Cloning and expression of type II collagen mRNA: evaluation as a candidate for canine oculo-skeletal dysplasia

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.

Molecular assembly of recombinant chicken type II collagen in the yeast Pichia pastoris

Effective treatment of rheumatoid arthritis can be mediated by native chicken type II collagen (nCCII), recombinant peptide containing nCCII tolerogenic epitopes (CTEs), or a therapeutic DNA vaccine encoding the full-length CCOL2A1 cDNA. As recombinant CCII (rCCII) might avoid potential pathogenic virus contamination during nCCII preparation or chromosomal integration and oncogene activation associated with DNA vaccines, here we evaluated the importance of propeptide and telopeptide domains on rCCII triple helix molecular assembly. We constructed pC- and pN-procollagen (without N- or C-propeptides, respectively) as well as CTEs located in the triple helical domain lacking both propeptides and telopeptides, and expressed these in yeast Pichia pastoris host strain GS115 (his4, Mut⁺) simultaneously with recombinant chicken prolyl-4-hydroxylase α and β subunits. Both pC- and pN-procollagen monomers accumulated inside P. pastoris cells, whereas CTE was assembled into homotrimers with stable conformation and secreted into the supernatants, suggesting that the large molecular weight pC-or pN-procollagens were retained within the endoplasmic reticulum whereas the smaller CTEs proceeded through the secretory pathway. Furthermore, resulting recombinant chicken type II collagen pCα1(II) can induced collagen-induced arthritis (CIA) rat model, which seems to be as effective as the current standard nCCII. Notably, protease digestion assays showed that rCCII could assemble in the absence of C- and N-propeptides or telopeptides. These findings provide new insights into the minimal structural requirements for rCCII expression and folding.

COL9A2 and COL9A3 mutations in canine autosomal recessive oculoskeletal dysplasia

Oculoskeletal dysplasia segregates as an autosomal recessive trait in the Labrador retriever and Samoyed canine breeds, in which the causative loci have been termed drd1 and drd2, respectively. Affected dogs exhibit short-limbed dwarfism and severe ocular defects. The disease phenotype resembles human hereditary arthro-ophthalmopathies such as Stickler and Marshall syndromes, although these disorders are usually dominant. Linkage studies mapped drd1 to canine chromosome 24 and drd2 to canine chromosome 15. Positional candidate gene analysis then led to the identification of a 1-base insertional mutation in exon 1 of COL9A3 that cosegregates with drd1 and a 1,267-bp deletion mutation in the 5' end of COL9A2 that cosegregates with drd2. Both mutations affect the COL3 domain of the respective gene. Northern analysis showed that RNA expression of the respective genes was reduced in affected retinas. These models offer potential for studies such as protein-protein interactions between different members of the collagen gene family, regulation and expression of these genes in retina and cartilage, and even opportunities for gene therapy.

Retinal dysplasia in wild otters (Lutra lutra )

Eyes from 88 otters found dead in south-west England between 1990 and 2000, were collected as part of a larger pathological study. Histopathological examination of 131 eyes revealed dysplastic changes such as rosetting and folding in the retinas of 26 of the otters. In the eyes of 42 of the otters there were postmortem and fixation-induced retinal detachment which complicated the differentiation of dysplastic from normal retina, but 11 eyes had folds which probably indicated a dysplastic pathology. The eyes of 18 of the otters had inflammatory or autolytic changes which precluded a definitive evaluation of their dysplastic status. Liver samples from 55 of the otters were analysed for a range of polychlorinated hydrocarbons and for vitamin A. The otters with dysplastic retinas had significantly lower concentrations of vitamin A and higher concentrations of dieldrin than the otters with normal retinas.

Expression of Sox9 and type IIA procollagen during ocular development and aging in transgenic Del1 mice with a mutation in the type II collagen gene

PURPOSE

To study the expression and distribution of transcription factor Sox9 and type IIA procollagen in the developing and aging eyes of normal and transgenic Dell mice carrying pro(alpha)1(II) collagen transgenes with a short deletion mutation, which cause ocular abnormalities in this mouse line.

METHODS

The eyes of Del1 mice were studied on embryonic days E14.5, E16.5 and E18.5, and at the ages of 4 and nine months, using their nontransgenic littermates as controls. Sox9 and pro(alpha)1(IIA) collagen were detected by RNase protection assay and immunohistochemistry.

RESULTS

RNase protection assay revealed Sox9 transcripts in the eyes of Del1 and control mice during development and aging. The mRNA for type IIA procollagen had a similar temporal expression pattern. On embryonic days E14.5, E16.5 and E18.5, Sox9 was located by immunohistochemistry in the nuclei and type IIA procollagen in the extracellular space of the developing retina. During growth and aging, the ocular expression of Sox9 mRNA and the immunohistochemical reaction for Sox9 antibody diminished, concomitant with the reduction in type II procollagen mRNA. However, at the age of nine months, levels of Sox9 and type IIA procollagen mRNAs were higher in the degenerating eyes of Del1 and control mice.

CONCLUSIONS

The similarities in the temporo-spatial distribution of Sox9 and type IIA procollagen suggest that this transcription factor is involved in the activation of type II collagen expression in the eye, as has been demonstrated in prechondrogenic mesenchyme and immature cartilage. The increased production of Sox9 and type IIA procollagen in the aging retina and vitreous is analogous to degenerating articular cartilage where attempted tissue repair has also been observed.

Cloning and characterization of opticin cDNA: evaluation as a candidate for canine oculo-skeletal dysplasia

Opticin, a novel member of the leucine-rich repeat (LRR) family, has been reported to bind to collagen fibrils. Many members of the LRR family of extracellular matrix proteins have been reported to bind to fibrillar collagen and regulate the diameter of collagen fibrils and lateral fusion between fibrils. Collagen fibrils are important for the maintenance of the vitreous body in the eye and growth plate cartilage of joints. Oculo-skeletal dysplasia (OSD) is a heterogeneous group of heritable genetic disorders affecting humans and a few breeds of dogs. Labrador retrievers and Samoyeds affected with non-allelic forms of OSD exhibit vitreous dysplasia and dwarfism, and could serve as an animal model for the disorder. To test the opticin gene as a candidate for OSD, canine opticin cDNA has been cloned and characterized. The predicted 327 amino acid sequence is 77% homologous to human opticin, and maintains characteristic structural domains including seven LRR domains, two cysteine clusters and potential O-linked glycosylation sites. It shows highest protein sequence identity to epiphycan (37%) and osteoglycin (31%) and belongs to the Class III family of LRR extracellular matrix proteins. In addition to ocular tissues and cartilage, opticin mRNA and protein have been identified in ligament, skin, muscle, and testes. No alteration of opticin expression at the protein level was observed in OSD affected dogs relative to normal controls. Based on linkage analysis using a newly identified intragenic single nucleotide polymorphism opticin has been excluded from having any causal association with the OSD loci in both Samoyeds and Labrador retrievers.