Construction of a recombinant bacterial plasmid containing a chick pro-alpha2 collagen gene sequence

Fibrous proteins: At the crossroads of genetic engineering and biotechnological applications

Fibrous proteins, such as silk, elastin and collagen are finding broad impact in biomaterial systems for a range of biomedical and industrial applications. Some of the key advantages of biosynthetic fibrous proteins compared to synthetic polymers include the tailorability of sequence, protein size, degradation pattern, and mechanical properties. Recombinant DNA production and precise control over genetic sequence of these proteins allows expansion and fine tuning of material properties to meet the needs for specific applications. We review current approaches in the design, cloning, and expression of fibrous proteins, with a focus on strategies utilized to meet the challenges of repetitive fibrous protein production. We discuss recent advances in understanding the fundamental basis of structure-function relationships and the designs that foster fibrous protein self-assembly towards predictable architectures and properties for a range of applications. We highlight the potential of functionalization through genetic engineering to design fibrous protein systems for biotechnological and biomedical applications.

Alterations of collagen mRNA expression during retinoic acid induced chondrocyte modulation: absence of untranslated alpha 1(I) mRNA in hyaline chondrocytes

Retinoic acid (RA) has been shown to rapidly modulate the collagen expression pattern of chondrocytes in vitro at doses of 1-10 microM. Embryonic chicken sternal chondrocytes stop synthesizing the cartilage-specific type II collagen within 2-4 days of RA treatment and turn on the synthesis of types I and III collagen and fibronectin. While suppression of type II collagen synthesis and onset of type III collagen and fibronectin synthesis have been shown to be regulated at the transcriptional level, conflicting data are available on a possible post-translational regulation of alpha 1(I) collagen gene expression. In this study we demonstrate by comparing a commonly used alpha 1(I) cDNA probe from the 3' end of the alpha 1(I) mRNA with a newly prepared alpha 1(I) cDNA probe from the 5' end (p1E1) that--in contrast to previous reports--chicken sternal chondrocytes do not contain untranslated alpha 1(I) mRNA which may become translatable after RA treatment. By in situ hybridization we show the absence of cytoplasmic alpha 1(I) mRNA from chondrocytes and its presence in the perichondrium of sternal cartilage. Perichondral cells might have contaminated sternal chondrocyte preparations, explaining low levels of alpha 1(I) mRNA seen by Northern hybridization and RNase protection assays of chicken sternal cartilage mRNA even with the p1E1 probe. We show by Northern hybridization and metabolic labeling with 3H-proline followed by SDS-gel electrophoresis that retinoic acid at 3 microM suppresses type II, IX, and X collagen gene expression within 2 days both at the mRNA and protein level and induces the onset of alpha 1(I), alpha 2(I), and alpha 1(III) expression within 3 days. No expression of CRABP, the cellular retinoic acid binding protein, was seen in RA-treated or control chondrocytes, indicating that CRABP protein is not involved in the RA-induced modulation of the chondrocytes.

Complete cDNA sequence of chicken vigilin, a novel protein with amplified and evolutionary conserved domains

The complete cDNA (4375 bp), coding for a new protein called vigilin, was isolated from chicken chondrocytes. The cDNA shows an open reading frame of 1270 amino acids which are organized in 14 tandemly repeated homologous domains. Each domain consists of two subdomains, one with a conserved sequence motif of 35 amino acids (subdomain A) and another one with a presumptive alpha-helical structure of 21-33 amino acids (subdomain B). 149 amino acids at the N-terminus and 71 amino acids at the C-terminus of vigilin do not show the characteristic domain structure. No sequence characteristic of a signal peptide has been found, which argues for an intracellular localisation of vigilin. Vigilin is highly expressed in freshly isolated chicken chondrocytes but little in chondrocytes after prolonged time in culture. Vigilin mRNA exists in two size species, 4.4 kb and 6.5 kb in length due to the usage of different polyadenylation sites. Comparison of the vigilin sequence with data bases showed a remarkable similarity to protein HX from Saccharomyces cerevisiae [Delahodde, A., Becam, A. M., Perea, J. & Jacq, C. (1986) Nucleic Acids Res. 14, 9213-9214]. The yeast protein consists of eight homologous domains with 11 conserved amino acid residues within a set of 35 amino acids. The N-terminal and C-terminal regions of vigilin and protein HX do not reveal any sequence similarity. These results, together with the demonstration of the characteristic vigilin sequence motif in a human cDNA clone, suggest that the repeats represent evolutionary conserved autonomous domains within a family of proteins found in yeast, chicken and man.

