Causative alleles for chondrodysplastic dwarfism, factor XI deficiency, and factor XIII deficiency in the Kumamoto sub-breed of Japanese Brown cattle.

Japanese Brown cattle are the second most popular Wagyu breed, and the Kumamoto sub-breed shows better daily gain and carcass weight. One of the breeding objectives for this sub-breed is to reduce genetic defects. Chondrodysplastic dwarfism and factor VIII deficiency have been identified as genetic diseases in the Kumamoto sub-breed. Previously, we detected individuals in the Kumamoto sub-breed with causative alleles of genetic diseases identified in Japanese Black cattle. In the current study, 11 mutations responsible for genetic diseases in the Wagyu breeds were analyzed to evaluate the risk of genetic diseases in the Kumamoto sub-breed. Genotyping revealed the causative mutations of chondrodysplastic dwarfism, factor XI deficiency, and factor XIII deficiency and suggested the appearance of affected animals in this sub-breed. DNA testing for these diseases is needed to prevent economic loses in beef production using the Kumamoto sub-breed.

Genomics of Dwarfism in Italian Local Chicken Breeds.

The identification of the dwarf phenotype in chicken is based on body weight, height, and shank length, leaving the differentiation between dwarf and small breeds ambiguous. The aims of the present study were to characterize the sequence variations associated with the dwarf phenotype in three Italian chicken breeds and to investigate the genes associated with their phenotype. Five hundred and forty-one chickens from 23 local breeds (from 20 to 24 animals per breed) were sampled. All animals were genotyped with the 600 K chicken SNP array. Three breeds were described as "dwarf", namely, Mericanel della Brianza (MERI), Mugellese (MUG), and Pepoi (PPP). We compared MERI, MUG, and PPP with the four heaviest breeds in the dataset by performing genome-wide association studies. Results showed significant SNPs associated with dwarfism in the MERI and MUG breeds, which shared a candidate genomic region on chromosome 1. Due to this similarity, MERI and MUG were analyzed together as a meta-population, observing significant SNPs in the LEMD3 and HMGA2 genes, which were previously reported as being responsible for dwarfism in different species. In conclusion, MERI and MUG breeds seem to share a genetic basis of dwarfism, which differentiates them from the small PPP breed.

PCYT1A Missense Variant in Vizslas with Disproportionate Dwarfism.

Disproportionate dwarfism phenotypes represent a heterogeneous subset of skeletal dysplasias and have been described in many species including humans and dogs. In this study, we investigated Vizsla dogs that were affected by disproportionate dwarfism that we propose to designate as skeletal dysplasia 3 (SD3). The most striking skeletal changes comprised a marked shortening and deformation of the humerus and femur. An extended pedigree with six affected dogs suggested autosomal recessive inheritance. Combined linkage and homozygosity mapping localized a potential genetic defect to a ~4 Mb interval on chromosome 33. We sequenced the genome of an affected dog, and comparison with 926 control genomes revealed a single, private protein-changing variant in the critical interval, PCYT1A:XM_038583131.1:c.673T>C, predicted to cause an exchange of a highly conserved amino acid, XP_038439059.1:p.(Y225H). We observed perfect co-segregation of the genotypes with the phenotype in the studied family. When genotyping additional Vizslas, we encountered a single dog with disproportionate dwarfism that did not carry the mutant PCYT1A allele, which we hypothesize was due to heterogeneity. In the remaining 130 dogs, we observed perfect genotype-phenotype association, and none of the unaffected dogs were homozygous for the mutant PCYT1A allele. PCYT1A loss-of-function variants cause spondylometaphyseal dysplasia with cone-rod dystrophy (SMD-CRD) in humans. The skeletal changes in Vizslas were comparable to human patients. So far, no ocular phenotype has been recognized in dwarf Vizslas. We propose the PCYT1A missense variant as a candidate causative variant for SD3. Our data facilitate genetic testing of Vizslas to prevent the unintentional breeding of further affected puppies.

Molecular Identification and Pathogenicity of Novel Duck-Origin Goose Parvovirus Isolated from Beak Atrophy and Dwarfism Syndrome of Waterfowls in the North of Vietnam.

