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

Characteristics of a Three-Generation Family with Stickler Syndrome Type I Carrying Two Different COL2A1 Mutations

Stickler Syndrome is typically characterized by ophthalmic manifestations including vitreous degeneration and axial lengthening that predispose to retinal detachment. Systemic findings consist of micrognathia, cleft palate, sensorineural hearing loss, and joint abnormalities. COL2A1 mutations are the most common, however, there is a lack of genotype-phenotype correlations. Retrospective, single-center case series of a three-generation family. Clinical features, surgical requirements, systemic manifestations, and genetic evaluations were collected. Eight individuals clinically displayed Stickler Syndrome, seven of whom had genetic confirmation, and two different COL2A1 mutations (c.3641delC and c.3853G>T) were identified. Both mutations affect exon 51, but display distinct phenotypes. The c.3641delC frameshift mutation resulted in high myopia and associated vitreous and retinal findings. Individuals with the c.3853G>T missense mutation exhibited joint abnormalities, but mild ocular manifestations. One individual in the third generation was biallelic heterozygous for both COL2A1 mutations and showed ocular and joint findings in addition to autism and severe developmental delay. These COL2A1 mutations exhibited distinct eye vs. joint manifestations. The molecular basis for these phenotypic differences remains unknown and demonstrates the need for deep phenotyping in patients with Stickler syndrome to correlate COL2A1 gene function and expression with ocular and systemic findings.

A CRISPR-engineered swine model of COL2A1 deficiency recapitulates altered early skeletal developmental defects in humans

Loss-of-function mutations in the COL2A1 gene were previously described as a cause of type II collagenopathy (e.g., spondyloepiphyseal dysplasia, Stickler syndrome type I), a major subgroup of genetic skeletal diseases. However, the pathogenic mechanisms associated with COL2A1 mutations remain unclear, and there are few large-mammal models of these diseases. In this study, we established a swine model carrying COL2A1 mutations using CRISPR/Cas9 and somatic cell nuclear transfer technologies. Animals mutant for COL2A1 exhibited severe skeletal dysplasia characterized by shortened long bones, abnormal vertebrae, depressed nasal bridge, and cleft palate. Importantly, COL2A1 mutant piglets suffered tracheal collapse, which was almost certainly the cause of their death shortly after birth. In conclusion, we have demonstrated for the first time that overt and striking skeletal dysplasia occurring in human patients can be recapitulated in large transgenic mammals. This model underscores the importance of employing large animals as models to investigate the pathogenesis and potential therapeutics of skeletal diseases.

Integrated analysis of COL2A1 variant data and classification of type II collagenopathies

The COL2A1 gene encodes the alpha-1 chain of type II procollagen. Type II collagen, comprised of three identical alpha-1 chains, is the major component of cartilage. COL2A1 gene variants are the etiologies of genetic diseases, termed type II collagenopathies, with a wide spectrum of clinical presentations. To date, at least 460 distinct COL2A1 mutations, identified in 663 independent probands, and 21 definite disorders have been reported. Nevertheless, a well-defined genotype-phenotype correlation has not been established, and few hot spots of mutation have been reported. In this study, we analyzed data of COL2A1 variants and clinical information of patients obtained from the Leiden Open Variation Database 3.0, as well as the currently available relevant literature. We determined the characteristics of the COL2A1 variants and distributions of the clinical manifestations in patients, and identified four likely genotype-phenotype correlations. Moreover, we classified 21 COL2A1-related disorders into five categories, which may assist clinicians in understanding the essence of these complex phenotypes and prompt genetic screening in clinical practice.

Molecular genetics of the COL2A1-related disorders

Type II collagen, comprised of three identical alpha-1(II) chains, is the major collagen synthesized by chondrocytes, and is found in articular cartilage, vitreous humour, inner ear and nucleus pulposus. Mutations in the collagen type II alpha-1 gene (COL2A1) have been reported to be responsible for a series of abnormalities, known as type II collagenopathies. To date, 16 definite disorders, inherited in an autosomal dominant or recessive pattern, have been described to be associated with the COL2A1 mutations, and at least 405 mutations ranging from point mutations to complex rearrangements have been reported, though the underlying pathogenesis remains unclear. Significant clinical heterogeneity has been reported in COL2A1-associated type II collagenopathies. In this review, we highlight current knowledge of known mutations in the COL2A1 gene for these disorders, as well as genetic animal models related to the COL2A1 gene, which may help us understand the nature of complex phenotypes and underlying pathogenesis of these conditions.

