Human pro alpha 1(I) collagen gene structure reveals evolutionary conservation of a pattern of introns and exons

An Update on the Clinical Efficacy and Safety of Collagen Injectables for Aesthetic and Regenerative Medicine Applications

Soft tissues diseases significantly affect patients quality of life and usually require targeted, costly and sometimes constant interventions. With the average lifetime increase, a proportional increase of age-related soft tissues diseases has been witnessed. Due to this, the last two decades have seen a tremendous demand for minimally invasive one-step resolutive procedures. Intensive scientific and industrial research has led to the recognition of injectable formulations as a new advantageous approach in the management of complex diseases that are challenging to treat with conventional strategies. Among them, collagen-based products are revealed to be one of the most promising among bioactive biomaterials-based formulations. Collagen is the most abundant structural protein of vertebrate connective tissues and, because of its structural and non-structural role, is one of the most widely used multifunctional biomaterials in the health-related sectors, including medical care and cosmetics. Indeed, collagen-based formulations are historically considered as the "gold standard" and from 1981 have been paving the way for the development of a new generation of fillers. A huge number of collagen-based injectable products have been approved worldwide for clinical use and have routinely been introduced in many clinical settings for both aesthetic and regenerative surgery. In this context, this review article aims to be an update on the clinical outcomes of approved collagen-based injectables for both aesthetic and regenerative medicine of the last 20 years with an in-depth focus on their safety and effectiveness for the treatment of diseases of the integumental, gastrointestinal, musculoskeletal, and urogenital apparatus.

Novel Deep Eutectic Solvent-Based Protein Extraction Method for Pottery Residues and Archeological Implications

Proteomic analysis of absorbed residues is increasingly used to identify the foodstuffs processed in ancient ceramic vessels, but detailed methodological investigations in this field remain rare. Here, we present three interlinked methodological developments with important consequences in paleoproteomics: the comparative absorption and identification of various food proteins, the application of a deep eutectic solvent (DES) for extracting ceramic-bound proteins, and the role of database choice in taxonomic identification. Our experiments with modern and ethnoarcheological ceramics show that DES is generally more effective at extracting ceramic-bound proteins than guanidine hydrochloride (GuHCl), and cereal proteins are absorbed and subsequently extracted and identifiedat least as readily as meat proteins. We also highlight some of the challenges in cross-species proteomics, whereby species that are less well-represented in databases can be attributed an incorrect species-level taxonomic assignment due to interspecies similarities in protein sequence. This is particularly problematic in potentially mixed samples such as cooking-generated organic residues deposited in pottery. Our work demonstrates possible proteomic separation of fishes and birds, the latter of which have so far eluded detection through lipidomic analyses of organic residue deposits in pottery, which has important implications for tracking the exploitation of avian species in various ancient communities around the globe.

An Overview of the Use of Equine Collagen as Emerging Material for Biomedical Applications

Type I collagen has always aroused great interest in the field of life-science and bioengineering, thanks to its favorable structural properties and bioactivity. For this reason, in the last five decades it has been widely studied and employed as biomaterial for the manufacture of implantable medical devices. Commonly used sources of collagen are represented by bovine and swine but their applications are limited because of the zoonosis transmission risks, the immune response and the religious constrains. Thus, type-I collagen isolated from horse tendon has recently gained increasing interest as an attractive alternative, so that, although bovine and porcine derived collagens still remain the most common ones, more and more companies started to bring to market a various range of equine collagen-based products. In this context, this work aims to overview the properties of equine collagen making it particularly appealing in medicine, cosmetics and pharmaceuticals, as well as its main biomedical applications and the currently approved equine collagen-based medical devices, focusing on experimental studies and clinical trials of the last 15 years. To the best of our knowledge, this is the first review focusing on the use of equine collagen, as well as on equine collagen-based marketed products for healthcare.

Synthesis and incorporation of an advanced lipid peroxidation end-product building block into collagen mimetic peptides

Advanced lipid peroxidation end-products (ALEs) accumulate with ageing and oxidative stress-related diseases. Despite their potential therapeutic value, there are no suitably protected ALE building blocks reported in the literature to enable their site-specific incorporation into synthetic peptides. The synthesis of an Fmoc-protected ALE building block, N^∈-(3-methylpyridinium)lysine (MP-lysine) and its incorporation into collagen model peptides is reported.