The aim of this study is to identify and characterize virus isolates (which are named for Bacgiang Agriculture and Forestry University [BAFU]) from diseased Cherry Valley duck and mule duck flocks and investigate the damage caused by a novel parvovirus-related virus (DuPV) to tissues and organs, including the brain, cerebellum, kidney, liver, lung, spleen, and spinal cord. The results of phylogenetic analysis show that DuPV-BAFU evolved from a goose lineage and duck parvoviruses rather than from Muscovy duck parvoviruses. In the genetic lineages, DuPVs were identified from the DuPV samples analyzed, and DuPV-BAFU was found to be closely clustered with two known goose origin parvoviruses (GPVa2006 and GPV1995) and a duck GPVs. Finally, structural modeling revealed that DuPV-BAFU and the closely related viruses GPVa2006 and GPV1995 possessed identical clusters of receptor-interacting amino acid residues in the VP3 protein, a major determinant of viral receptor binding and host specificity. Significantly, these three viruses differed from DuPVs, Muscovy duck parvoviruses, and other goose parvoviruses at these positions. These results also demonstrated that DuPV-BAFU represents a new variant of goose-origin parvovirus that currently circulates in ducklings and causes beak atrophy and dwarfism syndrome, as noted in the previous reports in Europe, Taiwan, and China. This new finding highlights the need for future surveillance of DuPV-BAFU in waterfowl in order to gain a better understanding of both the evolution and the biology of this emerging parvovirus in waterfowl.

Identificación molecular y patogenicidad de un nuevo parvovirus de ganso de origen en pato aislado del síndrome de atrofia del pico y enanismo de las aves acuáticas en el norte de Vietnam. El objetivo de este estudio es identificar y caracterizar aislados de virus detectados en la Universidad de Agricultura y Silvicultura de Bacgiang (BAFU) de parvadas de patos enfermos Cherry Valley e híbridos y también investigar el daño causado por un nuevo virus relacionado con parvovirus del pato (DuPV) en tejidos y órganos, incluidos el cerebro, el cerebelo, los riñones, el hígado, los pulmones, el bazo y la médula espinal. Los resultados del análisis filogenético mostraron que el virus DuPV-BAFU evolucionó a partir de un linaje de parvovirus de patos y gansos en lugar del parvovirus de patos reales. En los linajes genéticos, se identificaron virus DuPV a partir de las muestras de DuPV analizadas, y se encontró que el DuPV-BAFU estaba estrechamente agrupado con dos parvovirus conocidos de origen de ganso (GPVa2006 y GPV1995) y con parvovirus de pato. Finalmente, el modelado estructural reveló que el virus DuPV-BAFU y los virus estrechamente relacionados GPVa2006 y GPV1995 poseían grupos idénticos de residuos de aminoácidos que interactúan con el receptor en la proteína VP3, que es un determinante importante de la unión al receptor viral y la especificidad del huésped. Significativamente, estos tres virus diferían de los DuPV, los parvovirus del pato real y de otros parvovirus del ganso en estas posiciones. Estos resultados también demostraron que el virus DuPV-BAFU representa una nueva variante del parvovirus de origen ganso que actualmente circula en patitos y causa atrofia del pico y síndrome de enanismo, como se señaló en reportes anteriores en Europa, Taiwán y China. Este nuevo hallazgo destaca la necesidad de una vigilancia futura para el virus DuPV-BAFU en las aves acuáticas para comprender mejor tanto la evolución como la biología de este parvovirus emergente en las aves acuáticas.

Immunogenicity of an inactivated novel goose parvovirus vaccine for short beak and dwarfism syndrome in Cherry Valley ducks.

