Fibril-forming collagens in lamprey

Association of a bacterial collagen after hydroxyproline incorporation

Various bacterial collagen-like proteins have been previously described and shown to have a triple helical, (Gly-Xaa Yaa)n repeating structure. They are stable without needing any secondary modification of proline residues in the Yaa position to hydroxyproline, a characteristic feature of animal collagens. Hydroxyproline can, however, be introduced into recombinant bacterial collagen by co-translational incorporation during fermentation. However, this does not lead to full incorporation and introduces the hydroxyproline into both the Xaa and Yaa positions. It was suggested that the poor solubility of bacterial collagen samples with higher levels of incorporation of hydroxyproline could be due to an increase in protein association at neutral pH. In the present study, cryo-transmission electron microscopy was used to examine the nature and extent of any associations arising from hydroxyproline incorporation. This was examined further, using 2 smaller fragments, where the proline sites are predominantly in either the Xaa position or Yaa position. The present data confirm the importance of the presence of hydroxyproline in assisting in the association between collagen molecules.

Lamprey Wound Healing and Regenerative Effects: The Collaborative Efforts of Diverse Drivers

Skin is a natural barrier between the body and the external environment, and this important multifunctional organ plays roles in body temperature regulation, sensory stimulation, mucus secretion, metabolite excretion and immune defense. Lampreys, as ancient vertebrates, rarely experience infection of damaged skin during farming and efficiently promote skin wound healing. However, the mechanism underlying these wound healing and regenerative effects is unclear. Our histology and transcriptomics results demonstrate that lampreys regenerate a nearly complete skin structure in damaged epidermis, including the secretory glands, and will almost not be infected, even if experiencing full-thickness damage. In addition, ATGL, DGL and MGL participate in the lipolysis process to provide space for infiltrating cells. A large number of red blood cells migrate to the site of injury and exert proinflammatory effects, upregulating the expression of proinflammatory factors such as IL-8 and IL-17. Based on a lamprey skin damage healing model, adipocytes and red blood cells in the subcutaneous fat layer can promote wound healing, which provides a new approach for the study of skin healing mechanisms. Transcriptome data reveal that mechanical signal transduction pathways are mainly regulated by focal adhesion kinase and that the actin cytoskeleton plays an important role in the healing of lamprey skin injuries. We identified RAC1 as a key regulatory gene that is necessary and partially sufficient for wound regeneration. Insights into the mechanisms of lamprey skin injury and healing will provide a theoretical basis for overcoming the challenges associated with chronic healing and scar healing in the clinic.

A novel splicing pathogenic variant in COL1A1 causing osteogenesis imperfecta (OI) type I in a Chinese family

Background

Osteogenesis imperfecta (OI), a rare autosomal inheritable disorder characterized by bone fragility and skeletal deformity, is caused by pathogenic variants in genes impairing the synthesis and processing of extracellular matrix protein collagen type I. With the use of next‐generation sequencing and panels approaches, an increasing number of OI patients can be confirmed and new pathogenic variants can be discovered. This study sought to identify pathogenic gene variants in a Chinese family with OI I.

Methods

Whole‐exome sequencing was used to identify pathogenic variants in the proband, which is confirmed by Sanger sequencing and cosegregation analysis; MES, HSF, and Spliceman were used to analyze this splicing variant；qRT‐PCR was performed to identify the mRNA expression level of COL1A1 in patient peripheral blood samples; Minigene splicing assay was performed to mimic the splicing process of COL1A1 variants in vitro; Analysis of evolutionary conservation of amino acid residues and structure prediction of the mutant protein.

Results

A novel splicing pathogenic variant (c.3814+1G>T) was identified in this OI family by using whole‐exome sequencing, Sanger sequencing, and cosegregation analysis. Sequencing of RT‐PCR products from the COL1A1 minigene variant reveals a 132‐nucleotide (nt) insertion exists at the junction between exons 48 and exon 49 of the COL1A1 cDNA. Splicing assay indicates that the mutated minigene produces an alternatively spliced transcript which may cause a frameshift resulting in early termination of protein expression. The molecular analysis suggested that the altered amino acid is located at the C‐terminus of type I procollagen.

Conclusion

Our study reveals the pathogenesis of a novel COL1A1 splicing pathogenic variant c.3814+1G>T in a Chinese family with OI I.