Physicochemical studies on the copper(ii) binding by glycated collagen telopeptides

The strong interaction between advanced glycation end-products and Cu(ii) ions has been revealed using site-specifically glycated collagenous peptides.

Site-specific cross-linking of collagen peptides by lysyl advanced glycation endproducts

Cross-linking lysyl AGEs were synthesised and incorporated into two types of collagen peptides and now enable detailed analysis of the effects these cross-links have on biological systems.

Structural and functional studies on the interstitial collagen genes

An understanding of the molecular mechanisms which control expression of the type I and III collagen genes may provide a rational basis for the design of more effective therapeutic approaches to fibrotic diseases. The structure of the interstitial collagen genes is reviewed and potential sites which could control their expression are examined. One approach to the study of the regulation of these genes consists in DNA-mediated gene transfection experiments and is discussed in this paper.

Factors involved in the regulation of type I collagen gene expression: implication in fibrosis

Type I collagen, the major component of extracellular matrix in skin and other tissues, is a heterotrimer of two alpha1 and one alpha2 collagen polypeptides. The synthesis of both chains is highly regulated by different cytokines at the transcriptional level. Excessive synthesis and deposition of collagen in the dermal region causes thick and hard skin, a clinical manifestation of scleroderma. To better understand the causes of scleroderma or other tissue fibrosis, it is very important to investigate the molecular mechanisms that cause upregulation of the Type I collagen synthesis in these tissues. Several cis-acting regulatory elements and trans-acting protein factors, which are involved in basal as well as cytokine-modulated Type I collagen gene expression, have been identified and characterized. Hypertranscription of Type I collagen in scleroderma skin fibroblasts may be due to abnormal activities of different positive or negative transcription factors in response to different abnormally induced signaling pathways. In this review, I discuss the present day understanding about the involvement of different factors in the regulation of basal as well as cytokine-modulated Type I collagen gene expression and its implication in scleroderma research.

Sequence of normal canine COL1A1 cDNA and identification of a heterozygous alpha1(I) collagen Gly208Ala mutation in a severe case of canine osteogenesis imperfecta

The sequence of canine COL1A1 cDNA was determined from four overlapping COL1A1 RT-PCR products generated from canine fibroblast RNA. In the translated region, nucleotide identity between canine and human COL1A1 cDNA was 93.2%, although the canine sequence lacked nucleotides 204 to 215 in the region coding for the N-propeptide. Amino acid identity was 97.7%. Total RNA and type I collagen were collected from cultured skin fibroblasts of a 12-week-old male golden retriever with pathologic fractures suggestive of osteogenesis imperfecta (OI) and dentinogenesis imperfecta. Sequential, overlapping approximately 1,000-bp fragments of COL1A1 and COL1A2 cDNA were each amplified by RT-PCR using primers containing 5' T7 polymerase sites. These PCR products were transcribed with T7 RNA polymerase, hybridized into RNA duplexes, and cleaved at mismatch sites with RNase. The proband had an unique cleavage pattern for the fragment of COL1A1 mRNA spanning nucleotides 709 to 1,531. Sequence analysis identified a G to C point mutation for nucleotide 1,276, predicting a codon change from glycine (GGA) to alanine (GCA) for amino acid 208. This change disrupts the normal Gly-X-Y pattern of the collagen triple helix. Restriction enzyme digestion of the RT-PCR product was consistent with a heterozygous COL1A1 mutation. Type I collagen was labeled with 3H-proline, salt precipitated, and analyzed by SDS-PAGE. Pepsin digested alpha chains were over-hydroxylated, and procollagen processing was delayed. Thus, canine and human OI appear homologous in terms of clinical presentation, etiology, and pathogenesis.

