The COL6A1 and COL6A2 genes exist as a gene cluster and detect highly informative DNA polymorphisms in the telomeric region of human chromosome 21q

The pro-invasive factor COL6A2 serves as a novel prognostic marker of glioma

Background

Glioma is an incurable malignant lesion with poor outcome characterized by easy recurrence after surgery with or without radiotherapy and chemotherapy. Studies have shown that COL6A2 is closely related to the tumorigenesis and development of a variety of tumors. However, the role of COL6A2 in glioma and the relationship between COL6A2 and tumor infiltrating immune cells remain unclear.

Methods

Western blot, real-time PCR, a tissue microarray and immunohistochemistry were applied to detect COL6A2 mRNA and protein amounts in glioma, and all experiments were repeated three times. A tissue microarray of glioma samples was used for prognostic analysis. Detection of COL6A2 co-expression with immune genes using immunohistochemical methods, and tumor modeling using nude mice for prevention and treatment studies. Based on the mRNA expression of COL6A2, patients with glioma in TCGA were divided into the low and high COL6A2 expression groups, and GO and KEGG pathway analyses were performed. A PPI network was constructed using STRING, and the associations of COL6A2 with tumor-infiltrating immune cells and immune genes were analyzed in the CIBERSORT and TISIDB databases. COL6A2 mRNA and protein amounts were increased in glioma.

Results

Multiple-database and tissue microarray analyses showed that COL6A2 expression in glioma was associated with poor prognosis, Tissue microarray showed that COL6A2 was the highest expressed in WHO IV and significantly higher in TCGA-GBM than in TCGA-LGG. Immunohistochemistry can well demonstrate the co-expression of COL6A2 with immune genes in a tumor model established in nude mice, showing that interference with COL6A2 expression may have an inhibitory effect on tumors. The mRNA expression of COL6A2 was involved in 22 KEGG pathways, and GSEA analysis showed that 28 and 57 gene sets were significantly enriched at nominal p values <0.01 and <0.05, respectively, protein network revealed a tight interaction between COL6A2 and SPARC. The CIBERSORT database indicated that COL6A2 was correlated with 15 types of tumor-infiltrating immune cells, including M2 macrophages, CD8 T cells, neutrophils, gamma delta T cells, activated CD4 memory T cells, follicular helper T cells, M0 macrophages, M1 macrophages, regulatory T cells (Tregs), activated NK cells, eosinophils, activated mast cells, monocytes, activated dendritic cells, and resting CD4 memory T cells. The TISIDB database indicated that COL6A2 was significantly correlated with lymphocytes such as regulatory T cell, Type 17 T helper cell, Type 1 T helper cell, and immunomodulatory genes. In addition, COL6A2-related immune regulatory genes show that most immune regulatorygenes have prognostic value for glioma, and high-risk immune genes are notconducive to the survival of glioma patients.

Conclusions

COL6A2-related immune regulatory genes show that most immune regulatory genes have prognostic value for glioma, and high-risk immune genes are not conducive to the survival of glioma patients. COL6A2 may be a novel potential prognostic biomarker of glioma and associated with tumor-infiltrating immune cells in the tumor microenvironment, and interference with COL6A2 expression can inhibit tumor growth, which suggests COL6A2 as a potential target for future treatment.

Treatment of Chronic Dislocated Patella in a Skeletally Mature Down Syndrome Patient: A Case Report

CASE

A 55-year-old man with Down syndrome (DS) suffered from chronic irreducible right patellar dislocation. Imaging studies showed an attenuated appearance of the medial patellar retinaculum, and the tibial tubercle to trochlear groove distance measured 1.6 cm. Right medial patellofemoral ligament reconstruction (MPFLR) and lateral lengthening (LL) with proximalization of the tibial tubercle (PTT) were performed with good surgical outcomes.

CONCLUSION

The combination of MPFLR, LL, and PTT is a viable option for treating a skeletally mature DS patient with patellofemoral instability causing recurrent patellar dislocation.

The incudomalleolar articulation in Down syndrome (trisomy 21): a temporal bone study

HYPOTHESIS

One reason for conductive hearing loss (HL) in patients with Down syndrome (DS) is structural anomalies in the incudomalleolar joint (IMJ) that impair sound transmission.

BACKGROUND

The majority of hearing losses in patients with DS are conductive. One reason is the high incidence of inflammatory processes such as otitis media. However, in some patients, the middle ear seems to be normal. The assumption of structural disorders causing a HL is supported by a previous study revealing structural abnormalities of the incudostapedial joint (ISJ) in these patients.