A bio-imitating approach to fabricate an artificial matrix for cartilage tissue engineering using magnesium-polyphosphate and hyaluronic acid

Here we describe an cartilage-like material based on a hyaluronic acid-Mg/Ca-polyphosphate that is fabricated from a water-soluble Na-salt of energy-rich inorganic polyphosphate and soluble hyaluronic acid in the presence of water-insoluble CaCO₃.

Identification of a Novel Mutation in the COL2A1 Gene in a Chinese Family with Spondyloepiphyseal Dysplasia Congenita

Spondyloepiphyseal dysplasia congenita (SEDC) is an autosomal dominant chondrodysplasia characterized by disproportionate short-trunk dwarfism, skeletal and vertebral deformities. Exome sequencing and Sanger sequencing were performed in a Chinese Han family with typical SEDC, and a novel mutation, c.620G>A (p.Gly207Glu), in the collagen type II alpha-1 gene (COL2A1) was identified. The mutation may impair protein stability, and lead to dysfunction of type II collagen. Family-based study suggested that the mutation is a de novo mutation. Our study extends the mutation spectrum of SEDC and confirms genotype-phenotype relationship between mutations at glycine in the triple helix of the alpha-1(II) chains of the COL2A1 and clinical findings of SEDC, which may be helpful in the genetic counseling of patients with SEDC.

A genetic pedigree analysis to identify gene mutations involved in femoral head necrosis

The present study presents results from a linkage and mutation screening analysis aiming to identify the causative gene of femoral head necrosis, also known as osteonecrosis of femoral head (ONFH), in a Chinese pedigree. We collected clinical data on the osteonecrosis pedigree, and extracted blood and genomic DNA from the family members. Polymerase chain reaction (PCR) and direct sequencing allowed to identify a mutation in the COL2A1 gene of the proband; the clinical manifestations of the proband meet the criteria for osteonecrosis. The exons of COL2A1 were amplified by polymerase chain reaction and mutation screening was conducted by direct sequencing in all the family members. The locus was also sequenced in 50 unrelated healthy controls. The c.3665G>A heterozygous mutation was detected in patients of the pedigree, but not in healthy individuals. We conclude that a mutation in the COL2A1 gene is the causative agent of ONFH in this family. Therefore, this mutation may be associated with osteonecrosis in Chinese populations.

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.

A form of autosomal dominant spondyloepiphyseal dysplasia is caused by a glycine to alanine substitution in the COL2A1 gene

We report a family with an unusual form of autosomal dominant spondyloepiphyseal dysplasia characterized by infantile-onset disproportionate short stature with relative shortening of the spine, thoracic kyphosis, lumbar lordosis, scoliosis and premature osteoarthritis of the joints especially of the hips. Radiological findings include mild platyspondyly, vertebral end plate irregularity, irregular femoral necks, and dysplasia of the capital femoral epiphyses with flattening and irregularity present from childhood and mild variable epiphyseal dysplasia elsewhere in the skeleton. Intrafamilial variability is observed in the degree of short stature, severity of spinal and hip involvement and the age of onset of symptoms and complications. We demonstrate that this dysplasia is due to a glycine to alanine substitution in the COL2A1 gene (p.Gly862Ala), thereby expanding the phenotypic spectrum of dysplasias associated with defects in type II collagen.

