Mapping of the human COL5A1 gene to chromosome 9q34.3

A patient with Phelan-McDermid syndrome and dilation of the great vessels

We present a patient with Phelan-McDermid syndrome, a rare neurodevelopmental disorder caused by a 22q13 deletion, with the previously undescribed finding of progressive dilation of the great arteries. While congenital heart defects have been identified in patients previously, dilation of the great arteries has not been described to our knowledge.

Achilles Tendinopathy

Achilles tendinopathy is a common cause of disability. Despite the economic and social relevance of the problem, the causes and mechanisms of Achilles tendinopathy remain unclear. Tendon vascularity, gastrocnemius-soleus dysfunction, age, sex, body weight and height, pes cavus, and lateral ankle instability are considered common intrinsic factors. The essence of Achilles tendinopathy is a failed healing response, with haphazard proliferation of tenocytes, some evidence of degeneration in tendon cells and disruption of collagen fibers, and subsequent increase in noncollagenous matrix. Tendinopathic tendons have an increased rate of matrix remodeling, leading to a mechanically less stable tendon which is more susceptible to damage. The diagnosis of Achilles tendinopathy is mainly based on a careful history and detailed clinical examination. The latter remains the best diagnostic tool. Over the past few years, various new therapeutic options have been proposed for the management of Achilles tendinopathy. Despite the morbidity associated with Achilles tendinopathy, many of the therapeutic options described and in common use are far from scientifically based. New minimally invasive techniques of stripping of neovessels from the Kager's triangle of the tendo Achillis have been described, and seem to allow faster recovery and accelerated return to sports, rather than open surgery. A genetic component has been implicated in tendinopathies of the Achilles tendon, but these studies are still at their infancy.

Posterior tibial tendinopathy: what are the risk factors?

BACKGROUND

Posterior tibial tendinopathy (PTT) is the most common cause of acquired (progressive) flatfoot deformity in adults. To date, PTT research has mainly focused on management rather than on causal mechanisms. The etiology of PTT is likely to be multifactorial because both intrinsic and extrinsic risk factors have been reported. We sought to critically evaluate reported etiologic factors for PTT and consider the concept of genetic risk factors.

METHODS

A detailed review of the literature published after 1936 was undertaken using English-language medical databases.

RESULTS

No clear consensus exists as to the relative importance of the risk factors reported, and neither has any consideration been given to a possible genetic basis for PTT.

CONCLUSIONS

To date, studies have examined various intrinsic and extrinsic risk factors implicated in the etiology of PTT. The interaction of these factors with an individual's genetic background may provide valuable data and help offer a more complete risk profile for PTT. A properly constructed genetic association study to determine the genetic basis of PTT would provide a novel and alternative approach to understanding this condition.

Bilateral consecutive rupture of the quadriceps tendon in a man with BstUI polymorphism of the COL5A1 gene

A genetic component has been implicated in tendinopathies involving tendon rupture. Type V collagen, a quantitatively minor fibrillar collagen which forms heterotypic fibrils with type I collagen, plays a role in the regulation of the size and configuration of fibrils of the much more abundant component type I collagen. To date, no data on the genetic component of bilateral rupture of the quadriceps tendon have been reported. We describe the presence of BstUI polymorphism of the COL5A1 gene in a man with bilateral rupture of the quadriceps tendon. The COL5A1 (the variant rs12722, BstUI RFLP) can be a candidate gene associated with the development of bilateral quadriceps tendon rupture.

Genetic aspects of tendinopathy

Tendinopathy is characterised by a disorganised, haphazard healing response with no histological signs of inflammation. Research on tendon injuries is limited to the description of the condition and its management, and the pathogenesis is still ill defined. Together with known intrinsic and extrinsic factors, genetics may play a significant role in the aetiopathogenesis of tendinopathy. ABO and other closely linked genes, COL5A1, and tenascin-C have all been implicated in the aetiopathogenesis of tendinopathy. However, the precise role of these genes in causing or protecting individuals from developing tendinopathy is yet to be defined. An interaction between the various intrinsic and extrinsic factors with the genetic make-up of an individual may increase the likelihood of one individual developing tendinopathy over another. Tendinopathy may well be polygenic, involving complex interactions between multiple genes, and could possibly run in families. Further investigations should determine the exact role played by genetic influences in maintaining tendon homeostasis and pave the way for gene transfer therapy to be developed for the management of tendinopathies.

The COL5A1 gene and Achilles tendon pathology

PURPOSE

There is an increase in the incidence of Achilles tendon injuries as a result of the participation in physical activity. It has been suggested that some individuals have a genetic predisposition to Achilles tendon pathology (ATP). The aim of this study was to determine whether the alpha 1 type V collagen (COL5A1) gene, which encodes for a tendon protein, is associated with the symptoms of ATP.

METHODS

One-hundred and eleven Caucasian subjects diagnosed with ATP and 129 Caucasian control (CON) subjects were genotyped for the BstUI and DpnII restriction fragment length polymorphisms (RFLPs) within the COL5A1 gene.

RESULTS

There was a significant difference in the allele frequencies of the COL5A1 BstUI RFLP between the ATP and CON subjects (P=0.006). The frequency of the A2 allele was significantly higher in the CON group (29.8%) than in the ATP group (18.0%) (odds ratio of 1.9; 95% confidence interval (CI) 1.3-3.0; P=0.004). This allele had a stronger protective role when only the 72 patients diagnosed with chronic Achilles tendinopathy were analyzed (odds ratio of 2.6; 95% CI 1.5-4.5).