METHODS

In a retrospective analysis, histologic sections of the IMJ of 16 patients with DS were compared with 24 age- and sex-matched subjects with normal middle ear ossicles. The length of 8 parameters of the IMJ were measured at 3 positions and compared between the 2 groups.

RESULTS

Age (p = 0.318) and sex distribution (p = 1) for the DS group and the matched controls were comparable. The IMJs (p < 0.001) and the cartilage of patients with DS are significantly wider in most measurements compared with controls. However, the joint space is not significantly different in the 2 groups.

CONCLUSION

Conductive HL might be caused by a significantly wider IMJ in patients with DS supporting the findings of a previous study reporting similar findings for the ISJ. The etiology of these findings is unclear. Patients with DS have a high prevalence of deficient collagen synthesis. Immunohistochemical analysis may be needed to investigate the collagen structure of the ISJ and IMJ in patients with DS.

Down Syndrome Related Muscle Hypotonia: Association with COL6A3 Functional SNP rs2270669

Down syndrome (DS), the principal cause for intellectual disability, is also associated with hormonal, immunological, and gastrointestinal abnormalities. Muscle hypotonia (MH) and congenital heart diseases (CHD) are also frequently observed. Collagen molecules are essential components for maintaining muscle integrity and are formed by the assembly of three chains, alpha 1–3. The type VI collagen is crucial for cardiac as well as skeletal muscles. The COL α1 (VI) and α2 (VI) chains are encoded by genes located at the 21st chromosome and are expected to have higher dosage in individuals with DS. The α 3 (VI) chain is encoded by the COL6A3 located at the chromosome 2. We hypothesized that apart from COL6A1 and COL6A2, COL6A3 may also have some role in the MH of subjects with DS. To find out the relevance of COL6A3 in DS associated MH and CHD, we genotyped two SNPs in COL6A3, rs2270669 and rs2270668, in individuals with DS. Subjects with DS were recruited based on the Diagnostic and Statistical Manual for Mental Disorders-IV and having trisomy of the 21st chromosome. Parents of individuals with DS and ethnically matched controls were enrolled for comparison. Informed written consent was obtained for participation. Peripheral blood was used for isolation of genomic DNA. Target genetic loci were studied by DNA sequence analysis. Data obtained was subjected to population – as well as family-based statistical analysis. rs2270668 was found to be non-polymorphic in the studied population. rs2270669 showed significant association of the “C” allele and “CC” genotype with DS probands having MH (P = 0.02). Computational analysis showed that rs2270669 may induce structural and functional alterations in the COL α3 (VI). Interaction of COLα3 (VI) with different proteins, crucial for muscle integrity, was also noticed by computational methods. This pioneering study on COL6A3 with DS related MH thus indicates that rs2270669 “C” could be considered as a risk factor for DS related MH.

Down syndrome: orthopedic issues

PURPOSE OF REVIEW

The purpose of this review is to update the role of the orthopedic surgeon in the management of Down syndrome as these patients are living longer and participating in sporting activities.

RECENT FINDINGS

Approximately 20% of all patients with Down syndrome experience orthopedic problems. Upper cervical spine instability has the most potential for morbidity and, consequently, requires close monitoring. Other conditions such as scoliosis, hip instability, patellar instability and foot problems can cause disability if left untreated. In some of these conditions, early diagnosis can prevent severe disability.

SUMMARY

Surgical intervention in children with Down syndrome has a high risk of complications, particularly infection and wound healing problems. Careful anesthetic airway management is needed because of the associated risk of cervical spine instability.

Collagen type VI expression during cardiac development and in human fetuses with trisomy 21

The role played by specific extracellular matrix molecules in normal endocardial cushion differentiation into valves and septa remains to be established. In this respect, type collagen VI is of particular interest because genes encoding the alpha1 and alpha2 chains are located on chromosome 21, and defects involving the atrioventricular (AV) cushions are frequent in trisomy 21. Collagen VI expression was studied in normal human embryonic and fetal hearts (5-18 weeks of development) and compared by immunohistochemistry with results from fetuses (10-16 weeks of development) with trisomy 21. During normal endocardial cushion differentiation (5-8 weeks) there was marked collagen VI expression in the AV cushions, whereas only minor expression was seen in the outflow tract cushions. In the normal fetuses (10-18 weeks), collagen VI in the AV cushions had condensed into a marked zone on the atrial side of the leaflets, as well as subendocardially in other regions of high shear stress. Morphological defects involving the endocardial cushion-derived structures were present in all trisomy 21 cases. An abnormally large membranous septum was observed in three cases. An AV septal defect (AVSD) was present in two, while one had a ventricular septal defect (VSD). Two cases presented with a secondary atrial septal defect (ASDII), and one had an AVSD. Mild to moderate valve dysmorphia was found in all cases. Collagen VI staining in trisomy 21 was more intense than in the normal subjects; however, there were no differences in the spatial expression patterns. We conclude that collagen VI is expressed in the AV cushions and persists during valve differentiation. Collagen VI is more prominent in fetal trisomy 21 hearts than in normal hearts. We hypothesise that collagen VI has a role in the development of heart defects involving endocardial cushion differentiation-specifically in the AV canal, the most common site of malformations affecting children with trisomy 21.