Co-expression of collagens II and XI and alternative splicing of exon 2 of collagen II in several developing human tissues

Northern analyses, RNAase protection assays and in situ hybridizations were used to study the expression of the mRNA for the alpha 2 chain of collagen XI and the two different mRNAs generated from the collagen II gene through alternative splicing of exon 2 in several different tissues of 15-19-week-old fetuses. The highest expression levels of procollagen alpha 2(XI) and alpha 1(II) mRNAs were detected in cartilage, but, using long exposure times, Northern hybridization revealed the presence of the approximately 5.3 kb procollagen alpha 1(II) mRNA in most tissues analysed: calvarial and diaphyseal bone, striated and cardiac muscle, skin, brain, lung, kidney, liver, small intestine and colon. Both alternatively spliced forms of the mRNA were present in these tissues. In cartilage, the short form of the procollagen alpha 1(II) mRNA (without exon 2 sequences) was clearly more abundant, whereas in most of the non-cartilaginous tissues the long form was the predominant one. Low levels of procollagen alpha 2(XI) mRNA were also seen in non-cartilaginous tissues: calvarial and diaphyseal bone, kidney, skin, muscle, intestine, liver, brain, and lung. In all the other positive tissues except brain cortex, both collagen II and XI transcripts were observed. The localization of collagen II and XI signals was identical in cartilage, kidney and skin. However, in cartilage the signal with collagen II probe was much higher than that with the collagen alpha 2(XI) probe. In epidermis the situation was reversed. Our results show considerable co-expression and co-localization of procollagen alpha 1(II) and alpha 2(XI) mRNAs in many tissues of developing human fetuses. Since the collagen alpha 1(II) gene also codes for the alpha 3(XI) chain of collagen XI we propose that some, but not all, of the expression of the collagen II gene in non-cartilaginous tissues relates to collagen XI production.

Autoimmune recognition of cartilage collagens

Recent advances in basic research on the immune system and molecular biology of cartilage components have greatly increased our understanding of the role of autoimmunity in inflammatory diseases affecting joints, particularly rheumatoid arthritis. Many of these diseases are common and their complex pathogenesis probably involves a large number of genes polymorphic in the population as well as environmental factors. Characteristic features of inflammatory arthritis include expansion of the synovial tissue into a pannus containing lymphocytes and macrophages, autoimmune reactions against cartilage antigens, and erosion of cartilage. Since hyaline cartilage of the articular surfaces is the only structure within the joint known to contain joint-specific antigens this tissue is the prime suspect as the target of the autoimmune This review will first present the capacity of the immune system to discriminate between self and non-self structures, and then summarize our current understanding of the structures of cartilage collagens. Subsequently we will discuss how the immune system normally interacts with cartilage and how such interactions can lead to arthritis. We propose that collagen-induced arthritis (CIA) is valuable for understanding the autoimmune recognition of cartilage collagen which precedes the outbreak of arthritis and may perpetuate its chronicity, and serves as an animal model of rheumatoid arthritis.

Detection of sequence variants in the gene for human type II procollagen (COL2A1) by direct sequencing of polymerase chain reaction-amplified genomic DNA

The direct sequencing of the human type II procollagen (COL2A1) gene from polymerase chain reaction (PCR)-amplified genomic DNA is described. Thirty-two regions of the COL2A1 gene were asymmetrically amplified with intron primers which were specifically chosen to amplify a region spanning 500 to 800 bp of sequence encoding one or more exons and their accompanying intervening sequences. Primers for dideoxynucleotide sequencing of the PCR products were then designed to provide complete exon sequence information and to insure that intron:exon splice junction sequence data would be obtained. Amplification and sequencing reactions were performed on an automated workstation to facilitate the handling of multiple DNA templates. The procedure allowed efficient sequencing of over 25,000 bp of each allele of the COL2A1 gene per diploid genome. We used this method for the comparative analyses of COL2A1 sequences in DNA isolated from the blood of 42 unrelated individuals and we identified 21 neutral sequence variants in the gene. The sequence variations were confirmed by independent assays, including restriction enzyme digestion. The sequence variants described here will be important for identifying haplotypes of the type II procollagen gene that will be useful in defining a genetic etiology for diseases of cartilaginous tissues.

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.

Is the WKS motif the tissue-factor binding site for coagulation factor VII?

Human tissue factor (TF), the membrane-bound glycoprotein receptor for the blood-clotting factor VII/VIIa, contains in its extracellular domain three repeats of the rare motif, tryptophan-lysine-serine (WKS). Murine tissue factor, which binds human factor VII/VIIa poorly, contains only one WKS motif suggesting that the WKS motif may be involved in the binding of human factor VII/VIIa to human TF. Sequence analysis has revealed a WKS motif in 23 human proteins, seven of which are involved in the coagulation process. Another five WKS-containing proteins share some functional properties with the coagulation proteins. Analysis of the properties of these proteins provides some insight into the possible functional role of the WKS motif.