Type IIA procollagen amino propeptide is localized in human embryonic tissues

Type II procollagen is synthesized in two forms generated by the alternative splicing of its precursor mRNA. The alternatively spliced domain, exon 2, encodes the 69-amino-acid cysteine-rich region of the NH2 propeptide. Studies of mRNA expression have shown that the longer form, designated Type IIA procollagen, is synthesized by chondroprogenitor cells and various noncartilaginous tissues. The shorter form, Type IIB procollagen, is synthesized by differentiated chondrocytes. As the initial step in our investigations of the function of the Type IIA procollagen, the protein domain corresponding to exon 2 was created as a recombinant fusion protein and used to raise antibodies in rabbits. The resulting antiserum was specific for Type IIA procollagen NH2 propeptide as shown by ELISA, Western blotting, and immunofluorescent co-localization with the triple-helical domain of Type II collagen. Type IIA procollagen was identified in tissue culture medium of 54-day human fetal ribs. Confocal microscopy was used to localize the Type IIA NH2 propeptide in Day 50 and 53 human embryos. In the digital rays of the developing hand, where only Type IIA procollagen mRNA was detected, Type IIA procollagen NH2 propeptide was observed in the extracellular matrix. The presence of Type IIA procollagen NH2 propeptide was observed in the cartilage of the developing long bones of the lower arm and vertebral bodies even though these tissues synthesize Type IIB mRNA at this developmental stage. Type IIA procollagen NH2 propeptide was localized in the developing trachea, a cartilage that does not undergo endochondral bone formation. Type IIA NH2 propeptide was also localized in noncartilaginous tissues known to synthesize Type IIA mRNA, such as the intervertebral area, perichondrium, notochordal sheath, and neuroepithelium of the otic vesicle. In most tissues, co-localization with antiserum against the triple-helical domain of Type II collagen was observed. Positive immunoreactivity with the Type IIA NH2 propeptide antiserum indicates, for the first time, that this propeptide is present in the tissue. Co-localization of NH2 propeptide antibodies with the triple-helical domain of the collagen molecule suggests that Type IIA procollagen is intact in the extracellular matrix of these tissues. Taken together, these results strongly suggest that around cells that synthesize Type IIA procollagen mRNA, Type IIA procollagen NH2 propeptide is secreted and deposited into the extracellular matrix. In light of these results, we predict that Type IIA procollagen plays a role in differentiation of tissues that augments its purely architectural function.

Structure of the human type XIX collagen (COL19A1) gene, which suggests it has arisen from an ancestor gene of the FACIT family

Type XIX collagen is a newly discovered member of the FACIT (fibril-associated collagens with interrupted triple helices) group of extracellular matrix proteins. Based on the primary structure, type XIX collagen is thought to act as a cross-bridge between fibrils and other extracellular matrix molecules. Here we describe the complete exon/intron organization of COL19A1 and show that it contains 51 exons, spanning more than 250 kb of genomic DNA. The comparison of exon structures of COL19A1 and other FACIT family genes revealed several similarities among these genes. The structure of exons encoding the noncollagenous (NC) 1-collagenous (COL) 1-NC 2-COL 2-NC 3-COL 3-NC 4 domain of the alpha1(XIX) chain is similar to that of the NC 1-COL 1-NC 2-COL 3-NC 3 domain of the alpha2(IX) chain except for the NC 3 domain of alpha1(XIX). The exons encoding the COL 5-NC 6 domain of alpha1(XIX) are also similar to those of the COL 3-NC 4 domain of alpha1(IX) chain. Previously, COL19A1 was mapped to human chromosome 6q12-q14, where COL9A1 is also located. Likewise, the present work shows that the mouse Col19a1 gene is located on mouse chromosome 1, region A3, where Col9a1 has also been mapped. Taken together, the data suggest that COL19A1 and COL9A1 (Col19a1 and Col9a1) were duplicated from the same ancestor gene of the FACIT family. Three CA repeat markers with high heterozygosity were found in COL19A1. These markers may be useful for linkage analysis of age-related inheritable diseases involved in eyes and/or brain.

Collagen II containing a Cys substitution for arg-alpha1-519. Homotrimeric monomers containing the mutation do not assemble into fibrils but alter the self-assembly of the normal protein

A recombinant system was used to prepare human type II procollagen containing the substitution of Cys for Arg at alpha1-519 found in three unrelated families with early onset generalized osteoarthritis together with features of a mild chondrodysplasia probably best classified as spondyloepiphyseal dysplasia. In contrast to mutated procollagens containing Cys substitutions for obligatory Gly residues, the Cys substitution at alpha1-519 did not generate any intramolecular disulfide bonds. The results were consistent with computer modeling experiments that demonstrated that the alpha carbon distances were shorter with Cys substitutions for obligatory Gly residues than with Cys substitutions in the Y position residues in repeating -Gly-X-Y- sequences of the collagen triple helix. The mutated collagen did not assemble into fibrils under conditions in which the normal monomers polymerized. However, the presence of the mutated monomer in mixtures with normal collagen II increased the lag time for fibril assembly and altered the morphology of the fibrils formed.