Isolation and Characterisation of Major and Minor Collagens from Hyaline Cartilage of Hoki (Macruronus novaezelandiae)

The composition and properties of collagen in teleost (bony fish) cartilage have never been studied. In this study, we aimed to identify and characterise all collagen species in the nasal cartilage of hoki (Macruronus novaezelandiae). Four native collagen species were extracted using two techniques, and isolated with differential salt precipitation. We were able to assign the identity of three of these collagen species on the basis of solubility, SDS-PAGE and amino acid analyses. We found that hoki cartilage contains the major collagen, type II, and the minor collagens, type IX and type XI, which are homologous to those found in mammal and chicken cartilage. Using these extraction protocols, we also isolated a full-length type IX collagen from cartilage for the first time. In addition, we detected a 90 kDa, highly glycosylated collagen that has not been identified in any other species. For each isolate, structural and biochemical characterisations were performed using circular dichroism and Fourier transform infrared spectroscopy analyses, and the thermal denaturation properties were determined. Our results showed that the properties of hoki cartilage-derived collagens are similar to those of collagens in mammalian cartilage, indicating that teleost cartilage could provide biological ingredients for the development of biomaterials to treat cartilage-related illnesses.

Non-enzymatic decomposition of collagen fibers by a biglycan antibody and a plausible mechanism for rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory and destructive joint disorder that affects tens of millions of people worldwide. Normal healthy joints maintain a balance between the synthesis of extracellular matrix (ECM) molecules and the proteolytic degradation of damaged ones. In the case of RA, this balance is shifted toward matrix destruction due to increased production of cleavage enzymes and the presence of (autoimmune) immunoglobulins resulting from an inflammation induced immune response. Herein we demonstrate that a polyclonal antibody against the proteoglycan biglycan (BG) causes tissue destruction that may be analogous to that of RA affected tissues. The effect of the antibody is more potent than harsh chemical and/or enzymatic treatments designed to mimic arthritis-like fibril de-polymerization. In RA cases, the immune response to inflammation causes synovial fibroblasts, monocytes and macrophages to produce cytokines and secrete matrix remodeling enzymes, whereas B cells are stimulated to produce immunoglobulins. The specific antigen that causes the RA immune response has not yet been identified, although possible candidates have been proposed, including collagen types I and II, and proteoglycans (PG's) such as biglycan. We speculate that the initiation of RA associated tissue destruction in vivo may involve a similar non-enzymatic decomposition of collagen fibrils via the immunoglobulins themselves that we observe here ex vivo.

Segregation of type I collagen homo- and heterotrimers in fibrils

Normal type I collagen is a heterotrimer of two alpha1(I) and one alpha2(I) chains, but various genetic and environmental factors result in synthesis of homotrimers that consist of three alpha1(I) chains. The homotrimers completely replace the heterotrimers only in rare recessive disorders. In the general population, they may compose just a small fraction of type I collagen. Nevertheless, they may play a significant role in pathology; for example, synthesis of 10-15% homotrimers due to a polymorphism in the alpha1(I) gene may contribute to osteoporosis. Homotrimer triple helices have different stability and less efficient fibrillogenesis than heterotrimers. Their fibrils have different mechanical properties. However, very little is known about their molecular interactions and fibrillogenesis in mixtures with normal heterotrimers. Here we studied the kinetics and thermodynamics of fibril formation in such mixtures by combining traditional approaches with 3D confocal imaging of fibrils, in which homo- and heterotrimers were labeled with different fluorescent colors. In a mixture, following a temperature jump from 4 to 32 degrees C, we observed a rapid increase in turbidity most likely caused by formation of homotrimer aggregates. The aggregates promoted nucleation of homotrimer fibrils that served as seeds for mixed and heterotrimer fibrils. The separation of colors in confocal images indicated segregation of homo- and heterotrimers at a subfibrillar level throughout the process. The fibril color patterns continued to change slowly after the fibrillogenesis appeared to be complete, due to dissociation and reassociation of the pepsin-treated homo- and heterotrimers, but this remixing did not significantly reduce the segregation even after several days. Independent homo- and heterotrimer solubility measurements in mixtures confirmed that the subfibrillar segregation was an equilibrium property of intermolecular interactions and not just a kinetic phenomenon. We argue that the subfibrillar segregation may exacerbate effects of a small fraction of alpha1(I) homotrimers on formation, properties, and remodeling of collagen fibers.