Completion of the intron-exon structure of the gene for human type II procollagen (COL2A1): variations in the nucleotide sequences of the alleles from three chromosomes

A new procedure for preparing cosmid libraries was used to isolate three alleles for the human gene for type II procollagen (COL2A1). Over 20,000 bp of one allele were completely sequenced and over 10,000 bp of the two other alleles were sequenced. The data located and defined 26 exons and introns of the gene not previously analyzed. The results completed the structure of the gene except for the newly discovered exon 2A that undergoes alternative splicing (Ryan et al., 1990, Trans. Ann. Meet. Orthop. Res. Soc. 15:65). As a result, it is the most completely known structure of a gene for a human fibrillar collagen. The results confirm the previous impression that exon sizes are highly conserved among the genes for the three major fibrillar collagens. Comparison of clones from the three alleles defined five neutral variations in coding sequences and seven variations in the intron that also are probably neutral variations. The normal sequences and the variations in sequences will be important for identifying different alleles and haplotypes of the gene and for the analysis of genetic mutations in the gene that cause diseases of cartilage such as chondrodysplasias and osteoarthritis.

Efficient procedure for preparing cosmid libraries from microgram quantities of genomic DNA fragments size fractionated by gel electrophoresis

A modified procedure for preparing cosmid libraries from genomic DNA is described. Genomic DNA was partially digested with a restriction endonuclease, and DNA fragments of appropriate size fractionated by agarose gel electrophoresis. A cosmid library was prepared, prescreened, and used to isolate gene inserts with previously published procedures. In one series of experiments, a modified cosmid vector containing stuffer fragments was used to prepare cosmid libraries containing partial SphI digests of 25 to 35 kb. From 10(5) to 10(7) clones were obtained per microgram of size-fractionated genomic DNA. From 10 to 100 hybridization-positive clones of a single copy gene (COL2A1) were obtained from plates that were positive in the prescreening step. Restriction mapping of over 20 clones and nucleotide sequencing of over 20,000 bp in each of two clones indicated that the inserts were faithful copies of the gene. In another experiment, a standard cosmid vector was used to prepare a cosmid library containing partial BamHI fragments of 30 to 45 kb. Genomic libraries can be prepared with 5 to 20 micrograms of genomic DNA and a large number of clones containing 25 to 45 kb fragments of a single copy gene can be isolated in about three weeks.

Structure of cDNA clones coding for human type II procollagen. The alpha 1(II) chain is more similar to the alpha 1(I) chain than two other alpha chains of fibrillar collagens

Overlapping cDNA clones were isolated for human type II procollagen. Nucleotide sequencing of the clones provided over 2.5 kb of new coding sequences for the human pro alpha 1(II) gene and the first complete amino acid sequence of type II procollagen from any species. Comparison with published data for cDNA clones covering the entire lengths of the human type I and type III procollagens made it possible to compare in detail the coding sequences and primary structures of the three most abundant human fibrillar collagens. The results indicated that the marked preference in the third base codons for glycine, proline and alanine previously seen in other fibrillar collagens was maintained in type II procollagen. The domains of the pro alpha 1(II) chain are about the same size as the same domains of the pro alpha chains of type I and type III procollagens. However, the major triple-helical domain is 15 amino acid residues less than the triple-helical domain of type III procollagen. Comparison of hydropathy profiles indicated that the alpha chain domain of type II procollagen is more similar to the alpha chain domain of the pro alpha 1(I) chain than to the pro alpha 2(I) chain or the pro alpha 1(III) chain. The results therefore suggest that selective pressure in the evolution of the pro alpha 1(II) and pro alpha 1(I) genes is more similar than the selective pressure in the evolution of the pro alpha 2(I) and pro alpha 1(III) genes.

