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D J Prockop

Publications and source records attributed to D J Prockop.

At least 181 records · Page 10Linked to original sources
PubMed1991

Exclusion of COL1A1, COL1A2, and COL3A1 genes as candidate genes for Ehlers-Danlos syndrome type I in one large family.

Ehlers-Danlos syndrome (EDS) type I is a generalized connective tissue disorder, the major manifestations of which are soft, velvety hyperextensible skin and moderately severe joint hypermobility. The gene defect or defects causing EDS type I have not yet been defined, but previous observations suggested that the syndrome may be caused by mutations in the genes for type-I collagen (COL1A1 and COL1A2) or type-III collagen (COL3A1). Here, we performed linkage studies for these three genes in large Azerbaijanian family with EDS type I. Three polymorphisms in the COL3A1 gene, two in the COL1A1 gene, and one in the COL1A2 gene were tested using the polymerase chain reaction. The data obtained excluded linkage of any of the three genes to EDS type I in the family.

Base Sequence↗
PubMed1991

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.

Base Sequence↗
PubMed1991

Mutations in collagen genes: causes of rare and some common diseases in humans.

More than 70 mutations in the two structural genes for type I procollagen (COL1A1 and COL1A2) have been found in probands with osteogenesis imperfecta, a heritable disease of children characterized by fragility of bone and other tissues rich in type I collagen. The mutations include deletions, insertions, RNA splicing mutations, and single-base substitutions that convert a codon for glycine to a codon for an amino acid with a bulkier side chain. With a few exceptions, the most severe phenotypes of the disease are explained largely by synthesis of structurally defective pro alpha chains of type I procollagen that either interfere with the folding of the triple helix or with self-assembly of collagen into fibrils. The results emphasize the extent to which the zipperlike folding of the collagen triple helix and the self-assembly of collagen fibrils depend on the principle of nucleated growth whereby a few subunits form a nucleus and the nucleus is then propagated to generate a large structure with a precisely defined architecture. The principle of nucleated growth is a highly efficient mechanism for the assembly of large structures, but biological systems that depend extensively on nucleated growth are highly vulnerable to mutations that cause synthesis of structurally abnormal but partially functional subunits. Recently, several mutations in three other collagen genes (COL2A1, COL3A1, and COL4A5) have been found in probands with genetic diseases involving tissues rich in these collagens. Most of the probands have rare genetic diseases but a few appear to have phenotypes that are difficult to distinguish from more common disorders such as osteoarthritis, osteoporosis, and aortic aneurysms. Therefore, the results suggest that mutations in procollagen genes may cause a wide spectrum of both rare and common human diseases.

Animals↗
PubMed1991

A mutation in the pro alpha 2(I) gene (COL1A2) for type I procollagen in Ehlers-Danlos syndrome type VII: evidence suggesting that skipping of exon 6 in RNA splicing may be a common cause of the phenotype.

Fibroblasts from a proband with Ehlers-Danlos syndrome type VII synthesized approximately equal amounts of normal and shortened pro alpha 2(I) chains of type I procollagen. Nuclease S1 probe protection experiments with mRNA demonstrated that the pro alpha 2(I) chains were shortened because of a deletion of most or all of the 54 nucleotides in exon 6, the exon that contains codons for the cleavage site for procollagen N-proteinase. Sequencing of genomic clones revealed a single-base mutation that converted the first nucleotide of intron 6 from G to A. Therefore, the mutation was a change, in the -GT-consensus splice site, that produced efficient exon skipping. Allele-specific oligonucleotide hybridizations demonstrated that the proband's mother, father, and brother did not have the mutation. Therefore, the mutation was a sporadic one. Analysis of potential 5' splice sites in the 5' end of intron 6 indicated that none had favorable values by the two commonly employed techniques for evaluating such sites. The proband is the fourth reported proband with Ehlers-Danlos syndrome VII with a single-base mutation that causes skipping of exon 6 in the splicing of RNA from either the COL1A1 gene or COL1A2 gene. No other mutations in the two type I procollagen genes have been found in the syndrome. Therefore, such mutations may be a common cause of the phenotype. The primers developed should be useful in screening for the same or similar mutations causing the disease.

Alleles↗
PubMed1991

A single base mutation in type I procollagen (COL1A1) that converts glycine alpha 1-541 to aspartate in a lethal variant of osteogenesis imperfecta: detection of the mutation with a carbodiimide reaction of DNA heteroduplexes and direct sequencing of products of the PCR.

Skin fibroblasts from a proband with a lethal variant of osteogenesis imperfecta synthesized both apparently normal type I procollagen and a type I procollagen that had slow electrophoretic mobility because of posttranslational overmodifications. The thermal unfolding of the collagen molecules as assayed by protease digestion was about 2 degrees C lower than normal. It is surprising, however, that collagenase A and B fragments showed an essentially normal melting profile. Assay of cDNA heteroduplexes with a new technique involving carbodiimide modification indicated a mutation at about the codon for amino acid 550 of the alpha 1(I) chain. Subsequent amplification of the cDNA by the PCR and nucleotide sequencing revealed a single-base mutation that substituted an aspartate codon for glycine at position alpha 1-541 in the COL1A1 gene. The results here confirm previous indications that the effects of glycine substitutions in type I procollagen are highly position specific. They also demonstrate that a recently described technique for detecting single-base differences by carbodiimide modification of DNA heteroduplexes can be effectively employed to locate mutations in large genes.