Beta 1 integrin activation mediates adhesive differences between trisomy 21 and non-trisomic fibroblasts on type VI collagen

Trisomy 21 (Down syndrome) is a common genetic condition with a high incidence of congenital heart defects (CHD), particularly those involving abnormal development of the embryonic atrioventricular (AV) canal. Type VI collagen (Col VI) is expressed in the developing AV canal extracellular matrix, and has been associated with trisomy 21 AV canal defects in human genetic studies. Although the molecular mechanisms linking Col VI and trisomy 21 AV canal defects are not well understood, a computer model predicts increased cell adhesiveness is responsible for these CHD. We compared integrin-mediated cell adhesive properties for skin fibroblasts isolated from trisomy 21 and non-trisomic individuals on Col VI, fibronectin (FN) and type I collagen (Col I). Cell lines demonstrate similar adhesion profiles to FN and Col I, but all trisomy 21 cells display increased adhesive capacity for Col VI compared to non-trisomic fibroblasts. Cell adhesion to type VI collagen was shown to be GRGDS independent, but beta(1) integrin family dependent. Function-blocking antibodies identified alpha(3)beta(1) as the predominant integrin mediating trisomy 21 and non-trisomic skin fibroblast adhesion on Col VI. Trisomy 21 and non-trisomic fibroblasts display similar expression levels for each of the integrin receptors examined. A beta(1) integrin-activating antibody augments non-trisomic cell adhesion on Col VI, but has no effect upon trisomy 21 fibroblasts. These results demonstrate that beta(1) integrin family members mediate trisomy 21 and non-trisomic skin fibroblast adhesion for Col VI. Altered activation state of the beta(1) integrin is a mechanism responsible for increased trisomy 21 cell adhesion on Col VI.

Expression of type VI collagen in the developing mouse heart

During development, the embryonic atrioventricular (AV) endocardial cushions undergo a morphogenic process to form mature valve leaflets and the membranous septa in the heart. Several extracellular matrix (ECM) proteins are expressed in the developing AV endocardial cushions, but it remains to be established if any specific ECM proteins are necessary for normal cushion morphogenesis. Abnormal development of the cardiac AV valves is a frequent cause of congenital heart defects, particularly in infants with trisomy 21 (Down syndrome). The genes encoding the alpha1 and alpha2 chains of type VI collagen are located on human chromosome 21 within the region thought to be critical for congenital heart defects in trisomy 21 infants. This suggests that the type VI collagen alpha1(VI) and alpha2(VI) chains may be important in normal AV valve morphogenesis. As a first step in understanding the role of type VI collagen in valve development, the authors examined the normal spatial and temporal expression patterns of mRNA and protein for type VI collagen in the embryonic mouse heart. Ribonuclease protection assay analysis demonstrates cardiac expression of the type VI collagen for alpha1(VI), alpha2(VI), and alpha3(VI) transcripts beginning at embryonic days 11-11.5 of mouse development. In situ hybridization studies demonstrate a coordinated pattern of cardiac expression within the AV valves for each type VI collagen chain from embryonic day 11.5 through the neonatal period. Immunohistochemical studies confirm a concentrated type VI collagen localization pattern in the endocardial cushions from the earliest stages of valve development through the neonatal period. These data indicate that type VI collagen is expressed in the developing AV canal in a pattern consistent with cushion tissue mesenchymal cell migration and proliferation, and suggest that type VI collagen plays a role in the morphogenesis of the developing cardiac AV endocardial cushions into the valve leaflets and membranous septa of the heart.