Exclusion of the COL2A1 gene as the mutation site in diastrophic dysplasia

The involvement of the cartilage specific type II collagen gene (COL2A1) was studied in nine patients with diastrophic dysplasia in the Finnish population, where the prevalence of this chondrodystrophy clearly exceeds that reported for other populations. COL2A1 was chosen as the candidate gene based on previous morphological and chemical studies which suggested abnormal structure of type II collagen in diastrophic dysplasia. Southern analysis of the patients' DNA showed no disease related differences in any of the restriction fragments covering the 30 kb COL2A1 gene. As a second approach, the nine patients and their 74 relatives were studied for the inheritance of the type II collagen gene. Three of the patients with diastrophic dysplasia were not homozygous for the intragenic RFLP markers, which suggests that the disease is not linked to the type II collagen gene. Multipoint linkage analysis gave a lod score of -2.95, which conclusively excluded the COL2A1 gene as the mutation site in diastrophic dysplasia in these families.

Predisposition to familial osteoarthrosis linked to type II collagen gene

The genetic background of two families, in whom a predisposition to primary osteoarthrosis is inherited as a dominant trait, was investigated. Use of restriction fragment length polymorphisms within and around the type II collagen gene on chromosome 12 revealed a linkage between this cartilage-specific gene and primary osteoarthrosis.

Organization of the exons coding for pro alpha 1(II) collagen N-propeptide confirms a distinct evolutionary history of this domain of the fibrillar collagen genes

The organization of the exons coding for the N-terminal portion of human type II procollagen has been determined. Aside from inferring the previously unknown primary structure of type II N-propeptide, this study has revealed that this coding domain of the gene exhibits an organization uniquely distinct from those of type I and type III collagens. This finding substantiates the notion that the N-propeptide coding domains of the fibrillar collagen genes evolved under less stringent selection than those encoding the C-propeptide and triple helical regions.

Molecular mechanisms of collagen gene expression

Collagens are a structurally and functionally heterogenous group of proteins encoded by a family of genes that share evolutionary history. Collagen gene expression is regulated both in developmental, tissue-specific manners as well as in response to a variety of biologic and pharmacologic inducers. In the present review we have attempted to synthesize a conceptual overview of the available information from studies aimed at deciphering the molecular mechanisms of collagen gene expression. We have chosen to focus our discussion mainly, although not exclusively, to observations relating to type I collagen gene for a number of practical reasons. The underlying theme that emerges from this survey of the literature is that the regulation of collagen gene expression is complex, utilizing transcriptional, posttranscriptional and translational mechanisms. Although the transcriptional control mechanisms that involve activation and modulation of collagen gene transcription by RNA polymerase II appear to predominate, preferential stabilization of collagen mRNAs and modulation of translational discrimination appear to play significant roles in the regulation of collagen biosynthesis under some physiological situations. Molecular organization of the regulatory regions of collagen genes reveal a mosaic of subdomains with overlapping sequence motifs, involved in positive and negative transcriptional regulation. The precise identity of the cis-acting subdomains of the promoter/enhancer-proximal DNA of collagen gene and how they interact with the trans-acting nuclear protein(s) have yet to be elucidated and will remain the focus of future studies.

Genetic markers on chromosome 7

Chromosome 7 is frequently associated with chromosome aberrations, rearrangements, and deletions. It also contains many important genes, gene families, and disease loci. This brief review attempts to summarise these and other interesting aspects of chromosome 7. With the rapid accumulation of cloned genes and polymorphic DNA fragments, this chromosome has become an excellent substrate for molecular genetic studies.

The Stickler syndrome: evidence for close linkage to the structural gene for type II collagen

The Stickler syndrome is an autosomal dominant hereditary disorder of connective tissue with pleiotropic features including premature osteoarthropathy, mild spondyloepiphyseal dysplasia, vitreoretinal degeneration, and the Pierre-Robin sequence. Genetic linkage studies in two families with the Stickler syndrome have been performed using restriction fragment length polymorphisms associated with the structural gene for type II collagen, COL2A1. No recombinants between the Stickler phenotype and COL2A1 were observed. The total LOD score for linkage of the Stickler syndrome and COL2A1 at a recombination fraction (theta) of zero is 3.59. These findings suggest that, at least in some families, the mutation causing Stickler syndrome affects the structural locus for type II collagen.

