Assessment of collagen genes involved in fragmented medial coronoid process development in Labrador Retrievers as determined by affected sibling-pair analysis

OBJECTIVE: To evaluate the involvement of various collagen genes in the development of fragmented medial coronoid process (FCP) in Labrador Retrievers. SAMPLE POPULATION: 93 dogs originating from 13 litters were used in the study; FCP was diagnosed in 35 dogs, and each affected dog had at least 1 sibling that was also affected. Twelve dams and sires were included in the analysis. All dogs were purebred Labrador Retrievers except for 2 litters (offspring of a female Golden Retriever-Labrador Retriever mixed-breed dog). PROCEDURES: For each dog, DNA was isolated from blood samples. Polymorphic microsatellite markers adjacent to 14 candidate genes (ie, COL1A1, COL1A2, COL2A1, COL3A1, COL5A1, COL5A2, COL6A3, COL9A1, COL9A2, COL9A3, COL10A1, COL11A1, COL11A2, and COL24A1) were analyzed by use of PCR assays; genotypes were determined via automated detection of DNA products. The level of allele sharing between pairs of affected siblings was assessed. RESULTS: Among the 93 dogs, allele sharing of the 14 collagen genes was determined as follows: COL1A1, 45%; COL1A2, 47%; COL2A1, 37%; COL3A1, 32%; COL5A1, 43%; COL5A2, 32%; COL6A3, 36%; COL9A1, 45%; COL9A2, 49%; COL9A3, 38%; COL10A1, 46%; COL11A1, 52%; COL11A2, 47%; and COL24A1, 47%. CONCLUSIONS AND CLINICAL RELEVANCE: Because siblings share 50% of their genome at random, the fact that the percentages of allele sharing among the analyzed collagen genes were not significantly > 50% indicates that these genes are not determinant candidates for FCP in Labrador Retrievers. The gene for the vitamin D receptor could also be excluded because of its proximity to COL2A1.     

Polymorphic microsatellite markers for genetic analysis of collagen genes in suspected collagenopathies in dogs

Defects in collagen proteins cause a variety of disorders in humans. It can be expected that collagen gene mutations are involved in collagenopathies in dogs. The collagen genes COL3A1, COL5A1, COL5A2, COL6A1, COL6A3, COL9A1, COL9A2, COL9A3, COL10A1 and COL11A1 were identified on the canine genome based on the homology with the human genes. Simple sequence repeats (microsatellites) were found in the chromosomal regions of these genes and investigated for polymorphism in Labrador Retrievers, Bernese Mountain dogs, Boxer dogs and German Shepherd dogs by PCR and subsequent detection of the DNA products. Nine informative microsatellite markers were identified. The markers closely situated to COL9A1, COL9A2 and COL9A3 were used to investigate the involvement of the genes in cranial cruciate ligament rupture in Boxer dogs. It was found that these genes are probably not involved in this abnormality. The markers described here will be useful for a candidate gene approach of suspected collagenopathies specific to dog breeds.     

Inherited retinal dysplasia and persistent hyperplastic primary vitreous in Miniature Schnauzer dogs

The objectives of this study were to define the clinical syndrome of retinal dysplasia and persistent primary vitreous in Miniature Schnauzer dogs and determine the etiology. We examined 106 Miniature Schnauzers using a biomicroscope and indirect ophthalmoscope. The anterior and posterior segments of affected dogs were photographed. Four enucleated eyes were examined using routine light microscopy and scanning electron microscopy. A pedigree was constructed and related dogs were test-bred to define the mode of inheritance of this syndrome. Congenital retinal dysplasia was confirmed in 24 of 106 related Miniature Schnauzer dogs. Physical and postmortem examinations revealed that congenital abnormalities were limited to the eyes. Biomicroscopic, indirect ophthalmoscopic, and neuro-ophthalmic examinations confirmed that some of these dogs were blind secondary to bilateral retinal dysplasia and detachment (nonattachment) (n = 13), and the remainder had generalized retinal dysplasia (n = 11). Fifteen of these dogs were also diagnosed with unilateral (n = 9) or bilateral (n = 6) persistent hyperplastic primary vitreous. Nutritional, infectious, or toxic etiologies were not evident on physical, postmortem, light microscopic, or transmitting and scanning electron microscopic examination of four affected Miniature Schnauzers. We examined the pedigree and determined that an autosomal recessive mode of inheritance was most likely. Three test-bred litters including those from affected parents, carrier and affected parents, and carrier parents confirmed this mode of inheritance. This study confirms that retinal dysplasia and persistent hyperplastic primary vitreous is a congenital abnormality that is inherited as an autosomal recessive condition in Miniature Schnauzers.     