Human and chick alpha 2(I) collagen mRNA: comparison of the 5' end in osteoblasts and fibroblasts

Type I collagen, a heterotrimer of two alpha 1(I) chains and one alpha 2(I) chain, is the major structural protein of bone, skin, and tendon. The collagen of patients with bone diseases has been studied in skin fibroblasts instead of osteoblasts because the genes for type I collagen are single-copy genes. While these studies should detect structural changes in the gene, they might fail to detect defects in processes which are dependent on tissue-specific expression. The studies reported here sought to determine whether the expression of type I collagen in skin and bone was characterized by the use of alternate promoters or alternative splicing in the N-propeptide region. Primer extension and nuclease S1 protection experiments were used to analyze the structure of the alpha 2(I) mRNA from the 5' end of the gene through the N-telopeptide coding region (exons 1-6) in human and chick osteoblasts and fibroblasts. The protection and primer extension experiments using human and chick mRNA demonstrated identical routes of splicing in skin and bone at the first five splice junctions. These studies provide reassurance that information obtained from the study of type I collagen in fibroblasts may be extrapolated to bone.

Regulation of type I collagen synthesis. Total pro alpha 1(I) and pro alpha 2(I) mRNAs are maintained in a 2:1 ratio under varying rates of collagen synthesis

The type I collagen molecule contains two alpha 1(I) chains and one alpha 2(I) chain. Previous investigations, using embryonic chick calvaria, have indicated that the two chains are synthesized in a 2:1 ratio which is controlled at a pretranslational level, since the cells contain twice as much translatable pro alpha 1(I) mRNA as pro alpha 2(I) mRNA. The present report describes hybridization analyses of the cellular levels of total cellular RNAs coding for the pro alpha 1(I) and pro alpha 2(I) chains, using as probes two cloned cDNAs complementary to chick pro alpha 1(I) and pro alpha 2(I) mRNA, respectively. Total cellular RNA was extracted from embryonic chick calvaria, pro alpha 1(I) and pro alpha 2(I) RNA sequences were quantified by Northern hybridization using conditions ensuring that hybridization efficiency and specific radioactivity were the same for the two probes. Similar analyses were carried out on RNA extracted from calvaria with different levels of collagen synthesis after culture in the presence or absence of ascorbic acid. The results for all samples analyzed indicate that total cellular pro alpha 1(I) and pro alpha 2(I) mRNAs are present in a 2:1 ratio which is maintained even during variations in collagen synthesis rate. There is no evidence for regulation mediated by different rates of processing of mRNA precursors, although preferential degradation of the pro alpha 2(I) gene transcript cannot be excluded. Thus, the synthesis of type I procollagen chains is presumably coordinated by transcriptional control.

Malignant transformation and tumor promoter treatment increase levels of a transcript for a secreted glycoprotein

The major excreted protein of transformed mouse fibroblasts, a secreted, mannose 6-phosphate-containing glycoprotein, is induced in nontransformed cells by a variety of transforming agents, by phorbol esters, and by platelet-derived growth factor. We report here the molecular cloning of the cDNA encoding this protein and demonstrate that its induction is a consequence of enhanced mRNA levels for major excreted protein in both tetradecanoyl phorbol acetate-treated 3T3 cells and 3T3 cells transformed by a variety of retroviruses or retroviral oncogenes. These results indicate that tumor promoters and retroviral transformation might share a common pathway of action in cultured cells and that major excreted protein is a molecular marker for the growth response of cells to these agents.

