Two MC1R loss-of-function alleles in cream-coloured Australian Cattle Dogs and white Huskies.

Loss-of-function variants in the MC1R gene cause recessive red or yellow coat-colour phenotypes in many species. The canine MC1R:c.916C>T (p.Arg306Ter) variant is widespread and found in a homozygous state in many uniformly yellow- or red-coloured dogs. We investigated cream-coloured Australian Cattle Dogs whose coat colour could not be explained by this variant. A genome-wide association study with 10 cream and 123 red Australian Cattle Dogs confirmed that the cream locus indeed maps to MC1R. Whole-genome sequencing of cream dogs revealed a single nucleotide variant within the MITF binding site of the canine MC1R promoter. We propose to designate the mutant alleles at MC1R:c.916C>T as e1 and at the new promoter variant as e2 . Both alleles segregate in the Australian Cattle Dog breed. When we considered both alleles in combination, we observed perfect association between the MC1R genotypes and the cream coat colour phenotype in a cohort of 10 cases and 324 control dogs. Analysis of the MC1R transcript levels in an e1 /e2 compound heterozygous dog confirmed that the transcript levels of the e2 allele were markedly reduced with respect to the e1 allele. We further report another MC1R loss-of-function allele in Alaskan and Siberian Huskies caused by a 2-bp deletion in the coding sequence, MC1R:c.816_817delCT. We propose to term this allele e3 . Huskies that carry two copies of MC1R loss-of-function alleles have a white coat colour.

Canine NAPEPLD-associated models of human myelin disorders.

Canine leukoencephalomyelopathy (LEMP) is a juvenile-onset neurodegenerative disorder of the CNS white matter currently described in Rottweiler and Leonberger dogs. Genome-wide association study (GWAS) allowed us to map LEMP in a Leonberger cohort to dog chromosome 18. Subsequent whole genome re-sequencing of a Leonberger case enabled the identification of a single private homozygous non-synonymous missense variant located in the highly conserved metallo-beta-lactamase domain of the N-acyl phosphatidylethanolamine phospholipase D (NAPEPLD) gene, encoding an enzyme of the endocannabinoid system. We then sequenced this gene in LEMP-affected Rottweilers and identified a different frameshift variant, which is predicted to replace the C-terminal metallo-beta-lactamase domain of the wild type protein. Haplotype analysis of SNP array genotypes revealed that the frameshift variant was present in diverse haplotypes in Rottweilers, and also in Great Danes, indicating an old origin of this second NAPEPLD variant. The identification of different NAPEPLD variants in dog breeds affected by leukoencephalopathies with heterogeneous pathological features, implicates the NAPEPLD enzyme as important in myelin homeostasis, and suggests a novel candidate gene for myelination disorders in people.

Genomic comparison of bovine papillomavirus 1 isolates from bovine, equine and asinine lesional tissue samples.

Several attempts have been made to categorize equid- and bovid-specific bovine papillomavirus 1 (BPV1) isolates based on sequence tags. This study includes newly determined sequence information from 33 BPV1 isolates of equine, asinine and bovine origin and investigates sequence bias due to host species. Twenty of the viral genomes were sequenced over their entire length and a further thirteen were sequenced, including flanking sequences, at two specific sites, the LCR and the E5 ORF. Alignment and analyses of the sequences did not reveal statistically significant site differences between the sequences of bovine and equid origin. None of the proposed sites of divergence noted by other authors demonstrated significant species-specific characteristics. Our results suggest that BPV1 is shared between equine, asinine and bovine host species, and that viral transfer between bovines and equids is a repeated and ongoing phenomenon.

Neuronal ceroid lipofuscinosis (NCL) is caused by the entire deletion of CLN8 in the Alpenländische Dachsbracke dog.

