Cutaneous mucinosis in shar-pei dogs is due to hyaluronic acid deposition and is associated with high levels of hyaluronic acid in serum

A review of cutaneous hypersensitivity reactions in dogs: A diagnostician's guide to allergy

Allergic dermatoses are common in people and domestic animals. Resultant lesions are routinely biopsied and submitted for histological examination to confirm a diagnosis or rule out diseases with overlapping or atypical clinical features. Diagnostic pathologists and clinicians are often faced with the difficult task of determining whether an allergic reaction pattern is present on both the microscopic and macroscopic levels and correlating histopathologic findings with clinical and historical data to achieve a precise clinical diagnosis. The bulk of the current veterinary literature on allergic dermatoses focuses on atopic dermatitis in dogs, distantly followed by cats, horses, and other animals. The objectives of this review are to demonstrate the key histopathologic and clinical diagnostic features of the various allergy-mediated reaction patterns, and to provide diagnosticians with a practical guide for clinicopathological correlations. Current concepts in the pathophysiology of immediate hypersensitivity reactions, with a focus on atopic dermatitis, are discussed. Points of potential histopathologic overlap between the "classic" allergic reaction pattern and less common inflammatory, predominately eosinophilic, conditions that may mimic this pattern will be discussed with the goal of highlighting the critical need for collaboration between pathologists and clinicians in furthering patient care.

A survey on Shar Pei autoinflammatory disease in the United Kingdom

OBJECTIVES

To characterise the fever episodes attributed to Shar Pei autoinflammatory disease and to identify common diagnostic and management strategies in the United Kingdom. A secondary objective was to determine risk factors associated with Shar Pei autoinflammatory disease fever episodes.

METHODS

A retrospective survey was performed to characterise episodes of Shar Pei autoinflammatory disease fever and to identify commonly used treatments in affected dogs. Clinical data were collected from owners and veterinarians. Frequencies of previously proposed risk factors (skin thickness and folding, muzzle conformation) and comorbid conditions were compared between dogs that had exhibited fever episodes consistent with Shar Pei autoinflammatory disease and those who had not.

RESULTS

At least one episode of fever attributed to Shar Pei autoinflammatory disease was reported in 52 of 106 (49%) Shar Pei. Nine other dogs had fever episodes consistent with Shar Pei autoinflammatory disease reported by their owners but not by veterinarians. Median rectal temperature at presentation for Shar Pei autoinflammatory disease fever was 40.1°C [104.2°F] (39.9 to 41.3°C [103.8 to 106.3°F]) and owners reported associated hyporexia (n=33, 63%) and vomiting (n=8, 15%) more frequently than veterinary records (n=22, 42% and n=0, 0%, respectively). The median number of veterinary appointments for Shar Pei autoinflammatory disease was two per dog (1 to 15) while owners reported a median of four episodes per dog per year. None of the assessed phenotypic variants or comorbidities were significantly associated with exhibiting Shar Pei autoinflammatory disease fever episodes.

CLINICAL SIGNIFICANCE

Episodes of Shar Pei autoinflammatory disease fever were reported approximately twice as frequently by owners compared to veterinary records, suggesting the burden of this condition may be underestimated by veterinarians. Specific risk factors for Shar Pei autoinflammatory disease fever were not identified.

Case report: Sublingual mucinosis in a dog

A 11-month-old male intact Shar-Pei (26. 5 kg) was presented for a bilateral sublingual swelling of 4 months duration. The exploration of the oral cavity highlighted the presence of bilateral sublingual swellings, primarily consistent with bilateral ranula. The bilateral disease was treated with two subsequent surgeries 4 weeks apart. During the surgery, after removing an elliptical portion of the mucosa of the sublingual swelling, the presence of gelatinous tissue was visualized, and no saliva was present. The result of histological exam was oral mucinosis. At the subsequent follow-up the dog was in excellent conditions, without any symptoms. 1 month after the last operation, the dog underwent a visit in sedation to better evaluate the oral cavity. Both surgical sites were well-healed and without the presence of relapses. Upon 8 months follow-up the patient remained free of disease. This is the first reported case of oral mucinosis in sublingual mucosa in dogs. In this case the surgical treatment was curative.