Autosomal recessive severe combined immunodeficiency of Jack Russell terriers.

Because of unexplained mortality among 33 sibling offspring of a single pair of dogs, a family of Jack Russell Terriers was investigated. Twelve pups, 5 male and 7 female, died between 8 and 14 weeks of age. Six of those animals died in the field within 50 hours following vaccination with modified live vaccines. Subsequent histopathologic examination revealed the absence of splenic white pulp in 4 dogs and hepatic inclusions diagnostic for adenoviral infection in 2 dogs. Two additional litters yielded 2 pups with the same splenic and hepatic lesions. These observations led to a detailed study of 7 siblings whelped specifically for this investigation. Four of these 7 siblings had a profound lymphopenia and a decrease in serum immunoglobulins. Six of these dogs were necropsied at 7 weeks of age, and 4 of them had marked hypoplasia of all lymphoid tissue. The affected pups had an 86% decrease in mean thymic weight, with poor corticomedullary differentiation, and very few CD3-positive (T cell) thymocytes were detected immunohistochemically. However, the affected thymic tissue stained intensely with a immunochemical stain for cytokeratin. The other affected lymphoid tissues were identified histologically only by stromal architectural characteristics. Lymph nodes lacked both CD3 and CD79a (B cell) positive cells. The analyzed breeding data were consistent with an autosomal recessive mode of inheritance. This canine severe combined immunodeficiency has immunologic and pathologic features similar to those observed in immunodeficient C.B-17 mice and Arabian horses.     

Evidence of Inheritance of Intrahepatic Portosystemic Shunts in Irish Wolfhounds

Background: The etiogenesis of congenital portosystemic shunt in dogs is not understood. In Irish Wolfhounds, intrahepatic portosystemic shunt (IHPSS) is thought to be hereditary, but the mode of inheritance is unknown.
Objectives: To document the genetic background and investigate the potential mode of inheritance of IHPSS in Irish Wolfhounds.
Animals: Three mature, privately owned, affected siblings and their progeny produced in 2 litters.
Methods: Prospective, observational study. Two test matings of 1 affected sire with 2 of his affected sisters were used to determine the inheritance pattern. Affection status was determined by measuring venous blood ammonia concentrations, detection of the shunt by ultrasonography and confirmation during surgical attenuation of the intrahepatic shunting vessel.
Results: In 1 litter of 5 pups all had an IHPSS. In the other litter 5 of 11 pups were affected. Both left- and right-sided shunts occurred in both litters. No sex predisposition was evident among affected dogs.
Conclusions and Clinical Importance: Our results show that IHPSS in Irish Wolfhounds is a familial disorder that is likely genetic. It is unlikely that the mode of inheritance is monogenic. A digenic, triallelic trait could explain the observed occurrence of IHPSS but other modes of inheritance cannot be excluded.     

Collie eye anomaly in the rough collie in Sweden: genetic transmission and influence on offspring vitality

Between 1989 and 1997, 8204 rough collies were examined for collie eye anomaly (CEA) at up to 10 weeks of age. All dogs were positively identified and the results were registered under the Swedish Kennel Club genetic health programme. A significant decrease in litter size occurred if one of two affected parents had coloboma (3.8 pups) compared with litters from two chorioretinal dysplasia- (CRD-) affected collies (5.2 pups) or litters by two normal collies (5.0 pups), indicating an influence of the coloboma genotype on offspring vitality. The prevalence of CRD in pups from normal x normal matings and CRD x CRD matings was significantly different from that expected under simple autosomal recessive inheritance (43 per cent versus 25 per cent and 85 per cent versus 100 per cent). The results are compatible with polygenic inheritance but not with simple autosomal recessive inheritance. CRD prevalence in offspring of CRD x coloboma matings was significantly lower than in pups of CRD x CRD matings, reflecting effects of the coloboma genotype on vitality. These results have important implications for breeding programmes and the genetic control of CEA.     