Duck short beak and dwarfism syndrome (SBDS) is a viral infectious disease caused by novel goose parvovirus (NGPV), which has been responsible for serious economic losses to the Chinese duck industry in recent years. Currently, there is no effective vaccine against this disease. In this study, we developed an inactivated virus vaccine candidate for SBDS based on NGPV strain DS15 isolated from a duck in China. Immune efficacy was evaluated in 112 ducks, which were randomly divided into vaccination, challenge-control, vaccination-challenge, and blank control groups (28 per group). Clinical characteristics, antibodies, virus excretion, viremia, and pathological changes were monitored. No morbidity or death was observed in the immunized ducks, which showed normal weight and a good mental state. High levels of serum antibodies (optical density at 450 nm of ~ 0.63) were detected in ducks immunized with the inactivated vaccine at 7 days post-vaccination (dpv), and the titer of virus-neutralizing antibodies increased from 1:23 to 1:28.5 from 7 to 42 dpv. Measurement of the viral load in anal swab, serum, and tissue samples showed that vaccination significantly inhibited the replication of NGPV in immunized ducks. Moreover, NGPV could not be isolated from the spleens of immunized or vaccinated and challenged ducks. Collectively, these results demonstrate that the newly developed inactivated NGPV vaccine, administered in an oil emulsion adjuvant, possesses good immunogenicity and represents a potentially powerful tool for SBDS prevention and control.

VP2 virus-like particles elicit protective immunity against duckling short beak and dwarfism syndrome in ducks.

Duckling short beak and dwarfism syndrome virus (SBDSV), an emerging goose parvovirus, has caused short beak and dwarfism syndrome (SBDS) in Chinese duck flocks since 2015. Presently, there is no commercial vaccine against SBDS. In the present study, a virus-like particle (VLP)-based candidate vaccine was developed against this disease. A baculovirus expression system was used to express the SBDSV VP2 protein in Sf9 cells. Immunofluorescence assay, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting were used to confirm protein expression. Furthermore, transmission electron microscopy was used to observe the formation of VLPs. VLPs were formulated into an oil-adjuvanted maternal vaccine to evaluate humoral responses in breeding ducks via latex particle agglutination inhibition assay (LPAI) and microneutralization assay. The offspring were challenged with SBDSV to test the protective efficacy. A single dose of SBDSV was able to induce the high level of LPAI antibodies in ducks, with LPAI and neutralization peak titres of 4.9 ± 1.20 log2 and 7.1 ± 1.20 log2, respectively, at 4 weeks post-vaccination (wpv). The average LPAI titre of yolk antibodies in duck eggs receiving 2 doses (first and boost doses) of the vaccine was 5.3 ± 1.09 log2 at 4 weeks post-boost. The protective efficacy of the maternal vaccine was 87.5%-100%. These results indicate that SBDSV VLPs can be a promising vaccine candidate for controlling SBDS.

Palaeohistology reveals a slow pace of life for the dwarfed Sicilian elephant.

The 1-m-tall dwarf elephant Palaeoloxodon falconeri from the Pleistocene of Sicily (Italy) is an extreme example of insular dwarfism and epitomizes the Island Rule. Based on scaling of life-history (LH) traits with body mass, P. falconeri is widely considered to be 'r-selected' by truncation of the growth period, associated with an early onset of reproduction and an abbreviated lifespan. These conjectures are, however, at odds with predictions from LH models for adaptive shifts in body size on islands. To settle the LH strategy of P. falconeri, we used bone, molar, and tusk histology to infer growth rates, age at first reproduction, and longevity. Our results from all approaches are congruent and provide evidence that the insular dwarf elephant grew at very slow rates over an extended period; attained maturity at the age of 15 years; and had a minimum lifespan of 68 years. This surpasses not only the values predicted from body mass but even those of both its giant sister taxon (P. antiquus) and its large mainland cousin (L. africana). The suite of LH traits of P. falconeri is consistent with the LH data hitherto inferred for other dwarfed insular mammals. P. falconeri, thus, not only epitomizes the Island Rule but it can also be viewed as a paradigm of evolutionary change towards a slow LH that accompanies the process of dwarfing in insular mammals.

PRKG2 Splice Site Variant in Dogo Argentino Dogs with Disproportionate Dwarfism.