Inheritance of Monogenic Hereditary Skin Disease and Related Canine Breeds

The plasticity of the genome is an evolutionary factor in all animal species, including canines, but it can also be the origin of diseases caused by hereditary genetic mutation. Genetic changes, or mutations, that give rise to a pathology in most cases result from recessive alleles that are normally found with minority allelic frequency. The use of genetic improvement increases the consanguinity within canine breeds and, on many occasions, also increases the frequency of these recessive alleles, increasing the prevalence of these pathologies. This prevalence has been known for a long time, but mutations differ according to the canine breed. These genetic diseases, including skin diseases, or genodermatosis, which is narrowly defined as monogenic hereditary dermatosis. In this review, we focus on genodermatosis sensu estricto, i.e., monogenic, and hereditary dermatosis, in addition to the clinical features, diagnosis, pathogeny, and treatment. Specifically, this review analyzes epidermolytic and non-epidermolytic ichthyosis, junctional epidermolysis bullosa, nasal parakeratosis, mucinosis, dermoid sinus, among others, in canine breeds, such as Golden Retriever, German Pointer, Australian Shepherd, American Bulldog, Great Dane, Jack Russell Terrier, Labrador Retriever, Shar-Pei, and Rhodesian Ridgeback.

Genes of Congenital Dermatologic Disorders in Dogs—A Review

This article presents an overview of up-to-date identified genes responsible for congenital canine skin diseases of dogs and the characteristics of these diseases. Congenital skin diseases constitute a specific group of dermatologic disorders that plays an important role in breeding of purebred dogs. They include primary seborrhoea, ichthyosis, hereditary nasal parakeratosis, dermatomyositis, colour dilution alopecia, skin mucinosis, dermoid sinus, lethal acrodermatitis, acral mutilation syndrome, keratoconjunctivitis sicca, ichthyosiform dermatosis, bullous epidermolysis, exfoliative dermal lupus erythematosus, congenital footpad hyperkeratosis and sebaceous adenitis. In the majority of cases, their occurrence is linked to particular breeds. In more than half of these diseases a specific defective gene variant responsible for the disease has been identified. Genetic tests for identification of the relevant defective genes serve as an important tool in the diagnostics of diseases in veterinary practice and in breeding of purebred dogs.

Connective Tissue Disorders in Domestic Animals

Though soft tissue disorders have been recognized and described to some detail in several types of domestic animals and small mammals for some years, they remain uncommon. Because of their low prevalence, not much progress has been made not only in improved diagnosis but also in our understanding of the biochemical basis and pathogenesis of these diseases in animals. Ehlers-Danlos syndrome (EDS) described in dogs already in 1943 and later in cats has only minor impact on the well-being of the dog as its effects on skin of these animals are rather limited. The involved skin is thin and hyperextensible with easily inflicted injuries resulting in hemorrhagic wounds and atrophic scars. Joint laxity and dislocation common in people are less frequently found in dogs. No systemic complications, such as organ rupture or cardiovascular problems which have devastating consequences in people have been described in cats and dogs. The diagnosis is based on clinical presentation and on light or electron microscopic features of disorganized and fragmented collagen fibrils. Several case of bovine and ovine dermatosparaxis analogous to human Ehlers-Danlos syndrome type VIIC were found to be caused by mutations in the procollagen I N-proteinase (pnPI) or ADAMTS2 gene, though mutations in other sites are likely responsible for other types of dermatosparaxis. Cattle suffering from a form of Marfan syndrome (MFS) were described to have aortic dilatation and aneurysm together with ocular abnormalities and skeletal involvement. As in people, mutations at different sites of bovine FBN1 may be responsible for Marfan phenotype. Hereditary equine regional dermal asthenia (HERDA), or hyperelastosis cutis, has been recognized in several horse breeds as affecting primarily skin, and, occasionally, tendons. A mutation in cyclophilin B, a chaperon involved in proper folding of collagens, has been identified in some cases. Warmblood fragile foal syndrome (WFFS) is another Ehlers-Danlos-like disorder in horses, affecting primarily Warmbloods who present with skin fragility and joint hyperextensibility. Degenerative suspensory ligament desmitis (DSLD) affects primarily tendons and ligaments of certain horse breeds. Data from our laboratory showed excessive accumulation of proteoglycans in organs with high content of connective tissues. We have identified increased presence of bone morphogenetic protein 2 (BMP2) in active foci of DSLD and an abnormal form of decorin in proteoglycan deposits. Our most recent data obtained from next generation sequencing showed disturbances in expression of genes for numerous proteoglycans and collagens.