Characterization of the human alpha 1(VI) collagen promoter and its comparison with human alpha 2(VI) promoters

From a human cosmid library, we isolated a clone (5B) with an insert of 32 kb, encoding the amino-terminal and the 5'-end flanking region of the alpha 1(VI) collagen gene. Exon 1 was found to be 194 bp and contain the 5' untranslated region plus 97 bp coding sequence. Exon 2 consists of 130 bp, a size that is conserved across the chicken and mouse species. S1-nuclease-protection assays and primer-extension analysis, using mRNA from human dermal fibroblasts, show the presence of multiple transcription start sites located in a region of approximately 20 nucleotides. Canonical TATA and CAAT boxes, as found in the chicken and mouse alpha 1 promoters, were absent in the human alpha 1(VI) promoter. The promoter region from positions -1 to -190, is a polypyrimidine/polypurine-rich region containing 12 CCCTCCCC (CT element consensus) sequences and has multiple potential binding sites for the Sp1, and AP2 transcription factors. These regulatory proteins bind to the alpha 2(VI) promoters [Saitta, B. & Chu, M.-L. (1994) Eur. J. Biochem. 223, 675-682]. To test the transcriptional activity of the alpha 1 promoter, transient transfection experiments of the DNA constructs were performed in human dermal fibroblasts and in human fibrosarcoma (HT1080) cell lines. The DNA constructs drive the expression of the chloramphenicol acetyl transferase (CAT) gene. The results show strong CAT activity for the constructs at positions -1700, -298 and -257, while low activity was found for the constructs at positions -4400, -142 and -5 when transfected in fibroblasts. The experiments also identified positive and negative regulatory regions in the alpha 1(VI) promoter CAT constructs when transfected in fibroblasts, but did not identify them in the fibrosarcoma cells.

A novel transcription factor and two members of the Sp 1 multigene family regulate the activity of the alpha 2 (VI) collagen promoter

For a better understanding of the processes that lead to the activation or inhibition of type VI collagen synthesis, we have identified and characterized the cis-acting elements of the chicken alpha 2 (VI) collagen promoter. This promoter encompasses four sites, termed S1, S2, X and S3, which interact with nuclear factors. Sites S1, S2 and S3 are each recognized by the same two proteins that belong to the Sp 1 multigene family. Site X appears to interact with a novel transcription factor of 43 kDa. When a fragment containing all four of the elements is placed in front of a reporter gene, the resulting construct is able to induce a high level of transcription in chicken fibroblasts. As soon as a single element is deleted from this construct, the activity decreases drastically. Thus, the four elements are essential for the transcriptional activation of the alpha 2 (VI) collagen gene.

Genetic variation in the COL6A1 region is associated with congenital heart defects in trisomy 21 (Down's syndrome)

Genetic variation in the COL6A1-COL6A2 gene cluster on chromosome 21 was studied in 113 controls and 58 European families (including control and family subgroups of British/Irish origin) having a child with trisomy 21. There were statistically significant differences among subgroups of trisomic children with and without congenital heart defects (CHD) in distributions of definitive, 3-RFLP haplotype classes received from their nondisjoining and disjoining parents. Haplotypes received by trisomic children with CHD from their disjoining parents were not a random sample of controls' haplotypes. Analysis of parental single-RFLP genotypes and linkage disequilibrium patterns confirmed this parent subgroup differed from a random sample of controls. There were no significant differences in parent subgroup genotype distribution at any of nine control loci distributed along chromosome 21q. This sample showed an association between genetic variation in the COL6A1 gene region and congenital heart defects in trisomy 21.

Alterations of the fetal extracellular matrix in the nuchal oedema of Down's syndrome

Elevations in the lateral and dorsal neck region are known to be highly correlated with chromosomal aberrations in human fetuses. However, the morphology of the elevations is poorly described. Only in the case of Turner's syndrome has lymphatic vessel formation been shown to be deficient leading to swellings in the nuchal area. In Down's syndrome, non-echogenic nuchal oedemata can be visualized in ultrasound scan between the 10th and 15th week of gestation. In the present study, alterations in the extracellular matrix (ECM) of the skin in trisomy 21 fetuses were found to be the morphological basis of the nuchal oedema. The distribution of collagen type VI differs from that in normal fetuses, both in nuchal and leg skin. Collagen VI forms a denser mesh in trisomy 21 than in normal fetal skin, hyaluronan (HA) being the main glycosaminoglycan (GAG) component as judged from the appearance of the TEM precipitate after fixation in the presence of tannic acid. Nuchal oedema in Down's syndrome is therefore found to be an interstitial oedema. The interstitial fluid is bound to HA, leading to a swelling of the fetal dermis. No cysts or dilated vessels were found in the oedematous tissue. The presence of a high amount of HA during development can influence the behaviour of migrating cell populations, which might have a bearing on the pathogenesis of Down's syndrome.