Dwarfism phenotypes occur in many species and may be caused by genetic or environmental factors. In this study, we investigated a family of nine Dogo Argentino dogs, in which two dogs were affected by disproportionate dwarfism. Radiographs of an affected dog revealed a decreased level of endochondral ossification in its growth plates, and a premature closure of the distal ulnar physes. The pedigree of the dogs presented evidence of monogenic autosomal recessive inheritance; combined linkage and homozygosity mapping assigned the most likely position of a potential genetic defect to 34 genome segments, totaling 125 Mb. The genome of an affected dog was sequenced and compared to 795 control genomes. The prioritization of private variants revealed a clear top candidate variant for the observed dwarfism. This variant, PRKG2:XM_022413533.1:c.1634+1G>T, affects the splice donor site and is therefore predicted to disrupt the function of the PKRG2 gene encoding protein, kinase cGMP-dependent type 2, a known regulator of chondrocyte differentiation. The genotypes of the PRKG2 variant were perfectly associated with the phenotype in the studied family of dogs. PRKG2 loss-of-function variants were previously reported to cause disproportionate dwarfism in humans, cattle, mice, and rats. Together with the comparative data from other species, our data strongly suggest PRKG2:c.1634+1G>T to be a candidate causative variant for the observed dwarfism phenotype in Dogo Argentino dogs.

Molecular characteristics and phylogenetic analysis of novel goose parvovirus strains associated with short beak and dwarfism syndrome.

Short beak and dwarfism syndrome (SBDS) emerged in Cherry Valley duck flocks in China in 2015, and novel goose parvovirus (NGPV) was shown to be the etiological agent of SBDS. To date, it is not known whether SBDS-related NGPV isolates possess common molecular characteristics. In this study, three new NGPV strains (namely, SDHT16, SDJN19, and SDLC19) were isolated from diseased ducks showing typical signs of SBDS and successfully passaged in embryonated goose or Cherry Valley duck eggs. The complete genome sequences of these NGPV strains were 98.9%-99.7% identical to each other but showed slightly less similarity (95.2%-96.1% identity) to classical GPV strains. A total of 16 common amino acid substitutions were present in the VP1 proteins of six NGPV strains (SDHT16, SDJN19, SDLC19, QH, JS1, and SDLC01) compared with the classical Chinese GPV strains, nine of which were identical to those found in European GPV strain B. The non-structural protein Rep1 of the six NGPV strains had 12 common amino acid substitutions compared with the classical GPV strains. Phylogenetic analysis indicated that the Chinese NGPV strains clustered with the European SBDS-related NGPV strains, forming a separate branch that was distinct from the group formed by the classical GPV strains. The present study shows the common molecular characteristics of NGPV isolates and suggests that the Chinese NGPV isolates probably share a common ancestor with European SBDS-related NGPV strains.

Aggrecan, IL-1ß, IL-6, and TNF-α profiles in the Articular Cartilage of Miniature Horses with Chondrodysplastic Dwarfism.

Dwarfism is a skeletal disorder that causes abnormal growth. In Miniature horses, dwarfism can occur as chondrodysplastic dwarfism, an autosomal recessive disorder associated with five mutations (D1, D2, D3*, D4 and c.6465A > T variant) in the aggrecan (ACAN) gene. The aim of this study was to evaluate the expression of aggrecan (at the gene and protein level) and specific cytokines (IL-1ß, IL-6, and TNF-α) in the articular cartilage of Miniature horses with chondrodysplastic dwarfism (D4/c.6465A > T genotype). Metatarsal bone samples from eight dwarf Miniature horses were collected for histopathological analysis, and articular cartilage was collected to detect and quantify aggrecan levels through Western blotting and determine the relative expression levels of ACAN, IL-1ß, IL-6, and TNF-α through qPCR. All affected animals presented chondrodysplasia-like lesions with disorganization of the chondrocyte layers and reduced the amount of an extracellular matrix. No significant difference in aggrecan expression levels in uncleaved samples from the dwarf and control groups (composed of phenotypically normal animals of similar age and breed (P = .7143)) was found using Western blotting. qPCR revealed that ACAN gene expression was higher in the affected animals than in normal animals (P = .0119). No significant difference in cytokine levels was detected between the groups. Mutant aggrecan may interfere with normal cellular function, leading to chondrodysplasia and the observed phenotypic findings.