Validation of a commercial human ELISA to measure hyaluronic acid concentration in feline plasma

Our goal was to validate a human hyaluronic acid (HA) ELISA (Hyaluronic acid plus ELISA; TECOmedical Group) for use in feline plasma. Plasma from 5 healthy cats and 5 critically ill cats was used for validation of the assay. Validation methods performed included intra- and inter-assay variability, spike-and-recovery, and dilutional linearity. All measurements were performed in duplicate. The precision study revealed good intra-assay CV of 7.4-8.9%; inter-assay CV was 3.4-4.2%. Extraction efficiency via spiking tests yielded mean recovery of 89.6%. The assay met criteria for acceptable linearity using 3 serial dilutions. Our results demonstrate that this commercial HA ELISA had acceptable analytical performance using feline plasma and could be a useful tool in the veterinary clinical research setting.

Concentration of extracellular vesicles isolated from blood relative to the clinical pathological status of dogs with mast cell tumours

Extracellular vesicles (EVs) are membrane-enclosed fragments shed from all cell types, including tumour cells. EVs contain a wide range of proteins, biolipids and genetic material derived from mother cells and therefore may be potential biomarkers for tumour diagnosis, disease progression and treatment success. We studied the effect of canine mast cell tumours (MCTs) on EV concentrations in blood isolates in association with MCT's histological grade, Ki-67 proliferative index, KIT-staining pattern and number of PLT. The average EV concentration in blood isolates from nine dogs with MCTs was considerably higher than that in blood from eight healthy dogs. But there were no statistically significant differences in EVs concentration in the population of dogs with MCT according to a different histological grade of malignancy (Patnaik, Kiupel), KIT-staining pattern and Ki-67 proliferation index. The results show that these variables statistically do not significantly predicted EV concentrations in blood isolates (P > .05), except the KIT-staining pattern I which added statistically significantly to the prediction (P < .05). The results confirmed the impact of neoplasms on the morphological changes to cell membranes, which result in greater vesiculability and higher EV concentrations.

Whole genome sequencing identifies missense mutation in MTBP in Shar-Pei affected with Autoinflammatory Disease (SPAID)

BACKGROUND

Autoinflammatory diseases in dogs are characterized by complex disease processes with varying clinical signs. In Shar-Pei, signs of inflammation including fever and arthritis are known to be related with a breed-specific predisposition for Shar-Pei Autoinflammatory Disease (SPAID).

RESULTS

Clinical and histopathological examinations of two severely SPAID-affected Shar-Pei revealed signs of inflammation including fever, arthritis, and perivascular and diffuse dermatitis in both dogs. A multifocal accumulation of amyloid in different organs was found in one SPAID-affected case. Whole genome sequencing resulted in 37 variants, which were homozygous mutant private mutations in SPAID-affected Shar-Pei. Nine SNVs with predicted damaging effects and three INDELs were further investigated in 102 Shar-Pei affected with SPAID, 62 unaffected Shar-Pei and 162 controls from 11 different dog breeds. The results showed the missense variant MTBP:g.19383758G > A in MTBP to be highly associated with SPAID in Shar-Pei. In the region of this gene a large ROH (runs of homozygosity) region could be detected exclusively in the two investigated SPAID-affected Shar-Pei compared to control dog breeds. No further SPAID-associated variant with predicted high or moderate effects could be found in genes identified in ROH regions. This MTBP variant was predicted to affect the MDN2-binding protein domain and consequently promote proinflammatory reactions. In the investigated group of Shar-Pei older than six years all dogs with the mutant genotype A/A were SPAID-affected whereas SPAID-unaffected dogs harbored the homozygous wildtype (G/G). Shar-Pei with a heterozygous genotype (G/A) were shown to have a 2.13-fold higher risk for disease development, which gave evidence for an incomplete dominant mode of inheritance.

CONCLUSIONS

The results of this study give strong evidence for a variant in MTBP related with proinflammatory processes via MTBP-MDM2 pathway. Thus, these results enable a reliable detection of SPAID in Shar-Pei dogs.

Analogs of human genetic skin disease in domesticated animals

Genetic skin diseases encompass a vast, complex, and ever expanding field. Recognition of the features of these diseases is important to ascertain a correct diagnosis, initiate treatment, consider genetic counseling, and refer patients to specialists when the disease may impact other areas. Because genodermatoses may present with a vast array of features, it can be bewildering to memorize them. This manuscript will explain and depict some genetic skin diseases that occur in both humans and domestic animals and offer a connection and memorization aid for physicians. In addition, we will explore how animal diseases serve as a model to uncover the mechanisms of human disease. The genetic skin diseases we will review are pigmentary mosaicism, piebaldism, albinism, Griscelli syndrome, ectodermal dysplasias, Waardenburg syndrome, and mucinosis in both humans and domesticated animals.