Distribution of extracellular matrix components in nuchal skin from fetuses carrying trisomy 18 and trisomy 21

We have investigated histologically the elevations of the skin in dorsal and lateral neck (nuchal) regions of human fetuses carrying karyotypes of trisomy 18 (Edwards' syndrome) and trisomy 21 (Down's syndrome). Cavities filled with interstitial fluid were found in the dermis, epidermal basement membrane and occasionally in the epidermis of trisomy-18 fetuses, but were not delineated by an epithelium or basement membrane as judged by the absence of immunostaining for laminin, collagen IV and collagen VII. Dilated vessels were also found at the interface between dermis and subcutis. Neither normal fetal skin nor that of trisomy-21 fetuses contained cavities or dilated vessels. In order to detect possible alterations of the extracellular matrix in trisomy-18 and trisomy-21 skin, the distribution of glycoproteins, glycosaminoglycans and proteoglycans was studied immunohistochemically. In trisomy-21 and control skin, the dermis stained intensely for fibronectin, whereas the subcutis reacted only weakly. In trisomy-18 skin, the stronger staining for fibronectin appeared in the subcutis, and the prevailing collagen type was collagen III, collagen type I being absent. In the skin of trisomy-21 fetuses, collagen VI was more irregularly arranged and densely packed, whereas collagen I was more widely spaced than in normal fetuses. More hyaluronan was present in the dermis and subcutis of trisomy-21 fetuses than in that of trisomy-18 and control fetuses. A correlation seems to exist between undelimited cavities and collagen III in trisomy-18 skin, and between hyaluronan and the specific arrangement of collagen in trisomy-21 skin.

Unusual genotypes in the COL6A1 gene in parents of children with trisomy 21 and major congenital heart defects

Collagen type VI is a candidate for a role in the pathogenesis of congenital heart defects (CHD) in Down's syndrome. Three restriction fragment length polymorphisms of the COL6A1 gene were used to determine COL6A1 genotypes in 50 families of affected children with trisomy 21 (29 with congenital heart defects and 21 without) and 37 unrelated volunteers. We found seven unusual genotypes in the parents of affected children with Down's syndrome, five being unique to the parents of children with trisomy 21 and CHD. There were no unusual genotypes associated with other chromosome 21 loci. No single COL6A1 genotype was associated with CHD. Thus, the unusual genotypes unique to parents of affected children suggest that genetic variation in the COL6A1 gene region contributes to the pathogenesis of CHD in Down's syndrome.

Collagen genes: mutations affecting collagen structure and expression

It is to be expected that more collagen genes will be identified and that additional heritable connective tissue diseases will be shown to arise from collagen mutations. Further progress will be fostered by the coordinated study of naturally occurring and induced heritable connective tissues diseases. In some instances, human mutations will be studied in more detail using transgenic mice, while in others, transgenic studies will be used to determine the type of human phenotype that is likely to result from mutations of a given collagen gene. Further studies of transcriptional regulation of the collagen genes will provide the prospect for therapeutic control of expression of specific collagen genes in patients with genetically determined collagen disorders as well as in a wide range of common human diseases in which abnormal formation of the connective tissues is a feature.

Chromosomal assignment of a gene encoding a new collagen type (COL15A1) to 9q21 --> q22

The collagens constitute a large family of extracellular matrix components primarily responsible for maintaining the structure and biological integrity of connective tissue. These proteins exhibit considerable diversity size, sequence, tissue distribution, and molecular composition. Fourteen types of homo- and/or heterotrimeric molecules, thus far reported, are encoded by a minimum of 27 genes. Nineteen of these genes, including several that are closely linked, have been assigned to 10 separate autosomes, and one collagen gene has been mapped to the X chromosome. We have isolated a 2.1-kb human cDNA clone coding for a collagen molecule different in sequence and structure from types I-XIV collagens. This polypeptide has been designated the alpha 1 chain of type XV collagen. To determine the location of the corresponding gene, the cDNA clone was hybridized to rodent-human hybrid DNAs and to human metaphase chromosomes. The results obtained using the hybrid cell lines showed that this newly identified collagen gene, COL15A1, is present in the pter --> q34 region of chromosome 9. In situ hybridization allowed sublocalization to 9q21 --> q22, a region to which no other collagen genes had previously been assigned. Our data further demonstrate the complex arrangement of the many collagen genes in the human genome.