Changes in thermal stability and microunfolding pattern of collagen helix resulting from the loss of alpha2(I) chain in osteogenesis imperfecta murine

Homozygous mutations resulting in formation of alpha1(I)(3) homotrimers instead of normal type I collagen cause mild to severe osteogenesis imperfecta (OI) in humans and mice. Limited studies of changes in thermal stability of type I homotrimers were reported previously, but the results were not fully consistent. We revisited this question in more detail using purified tendon collagen from wild-type (alpha1(I)(2)alpha2(I) heterotrimers) and oim (alpha1(I)(3)) mice as well as artificial alpha1(I)(3) homotrimers obtained by refolding of rat-tail-tendon collagen. We found that at the same heating rate oim homotrimers completely denature at approximately 2.5deg.C higher temperature than wild-type heterotrimers, as determined by differential scanning calorimetry. At the same, constant temperature, homotrimers denature approximately 100 times slower than heterotrimers, as determined by circular dichroism. Detailed analysis of proteolytic cleavage at different temperatures revealed that microunfolding of oim homotrimers and wild-type heterotrimers occurs at similar rate but within a number of different sites. In particular, the weakest spot on the oim triple helix is located approximately 100 amino acid residues from the C-terminal end within the cyanogen bromide peptide CB6. The same microunfolding site is also present in wild-type collagen, but the weakest spot of the latter is located close to the N-terminal end of CB8. Amino acid analysis and differential gel electrophoresis showed virtually no posttranslational overmodification of oim mouse tendon collagen. Moreover, thermal stability and microunfolding of artificial rat-tail-tendon homotrimers were similar to oim homotrimers. Thus, the observed changes are associated with difference in the amino acid composition of alpha1(I) and alpha2(I) chains rather than posttranslational overmodification.

Osteogenesis imperfecta murine: interaction between type I collagen homotrimers

Types I, II, and III collagens are believed to have evolved from the same homotrimer ancestor and they have substantial sequence homology, but type I molecules are alpha1(I)(2)alpha2(I) heterotrimers, unlike homotrimeric types II and III. It is believed that the alpha2(I) chain first appeared in lower vertebrates and that it plays a particularly important role in bone formation. For instance, spontaneous mutations resulting in non- functional alpha2 chains and formation of type I homotrimers cause severe bone pathology (osteogenesis imperfecta) in humans and in animals. However, the exact role of the alpha2 chain is not known. Here, we report measurements of intermolecular forces between collagen helices in native and reconstituted fibers composed of type I homotrimers, heterotrimers and their mix. For comparison, we report forces between type II homotrimers in reconstituted fibers. In agreement with previous studies, we find that the absence of the alpha2 chain reduces temperature-favored attraction between collagen helices, either because of the difference in amino acid sequence of the alpha1 and alpha2 chains or because of more extensive post-translational modification of homotrimers. We find that forces between helices in fibers from type I (as well as type II) homotrimers are not sensitive to pH between pH 6 and 7.5, in contrast to type I heterotrimers. Apparently, the effect of pH is related to extra histidine residues present on alpha2 chains but not on alpha1 chains. Finally, our measurements indicate that the alpha2 chain is responsible for binding some soluble compound(s), possibly glycosaminoglycans, whose displacement results, e.g., in the loss of tendon crystallinity. The ability of the alpha2 chain to bind non-collagen matrix components may be particularly important for bone matrix formation and mineralization.

Improvement of shark type I collagen with microbial transglutaminase in urea

In the presence of urea, type I collagen could form a gel with crosslinks with microbial transglutaminase (MTGase). Collagen self-assembly was accelerated with the addition of MTGase. The proportion of reconstructed collagen fibrils was raised with the addition of MTGase. MTGase-treated collagen gel remained gelled at high temperatures at which collagen denatured. By treatment with MTGase, collagen could form the gel under impossible condition to collagen self-assembly, and that denaturation temperature was raised.

Structure of a full-length cDNA clone for the pro-alpha1(V/XI) collagen chain of red seabream

The cDNA of type V/XI collagen alpha1 (rsCOL) chain has been isolated from cells established from eyed-period eggs of red seabream, Pagrus major, and sequenced. The amino acid sequence deduced from red seabream alpha1(V/XI) chain resembles that of type XI collagen alpha1 chain. On the other hand, tissue distribution of rsCOL resembles that of type V collagen based on RT-PCR analysis. This is the first report of the cloning of the full-length cDNA of type V/XI collagen alpha1 chain from fish.