Skeletal Manifestations of Heritable Disproportionate Dwarfism in Cats as Determined by Radiography and Magnetic Resonance Imaging.

OBJECTIVE: The aim of this study was to characterize the radiographic alignment of thoracic and pelvic limbs and evaluate for intervertebral disc disease in cats with feline disproportionate dwarfism (FDD). STUDY DESIGN: Observational cross-sectional study. Radiographic joint orientation angles were measured in 10 thoracic and pelvic limbs from 5 FDD cats and compared with those angles measured in 24 thoracic limbs and 100 pelvic limbs from skeletally normal cats. Magnetic resonance imaging of the spine was performed in 2 FDD cats for the evaluation of pathology of the intervertebral discs or vertebrae. RESULTS: All limbs from FDD cats possessed deformities. FDD humeri demonstrated procurvatum proximally, and recurvatum distally in the sagittal plane, but showed no difference in the frontal plane. FDD radii possessed excessive recurvatum proximally, and procurvatum distally in the sagittal plane, and varus proximally and valgus distally in the frontal plane. Whereas no torsion was discernible in the humeri, all radii had external torsion. In the frontal plane, FDD femurs exhibited varus both proximally and distally whereas the tibia possessed proximal valgus and distal varus. No torsion in the pelvic limbs was observed. No spinal pathology was detected in the FDD cats included in the original study. CONCLUSION: Feline disproportionate dwarfism results in significant appendicular deformity in all limbs. The incidence of intervertebral disc degeneration in FDD cats is inconclusive.

Canine DVL2 variant contributes to brachycephalic phenotype and caudal vertebral anomalies.

A frameshift deletion variant in the Wnt pathway gene dishevelled 2 (DVL2) is associated with a truncated, kinked tail ("screw tail") in English Bulldogs, French Bulldogs and Boston Terriers. These breeds are also characterized by distinctive morphological traits, including a wide head, flat face and short-limbed dwarfism, which are characteristic of Robinow syndrome in humans, caused by defects in genes such as DVL1 and DVL3. Based on these phenotypic and genetic similarities, it has previously been hypothesized that the canine DVL2 variant results in a syndromic phenotype called the Robinow-like syndrome. In our study, we investigated the distribution of the DVL2 variant in 1954 dogs from 15 breeds, identifying breeds with allele variation and enabling the dissection of the genotype-phenotype correlation for the first time. With CT examinations in American Staffordshire Terriers, we confirmed that the DVL2 allele is associated with caudal vertebral malformations and a brachycephalic phenotype. We also hypothesize that the variant may be linked to additional health conditions, including brachycephalic obstructive airway syndrome and congenital heart defects. Altogether, our study strengthens the role of DVL2 as one of the contributors to the "bulldog type" morphology and features on the spectrum of human Robinow syndrome.

A de novo frameshift mutation in ZEB2 causes polledness, abnormal skull shape, small body stature and subfertility in Fleckvieh cattle.

Polledness in cattle is an autosomal dominant trait. Previous studies have revealed allelic heterogeneity at the polled locus and four different variants were identified, all in intergenic regions. In this study, we report a case of polled bull (FV-Polled1) born to horned parents, indicating a de novo origin of this polled condition. Using 50K genotyping and whole genome sequencing data, we identified on chromosome 2 an 11-bp deletion (AC_000159.1:g.52364063_52364073del; Del11) in the second exon of ZEB2 gene as the causal mutation for this de novo polled condition. We predicted that the deletion would shorten the protein product of ZEB2 by almost 91%. Moreover, we showed that all animals carrying Del11 mutation displayed symptoms similar to Mowat-Wilson syndrome (MWS) in humans, which is also associated with genetic variations in ZEB2. The symptoms in cattle include delayed maturity, small body stature and abnormal shape of skull. This is the first report of a de novo dominant mutation affecting only ZEB2 and associated with a genetic absence of horns. Therefore our results demonstrate undoubtedly that ZEB2 plays an important role in the process of horn ontogenesis as well as in the regulation of overall development and growth of animals.