Isolation of 115 human chromosome 8-specific expressed-sequence tags by exon amplification

Exon-amplification experiments were undertaken to isolate potentially transcribable sequences from cosmid clones that previously had been mapped to subchromosomal bands of human chromosome 8 by fluorescence in situ hybridization. From 253 cosmids subjected to this procedure so far, we isolated 169 fragments and confirmed that they had been derived from the original cosmid clones. Among them, 38 revealed homology to repetitive DNA sequences such as Alu and L1 elements. The other 131 were unique sequences, but of these only 115 contained discernible open reading frames. Among these 115 sequences, 15 were identical to parts of six known genes listed in the public database. On the basis of information derived from mapping the original cosmid clones, we were able to localize two of these known genes, zinc finger protein 7 and heat shock transcription factor 1, to 8q24.3. Furthermore, we have proven that some of these clones are parts of the transcribed products by an exon connection method or by isolation of a novel cDNA that is homologous to murine clathrin-associated protein. The expressed-sequence tags isolated here will be useful resources for a transcriptional map of chromosome 8 and for isolation of new genes.

Naturally occurring antisense transcripts are present in chick embryo chondrocytes simultaneously with the down-regulation of the alpha 1 (I) collagen gene

It has previously been shown that very low steady state levels of alpha 1 (I) collagen mRNA are present in chick embryo sternal chondrocytes (Askew, G. R., Wang, S., and Lukens, L. N. (1991) J. Biol. Chem. 266, 16834-16841), yet nuclear run-on experiments with double-stranded cDNA probes indicated a high transcription rate at this locus. These findings were investigated in this study using single-stranded probes, where nuclear run-on experiments showed that antisense transcription of the alpha 1 (I) collagen gene was occurring in chondrocytes, while sense strand transcription was down-regulated. Treatment of these chondrocytes with 5-bromo-2'-deoxyuridine (BrdU), which causes the cells to resemble their mesenchymal precursors, resulted in an antiparallel situation, where antisense transcription was lost, and instead, sense strand transcription was acquired, suggesting that the reverse switch from sense to antisense transcription occurs during chondrogenesis. Very large (> 10 kilobases) and heterogeneous antisense transcripts of moderate stability were shown to span both ends of the gene in chondrocytes, while their absence was shown in BrdU-treated chondrocytes, chick embryo fibroblasts, and a variety of other tissues. The function of these antisense transcripts is so far unknown, but their unusual chondrocyte-specific appearance, concurrent with little or no sense strand transcription, suggests a possible functional role in the down-regulation of the alpha 1 (I) collagen gene.

Dorsal-ventral patterning of the Drosophila embryo depends on a putative negative growth factor encoded by the short gastrulation gene

Pattern formation in the dorsal region of the Drosophila embryo depends on the activity of a small group of zygotically acting genes. dpp, a key gene in this group, encodes a TGF-beta-like product (Dpp) that has been proposed to function as a morphogen with peak levels of Dpp-specifying amnioserosa, the dorsal-most cell type, and lower Dpp levels specifying dorsal ectoderm. The short gastrulation gene also contributes to patterning the dorsal region, but unlike the other genes involved in this process, sog activity is only required in ventral cells. Genetic evidence indicates that sog functions to antagonize dpp activity. In this report we present further phenotypic characterization of sog mutant embryos in dorsal and lateral regions and describe the cloning of the sog locus. sog is expressed in a broad lateral stripe of cells that abuts the dorsal territory of dpp-expressing cells. sog is predicted to encode a protein with an internal signal sequence and a large extracellular domain containing four repeats of a novel motif defined by the spacing of 10 cysteine residues that is distantly related to domains present in thrombospondin and procollagen. We propose that one or more of these cysteine repeats can be liberated by proteolytic cleavage of the primary Sog protein. These putative soluble Sog peptides may then diffuse into the dorsal region to antagonize the activity of Dpp, leading to the subdivision of the dorsal territory into amnioserosa and dorsal ectoderm.