Regulation of a collagen gene promoter by the product of viral mos oncogene

Oncogenic transformation of cells produces important changes in the biosynthetic pattern of certain cellular proteins. For example, the synthesis of type I collagen in transformed fibroblasts is severely reduced as a result of changes in transcription. Here we report the results of DNA-mediated transfection experiments using recombinant plasmids in which the promoter region of the alpha 2(I) collagen gene is fused to an easily recognizable marker gene, and cell lines expressing the marker gene are isolated. Our data show that the expression of the marker gene fused to the cloned alpha 2(I) collagen promoter is strongly inhibited by v-mos transformation, suggesting that a common mechanism inhibits both the transfected and endogeneous alpha 2(I) collagen promoters.

Malignant transformation and tumor promoter treatment increase levels of a transcript for a secreted glycoprotein

The major excreted protein of transformed mouse fibroblasts, a secreted, mannose 6-phosphate-containing glycoprotein, is induced in nontransformed cells by a variety of transforming agents, by phorbol esters, and by platelet-derived growth factor. We report here the molecular cloning of the cDNA encoding this protein and demonstrate that its induction is a consequence of enhanced mRNA levels for major excreted protein in both tetradecanoyl phorbol acetate-treated 3T3 cells and 3T3 cells transformed by a variety of retroviruses or retroviral oncogenes. These results indicate that tumor promoters and retroviral transformation might share a common pathway of action in cultured cells and that major excreted protein is a molecular marker for the growth response of cells to these agents.

Isolation of cDNA and genomic DNA clones encoding type II collagen

A cDNA library constructed from total chick embryo RNA was screened with an enriched fraction of type II collagen mRNA. Two overlapping cDNA clones were characterized and shown to encode the COOH propeptide of type II collagen. In addition, a type II collagen clone was isolated from a Charon 4A library of chick genomic fragments. Definitive identification of the clones was based on DNA sequence analysis. The 3' end of the type II collagen gene appears to be similar to that of other interstitial collagen genes. Northern hybridization data indicates that there is a marked decrease in type II collagen mRNA levels in chondrocytes treated with the dedifferentiating agent 5-bromodeoxyuridine. The major type II collagen mRNA species is 5300 bases long, similar to that of other interstitial collagen RNAs.

Construction of a cDNA clone corresponding to mouse alpha 1(IV) procollagen

A new procedure for the synthesis of double stranded cDNA, based upon release of mRNA by "in vitro" translation, was used to clone type IV collagen. Collagen synthesizing polysomes selectively isolated from a mouse parietal yolk sac carcinoma (PYS-2) were used for translation in an heterologous cell-free system. Translation products were collagenase-sensitive and displayed an electrophoretic mobility correspondent to type IV collagen. Translation released mRNA was employed to construct a 100 base pairs long cDNA clone which hybridized to a 7,800 nucleotides long mRNA. Peptides synthesized by "in vitro" translation of hybrid selected mRNA displayed an electrophoretic mobility compatible with that of alpha 1 (IV) collagen, were sensitive to collagenase and were immunoprecipitated by anti-type IV collagen antibody.

Isolation and characterization of genomic clones corresponding to the human type II procollagen gene

A recombinant human DNA library was screened using probes corresponding to the chick alpha 1 (II) procollagen gene. This resulted in the isolation of 2 different genomic clones, LgHCol(II)a and LgHCol(II)b. LgHCol(II)a was identified as corresponding to the alpha 1(II) gene by comparative hybridization and DNA sequence analysis. DNA sequence established that LgHCol(II)a extends at least from amino acid 694 of the triple helix through 54 amino acids of the COOH-propeptide. Hybridization with a probe containing only the exon at the 3' end of the chicken gene suggests that the clone contains the 3' end of the human gene. Thus LgHCol(II)a contains approximately 40% of the coding sequences of the human type II collagen gene.