Benign familial juvenile epilepsy in Lagotto Romagnolo dogs

BACKGROUND: Idiopathic childhood epilepsies with benign outcomes are well recognized in human medicine, but are not reported in veterinary literature. We recognized such a neurologic syndrome in Lagotto Romagnolo dogs. ANIMALS: Twenty-five Lagotto Romagnolo puppies from 9 different litters examined because of simple or complex focal seizures and 3 adult Lagotto Romagnolo dogs exhibiting similar clinical signs were used. METHODS: Clinical and diagnostic evaluations of affected dogs were conducted, including electromyography, electroencephalography, and other testing. RESULTS: Seizures in puppies began at 5 to 9 weeks of age and usually resolved spontaneously by 8 to 13 weeks. Those with the most severe seizures also had signs of neurologic disease between these seizures, including generalized ataxia and hypermetria. There were no abnormalities in routine laboratory screenings of blood, urine, and cerebrospinal fluid. Electromyography, brainstem auditory-evoked potentials, and magnetic resonance imaging revealed no specific and consistent abnormalities. Fourteen of 16 (87.5%) affected puppies and 2 of 3 (67%) adult dogs revealed epileptiform activity in the electroencephalogram. Histopathologic examination in 1 puppy and 1 adult dog revealed lesions of Purkinje cell inclusions and vacuolation of their axons restricted to the cerebellum. Pedigree analysis suggests an autosomal recessive mode of inheritance. CONCLUSIONS AND CLINICAL IMPORTANCE: This disorder, with simple or complex focal seizures and cerebellar lesions, represents a newly recognized epileptic syndrome in dogs.     

Expression of fibrosis-related genes in canine chronic hepatitis

Molecular regulation of fibrosis in chronic canine hepatitis is poorly understood. The authors employed quantitative polymerase chain reaction (PCR) to determine the expression levels of genes reported to be related to fibrosis in other species (human, mouse, and rat) and to elucidate the relationship of these genes with the degree of fibrosis and the presence or absence of ascites and/or jaundice in dogs with hepatitis. Nine fibrosis-related genes were assayed: PDGFB, PDGFD, MMP2, TIMP1, THBS1, COL1A1, COL3A1, TGFB1, and TGFB2. Liver samples of 15 dogs with chronic hepatitis and 4 healthy control dogs were obtained via laparoscopic biopsy and subjected to histologic and quantitative PCR analyses. The expression of all 9 genes showed significant positive correlation (P<.01, r>.70) with the degree of fibrosis. Furthermore, the expression levels of all genes except TGFB1 were significantly higher (P<.05) in dogs with hepatic failure-related symptoms (ascites/jaundice). Results suggest that these 9 genes are integral to the development of fibrosis in canine chronic hepatitis.     

Type III von Willebrand's disease in Dutch kooiker dogs

Summary

Type III von Willebrand's disease (vWD) was diagnosed in 38 Dutch kooiker dogs. Ten male and 9 female probands had been referred independently of each other to the Utrecht University Clinic for Companion Animals because of a moderate to severe bleeding tendency. Screening of 717 Dutch kooiker dogs, including 356 puppies, detected vWD in another 19 dogs. Diagnosis was based on non‐detectable amounts (< 1.6%) of von Willebrand factor antigen (vWF:Ag) in plasma by ELISA. Capillary bleeding time (CBT) was prolonged (> 10 min) and polybrene cofactor activity (vWF:PbCo) was not detectable in 11 dogs tested. No distinguishable protein bands were detected by multimer analysis. As in Scottish terriers with type III vWD, factor VIII clotting activity (F_VIII:C) in affected Dutch kooiker dogs was decreased but considerably less than in humans with type III vWD. A recessive mode of inheritance was indicated by the normal or subnormal but measurable amounts of vWF:Ag in the plasma of eight pairs of parents of affected dogs. The F₁ offspring resulting from the experimental mating of two affected dogs consisted of three affected males and four affected females. In 39 obligatory carriers vWF:Ag ranged from 30% to 114% with median and mean vWF values of 64% and 64.2%, respectively, and was subnormal (< 50%) in only 9 animals.     