The canine era: the rise of a biomedical model

Since the annotation of its genome a decade ago, the dog has proven to be an excellent model for the study of inherited diseases. A large variety of spontaneous simple and complex phenotypes occur in dogs, providing physiologically relevant models to corresponding human conditions. In addition, gene discovery is facilitated in clinically less heterogeneous purebred dogs with closed population structures because smaller study cohorts and fewer markers are often sufficient to expose causal variants. Here, we review the development of genomic resources from microsatellites to whole-genome sequencing and give examples of successful findings that have followed the technological progress. The increasing amount of whole-genome sequence data warrants better functional annotation of the canine genome to more effectively utilise this unique model to understand genetic contributions in morphological, behavioural and other complex traits.

Absolute quantification reveals the stable transmission of a high copy number variant linked to autoinflammatory disease

BACKGROUND

Dissecting the role copy number variants (CNVs) play in disease pathogenesis is directly reliant on accurate methods for quantification. The Shar-Pei dog breed is predisposed to a complex autoinflammatory disease with numerous clinical manifestations. One such sign, recurrent fever, was previously shown to be significantly associated with a novel, but unstable CNV (CNV_16.1). Droplet digital PCR (ddPCR) offers a new mechanism for CNV detection via absolute quantification with the promise of added precision and reliability. The aim of this study was to evaluate ddPCR in relation to quantitative PCR (qPCR) and to assess the suitability of the favoured method as a genetic test for Shar-Pei Autoinflammatory Disease (SPAID).

RESULTS

One hundred and ninety-six individuals were assayed using both PCR methods at two CNV positions (CNV_14.3 and CNV_16.1). The digital method revealed a striking result. The CNVs did not follow a continuum of alleles as previously reported, rather the alleles were stable and pedigree analysis showed they adhered to Mendelian segregation. Subsequent analysis of ddPCR case/control data confirmed that both CNVs remained significantly associated with the subphenotype of fever, but also to the encompassing SPAID complex (p < 0.001). In addition, harbouring CNV_16.1 allele five (CNV_16.1|5) resulted in a four-fold increase in the odds for SPAID (p < 0.001). The inclusion of a genetic marker for CNV_16.1 in a genome-wide association test revealed that this variant explained 9.7 % of genetic variance and 25.8 % of the additive genetic heritability of this autoinflammatory disease.

CONCLUSIONS

This data shows the utility of the ddPCR method to resolve cryptic copy number inheritance patterns and so open avenues of genetic testing. In its current form, the ddPCR test presented here could be used in canine breeding to reduce the number of homozygote CNV_16.1|5 individuals and thereby to reduce the prevalence of disease in this breed.

Inflammatory, immunological, and intestinal disease biomarkers in Chinese Shar-Pei dogs with marked hypocobalaminemia

Chinese Shar-Pei dogs have a high prevalence of hypocobalaminemia and are commonly presented with clinical signs suggestive of severe and long-standing gastrointestinal disease such as diarrhea, vomiting, and/or weight loss. The aim of the current study was to evaluate serum concentrations of inflammatory markers, markers for intestinal disease, and immunological markers in Shar-Peis with hypocobalaminemia or normocobalaminemia (serum cobalamin concentrations within the reference interval). Serum samples from Shar-Peis were collected from various parts of the United States. Serum concentrations of inflammatory markers (i.e., C-reactive protein [CRP], calprotectin [CP], and S100A12), hyaluronic acid (HA, a marker for cutaneous mucinosis), and analytes commonly altered in chronic intestinal diseases (i.e., albumin, zinc, alpha1-proteinease inhibitor [α1PI], immunoglobulin [Ig]A, and IgM) were compared between Shar-Peis with hypocobalaminemia and Shar-Peis with normocobalaminemia. Serum concentrations of CRP, CP, S100A12, HA, zinc, and cα1-PI concentrations did not differ between hypocobalaminemic and normocobalaminemic Shar-Peis (P > 0.05). Serum concentrations of albumin were significantly lower in hypocobalaminemic Shar-Peis (median: 2.5 g/dl) than in normocobalaminemic Shar-Peis (median: 2.9 g/dl; P < 0.0001). Higher serum IgA concentrations and lower serum IgM concentrations were observed in hypocobalaminemic Shar-Peis (median: 1.7 g/l and 0.8 g/l, respectively) than in normocobalaminemic Shar-Peis (median: 0.7 g/l and 1.9 g/l, respectively; both P < 0.0001). In conclusion, no difference was found in serum concentrations of CRP, CP, S100A12, and HA between hypocobalaminemic and normocobalaminemic Shar-Peis whereas some differences were observed in analytes (e.g., albumin, IgA, and IgM) that may be altered in patients with chronic enteropathies.