Construction and characterization of type II collagen complementary deoxyribonucleic acid clones

The mRNA for type II collagen was purified from embryonic chick sternum or from purified sternal chondrocytes with guanidine thiocyanate as the extractant. Double-stranded cDNAs to procollagen mRNAs from sternum were synthesized and dC-tailed. After annealing with PstI-cleaved, dG-tailed pBR322, this DNA was used to transform Escherichia coli X1776. Transformed colonies were screened by colony hybridization to type I and II collagen cDNAs. Clones that preferentially hybridized to type II cDNA were characterized further. Four such cDNA clones, pCgII-2, 3, 10 and 12, with inserts of 400, 320, 260 and 750 bp, have been identified as type II collagen cDNA clones by several criteria, including their preference for hybridizing with type II rather than type I collagen mRNAs in hybrid-selected translation experiments.

The collagen alpha-2 chain gene

A number of DNA sequences specific for collagen messenger RNAs and genes have been isolated, cloned in bacterial plasmids or bacteriophages, and studied in detail. Such sequences have been used to study regulatory mechanisms underlying the production of type I collagen in fibroblasts in culture, fibroblasts after viral transformation, and in tissues and organs during embryonic and fetal development. It is clear that a variety of mechanisms, transcriptional, translational and post-translational, are used by cells to regulate collagen production. The study of isolated collagen gene fragments coding for the alpha 2 collagen chain in sheep and chick have shown that many genes are very large, and are interrupted by as many as 50 intervening sequences. Additionally, the structure of the genes in the regions coding for the helical regions of the protein provides evidence that collagen genes may have arisen from the reduplication of a DNA segment containing a primordial collagen gene sequence. The availability of specific cloned collagen gene sequences will allow the precise chromosomal location of the collagen genes as well as the number and the linkage relationships between these genes. In addition, genetic disorders of connective tissue where alterations in collagen structure are implicated will now be amenable to analysis at the DNA level.

Construction and partial characterization of two recombinant cDNA clones for procollagen from chicken cartilage

Type II procollagen mRNA has been partially purified from embryonic chick sternal cartilage by guanidine hydrochloride extraction, sucrose gradient sedimentation and Sepharose 4B chromatography. Double stranded cDNA was synthesized using AMV reverse transcriptase and E. coli DNA polymerase I, tailed using terminal transferase and inserted into the Pst I site of pBR322. Two putative type II procollagen cDNA clones have been characterized. Both plasmids hybridize to 2 sternal RNA species, a major species of 5.3 kb and a minor species of 7 kb. These RNAs are present in total RNA from sterna and differentiated limb bud cultures but are not detected in RNA from stage 24 limb bud which has not yet differentiated to cartilage or in RNA from calvaria. The time of appearance of these RNAs during the differentiation of limb mesenchyme in culture parallels the appearance of translatable type II procollagen mRNA.

Structure of the promoter for chicken alpha 2 type I collagen gene

The chicken alpha 2 type I collagen gene is 38 kilobases long and its coding information is subdivided into more than 50 exons. In the current study, we used primer extension and S1 nuclease mapping to determine the sequence of the 5' end of alpha 2 collagen mRNA and to locate the start site for transcription of the alpha 2 collagen gene. The DNA sequence around the start site for transcription shows a typical Goldberg-Hogness sequence, 5' T-A-T-A-A-A-T 3', between -33 and -26 and a 5' G-C-C-C-A-T-T 3' sequence ("CAT" box) between -84 and -78. Three AUGs are found in the initial portion of the mRNA, the first from +54 to +56, the second from +117 to +119, and the third from +134 to +136. The first two AUGs are followed by short coding sequences that could specify a hexapeptide a tetrapeptide, respectively. Only the third AUG is followed by an open reading frame coding for a sequence that presents considerable homology with the previously determined amino acid sequence of prepro alpha 1 collagen. In the promoter region sequence there are several extensive dyads of symmetry. Three of these inverted repeats which precede the start site for transcription overlap each other and may have a role in the developmental regulation of this gene.