Neuronal ceroid lipofuscinoses (NCLs) are inherited lysosomal storage diseases that have been described in a variety of dog breeds, where they are caused by different mutations in different genes. However, the causative gene defect in the breed Alpenländische Dachsbracke remained unknown so far. Here we present two confirmed cases of NCL in Alpenländische Dachsbracke dogs from different litters of the same sire with a different dam harboring the same underlying novel mutation in the CLN8 gene. Case 1, a 2-year-old male Alpenländische Dachsbracke was presented with neurological signs including disorientation, character changes including anxiety states and aggressiveness, sudden blindness and reduction of food intake. Magnetic resonance imaging (MRI) scans showed cerebral atrophy with dilation of all cerebral ventricles, thinning of the intermediate mass of the thalamus and widening of the cerebral sulci. Postmortem examination of the central nervous system (CNS) showed neuronal loss in the cerebral cortex, cerebellum and spinal cord with massive intracellular deposits of ceroid pigment. Additional ceroid-lipofuscin deposits were observed in the enteric nervous system and in macrophages within spleen, lymph nodes and lung. Ultrastructural analyses confirmed NCL with the presence of osmiophilic membrane bounded lamellar-like structures. Case 2, a 1,5-year old female Alpenländische Dachsbracke was presented with progressive generalized forebrain disease including mental changes such as fearful reactions to various kinds of external stimuli and disorientation. The dog also displayed seizures, absence of menace reactions and negative cotton-ball test with normal pupillary light reactions. The clinical and post mortem examination yielded similar results in the brain as in Case 1. Whole genome sequencing of Case 1 and PCR results of both cases revealed a homozygous deletion encompassing the entire CLN8 gene as the most likely causative mutation for the NCL form observed in both cases. The deletion follows recessive inheritance since the dam and a healthy male littermate of Case 1 were tested as heterozygous carriers. This is the first detailed description of CLN8 gene associated NCL in Alpenländische Dachsbracke dogs and thus provides a novel canine CLN8 model for this lysosomal storage disease. The presence of ceroid lipofuscin in extracerebral tissues may help to confirm the diagnosis of NCL in vivo, especially in new dog breeds where the underlying mutation is not known.

Hepatic fungal infection in a young beagle with unrecognised hereditary cobalamin deficiency (Imerslund-Gräsbeck syndrome).

A 12-month-old beagle presented for anorexia, pyrexia and vomiting. The dog had been treated intermittently with antibiotics and corticosteroids for inappetence and lethargy since five months of age. Previous laboratory abnormalities included macrocytosis and neutropenia. At presentation, the dog was lethargic, febrile and thin. Laboratory examination findings included anaemia, a left shift, thrombocytopenia, hypoglycaemia and hyperbilirubinaemia. Multiple, small, hypoechoic, round hepatic lesions were observed on abdominal ultrasound. Cytological examination of hepatic fine needle aspirates revealed a fungal infection and associated pyogranulomatous inflammation. The dog's general condition deteriorated despite supportive measures and treatment with fluconazole, and owners opted for euthanasia before hypocobalaminaemia was identified. Subsequent genomic analysis revealed a CUBN:c.786delC mutation in a homozygous state, confirming hereditary cobalamin malabsorption (Imerslund-Gräsbeck syndrome). Similar to human infants, dogs with Imerslund-Gräsbeck syndrome may rarely be presented for infectious diseases, distracting focus from the underlying primary disorder.

IL26 gene inactivation in Equidae.

Interleukin-26 (IL26) is a member of the IL10 cytokine family. The IL26 gene is located between two other well-known cytokines genes of this family encoding interferon-gamma (IFNG) and IL22 in an evolutionary conserved gene cluster. In contrast to humans and most other mammals, mice lack a functional Il26 gene. We analyzed the genome sequences of other vertebrates for the presence or absence of functional IL26 orthologs and found that the IL26 gene has also become inactivated in several equid species. We detected a one-base pair frameshift deletion in exon 2 of the IL26 gene in the domestic horse (Equus caballus), Przewalski horse (Equus przewalskii) and donkey (Equus asinus). The remnant IL26 gene in the horse is still transcribed and gives rise to at least five alternative transcripts. None of these transcripts share a conserved open reading frame with the human IL26 gene. A comparative analysis across diverse vertebrates revealed that the IL26 gene has also independently been inactivated in a few other mammals, including the African elephant and the European hedgehog. The IL26 gene thus appears to be highly variable, and the conserved open reading frame has been lost several times during mammalian evolution.

Polymorphisms in the ABCB1 gene in phenobarbital responsive and resistant idiopathic epileptic Border Collies.