Genomic sequence of mouse COL1A1 encoding the collagen propeptides

The nucleotide sequences of the mouse pro alpha 1(I) gene regions coding for the N- and C-propeptides is reported. The exon-intron structure was highly homologous to human COL1A1 and the deduced amino acid sequences of the N- and C-propeptides showed 67% and 91% identity with the human sequence. This gene sequence information will allow the production of specific gene mutations by site-directed mutagenesis to study the structure and function of these important propeptide domains.

Extracellular matrix formation by epithelial cells from human polycystic kidney cysts in culture

Cells from the cysts of patients with autosomal dominant polycystic kidney disease (PKD) were grown in vitro under standard conditions without the aid of collagen-pretreated surfaces, and both the synthesis and composition of the extracellular matrix were investigated. At confluence, PKD cells presented the typical features of epithelial cells, but showed a different collagen composition from fibroblasts. Compared with normal tubular epithelia (NTE), PKD monolayers produced an excess of extracellular matrix, which accounted for 30% of the total incorporation of [3H] proline, although this value was considerably lower (by a factor of 10) in the case of NTE. Immunohistochemical and electrophoretic techniques revealed a complex collagen composition in the extracellular matrix which included [alpha (III)]3 and collagen IV. However, part of the collagen components remained unidentified in spite of the fact that they exhibited a typical M(r) of alpha 1(I) and alpha 2(I) in the presence of urea. Immunoprecipitation with monospecific antibodies and Northern blotting with specific probes failed to recognize alpha 1(I) and alpha 2(I), but demonstrated their presence in fibroblasts. Purification and cyanogen bromide digestion demonstrated a strong interhomology in fingerprint peptide composition among the uncharacterized collagens synthesized by PKD cells, thus suggesting a common identity. These observations document a markedly augmented production of extracellular matrix by PKD cultured cells in vitro, and show the presence of collagens which do not share homologies with the major collagen molecules. A better characterization of extracellular matrix composition is central to any comprehension of the cytogenetic mechanisms in vivo.

Peptides derived from two separate domains of the matrix protein thrombospondin-1 have anti-angiogenic activity

Thrombospondin-1 (TSP1) is a large modular matrix protein containing three identical disulfide-linked 180-kD chains that inhibits neovascularization in vivo (Good et al., 1990). To determine which of the structural motifs present in the 180-kD TSP1 polypeptide mediate the anti-angiogenic activity, a series of protease-generated fragments were tested using several in vitro and in vivo assays that reflect angiogenic activity. The majority of the anti-angiogenic activity of TSP1 resides in the central 70-kD stalk region which alone could block neovascularization induced by bFGF in the rat cornea in vivo and inhibit both migration in a modified Boyden chamber and [3H]thymidine incorporation stimulated by bFGF in cultured capillary endothelial cells. Although TSP1 has been shown to bind active TGF beta 1, this cytokine could not account for the inhibitory effects of the stalk region of TSP1 on cultured endothelial cells. Peptides and truncated molecules were used to further localize inhibitory activity to two domains of the central stalk, the procollagen homology region and the properdin-like type 1 repeats. Trimeric recombinant TSP1 containing NH2-terminal sequences truncated after the procollagen-like module inhibited endothelial cell migration in vitro and corneal neovascularization in vivo whereas trimeric molecules truncated before this domain were inactive as was the NH2-terminal heparin-binding domain that is present in both recombinant molecules. A series of peptides from the procollagen-like region, the smallest of which consisted of residues 303-309 of TSP1, inhibited angiogenesis in vivo in the rat cornea and the migration of endothelial cells in vitro. A 19-residue peptide containing these sequences blocked vessel formation in the granulation tissue invading a polyvinyl sponge implanted into the mouse. Nineteen residue peptides derived from two of the three type 1 repeats present in the intact TSP1 molecule blocked neovascularization in vivo in the rat cornea and inhibited the migration of cultured endothelial cells with ED50's of 0.6-7 microM. One of these peptides, containing residues 481-499 of TSP1, also inhibited vessel formation in granulation tissue invading sponges in vivo. These results suggest that the large TSP1 molecule employs at least two different structural domains and perhaps two different mechanisms to accomplish a single physiological function, the inhibition of neovascularization. The definition of short peptides from each of these domains that are able to block the angiogenic process may be of use in designing targeted inhibitors of the pathological neovascularization that underlies many diseases.