Mutated beta-actin gene: coexpression with an unmutated allele in a chemically transformed human fibroblast cell line

By in vitro translation, we have identified the mRNA species that codes for a novel actin polypeptide (Ax-actin) in the chemically transformed human fibroblast line HuT-14. The relatedness of the coding sequences of the Ax- and beta-actin genes is indicated by our finding that pcDd actin ITL-I DNA, a recombinant plasmid DNA that contains a DNA sequence complementary to actin mRNA of Dictyostelium discoideum, hybridizes both the Ax-actin mRNA and the beta-actin mRNA but not the gamma-actin mRNA. In contrast, pcHa-1 DNA, a recombinant plasmid constructed by cloning a DNA sequence complementary to human actin mRNA from HuT-14 cells into pBR322, hybridized to all three mRNA species. In addition, no difference was observed between Ax- and beta-actin mRNAs when their molecular size was determined either by sucrose density gradient sedimentation or by methyl mercury agarose gel electrophoresis. Southern blot transfer of radioactive pcDd actin DNA to restriction endonuclease-digested Hut-14 DNA produced only a single hybrid band (a 6-kilobase fragment); the pcHa-1 DNA probe detected one additional band (a 3-kilobase fragment). These results suggest that HuT-14 cells contain only one copy per haploid genome for Ax- or beta-actin. When considered together with recent determination of the entire amino acid sequences of Ax- and beta-actin, our findings indicate that Ax-actin is the product of a mutated beta-actin gene and are evidence for the occurrence of a mutation in a chemically transformed cell.

Cloning a cDNA for the pro-alpha 2 chain of human type I collagen

Poly(A)-RNA enriched for type I procollagen sequences was isolated from normal human fibroblasts and used as template to synthesize double-stranded cDNA with avian myeloblastosis virus (AMV) reverse transcriptase. After the ends had been blunted with nuclease S1 and dGMP tails had been added with terminal deoxynucleotidyltransferase, the double-stranded cDNA was annealed with pBR322 DNA that had previously been cleaved with EcoRI, blunted with AMV reverse transcriptase, and dCMP-tailed with terminal deoxynucleotidyltransferase. The chimeric molecule was used to transform Escherichia coli strain HB101. Ninety-five recombinant clones were obtained and screened by dot hybridization analysis using 32P-labeled cDNA synthesized from the original poly(A)-RNA collagen-enriched population. Three positive clones were isolated and further characterized by blot hybridization techniques and by EcoRII digestion. One clone with an insert of 2.2 kilobases was shown to contain sequences encoding for the pro-alpha 2 chain of human type I procollagen. DNA sequence analysis of a 172-nucleotide fragment demonstrated that the cloned cDNA extends from amino acid position 450 of the alpha 2 chain to the middle of the COOH-terminal propeptide.

Regulation or procollagen messenger ribonucleic acid levels in Rous sarcoma virus transformed chick embryo fibroblasts

Using cloned cDNAs for pro-alpha 1 and pro-alpha 2 collagen messenger ribonucleic acid (mRNA), we have investigated the regulation of collagen mRNA levels in Rous sarcoma virus (RSV) transformed chick embryo fibroblasts (CEF). We find that both pro-alpha 1 and pro-alpha 2 mRNA levels are decreased approximately 10-fold in CEF transformed by either the Bryan high-titer strain or the Schmidt-Ruppin strain of RSV. Using temperature-sensitive mutants in the transforming gene src, we also investigated the rate of change in the levels of the two mRNA species. We employed mutants of both the Bryan high-titre strain (BHTa) and the Schmidt-Ruppin strain (ts68). With both mutants the results were similar. Upon shift from the permissive temperature (35 degrees C) to the non-permissive temperature (41 degrees C), collagen mRNA synthesis, did not increase until more than 5 h had passed, suggesting that action of src on collagen gene expression is indirect. Upon shift from 41 to 35 degrees C, collagen mRNA levels fell with a half-life of 10 h. Whether this fall reflects the half-life of procollagen mRNA or an effect of src on procollagen RNA stability is unclear. Both pro-alpha 1 and pro-alpha 2 mRNA levels were coordinately controlled.