Evaluation of a new variant in the aggrecan gene potentially associated with chondrodysplastic dwarfism in Miniature horses.

Chondrodysplastic dwarfism in Miniature horses is an autosomal recessive disorder previously associated with four mutations (D1, D2, D3*, and D4) in the aggrecan (ACAN) gene. The aim of this study was to identify additional variants in the candidate ACAN gene associated with chondrodysplastic dwarfism in Miniature horses. Fifteen dwarf Miniature horses were found to possess only one of the dwarfism-causing variants, and two possessed none of the variants. The ACAN exons (EquCab3.0) of seven dwarf Miniature horses were sequenced. A missense SNP in coding exon 11 (g.95271115A > T, c.6465A > T-RefSeq XM_005602799.2), which resulted in the amino acid substitution p.Leu2155Phe (RefSeq XP_005602856.2), was initially associated with the dwarf phenotype. The variant was tested and found present in 14 dwarf foals as well as one parent of each, and both parents of a dwarf possessing two copies. Genetic testing of 347 phenotypically normal Miniature horses demonstrated that none had more than one of the dwarf alleles or c.6465A > T. However, a study of large breeds revealed the presence of c.6465A > T, which was present in homozygosis in two Mangalarga Marchador horses. We suggest that c.6465A > T as a marker of disequilibrium or complex interactions in the Miniature horse genome could contribute to the associated dwarfism.

De novo stop-lost germline mutation in FGFR3 causes severe chondrodysplasia in the progeny of a Holstein bull.

Fifteen cases of chondrodysplasia characterized by disproportionate dwarfism occurred in the progeny of a single Holstein bull. A de novo mutation event in the germline of the sire was suspected as cause. Whole-genome sequencing revealed a single protein-changing variant in the stop codon of FGFR3 gene on chromosome 6. Sanger sequencing of EDTA blood proved that this variant occurred de novo and segregates perfectly with the observed phenotype in the affected cattle family. FGFR3 is an important regulator gene in bone formation owing to its key role in the bone elongation induced by FGFR3-dimers. The detected paternally inherited stop-lost variant in FGFR3 is predicted to add 93 additional amino acids to the protein's C-terminus. This study provides a second example of a dominant FGFR3 stop-lost variant as a pathogenic mutation of a severe form of chondrodysplasia. Even though FGFR3 is known to be associated with dwarfism and growth disorders in human and sheep, this study is the first to describe FGFR3-associated chondrodysplasia in cattle.

Heterozygotes for ACAN dwarfism alleles in horses have reduced stature.

Homozygous and compound heterozygous Miniature horses for ACAN alleles D1, D2, D3* and D4 exhibit chondrodysplastic dwarfism (OMIA 001271-9796). In a previous study, the carrier rate for these four alleles, combined, was 26.2%. The purpose of this study was to investigate whether carriers of these dwarfism-causing alleles had a shorter withers height than non-carriers. A total of 245 Miniature horses were tested for these four ACAN alleles and also were measured for withers height. Of these horses, 98 were carriers and 147 were non-carriers. A statistically significant difference of 1.43 inches was observed with the carriers being shorter (P = 1.72E - 11). The range of heights for the two groups overlapped, indicating that other factors, including genes, have an impact on withers height. However, the high carrier rate of these dwarfism-causing variants may be due to selection for decreased height.

Description of the D4/D4 genotype in Miniature horses with dwarfism.

Four causative mutations (D1, D2, D3*, and D4) of chondrodysplastic dwarfism have been described in the equine aggrecan (ACAN) gene. Homozygotes for one of these mutations and heterozygotes for any combination of these mutations exhibit the disproportionate dwarfism phenotype. However, no case description of homozygotes for D4 (D4/D4) has been reported in the literature, to our knowledge. We report 2 Miniature horses with the genotype D4/D4 in the ACAN gene. Clinically, the 2 dwarfs had a domed head that was large compared to the rest of the body, mandibular prognathism, and short and bowed limbs, mainly in the proximal region of the metatarsal bones. Radiographic examination revealed contour irregularities of the subchondral bone in the long bones and confirmed mandibular prognathism; histopathology revealed irregular chondrocyte organization. To determine the genotypes of the horses, we performed DNA extraction from white blood cells, PCR, and Sanger sequencing. Genotyping demonstrated that these 2 animals had the D4/D4 genotype in the ACAN gene. The D4/D4 dwarfs were clinically similar to animals with the other ACAN genotypes reported for this disease. Identification of heterozygous animals makes mating selection possible and is the most important control measure to minimize economic losses and casualties.