BACKGROUND: Variation in the ABCB1 gene is believed to play a role in drug resistance in epilepsy. HYPOTHESIS/OBJECTIVES: Variation in the ABCB1 gene encoding the permeability-glycoprotein could have an influence on phenobarbital (PB) resistance, which occurs with high frequency in idiopathic epileptic Border Collies (BCs). ANIMALS: Two hundred and thirty-six client-owned BCs from Switzerland and Germany including 25 with idiopathic epilepsy, of which 13 were resistant to PB treatment. METHODS: Prospective and retrospective case-control study. Data were collected retrospectively regarding disease status, antiepileptic drug (AED) therapy, and drug responsiveness. The frequency of a known mutation in the ABCB1 gene (4 base-pair deletion in the ABCB1 gene [c.296_299del]) was determined in all BCs. Additionally, the ABCB1 coding exons and flanking sequences were completely sequenced to search for additional variation in 41 BCs. Association analyses were performed in 2 case-control studies: idiopathic epileptic and control BCs and PB-responsive and resistant idiopathic epileptic BCs. RESULTS: One of 236 BCs (0.4%) was heterozygous for the mutation in the ABCB1 gene (c.296_299del). A total of 23 variations were identified in the ABCB1 gene: 4 in exons and 19 in introns. The G-allele of the c.-6-180T > G variation in intron 1 was significantly more frequent in epileptic BCs resistant to PB treatment than in epileptic BCs responsive to PB treatment (P(raw) = .0025). CONCLUSIONS AND CLINICAL IMPORTANCE: A variation in intron 1 of the ABCB1 gene is associated with drug responsiveness in BCs. This might indicate that regulatory mutations affecting the expression level of ABCB1 could exist, which may influence the reaction of a dog to AEDs.

A comparative radiation hybrid map of sheep chromosome 10.

Comparative radiation hybrid (RH) maps of individual ovine chromosomes are essential to identify genes governing traits of economic importance in sheep, a livestock species for which whole genome sequence data are not yet available. The USUoRH5000 radiation hybrid panel was used to generate a RH map of sheep chromosome 10 (OAR10) with 59 markers that span 1,422 cR over an estimated 92 Mb of the chromosome, thus providing markers every 2 Mb (equivalent to every 24 cR). The markers were derived from 46 BAC end sequences (BESs), a single EST, and 12 microsatellites. Comparative analysis showed that OAR10 shares remarkable conservation of gene order along the entire length of cattle chromosome 12 and that OAR10 contains four major homologous synteny blocks, each related to segments of the homologous human chromosome 13. Extending the comparison to the horse, dog, mouse, and chicken genome showed that these blocks share conserved synteny across species.

Beta-tubulin complementary DNA sequence variations observed between cyathostomins from benzimidazole-susceptible and -resistant populations.

The molecular mechanism of benzimidazole (BZ) resistance in cyathostomins of horses is still unclear. Previous studies revealed that the TTC or TAC polymorphism in codon 200 of the beta-tubulin isotype 1 gene is not as strictly correlated with BZ resistance as in trichostrongyles in sheep. To identify further sites of polymorphism within the beta-tubulin gene related to BZ resistance, complete complementary DNAs (cDNAs) encoding beta-tubulin of adult worms of Cylicocyclus nassatus, Cyathostomum pateratum, Cyathostomum coronatum, Cyathostomum catinatum, Cylicostephanus longibursatus, and Cylicostephanus goldi of a BZ-resistant cyathostomin population were characterized using specific primers. The cDNA sequence of each species spans 1,429 bp, encoding a protein of 448 amino acids. The interspecific identities are 95.2-99.6% at the nucleotide and 98.7-100.0% at the peptide level. The comparison of the amino acid sequences of individuals isolated from the BZ-resistant cyathostomin population with those from individuals of Cc. nassatus, Cy. coronatum, Cy. pateratum, and Cy. catinatum of a BZ-susceptible one showed differing amino acids in 11 positions. The commonness of a phenylalanine to tyrosine mutation at position 167 in all the 6 cyathostomin species isolated from a BZ-resistant population suggests its involvement in the molecular mechanism in BZ resistance.

Equine cyathostomins.

This collection of articles provides an in depth account of five presentations delivered during the Symposium on Equine Cyathostomins held at the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP), New Orleans, Louisiana,10­14 August 2003. The symposium was organized and chaired by Ray M. Kaplan and Jacqui B. Matthews and focused on new developments in two major areas of current importance: the immunobiology of cyathostomin­horse interactions and anthelmintic resistance.