Purification and characterization of a transformation-dependent protein secreted by cultured murine fibroblasts

The major excreted protein (MEP) of transformed mouse fibroblasts has been purified, and monospecific antisera against it have been prepared. Synthesis and secretion of this protein have previously been shown to be stimulated by transformation or treatment with tumor-promoting phorbol esters, but its function is still not known [Gottesman, M. M. (1978) Proc, Natl. Acad. Sci. U.S.A. 75, 2767--2771; Gottesman, M. M., & Sobel, M. E. (1980) Cell (Cambridge, Mass.) 19, 449--455]. The purified protein shows charge heterogeneity by two-dimensional gel electrophoresis; the major intracellular and extracellular species have a molecular weight of 35 000 and a pI of 6.8--7.3. The purified secreted protein contains approximately 5--10% neutral sugar by weight and binds specifically to a concanavalin A--Sepharose affinity column. Translation of messenger ribonucleic acid (mRNA) from cells actively synthesizing MEP in cell-free reticulocyte or wheat germ systems, which are reported to be unable to glycosylate translated proteins, results in a product of Mr 33 000 which is presumably devoid of neutral sugar. However, on two-dimensional electrophoresis, the MEP mRNA translation products continue to show charge heterogeneity similar to that seen in intact cells, suggesting that there may be multiple coordinately controlled mRNAs for MEP or a single mRNA species which can be translated in a variety of ways.

Decrease in the levels of nuclear RNA precursors for alpha 2 collagen in Rous sarcoma virus transformed fibroblasts

We have examined the levels of type I alpha 2 collagen RNA precursors, containing both intron and exon sequences in nuclear RNA preparations of chick embryo fibroblasts (CEF) and of CEF transformed by the Schmidt-Rupin strain of Rous sarcoma virus (RSV). We have used two different fragments of chick alpha 2 collagen genomic DNA as hybridization probes in S1 mapping experiments. Each of these DNA probes contains an entire intron. Our results indicate that the levels of the primary transcript of alpha 2 collagen RNA are much lower in RSV-CEF than in CEF. They suggest, but do not prove that the effect of the transforming protein p60src on the synthesis of alpha 2 collagen is mediated by a transcriptional control mechanism.

Isolation and characterization of overlapping genomic clones covering the chicken alpha 2 (type I) collagen gene

A series of overlapping recombinant clones, which cover the alpha 2 (type I) collagen gene, have been isolated by stepwise screening of two libraries of chicken genomic DNA fragments. The first genomic clone was isolated by using a cloned cDNA containing alpha 2 collagen DNA sequences as hybridization probe. The other clones were obtained by a sequence of screenings using defined fragments of the successive genomic clones as hybridization probes. Several types of experiments indicated that the DNA of these clones are truly overlapping and span 55 kilobase pairs of contiguous DNA sequences in the chicken genome. Sequence analysis of small DNA segments of some of these clones confirm that they contain coding sequences which specify alpha 2 collagen. Electron microscopic analysis of hybrids between type I alpha 2 collagen mRNA and the overlapping genomic clones indicates that the chicken alpha 2 collagen gene has a length of at least 37 kilobases, about 7.4 times longer than the corresponding translatable cytoplasmic mRNA. The coding information for alpha 2 collagen is distributed in more than 50 coding sequences which are interrupted by intervening sequences of various sizes. The structure of the gene implies that the conversion of precursor RNA to mature mRNA for alpha 2 collagen includes at least 50 splicing events.