Biosynthesis of frog skin mucins: cysteine-rich shuffled modules, polydispersities and genetic polymorphism

1. Frog integumentary mucins (FIM-A.1, FIM-B.1 and FIM-C.1) consist of typical threonine-rich highly O-glycosylated (semi)repetitive domains, and cysteine-rich modules, i.e. the P-domain, the short consensus repeat and a region with high similarity to the C-terminal end of von Willebrand factor (designated here CC29-motif). 2. These modules are thought to be involved in protein-protein interactions and they have been observed in a variety of extracellular proteins. In FIMs, these modules may be involved in oligomerization processes leading to an entangled mucin network. 3. Polydispersities have been detected in FIM-B.1 and FIM-C.1 within single individuals. Multiple transcripts are probably generated by alternative splicing of a huge array of different (semi)repetitive cassettes encoding the threonine-rich domains. 4. Furthermore, genetic polymorphism is observed between different individuals, probably due to allelic variations in the number of (semi)repetitive cassettes.

Fetal antigen 2: an amniotic protein identified as the aminopropeptide of the alpha 1 chain of human procollagen type I

Fetal antigen (FA2) was purified from second trimester human amniotic fluid by immunospecific chromatography, gel filtration and reversed-phase chromatography. Gel filtration revealed two molecular forms of FA2 eluting at volumes corresponding to an M(r) of approximately 100 kDa and 30 kDa. SDS-PAGE analysis gave an M(r) = 27 kDa under reducing and non-reducing conditions for both forms, whereas the exact M(r) determined by mass spectrometry was 14,343 +/- 3 Da. FA2 was N-terminally blocked and after tryptic digestion the amino acid composition and sequences of the peptides showed identity with the aminopropeptide of the alpha 1 chain of human procollagen type I as determined by nucleotide sequences. After oxidative procedures normally employed for radio-iodination (iodogen and chloramine-T), FA2 lost its immunoreactivity. An antigen which cross-reacted with polyclonal rabbit anti-human FA2 was demonstrated in fetal calf serum. Gel filtration with analysis of fractions by inhibition ELISA showed that the bovine homologue was present in the same molecular forms as those in human amniotic fluid, and immunohistochemical analysis with anti-human FA2 showed that its distribution in bovine skin was identical to that of FA2 in human skin. FA2 is a circulating form of the aminopropeptide of the alpha 1 chain of procollagen type I, and this is the first description of its isolation and structural characterization in humans.

A novel transforming protein (SHC) with an SH2 domain is implicated in mitogenic signal transduction

A new SH2-containing sequence, SHC, was isolated by screening cDNA libraries with SH2 representative DNA probes. The SHC cDNA is predicted to encode overlapping proteins of 46.8 and 51.7 kd that contain a single C-terminal SH2 domain, and an adjacent glycine/proline-rich motif with regions of homology with the alpha 1 chain of collagen, but no identifiable catalytic domain. Anti-SHC antibodies recognized three proteins of 46, 52, and 66 kd in a wide range of mammalian cell lines. These SHC proteins complexed with and were phosphorylated by activated epidermal growth factor receptor. The physical association of SHC proteins with activated receptors was recreated in vitro by using a bacterially expressed SHC SH2 domain. NIH 3T3 mouse fibroblasts that constitutively overexpressed SHC acquired a transformed phenotype in culture and formed tumors in nude mice. These results suggest that the SHC gene products couple activated growth factor receptors to a signaling pathway that regulates the proliferation of mammalian cells.

Structural comparison of the chicken genes for alpha 1(VI) and alpha 2(VI) collagen

The chicken alpha 1(VI) polypeptide is encoded by a single gene spanning 21 kbp of genomic DNA. This gene is composed of 34 exons and 33 introns. Its structure is closely related to that of the alpha 2(VI) collagen gene, suggesting that the two genes evolved by gene duplication. Both genes contain 19 exons coding for the triple-helical domain. These exons are multiples of 9 bp (27, 36, 45, 54, 63 and 90 bp) and encode an integral number of collagenous Gly-Xaa-Yaa triplets. Since there is no convincing correlation to a building block of 54 bp, it is unlikely that type VI collagen has evolved from a primordial 54-bp module as suggested for all fibrillar collagens.