Altered collagen structure in mouse tail tendon lacking the alpha 2(I) chain

Type I collagen is the most prevalent member of the fibril forming family of collagens in higher vertebrates and its heterotrimeric form is comprised of two alpha 1(I) chains and one alpha2(I) polypeptide chain. The functional importance of having two distinct chain types in type I collagen is largely undefined. The existence of a mouse model with a Cola-2 gene mutation (termed oim) that results in non-functional pro alpha 2(I) chains presents a unique opportunity to explore changes in collagen structure resulting from the complete (oim/oim mice) and partial (oim/+ mice) loss of functional alpha 2(I) chains. Tail tendon is a tissue with a well-defined, hierarchical organization of type I collagen. X-ray diffraction studies on oim/oim versus control tendons indicate that the total absence of alpha 2(I) chains results in a decrease in the order of axial packing and a loss of crystalline lateral packing. This suggests that the non-equivalence of three chains is an important determinant of lateral interactions between adjacent molecules and may be involved in the long-range axial order in type I collagen-containing tissues. Both homotrimeric and heterotrimeric type I collagen molecules are found in heterozygous oim mice and these appear to be present in the same co-polymeric fibrils, preventing crystalline lateral packing. In addition to these changes at a fibrillar level, the absence of the alpha 2(I) chain results in an increased enzymatic susceptibility at one site. The oim/oim mice are observed to have reduced body size and smaller tendon bundles, which may be a consequence of these molecular and fibrillar changes in collagen. Furthermore, it is likely that a similar alteration in the molecular packing of collagen in bone fibrils contributes to the osteopenia and decreased bone strength in mice with the oim mutation that are also characteristic of human osteogenesis imperfecta.

Chondrogenesis of a non-collagen-based cartilage in the sea lamprey,Petromyzon marinus

Chondrogenesis of the trabeculae, non-collagen-based cartilages in prolarval stages of the sea lamprey, Petromyzon marinus, was examined by light and electron microscopy. Chondrogenesis of the trabecular cartilages in prolarval lampreys commenced with the formation of mesenchymal condensations. Two peaks in mesenchymal cell density occurred, one prior to condensation formation and a second immediately before cartilage differentiation. The possibility of inductive influences by epithelio-mesenchymal interactions on the initiation of chondrogenesis is discussed. Bilateral condensations first appeared by day 17 post fertilization ventromedial to the eyes in a band of tightly packed yolk-laden mesenchymal cells that represent neural crest derived tissue. Cartilage differentiation occurred by day 19 post fertilization and was indicated by the presence of matrix-synthesizing organelles and the first ultrastructural appearance in the extracellular matrix of lamprin, a structural protein unique to lamprey cartilage. Lamprin was initially deposited as discrete 15- to 40-nm globules. Subsequently, lamprin appeared as fibrils aggregated into branching and parallel arrays arranged in pericellular, territorial, and interterritorial zones. Lengthening of the trabecular cartilages was primarily by appositional growth at the rostral end. The timing of the appearance of trabecular cartilages in prolarval stages likely reflects the functional importance of these structures for supporting the brain as the lamprey initiates burrowing behaviour.

Purification and crystallization of 15-lipoxygenase from rabbit reticulocytes

We report a new purification of rabbit reticulocyte 15-lipoxygenase that has resulted in the first crystallization of a mammalian lipoxygenase. The enzyme was purified to homogeneity (greater than 98% pure by SDS-PAGE) using high pressure liquid chromatography on hydrophobic-interaction, hydroxyapatite and cation-exchange columns. Crystals were grown by the vapor diffusion method from concentrated solutions of the protein in sodium phosphate buffer, pH 7.0. The hexagonal, rod-shaped crystals were on average 0.09 mm x 0.09 mm x 0.4 mm, with approximate unit cell dimensions of a = b = 260 A, c = 145 A. The crystals diffract to 5 A resolution.

Characterization of two genetically distinct type I-like collagens from lamprey (Entosphenus japonicus)

1. Type I-like collagens were isolated by limited pepsin digestion from various tissues of lamprey, a member of the cyclostomes. 2. Characterization of these collagens revealed the tissue-specific existence of two genetically distinct molecular species, each possessing the typical heterotrimeric nature of (alpha 1)2 alpha 2; one was designated skin collagen which existed in dermis and the other was designated body collagen which was distributed in muscle, intestine and cartilage. 3. The body collagen resembled invertebrate Type I-like collagens in many respects, whereas the skin collagen had a primordial form of vertebrate Type I collagen.