Biology of hyaluronan: Insights from genetic disorders of hyaluronan metabolism

Hyaluronan is a rapidly turned over component of the vertebrate extracellular matrix. Its levels are determined, in part, by the hyaluronan synthases, HAS1, HAS2, and HAS3, and three hyaluronidases, HYAL1, HYAL2 and HYAL3. Hyaluronan binding proteins also regulate hyaluronan levels although their involvement is less well understood. To date, two genetic disorders of hyaluronan metabolism have been reported in humans: HYAL1 deficiency (Mucopolysaccharidosis IX) in four individuals with joint pathology as the predominant phenotypic finding and HAS2 deficiency in a single person having cardiac pathology. However, inherited disorders and induced mutations affecting hyaluronan metabolism have been characterized in other species. Overproduction of hyaluronan by HAS2 results in skin folding and thickening in shar-pei dogs and the naked mole rat, whereas a complete deficiency of HAS2 causes embryonic lethality in mice due to cardiac defects. Deficiencies of murine HAS1 and HAS3 result in a predisposition to seizures. Like humans, mice with HYAL1 deficiency exhibit joint pathology. Mice lacking HYAL2 have variably penetrant developmental defects, including skeletal and cardiac anomalies. Thus, based on mutant animal models, a partial deficiency of HAS2 or HYAL2 might be compatible with survival in humans, while complete deficiencies of HAS1, HAS3, and HYAL3 may yet be recognized.

Congenital Ichthyosis in 14 Great Dane Puppies With a New Presentation

The present study describes a generalized congenital skin condition in 14 Great Dane puppies. Macroscopically, all dogs showed generalized gray to yellow scaling and skin wrinkles on the head and all 4 extremities. Skin sections were histologically examined using hematoxylin and eosin, Heidenhain's Azan, and Sudan red III staining methods and by conducting the alcian blue/periodic acid Schiff (AB/PAS) reaction technique on sections. Furthermore, incubation with hyaluronidase was performed. Skin samples were ultrastructurally analyzed using transmission electron microscopy. All affected Great Dane puppies had epidermal and follicular orthokeratotic hyperkeratosis, enlarged keratohyaline granules, vacuolated keratinocytes, and accumulations of an eosinophilic and alcianophilic, lipid-rich material within dilated hair follicular lumina and the cytoplasm of sebocytes. The macroscopic, histopathologic, and ultrastructural skin changes in all 14 Great Dane puppies indicate a new variant of a primary disorder of cornification with congenital, non-epidermolytic, lamellar ichthyosiform appearance.

Thorough investigation of a canine autoinflammatory disease (AID) confirms one main risk locus and suggests a modifier locus for amyloidosis

Autoinflammatory disease (AID) manifests from the dysregulation of the innate immune system and is characterised by systemic and persistent inflammation. Clinical heterogeneity leads to patients presenting with one or a spectrum of phenotypic signs, leading to difficult diagnoses in the absence of a clear genetic cause. We used separate genome-wide SNP analyses to investigate five signs of AID (recurrent fever, arthritis, breed specific secondary dermatitis, otitis and systemic reactive amyloidosis) in a canine comparative model, the pure bred Chinese Shar-Pei. Analysis of 255 DNA samples revealed a shared locus on chromosome 13 spanning two peaks of association. A three-marker haplotype based on the most significant SNP (p<2.6×10⁻⁸) from each analysis showed that one haplotypic pair (H13-11) was present in the majority of AID individuals, implicating this as a shared risk factor for all phenotypes. We also noted that a genetic signature (F_ST) distinguishing the phenotypic extremes of the breed specific Chinese Shar-Pei thick and wrinkled skin, flanked the chromosome 13 AID locus; suggesting that breed development and differentiation has played a parallel role in the genetics of breed fitness. Intriguingly, a potential modifier locus for amyloidosis was revealed on chromosome 14, and an investigation of candidate genes from both this and the chromosome 13 regions revealed significant (p<0.05) renal differential expression in four genes previously implicated in kidney or immune health (AOAH, ELMO1, HAS2 and IL6). These results illustrate that phenotypic heterogeneity need not be a reflection of genetic heterogeneity, and that genetic modifiers of disease could be masked if syndromes were not first considered as individual clinical signs and then as a sum of their component parts.