Adult↗
PubMed1990

Mutations that substitute serine for glycine alpha 1-598 and glycine alpha 1-631 in type I procollagen. The effects on thermal unfolding of the triple helix are position-specific and demonstrate that the protein unfolds through a series of cooperative blocks.

Cultured skin fibroblasts from two probands with lethal variants of osteogenesis imperfecta synthesized type I procollagen that was posttranslationally over-modified. Analysis of cDNAs and genomic DNAs from the two probands demonstrated that proband I had a single-base mutation that converted the codon for glycine alpha 1-631 to a codon for serine, and proband II had a single-base mutation that converted the codon for glycine alpha 1-598 to a codon for serine. Although the two serine-for-glycine substitutions were separated by only 35 residues, they had markedly different effects on the thermal unfolding of the collagen triple helix as assayed by brief protease digestion. The type I procollagen from proband I (serine alpha 1-631) had an essentially normal temperature for thermal unfolding. In contrast, type I procollagen from proband II (serine alpha 1-598) was cleaved to readily identifiable intermediate fragments of about 630 residues at 20 degrees C. With procollagens from both probands, collagenase A fragments containing the first 775 amino acids of the alpha chain domains had a lowered temperature for thermal unfolding as assayed by brief protease digestion. The collagenase A fragments from proband I were cleaved to intermediates of about 600 amino acids at 36 degrees C and to fragments of about 510 residues at 37 degrees C. The collagenase A fragments from proband II were cleaved to intermediates of about 630 residues at 32 degrees C, to fragments of about 600 residues at 36 degrees C, and to fragments of about 510 at 37 degrees C. The fragments of about 510 residues from both mutated procollagens were more stable to protease digestion than the collagenase A fragments of 775 residues from normal type I collagen. The results demonstrate that the effects of glycine substitutions on the thermal unfolding of type I collagen are highly position-specific. They also provide direct evidence for previous indications that the triple helix of the protein undergoes micro-unfolding of a series of relatively independent "cooperative blocks" in the predenaturation range of temperatures.

Base Sequence↗
PubMed1990

Identical G+1 to A mutations in three different introns of the type III procollagen gene (COL3A1) produce different patterns of RNA splicing in three variants of Ehlers-Danlos syndrome. IV. An explanation for exon skipping some mutations and not others.

Identical G+1 mutations in three different introns of the gene for type III procollagen (COL3A1) that cause aberrant splicing of RNA were found in three probands with life-threatening variants of Ehlers-Danlos syndrome. Because the three mutations were in a gene with multiple and homologous exons, they provided an interesting test for factors that influence aberrant splicing. The G+1 to A mutation in intron 16 caused extensive exon skipping, the G+1 to A mutation in intron 20 caused both use of a cryptic splice site and retention of all the intron sequences, and the G+1 to A mutation in intron 42 caused efficient use of a single cryptic splice site. The different patterns of RNA splicing were not explained by evaluation of potential cryptic splice sites in the introns by either their homology with 5'-splice sites from other genes or by their delta G(0)37 values for binding to U1 RNA. Instead, the results suggested that the patterns of aberrant RNA splicing were primarily determined by the relative rates at which adjacent introns were normally spliced.

Adenine↗
PubMed1990

Detection of single-base mutations by reaction of DNA heteroduplexes with a water-soluble carbodiimide followed by primer extension: application to products from the polymerase chain reaction.

A new method was developed for the detection of single-base mutations in DNA. The polymerase chain reaction was used to prepare DNA fragments of up to 1 kb. Fragments that differed by a single-base were combined, denatured and renatured to generate heteroduplexes. The heteroduplexes were reacted with a water-soluble carbodiimide under conditions in which the carbodiimide modified Gs and Ts that were not base paired. The DNA was then used as a template for primer extension with Taq DNA polymerase under conditions in which extension terminated at the site of the carbodiimide-modified base and generated a 32P-labeled fragment that was identified by polyacrylamide gel electrophoresis as a fragment smaller than the full length product. The procedure detected all four general classes of single-base mutations in several different sequence contexts. The site of the mutation was located to within about 15 bp. Extension with both a 5'- and a 3'-primer made it possible to confirm the site of the mutation in most DNA samples or detect a mutation in heteroduplexes even if a G or T in one strand was unreactive because of its sequence context. The procedure appears to have several advantages over previously published techniques.

Bacteriophages↗
PubMed1990

Collagen fibrils in vitro grow from pointed tips in the C- to N-terminal direction.

Growth of collagen fibrils was examined in a system in which collagen monomers are generated by specific enzymic cleavage of type IpCcollagen with procollagen C-proteinase. Fibrils formed at 37 degrees C had highly tapered and symmetrical pointed tips. The pattern of cross-striations in the pointed tips indicated that all the molecules were oriented so that the N-termini were directed towards the tip. At 29 degrees C and 32 degrees C, the fibrils formed were thicker. One end of fibrils formed at 29 degrees C was blunt, and the other was pointed. Growth of the fibrils was exclusively from pointed tips. Occasionally a spear-like projection appeared at a blunted end. The spear-like projection then became a new pointed tip for growth in the opposite direction. The results suggested a model for fibril growth with at least three distinct binding sites for monomers. In the model, the pointed tip is the site with the highest affinity for the binding of monomers and most probably defines the critical concentration for fibril assembly. The main shaft of the fibril is a site with very low affinity for binding. The blunted end defines a low-affinity binding site where monomers can bind in opposite orientation to produce growth from a new pointed end.

Binding Sites↗