Characterization of collagen synthesized by normal and chemically transformed rat liver epithelial cell lines

A rat liver epithelial cell line (K16) and a 2-[N-(acetoxyacetyl)amino]fluorine-transformed K16 cell line (W8) [Weinstein, I.B., Yamaguchi, R., Gerbert, R., & Kaighn, M.E. (1975) In Vitro 11, 130-141] synthesize and secrete similar quantities of collagenous proteins. The transformed cells produce more total protein so that the percent collagen produced is decreased compared to that of the parent cell line. The type of collagen produced by the transformants differed from that of the parent cell line. After limited pepsin digestion, the pepsin-resistant collagen molecules synthesized by K16 cells precipitated at 2.6 M NaCl and contained both alpha 1 (I) and alpha 2 chains in a 2.5:1 ratio. The collagen synthesized by the W8 cells precipitated at higher salt concentrations, and no pepsin-resistant alpha 2 chains could be demonstrated by CM-cellulose chromatography or gel electrophoresis. The cyanogen bromide peptides of the W8 alpha 1 chains did not cochromatograph with type I rat skin collagen cyanogen bromide peptides on CM-cellulose chromatography, whereas the alpha 1 chains of the K16 cells did cochromatograph. The conversion of procollagen to collagen was also decreased in the transformant cells. Therefore, the chemical transformation of K16 produced transformants with increased protein synthesis and altered collagen metabolism.

Isolation and characterization of genomic DNA coding for alpha 2 type I collagen

We have isolated and characterized a segment of the chick alpha 2 collagen gene by screening a library of chick genomic fragments using as hybridization probe an alpha 2 collagen cDNA clone. Several clones were isolated and one of them, lambda gCOL 204, was used for further studies. The DNA of lambda gCOL 204 hybridizes to a unique species of mRNA the size of alpha 2 collagen mRNA. This mRNA can be translated into a unique polypeptide which comigrates in SDS-gel electrophoresis with pro-alpha 2 collagen. Electron microscopic analysis by R-loop technique indicates that lambda gCOL 204 contains 7Kb of the alpha 2 collagen gene. This 7 Kb piece constitutes the 3' end of the gene. The same clone also contains 9 Kb of DNA that is immediately adjacent to the 3' end of the alpha 2 collagen gene. The cloned segment of the alpha 2 collagen gene is interrupted by 8 intervening sequences of various lengths. The coding sequences for collagen in this clone add up to approximately 1,800 bp, which correspond to about 1/3 of alpha 2 collagen mRNA. DNA sequence analysis of a small coding segment of lambda g COL 204 reveals a characteristic collagen type sequence which encodes for an amino acid sequence identical to a sequence found in calf alpha 2 collagen. The sequence of this region of the protein has not yet been determined for the chick alpha 2 collagen.

Unusual features in the nucleotide sequence of a cDNA clone derived from the common region of avian sarcoma virus messenger RNA

We have constructed a recombinant plasmid containing a 700-base pair (bp) cDNA copy of the common region present at the 3' end of Schmidt-Ruppin avian sarcoma virus (ASV) 21S mRNA. The cDNA was inserted into plasmid pBR322 at the Pst I site by the G-C tailing method. A restriction map of the cloned insert from a recombinant plasmid pSRI indicates that it corresponds to the 3' end of the ASV genome. R-loop analysis with ASV genomic RNA indicates that the insert is colinear with the ASV genome over most of its length. The sequence of 331 bp at the 3' end of the DNA insert was determined and shows that the insert contains extra sequences not found at the 3' end of ASV genomic RNA. Following the terminally redundant sequence of 20 bp that has been found at the extreme 3' end of genomic RNA is a sequence of 79 bp that is almost identical to that located immediately next to the 20-bp repeat at the 5' end of ASV genomic RNA. This is followed by 18 bp of unique sequence, possibly of host origin. The structure of the clone suggests that ASV mRNA may differ from genomic RNA at its 3' end and that 21S mRNA is transcribed from integrated ASV DNA and contains at its 3' end sequences derived both from the 5' end of the ASV genome and from host DNA adjacent to the site of integration. The presence of termination codons in all three reading frames suggests that the common region probably does not contain coding sequences. However, the presence of sequences that resemble probable promoter sites supports the possibility that this region may be involved in the regulation of transcription.