Evaluation of ultrasonography for measurement of skin thickness in Shar-Peis

OBJECTIVE

To determine whether high-frequency diagnostic ultrasonography is useful for assessment of skin thickness in Shar-Peis.

ANIMALS

10 healthy Shar-Peis and 10 healthy Beagles used as controls.

PROCEDURES

Ultrasonographic examination of the skin was performed on 4 cutaneous sites by use of a 13-MHz linear-array transducer, and the mean of 3 measurements was calculated. Ultrasonography results were compared with histologic findings of skin specimens stained with H&E, Alcian blue at a pH of 2.5, and Masson trichrome stains, with histometric measurements of skin thickness made by use of a microscope, and with measurements of skin thickness made by use of a plicometer. Ultrasonograpy results were also compared via age and sex of selected animals.

RESULTS

A clear correlation was detected between ultrasonography results and results of histologic and histometric analysis in both groups. In Shar-Peis, no correlation was found between ultrasonography results and age and sex, whereas in Beagles, a weak positive correlation was found only between skin thickness in dorsal cervical and frontal (on the rostral margins of the supraorbital processes) regions and age. A positive overall correlation was found in Shar-Peis between measurements made via ultrasonography and plicometery.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonography was a useful tool to assess skin thickness, and in Shar-Peis, it might be considered a valid alternative to invasive methods such as histologic examination to objectively estimate the severity of hereditary cutaneous hyaluronosis.

Copy number variation in the domestic dog

Differences in the content and organization of DNA, collectively referred to as structural variation, have emerged as a major source of genetic and phenotypic diversity within and between species. In addition, structural variation provides an important substrate for evolutionary innovations. Here, we review recent progress in characterizing patterns of canine structural variation within and between breeds, and in correlating copy number variants (CNVs) with phenotypes. Because of the extensive phenotypic diversity that exists within and between breeds and the tantalizing examples of canine CNVs that influence traits such as skin wrinkling in Shar-Pei, dorsal hair ridge in Rhodesian and Thai Ridgebacks, and short limbs in many breeds such as Dachshunds and Corgis, we argue that domesticated dogs are uniquely poised to contribute novel insights into CNV biology. As new technologies continue to be developed and refined, the field of canine genomics is on the precipice of a deeper understanding of how structural variation and CNVs contribute to canine genetic diversity, phenotypic variation, and disease susceptibility.

Increased HAS2-driven hyaluronic acid synthesis in shar-pei dogs with hereditary cutaneous hyaluronosis (mucinosis)

The Chinese shar-pei dog is known for its distinctive feature of wrinkled and thickened skin, defined as primary or hereditary cutaneous mucinosis. In a recent report, we identified the mucinous material deposited in the shar-pei skin as the polysaccharide hyaluronan (HA). In the present work, the molecular and cellular mechanisms underlying this phenotype have been identified in dermal fibroblasts isolated from shar-pei dogs. The production of HA, which appeared to be mainly associated with cell membrane protrusions and also intracellular, was higher in shar-pei fibroblasts than in control cells. The HA accumulation is related to a higher mRNA expression of the isoform HAS2 of the HA-synthesizing enzyme family, hyaluronan synthases (HAS). The higher expression of HAS2 in shar-pei fibroblasts was confirmed at the protein level. The other HAS isoenzymes, HAS1 and HAS3, and the HA-degrading enzymes, Hyal1 and Hyal2, were not differentially expressed in shar-pei fibroblasts compared with cells from control dogs. Fibroblasts from shar-pei dogs and from control dogs are morphologically different as observed by transmission electron microscopy. Scanning electron microscopy revealed a large number of cellular protrusions with associated globular deposits. Electron microscopy after labelling with biotinylated HA-binding protein confirmed an increased HA content in shar-pei fibroblasts, which could be localized in several subcellular structures. The authors propose the name hereditary cutaneous hyaluronosis (HCH) for affected dogs, because it better defines the cutaneous mucinosis of shar-pei dogs.