Heritability of multifocal retinal dysplasia in American Cocker Spaniels

Multifocal retinal dysplasia was detected in 96 American Cocker Spaniels. Affected dogs were part of approximately 500 American Cocker Spaniels examined from 1972 to 1976 in statewide survey clinics for inherited cataracts and progressive retinal atrophy. The dysplastic retina was observable ophthalmoscopically in dogs as young as 3 to 4 weeks and as old as 7 years. Ophthalmoscopic features varied, depending on whether the dysplastic foci were in the tapetal or non-tapetal portion of the fundus. Over the tapetum, dysplastic foci appeared as multiple small irregularities of diminished and altered tapetal reflectivity. In the non-tapetal fundus, dysplasia appeared as areas of decreased pigmentation. Blindness or other apparent visual deficits were not observed in affected dogs. Histologic examination of affected eyes revealed focal dysplasia limited to the retina and optic nerve. Abnormalities included localized areas of retinal folding, rosettes, and retinal pigment epithelium hypertrophy and hyperplasia. Pedigree analysis demonstrated that 71 of the 96 affected dogs were related and could be identified in an extended pedigree. A recessive mode of inheritance was suggested, because in 5 litters (born to 10 affected parents), all 23 progeny that lived were affected. A dominant or polygenic mode of inheritance could not be ruled out.     

An association study of 20 candidate genes with cryptorchidism in Siberian Husky dogs

Cryptorchidism (CO) as a common developmental defect in purebred dogs causes health concerns of reduced fertility and increases risk of testicular malignancies. A total of 49 single nucleotide polymorphisms (SNPs) discovered from 20 candidate genes was investigated to analyse their associations with CO in Siberian Huskies. The sibling‐transmission disequilibrium test on 38 discordant full‐sibs revealed seven SNPs in the collagen type II α 1 (COL2A1) gene were significantly (p < 0.05) or suggestively (p < 0.10) associated with CO. Further analyses showed that only one SNP (rs23358342) in this gene remained suggestively significant (p < 0.1) on a data set of full‐sibs with additional related dogs, but not significant on all 156 Siberian Huskies. Based on the statistical results and the involvement of COL2A1 in the testicle development and descent, we could not exclude COL2A1 as a potential candidate gene for CO in Siberian Huskies. Further studies are necessary to clarify these results from our relatively small sample size.     

Congenital keratoconjunctivitis sicca and ichthyosiform dermatosis in Cavalier King Charles spaniel dogs-part II: candidate gene study

Purpose To identify causative mutation(s) for congenital keratoconjunctivitis sicca and ichthyosiform dermatosis (CKCSID) in Cavalier King Charles spaniel (CKCS) dogs using a candidate gene approach. Methods DNA samples from 21 cases/parents were collected. Canine candidate genes (CCGs) for similar inherited human diseases were chosen. Twenty-eight candidate genes were identified by searching the Pubmed OMIM database (http://www.ncbi.nlm.nih.gov/omim). Canine orthologues of human candidate genes were identified using the Ensembl orthologue prediction facility (http://www.ensembl.org/index.html). Two microsatellites flanking each candidate gene were selected, and primers to amplify each microsatellite were designed using the Whitehead Institute primer design website (http://frodo.wi.mit.edu/primer3/). The microsatellites associated with all 28 CCGs were genotyped on a panel of 21 DNA samples from CKCS dogs (13 affected and eight carriers). Genotyping data was analyzed to identify markers homozygous in affected dogs and heterozygous in carriers (homozygosity mapping). Results None of the microsatellites associated with 25 of the CCGs displayed an association with CKCSID in the 21 DNA samples tested. Three CCGs associated microsatellites were monomorphic across all samples tested. Conclusions Twenty-five CCGs were excluded as cause of CKCSID. Three CCGs could not be excluded from involvement in the inheritance of CKCSID. Support Kennel Club Charitable Trust grant.     

