofibrosis (RCND) is a rare, naturally occurring inherited cancer syndrome observed in dogs. Genetic linkage analysis of an RCND-informative pedigree has identified a linkage group flanking RCND (CHP14-C05.377-C05.414-FH2383-C05. 771-[RCND-CPH18]-C02608-GLUT4-TP53-ZuBe Ca6-AHT141-FH2140-FH2594) thus localizing the disease to a small region of canine chromosome 5. The closest marker, C02608, is linked to RCND with a recombination fraction (theta) of 0.016, supported by a logarithm of odds score of 16.7. C02608 and the adjacent linked markers map to a region of the canine genome corresponding to portions of human chromosomes 1p and 17p. A combination of linkage analysis and direct sequencing eliminate several likely candidate genes, including tuberous sclerosis 1 and 2 genes (TSC1 and TSC2) and the tumor suppressor gene TP53. These data suggest that RCND may be caused by a previously unidentified tumor suppressor gene and highlight the potential for canine genetics in the study of human disease predisposition.

Chromosomal assignment of canine TSC2, PKD1 and CLN3 genes by radiation hybrid- and linkage analyses.

The canine tuberous sclerosis 2 (TSC2) gene has been mapped to canine chromosome 6 using a canine whole genome radiation hybrid panel. There is close linkage between canine TSC2 and the polycystic kidney disease 1 gene (PKD1), as has been observed in humans and other mammalian species. The gene responsible for the human juvenile form of neuronal ceroid lipofuscinosis (CLN3), maps close to TSC2 and PKD1 in humans, and is also syntenic in the dog. We further demonstrate linkage to a group of polymorphic markers assigned to canine chromosome 6 (CFA6).

Five new linkage groups in the canine linkage map.

Nineteen further polymorphic loci were typed on the DogMap reference panel. Five new linkage groups were identified. Additionally, five markers were added to earlier defined linkage groups. Three of the new linkage groups contain markers mapped earlier to specific dog chromosomes by physical mapping. These results make a further contribution to the canine genome map and provides more linkage groups physically assigned to known chromosomes.