A novel unstable duplication upstream of HAS2 predisposes to a breed-defining skin phenotype and a periodic fever syndrome in Chinese Shar-Pei dogs

Hereditary periodic fever syndromes are characterized by recurrent episodes of fever and inflammation with no known pathogenic or autoimmune cause. In humans, several genes have been implicated in this group of diseases, but the majority of cases remain unexplained. A similar periodic fever syndrome is relatively frequent in the Chinese Shar-Pei breed of dogs. In the western world, Shar-Pei have been strongly selected for a distinctive thick and heavily folded skin. In this study, a mutation affecting both these traits was identified. Using genome-wide SNP analysis of Shar-Pei and other breeds, the strongest signal of a breed-specific selective sweep was located on chromosome 13. The same region also harbored the strongest genome-wide association (GWA) signal for susceptibility to the periodic fever syndrome (p_raw = 2.3×10⁻⁶, p_genome = 0.01). Dense targeted resequencing revealed two partially overlapping duplications, 14.3 Kb and 16.1 Kb in size, unique to Shar-Pei and upstream of the Hyaluronic Acid Synthase 2 (HAS2) gene. HAS2 encodes the rate-limiting enzyme synthesizing hyaluronan (HA), a major component of the skin. HA is up-regulated and accumulates in the thickened skin of Shar-Pei. A high copy number of the 16.1 Kb duplication was associated with an increased expression of HAS2 as well as the periodic fever syndrome (p<0.0001). When fragmented, HA can act as a trigger of the innate immune system and stimulate sterile fever and inflammation. The strong selection for the skin phenotype therefore appears to enrich for a pleiotropic mutation predisposing these dogs to a periodic fever syndrome. The identification of HA as a major risk factor for this canine disease raises the potential of this glycosaminoglycan as a risk factor for human periodic fevers and as an important driver of chronic inflammation.

Shar-Pei dogs have two unique features: a breed defining “wrinkled” skin phenotype and a genetic disorder called Familial Shar-Pei Fever (FSF). The wrinkled phenotype is strongly selected for and is the result of excessive hyaluronan (HA) deposited in the skin. HA is a molecule that may behave in a pro-inflammatory manner and create a “danger signal” by being analogous to molecules on the surface of pathogens. FSF is characterized by unprovoked episodes of fever and/or inflammation and resembles several human autoinflammatory syndromes. Here we show that the two features are connected and have the same genetic origin, a regulatory mutation located close to a HA synthesizing gene (HAS2). The mutation is a 16.1 Kb duplication, the copy number of which correlates with HAS2 expression and disease. We suggest that the large amount of HA responsible for the skin condition predisposes to sterile fever and inflammation. HAS2 was previously not known to associate with autoinflammatory disease, and this finding is of wide interest since approximately 60% of human patients with periodic fever syndrome remain genetically unexplained. This investigation also demonstrates how strong artificial selection may affect not only desired and selected phenotypes, but also the health of domestic animals.

Man's best friend becomes biology's best in show: genome analyses in the domestic dog

In the last five years, canine genetics has gone from map construction to complex disease deconstruction. The availability of a draft canine genome sequence, dense marker chips, and an understanding of the genome architecture has changed the types of studies canine geneticists can undertake. There is now a clear recognition that the dog system offers the opportunity to understand the genetics of both simple and complex traits, including those associated with morphology, disease susceptibility, and behavior. In this review, we summarize recent findings regarding canine domestication and review new information on the organization of the canine genome. We discuss studies aimed at finding genes controlling morphological phenotypes and provide examples of the way such paradigms may be applied to studies of behavior. We also discuss the many ways in which the dog has illuminated our understanding of human disease and conclude with a discussion on where the field is likely headed in the next five years.

Use of transcutaneous external pacing during transvenous pacemaker implantation in dogs

The aim of this retrospective study was to evaluate the utility of transcutaneous external pacing (TEP) during transvenous pacemaker implantation in dogs. Eighty-two pacemakers were implanted in 77 dogs because of third-degree atrioventricular block (AVB) (58 cases; 70.7 per cent), sinus node dysfunction (SND) (nine cases; 11.0 per cent), high-grade second-degree AVB (six cases; 7.3 per cent), persistent atrial standstill (PAS) (four cases; 4.9 per cent), post-radiofrequency catheter ablation of the bundle of His (four cases; 4.9 per cent) and vasovagal syncope with atrial fibrillation (one case; 1.2 per cent). TEP was initiated during general anaesthesia after the onset of asystole or profound bradycardia, and stopped when permanent pacing was started. The use of TEP was necessary in 27 cases: 19 cases of third-degree AVB, five of SND, two of PAS and one of vasovagal syncope. External pacing was successful in all but two dogs.