Suspected inherited cerebellar neuroaxonal dystrophy in collie sheep dogs

A cerebellar neuroaxonal dystrophy in working collie sheep dogs from two properties in New Zealand and one property in Australia is described. Clinical signs developed from 2–4 months of age and included hypermetria, wide-based stance, difficulty in maintaining balance, intention tremor and ataxia. Numerous spheroids, associated with mild Wallerian degeneration, were present in the central cerebellar, adjacent peduncular and folia white matter, and associated cerebellar roof and lateral vestibular nuclei. The history of several affected pups in litters from successive matings of the same sire and dam is suggestive of an autosomal recessive mode of inheritance.     

Suspected inherited cerebellar neuroaxonal dystrophy in collie sheep dogs

A cerebellar neuroaxonal dystrophy in working collie sheep dogs from two properties in New Zealand and one property in Australia is described. Clinical signs developed from 2-4 months of age and included hypermetria, wide-based stance, difficulty in maintaining balance, intention tremor and ataxia. Numerous spheroids, associated with mild Wallerian degeneration, were present in the central cerebellar, adjacent peduncular and folia white matter, and associated cerebellar roof and lateral vestibular nuclei. The history of several affected pups in litters from successive matings of the same sire and dam is suggestive of an autosomal recessive mode of inheritance.     

Lung Injury Leading to Respiratory Distress Syndrome in Young Dalmatian Dogs

A progressive pulmonary disease resulting in severe respiratory failure and death in an average of 3 weeks was diagnosed in 11 young Dalmatian dogs. The dogs were from 4 litters, all genetically related by a common ancestor. The initial clinical signs were tachypnea and noisy respiration. Respiratory distress developed shortly before death and was characterized by strenuous and rapid respirations, along with cyanosis and vomiting. On blood gas analysis, there were severe arterial hypoxemia, hypercapma, and marked alveolar-arterial oxygen difference. Radiographically, a diffuse pattern of alveolar, interstitial, and peribronchial densities was observed in the lungs. Most dogs developed pneumomediastinum and gastroesophageal intussusception in the terminal phase of the disease. There was no response to treatment with antibiotics, corticosteroids, diuretics, or oxygen. At necropsy, the lungs were wet, heavy, and relatively airless. Absence of 1 kidney in 2 dogs and severe internal hydrocephalus in 2 dogs were additional necropsy findings. Pulmonary histopathology included metaplasia and atypia of the alveolar and bronchiolar epithelium, a nonpurulent inflammatory reaction characterized mainly by mononuclear cells and macrophages, eosinophilic hyaline membrane formation, and focal pulmonary fibrosis. The histological manifestations were typical of acute lung injury. Clinically, the findings were consistent with adult respiratory distress syndrome (ARDS), except for the relatively long course. No known risk factors for ARDS, such as trauma, toxin exposure, infection, or endotoxemia could be identified. The relationship of the other abnormalities (ie, renal aplasia, hydrocephalus) to the pulmonary disease also remains obscure. An inherited defect is suspected, because segregation analysis of the 4 litters suggests autosomal recessive inheritance.     

Clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia: 19 cases (1991-2005)

OBJECTIVE: To determine clinical, radiographic, and pathologic abnormalities in dogs with multiple epiphyseal dysplasia (MED). DESIGN: Retrospective case series. ANIMALS: 19 dogs with MED from 10 litters. PROCEDURES: The diagnosis was made on the basis of radiographs of the shoulder region and vertebral column. Ten dogs underwent necropsy. RESULTS: There were 11 Hygenhund, 6 Dunker, 1 Golden Retriever, and 1 English Pointer. Most dogs were examined because of lameness that developed at 5 to 8 months of age. The most common radiographic abnormality was a deficiency in ossification of the epiphyses, apophyses, and cuboidal bones of the appendicular skeleton and the epiphyses of the vertebrae; ossification of the metaphyses and the diaphyses typically were normal. Disease severity was consistent among littermates, but varied among dogs from different litters. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that MED is a rare condition in dogs characterized by a deficiency in ossification of the epiphyses of the long bones, the epiphyses of the vertebrae, the cuboidal bones, and the apophyses. Radiographic abnormalities were evident in dogs examined as young as 8 weeks of age, and most dogs had developed severe lameness by 5 to 8 months of age. The condition most likely had an autosomal recessive mode of inheritance, although genetic studies of mode of inheritance could not be performed.