Determination of the single polyadenylation site of the human pro alpha 1(II) collagen gene

Several cDNA clones for the human type II procollagen mRNA were isolated from a cartilage cDNA library. Six of the clones containing the longest inserts were subjected to restriction site mapping for alignment. All these six clones extended to the poly A tail. The longest clone, containing a 1470 bp insert, was named pHCAR3. Sequencing of pHCAR3 made it clear that neither of the two canonical AATAAA sequences of the human type II collagen gene is used as the polyadenylation signal. Two 60 bp stretches of high interspecies homology terminating in a hexanucleotide ATTAAA, located 23 nucleotides upstream of the poly A tail, apparently have an important role in determining the single polyadenylation signal for this gene. S1 protection experiments confirmed these observations.

Structure of the type II collagen gene

In summary, the exon/intron structure of the chicken type II collagen gene is identical with that of the chicken alpha 2(I) collagen gene and differs at only one known position from the human and mouse alpha 1(I) genes. However, the chicken type II gene is different from the chicken alpha 2(I) gene in that it is considerably shorter because of a much smaller average intron size and in that the G+C composition of the introns is much higher. The codon usage of the type II genes also shows characteristic differences. There is a single copy of the chick type II gene per haploid genome.

Nonrandom association of a type II procollagen genotype with achondroplasia

Achondroplasia is an autosomal dominant disorder that involves defective endochondral bone formation. Type II collagen is the predominant collagen of cartilage. We found a HindIII polymorphic site in the normal Caucasian population by using the type II procollagen gene probe pgHCol(II)A. The presence of this site yields a 7.0-kilobase (kb) band; its absence yields a 14.0-kb band. We found a significant deviation in genotype distribution and allele frequencies in a population of unrelated individuals with sporadic achondroplasia, compared with the normal control population. The HindIII genotype frequencies in 32 individuals with achondroplasia are 0.41 for the 7/7 genotype (controls, 0.08), 0.34 for the 7/14 genotype (controls, 0.54), and 0.25 for the 14/14 genotype (controls, 0.37). The apparent equilibrium excess of the "7" allele in individuals with achondroplasia may reflect either a predisposition for the mutation that causes achondroplasia or it could be the result of the achondroplasia-causing mutation. In either case, these findings suggest an association of the type II procollagen gene with achondroplasia.

A highly polymorphic region 3' to the human type II collagen gene

We have characterised a highly polymorphic region 1.3kb downstream of the human Type II collagen gene. It consists of a highly AT-rich tandem repetitive region (minisatellite) approximately 650bp long. Two alleles had been observed previously, differing in size by approximately 300bp. When this region was cloned from four unrelated individuals carrying the larger allele, DNA sequence data identified three alleles, suggesting far higher polymorphism than was originally supposed. This minisatellite was shown to be present in a single copy in the human genome, and to have arisen after the divergence of Old and New World monkeys.

Construction and identification of a cDNA clone for human type II procollagen mRNA

Double-stranded cDNA was constructed for poly(A)-containing RNA isolated from foetal human articular cartilage known to contain small amounts of pro alpha 1 (II) collagen mRNA. A 585 base pair PstI-EcoRI cDNA fragment was isolated and cloned into plasmid pBR322. A resulting recombinant plasmid pHCAR1 was shown to hybridize specifically to a 5.4 kilobase mRNA in cartilage but not in calvarial RNA. Definite identification of clone pHCAR1 was based on sequence analysis; marked homology with the corresponding chick gene and complete agreement with the human gene sequences available were observed.

Primary structure of the telopeptide and a portion of the helical domain of chicken type II procollagen as determined by DNA sequence analysis

A comparison of the nucleotide sequences of three new cDNA clones for chicken type II procollagen with the sequences of the other three types of chicken fibrillar procollagens reveals that the most conserved regions correlate with the positions of hydroxyproline, hydroxylysine, cysteine and lysine residues. On the basis of replacement-site-divergence calculations it is concluded that alpha 1(II) and alpha 1(I) procollagens diverged later than alpha 1(I) and alpha 2(I) procollagens.