Oculo-skeletal dysplasia in five Labrador Retrievers.

OBJECTIVE: To describe the clinical features and diagnostic findings of Labrador Retrievers with oculo-skeletal dysplasia (OSD). ANIMAL STUDIED: Five privately owned dogs. PROCEDURES: Medical records of dogs diagnosed with OSD from 2008 through 2018 were reviewed. Patients were excluded if lacking disease confirmation through genetic testing (Optigen RD/OSD). Information collected included signalment, physical and ophthalmic examination findings, results of ocular ultrasound and electroretinogram, and digital radiographs of forelimbs and pelvis. RESULTS: All five dogs were Labrador Retrievers, confirmed to be homozygote for the OSD mutation. The main physical abnormalities were vision deficits (5 dogs), short-limbed dwarfism (5), carpal valgus (4), and color dilution alopecia (4). The main ophthalmic anomalies were cataracts (10 eyes), vitreous syneresis (10), retinal separation (6), persistent hyperplastic primary vitreous (2), lens coloboma (2), microphakia (2), and persistent tunica vasculosa lentis (1). Ocular ultrasound and electroretinogram confirmed the diagnoses of retinal separations and persistent hyperplastic primary vitreous. Radiographic changes included shortening of ulna and curved radius (5 dogs), elbow incongruity and osteoarthritis (4 dogs), hip dysplasia (3), and coxofemoral osteoarthritis (2). Available follow-up information (2 dogs) showed progression of cataract from incipient to mature in one dog, necessitating cataract surgery, and progression of cataract and lameness in another dog. CONCLUSIONS: The clinical findings of OSD are described in five Labrador Retrievers. DNA testing is critical to diagnose OSD and help eradicate this condition from the breed. Progression of cataracts and osteoarthritis in dogs with OSD warrants yearly monitoring.

Clinical, histopathological and genetic characterisation of oculoskeletal dysplasia in the Northern Inuit Dog.

Seven Northern Inuit Dogs (NID) were diagnosed by pedigree analysis with an autosomal recessive inherited oculoskeletal dysplasia (OSD). Short-limbed dwarfism, angular limb deformities and a variable combination of macroglobus, cataracts, lens coloboma, microphakia and vitreopathy were present in all seven dogs, while retinal detachment was diagnosed in five dogs. Autosomal recessive OSD caused by COL9A3 and COL9A2 mutations have previously been identified in the Labrador Retriever (dwarfism with retinal dysplasia 1-drd1) and Samoyed dog (dwarfism with retinal dysplasia 2-drd2) respectively; both of those mutations were excluded in all affected NID. Nine candidate genes were screened in whole genome sequence data; only one variant was identified that was homozygous in two affected NID but absent in controls. This variant was a nonsense single nucleotide polymorphism in COL9A3 predicted to result in a premature termination codon and a truncated protein product. This variant was genotyped in a total of 1,232 dogs. All seven affected NID were homozygous for the variant allele (T/T), while 31/116 OSD-unaffected NID were heterozygous for the variant (C/T) and 85/116 were homozygous for the wildtype allele (C/C); indicating a significant association with OSD (p = 1.41x10-11). A subset of 56 NID unrelated at the parent level were analysed to determine an allele frequency of 0.08, estimating carrier and affected rates to be 15% and 0.6% respectively in NID. All 1,109 non-NID were C/C, suggesting the variant is rare or absent in other breeds. Expression of retinal mRNA was similar between an OSD-affected NID and OSD-unaffected non-NID. In conclusion, a nonsense variant in COL9A3 is strongly associated with OSD in NID, and appears to be widespread in this breed.