Translation and characterization of messenger RNAs in differentiating chicken cartilage

Total RNA, prepared from chicken limb bud cultures undergoing differentiation to cartilage, has been translated in a wheat germ cell-free protein-synthesizing system. Antibodies against chondroitin sulfate proteoglycan core protein immunoprecipitate a single component which migrates as a protein of 340,000 daltons in sodium dodecyl sulfate/polyacrylamide gels. The messenger RNA for this protein sediments at approximately 27 S in 70% formamide or aqueous sucrose gradients. The 340,000-dalton protein is present in cell-free translation products directed by RNA prepared from limb bud cultures and sternae and is absent in cell-free translation directed by RNA prepared from embryonic calvaria or liver. The level of synthesis of this protein is greatly reduced when RNA prepared from limb bud cultures inhibited from differentiation by BrdUrd is used. (Pre)pro alpha 1(I), -alpha 2(I), and -alpha 1(II) collagen bands have been identified on gels by electrophoresis of collagenase-digested or immunoprecipitated cell-free translation products directed by RNA from differentiating limb bud cultures, embryonic sternae, and embryonic calvaria.

Construction and characterization of pro alpha 1 collagen complementary deoxyribonucleic acid clones

Background

Probable sarcopenia is determined by a reduction in muscle strength assessed with the handgrip strength test or 5 times sit-to-stand test, and it is confirmed with a reduction in muscle quantity determined by dual-energy X-ray absorptiometry or bioelectrical impedance analysis. However, these parameters are not implemented in clinical practice mainly due to a lack of equipment and time constraints. Nowadays, the technical innovations incorporated in most smartphone devices, such as high-speed video cameras, provide the opportunity to develop specific smartphone apps for measuring kinematic parameters related with sarcopenia during a simple sit-to-stand transition.

Objective

We aimed to create and validate a sit-to-stand video analysis–based app for diagnosing sarcopenia in community-dwelling older adults and to analyze its construct validity with health-related risk factors and frailty.

Methods

A total of 686 community-dwelling older adults (median age: 72 years; 59.2% [406/686] female) were recruited from elderly social centers. The index test was a sit-to-stand video analysis–based app using muscle power and calf circumference as proxies of muscle strength and muscle quantity, respectively. The reference standard was obtained by different combinations of muscle strength (handgrip strength or 5 times sit-to-stand test result) and muscle quantity (appendicular skeletal mass or skeletal muscle index) as recommended by the European Working Group on Sarcopenia in Older People-2 (EWGSOP2). Sensitivity, specificity, positive and negative predictive values, and area under the curve (AUC) of the receiver operating characteristic curve were calculated to determine the diagnostic accuracy of the app. Construct validity was evaluated using logistic regression to identify the risks associated with health-related outcomes and frailty (Fried phenotype) among those individuals who were classified as having sarcopenia by the index test.

Results

Sarcopenia prevalence varied from 2% to 11% according to the different combinations proposed by the EWGSOP2 guideline. Sensitivity, specificity, and AUC were 70%-83.3%, 77%-94.9%, and 80.5%-87.1%, respectively, depending on the diagnostic criteria used. Likewise, positive and negative predictive values were 10.6%-43.6% and 92.2%-99.4%, respectively. These results proved that the app was reliable to rule out the disease. Moreover, those individuals who were diagnosed with sarcopenia according to the index test showed more odds of having health-related adverse outcomes and frailty compared to their respective counterparts, regardless of the definition proposed by the EWGSOP2.

Conclusions

The app showed good diagnostic performance for detecting sarcopenia in well-functioning Spanish community-dwelling older adults. Individuals with sarcopenia diagnosed by the app showed more odds of having health-related risk factors and frailty compared to their respective counterparts. These results highlight the potential use of this app in clinical settings.

Trial Registration

ClinicalTrials.gov NCT05148351; https://clinicaltrials.gov/study/NCT05148351

International Registered Report Identifier (IRRID)

RR2-10.3390/s22166010