Analysis of three restriction fragment length polymorphisms in the human type II procollagen gene

Cloned genomic DNA sequences corresponding to various regions of the human type II procollagen gene were used to analyze the DNA from 78 normal volunteers. Southern hybridization experiments detected polymorphic HindIII, BamHI, and EcoRI sites. The presence of the polymorphic HindIII site results in a 7.0-kilobase (kb) band, and the absence of this site results in a 14.0-kb band. When present, the BamH1 polymorphic site yields a 4.8-kb band, and when absent, yields a 7.2-kb band. The presence of the EcoRI polymorphic site results in a 3.7-kb band, and its absence results in a 7.0-kb band. Each polymorphic site was mapped. Analyses of the data demonstrated that the sites are present in overall gene frequencies of .39 for HindIII, .04 for BamHI, and .02 for EcoRI. Gene frequencies of the polymorphic sites were also studied with respect to race. The polymorphic sites are present in a Hardy-Weinberg distribution in the study population. Study of an extended family demonstrated that the segregation of the HindIII polymorphic site is consistent with Mendelian inheritance.

Identification and characterization of the human type II collagen gene (COL2A1)

The gene contained in the human cosmid clone CosHcol1, previously designated an alpha 1(I) collagen-like gene, has now been identified. CosHcol1 hybridizes strongly to a single 5.9-kilobase mRNA species present only in tissue in which type II collagen is expressed. DNA sequence analysis shows that this clone is highly homologous to the chicken alpha 1(II) collagen gene. These data together suggest that CosHcol1 contains the human alpha 1(II) collagen gene COL2A1. The clone appears to contain the whole gene (30 kilobases in length) and will be extremely useful in the study of cartilage development and for identifying those inherited chondrodystrophies in which defects occur in this gene.

Human alpha 1(III) and alpha 2(V) procollagen genes are located on the long arm of chromosome 2

The multigene procollagen family encodes probably greater than 20 genetically distinct but structurally related polypeptide chains. Recent characterization of human procollagen clones has allowed determination of functional domains within the proteins, genomic organization, and chromosomal location. Previously, we assigned the coordinately expressed type I genes (alpha 1 and alpha 2) to chromosomes 17 and 7, respectively, and now other investigators have mapped the type II gene to chromosome 12 [Strom, C. M., Eddy, R. L. & Shows, T. B. (1984) Somatic Cell Genet. 10, 651-655]. Recently, we isolated cDNA clones encoding the fourth interstitial procollagen, type III, and the alpha 2 chain of the type V cytoskeletal components. To determine whether these genes were clustered with alpha 1(I), alpha 2(I), or alpha 1(II) or were further dispersed in the genome, in situ hybridization of the alpha 1(III) and alpha 2(V) probes to metaphase chromosomes was carried out. Here we report a fourth autosome with procollagen gene loci but the first cytological evidence for linkage. By using normal and translocated cell lines, our results show that both the alpha 1(III) and alpha 2(V) procollagen genes map to the q24.3----q31 region of chromosome 2.

Analysis of cDNA and genomic clones coding for the pro alpha 1 chain of calf type II collagen

A bovine cDNA library constructed from fetal cartilage RNA was screened with a pro alpha 1(II) collagen specific chicken cDNA. A recombinant clone (Bc 7), with an insert of 1 kb, was identified and shown to contain sequences exhibiting 85% homology with the chicken pro alpha 1(II) collagen C-propeptide. Interspecies comparison strongly suggested that one potential glycosylation site present in the avian C-propeptide is not utilized, since this site is absent in the bovine chain. In addition, two overlapping genomic clones (Pal 3 and Pal 4) were isolated and partially characterized. These clones span 23 kb of DNA and contain approximately 17 kb of the pro alpha 1(II) calf gene. Sequencing of exon 1 has determined the length of the 3' untranslated region and the exact location of the polyadenylation attachment site.