Antibodies to dietary antigens in rheumatoid arthritis--possible molecular mimicry mechanism

Antibodies in serum from some patients with rheumatoid arthritis, recognize bovine albumin present in the milk, as determined by immunoprecipitation analysis from 125I-milk extracts. This antigen was also immunoprecipitated from bovine sera. These and ELISA studies showed that BSA is preferentially recognized over other proteins present in the milk. Panel studies demonstrated that although the average reactivity for BSA was high, only one third of the sera tested displayed a reactivity above the mean. The possibility of a molecular mimicry mechanism in RA between this food antigen and other human antigens was investigated. A sequence alignment analysis showed that the residues 141-157 of bovine albumin significantly differed from the corresponding fragment of human albumin, but were highly homologous with human collagen type I, C1q and vitamin D binding protein. In support of the immunogenicity of this fragment, we found that representative RA sera displayed a specific reactivity for a synthetic peptide containing the BSA residues responsible for the homology. Furthermore, most of the epitopes recognized on BSA by the RA sera seem to be conformationally dependent as heat denaturation or reduction followed by alkylation lead to a diminished recognition.

Completion of the last half of the structure of the human gene for the Pro alpha 1 (I) chain of type I procollagen (COL1A1)

The nucleotide sequences of the 3'-half of the human gene for the pro alpha(I) chain of type I procollagen (COL1A1) is presented. The results provide the nucleotide sequences for 26 introns not previously analyzed. The sequences that are presented, together with those previously published, make it possible to design primers for the polymerase chain reaction for amplifying and sequencing the gene. The availability of such primers will greatly facilitate the current search for mutations that can cause common and rare diseases of connective tissue.

Transforming growth factor-beta up-regulates type VII collagen gene expression in normal and transformed epidermal keratinocytes in culture

Transforming growth factor-betas (TGF-betas) have been shown to enhance the expression of extracellular matrix genes, including several collagens. In this study, the effects of TGF-beta 1 and TGF-beta 2 on the expression of the gene for type VII collagen, the major component of anchoring fibrils, in human epidermal cell cultures were examined. Incubation of human epidermal keratinocytes or oral epidermoid carcinoma KB cells with TGF-beta 1 or TGF-beta 2 markedly (up to 6.3-fold) elevated the alpha 1(VII) collagen mRNA levels. This elevation was accompanied by enhanced synthesis of type VII collagen, as demonstrated by indirect immunofluorescence with a monoclonal antibody. The results indicate that TGF-beta 1 and TGF-beta 2 have similar biological activities with respect to enhanced type VII collagen gene expression.

Exons--original building blocks of proteins?

In a recent paper, Walter Gilbert's group has estimated the number of original exons from which all extant proteins might have been constructed. The approach used is subjected to a critical analysis here. It is shown that there are flawed assumptions about both the mechanism and generality of exon-shuffling and in the sequence comparison procedures employed, the latter failing to distinguish chance similarity from similarity due to common ancestry. These methodological errors lead to the omission of many known cases of exon-shuffling and the inclusion of others which may not be genuine. In consequence, the analysis from the Gilbert group cannot give a reliable estimate of those modules that actually participated in exon-shuffling and provides no information on the number of protein archetypes that did not participate in these processes.

Genomic organization of the human procollagen alpha 1(II) collagen gene

The nucleotide sequence of the human procollagen alpha 1(II) collagen gene extending from within the first intron through exon 15, and part of the 15th intron has been determined. This sequence analysis (7056 bases) identifies the intron/exon organization of the region of this gene encoding the N-propeptide and part of the triple-helical domain. Structural comparison of this with the genes of other human fibrillar collagens shows considerable diversity in terms of size and number of introns and exons that encodes the N-propeptide domain. Although the genomic structure of the human procollagen alpha 1(II) gene is quite different from the rat procollagen alpha 1(II) gene, the nucleotide coding sequences are 89% identical.

How big is the universe of exons?

If genes have been assembled from exon subunits, the frequency with which exons are reused leads to an estimate of the size of the underlying exon universe. An exon database was constructed from available protein sequences, and homologous exons were identified on the basis of amino acid identity; statistically significant matches were determined by Monte Carlo methods. It is estimated that only 1000 to 7000 exons were needed to construct all proteins.