CONCLUSIONS

The COL5A1 BstUI RFLP is associated with ATP and more specifically, chronic Achilles tendinopathy. Individuals with an A2 allele of this gene are less likely of developing symptoms of chronic Achilles tendinopathy.

Transforming growth factor beta blocks cystogenesis by MDCK epithelium in vitro by enhancing the paracellular flux: implication of collagen V

Transforming growth factor beta (TGFbeta) determines a nearly complete inhibition of cystogenesis by MDCK cells grown in collagen I-enriched matrices in vitro. In order to elucidate the mechanism implicated in this phenomenon, we performed a series of experiments aimed at discovering a relevant role of extracellular matrix. TGFbeta (2 ng/ml) played a marked stimulatory effect on the expression of extracellular matrix by MDCK with a selective effect on collagen V (three to fourfold increase of protein and mRNA) and in parallel inhibited cystogenesis by 95%. Cotreatment with TGFbeta and anti-collagen V antibodies restored a normal cystogenesis. In analogy, when MDCK cells were grown in three-dimensional matrices containing collagen I and minor (10%) amounts of collagen V, cystogenesis was once again inhibited by 95%. To characterize the molecular mechanism activated by TGFbeta and collagen V, we looked at the electrophysiological characteristics of MDCK monolayers and found a drastic fall of transepithelial electrical resistance (TER) in both conditions. In parallel with the decrease in TER, TGFbeta and collagen V also induced the leakage of two high molecular weight tracers, i.e., [3H]-inulin and 150 kD FITC-Dextran, suggesting a perturbation of the paracellular permeability. Finally, TGFbeta at the relevant concentration did not stimulate apoptosis in our cellular model, as judged by propidium iodide staining and by in situ end labeling of DNA fragments. These observations suggest that TGFbeta inhibits cystogenesis by MDCK cells in vitro by altering the collagenic composition of the three-dimensional milieu where MDCK cells grow and form cysts. The molecular mechanism responsible for inhibition of cystogenesis is the increase of paracellular flux which overcomes the active transport of solutes and water inside cysts.

An exon skipping mutation of a type V collagen gene (COL5A1) in Ehlers-Danlos syndrome

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders characterised by skin hyperextensibility, joint hypermobility, easy bruising, and cutaneous fragility. Nine discrete clinical subtypes have been classified. We have investigated the molecular defect in a patient with clinical features of Ehlers-Danlos syndromes types I/II and VII. Electron microscopy of skin tissue indicated abnormal collagen fibrillogenesis with longitudinal sections showing a marked disruption of fibril packing giving very irregular outlines to transverse sections. Analysis of the collagens produced by cultured fibroblasts showed that the type V collagen had a population of alpha 1 (V) chains shorter than normal. Peptide mapping suggested a deletion within the triple helical domain. RTPCR amplification of mRNA covering the whole of this domain of COL5A1 showed a deletion of 54 bp. Although six Gly-X-Y triplets were lost, the essential triplet amino acid sequence and C-propeptide structure were maintained allowing mutant protein chains to be incorporated into triple helices. Genomic DNA analysis identified a de novo G+3-->T transversion in a 5' splice site of one COL5A1 allele. This mutation is analogous to mutations causing exon skipping in the major collagen genes, COL1A1, COL1A2, and COL3A1, identified in several cases of osteogenesis imperfecta and EDS type IV. These observations support the hypothesis that type V, although quantitatively a minor collagen, has a critical role in the formation of the fibrillar collagen matrix.

A new biallelic DNA polymorphism of the human COL5A1 gene

A cDNA probe of the human COL5A1 gene detects a frequent biallelic PstI polymorphism. Allele A has a frequency of 54% whereas that of allele B is 46%. This restriction fragment length polymorphism provides a useful marker for linkage analysis in 9q34.3.

A disease locus for hereditary haemorrhagic telangiectasia maps to chromosome 9q33-34

Hereditary haemorrhagic telangiectasia (HHT), or Osler-Weber-Rendu disease, is an autosomal dominant vascular dysplasia of unknown pathogenesis leading to 'widespread' dermal, mucosal and visceral telangiectases and recurrent haemorrhage. We have mapped the HHT gene, by linkage analysis, to markers on 9q33-34 in two large multi-generation families. Haplotype analysis and mapping of recombination breakpoints gives a 4 cM interval between D9S61 and D9S63 as the most likely location of the gene. The closest marker, D9S65, is estimated to be within 1 cM of the gene and shows a combined lod score of 11.41. Two potential candidate genes, COL5A1 and ZNF79, are also located within 9q33-34. These results provide a starting point for the eventual cloning of the HHT gene.

Are the nail-patella syndrome and the autosomal Goltz-like syndrome the phenotypic expressions of different alleles at the COL5A1 locus?

The COL5A1 gene, which encodes the pro alpha 1(V) chain, was recently mapped to 9q34.3 in the same region as the nail-patella locus. This was taken as an indication that the nail-patella syndrome may be an inherited connective tissue disorder. We demonstrate COL5A1 heterozygous deletion and fibroblast under-expression of alpha 1(V) chains in a girl with an unbalanced translocation resulting in 9q32-->qter monosomy. The patient presents dysplastic nails, a sign typical of nail-patella syndrome, but normal patella. Moreover, she has skin and bone disorders similar to those found in the Goltz syndrome. We suggest that monosomy for the COL5A1 gene is responsible for these connective tissue disorders. Accordingly, the nail-patella syndrome could be attributable to mutations inside the COL5A1 gene rather than to a deletion of it.