Isolation and partial characterization of the entire human pro alpha 1(II) collagen gene

Using a cDNA probe specific for the bovine Type II procollagen, a series of overlapping genomic clones containing 45 kb of contiguous human DNA have been isolated. Sequencing of a 54 bp exon, number 29, provided direct evidence that the recombinant clones bear human Type II collagen sequences. Localization of the 5' and 3' ends of the gene indicated that the human Type II collagen gene is 30 kb in size. This value is significantly higher than that of the homologous avian gene. The segregation of a polymorphic restriction site in informative families conclusively demonstrated that the Type II gene is found in a single copy in the human haploid genome. Finally, sequencing of a triple helical domain exon has confirmed that a rearrangement leading to the fusion of two exons occurred in the pro alpha 1(I) gene, following the divergence of the fibrillar collagens.

Copy number of the chicken type II procollagen gene

The copy number of the type II procollagen gene has been determined by quantitative hybridization of cloned DNA to Southern blots of total cellular DNA from chicken. Two different DNA probes have been used. One contains the 289 base pair exon coding for the junction between the triple helical domain and the carboxyl-terminal propeptide and the other contains an 162 base pair exon coding for amino acids 712-765 of the triple helical domain. Both fragments hybridize to single bands present at one copy per haploid genome in genomic DNA from chicken liver or sternal cartilage after these DNAs are cleaved with either HinfI of PstI. When the hybridization stringency and washing conditions were modified sufficiently to stabilize hybridization of heteroduplexes with up to 31% mismatch, no additional hybridizing fragments were detected. These results show that there is not a second copy of this gene or a pseudogene which is more closely related to the type II procollagen gene than the alpha 1 type I procollagen gene. These studies suggest that the cartilage 3 alpha collagen chain, which appears to be very similar to the alpha 1 (II) collagen chain, is encoded by the type II procollagen gene but is differently processed than the major type II gene product, and that the alpha 1 (II) Minor chain identified in bovine type II collagen preparations most likely represents an allelic form of type II collagen rather than a product of a different gene.

Molecular cloning and carboxyl-propeptide analysis of human type III procollagen

Two human cDNA libraries prepared from normal fibroblast (GM3348) and rhabdomyosarcoma (CCL136) mRNAs were screened under cross hybridization conditions with a genomic fragment coding for exons 2 and 3 of the avian type III procollagen COOH-propeptide (Yamada, Y., Mudryj, M., Sullivan, M. and deCrombrugghe, B. (1983) J. Biol. Chem. 258, 2758-2761). One cDNA clone containing a 1.12 kb insert was isolated from the CCL136 library and later used to identify a GM3348 derived clone with a 2.4 kb insert. Comparison of the human and avian type III C-terminal propeptides revealed much more divergence in the first 54 amino acids following the terminal cysteine of the triple helical region than is present in the alpha 1(I) and alpha 2(I) procollagen chains of these species. Analysis of poly (A+) RNA from normal human fibroblast and tumor cell lines showed that they differed greatly in the relative amounts of alpha 1(I), alpha 2(I), and alpha 1(III) mRNAs. Furthermore, as we previously reported for the alpha 1(I) and alpha 2(I) transcripts, multiple mRNAs also hybridize to the cloned alpha 1(III) DNA.

Localization of human type II procollagen gene (COL2A1) to chromosome 12

DNA was prepared from 39 human-mouse somatic cell hybrid lines, and mouse and human parental cell lines. The DNA was digested to completion with EcoRI and Southern filters were prepared. These filters were hybridized at high stringency conditions to the human genomic subclone phHCol(II) A which corresponds to the human alpha 1(type II) procollagen gene (COL2A1). The mouse DNA yielded a single band at greater than 10 kb, whereas the human DNA had the expected single band at 4.8kb. Analyses of these human-mouse cell hybrids demonstrated that the human alpha 1(type II) procollagen gene segregates with chromosome 12.

Identification of messenger RNA for human type II collagen

Total RNA was purified from human fetal calvaria and articular cartilage. Messenger RNAs for type I and II collagens were identified by hybridization using cDNA clones for chicken pro alpha 1(I)-, pro alpha 2(I)- and pro alpha 1(II)collagen mRNAs and by analysis of cell-free translation products of these RNAs by polyacrylamide gel electrophoresis. The size of human pro alpha 1(II)collagen mRNA is approx. 5100 bases. Translatability of cartilage specific type II collagen mRNA was found to be concentration dependent: with increasing total RNA concentrations the relative translation of type II collagen mRNA was reduced with respect to type I mRNAs.