[Hyaluronan, embryogenesis and morphogenesis]

Hyaluronan is a major carbohydrate component of the extracellular matrix. Besides its structural role, it also appears to regulate cell transformation and migration during embryogenesis in vertebrates. Hyaluronan is synthesized by hyaluronan synthetases, transmembrane proteins expressed at several embryonic stages, as early as gastrulation. Inactivation or upregulation of hyaluronan synthetases elicits cardiac or skeletal development anomalies (atrioventricular septal defects caused by abnormal endocardial cushion formation, impaired chondrogenesis). Hyaluronidases degrade hyaluronan and interact with cell surface receptors involved in cell activation. Hyluronan binds not only extracellular matrix glycoproteins, but also cell surface receptors (CD44, RHAMM) also involved in cell signalling, differentiation and proliferation pathways. It facilitates migration and transformation and decreases contact inhibition. Hence, hyaluronan has a central regulating role during embryogenesis.

Hereditary cutaneous mucinosis in shar pei dogs is associated with increased hyaluronan synthase-2 mRNA transcription by cultured dermal fibroblasts

Shar pei dogs are known for the distinctive feature of thick, wrinkled skin as a consequence of high dermal mucin content. Excessive dermal deposition of mucinous substance leading to severe skin folding, and/or to the more severe vesicular form characterized by dermal vesicles or bullae, is highly prevalent in this breed and is known as idiopathic mucinosis. Hyaluronic acid (HA) is the main component that accumulates in the dermis, and high levels of HA have also been detected in the serum of shar pei dogs. In this study, the cellular and molecular mechanisms underlying cutaneous mucinosis of shar pei dogs were investigated. Thirteen shar pei dogs and four control dogs of other breeds were included. In primary dermal fibroblast cultures, transcription of the family of hyaluronan synthases (HAS) involved in HA synthesis, and of hyaluronidases (HYAL) involved in HA degradation, were studied by reverse transcriptase polymerase chain reaction. The location of HA in cell cultures was studied by immunofluorescence and confocal laser microscopy. Dermal fibroblasts transcribed HAS2, HAS3, HYAL1 and HYAL2, but no amplification for HAS1 was found. A higher transcription of HAS2 was demonstrated in shar pei dogs compared with control dogs. By confocal microscopy, HA was detected as a more diffuse and intense network-like pattern of green fluorescence in the fibroblast cells of shar pei dogs in comparison with control dogs. Together, these results provide additional evidence that hereditary cutaneous mucinosis in shar pei dogs may be a consequence of over-transcription or increased activity of HAS2.

Tracking footprints of artificial selection in the dog genome

The size, shape, and behavior of the modern domesticated dog has been sculpted by artificial selection for at least 14,000 years. The genetic substrates of selective breeding, however, remain largely unknown. Here, we describe a genome-wide scan for selection in 275 dogs from 10 phenotypically diverse breeds that were genotyped for over 21,000 autosomal SNPs. We identified 155 genomic regions that possess strong signatures of recent selection and contain candidate genes for phenotypes that vary most conspicuously among breeds, including size, coat color and texture, behavior, skeletal morphology, and physiology. In addition, we demonstrate a significant association between HAS2 and skin wrinkling in the Shar-Pei, and provide evidence that regulatory evolution has played a prominent role in the phenotypic diversification of modern dog breeds. Our results provide a first-generation map of selection in the dog, illustrate how such maps can rapidly inform the genetic basis of canine phenotypic variation, and provide a framework for delineating the mechanistic basis of how artificial selection promotes rapid and pronounced phenotypic evolution.

Blood hyaluronic acid as a marker for canine cirrhosis

Blood hyaluronic acid (HA) concentration was measured in dogs with various liver diseases to determine its relationship with histological fibrosis of the liver. The blood HA concentration significantly increased in dogs with chronic liver diseases compared with extrahepatic diseases and control. Furthermore, the median blood HA concentration in dogs with liver cirrhosis (500 microg/l; range, 151-1970 microg/l) was significantly higher than dogs with non-cirrhotic liver diseases (153 microg/l; range, 15-477 microg/l). In histochemical analysis, HA was distributed primarily in the fibrotic area in dogs with chronic liver diseases. As a conclusion, the blood HA concentration was significantly increased in dogs with chronic liver diseases, especially those with cirrhosis. Measurement of the blood HA levels of dogs with suspected liver disease can be a useful diagnostic aid for canine cirrhosis.