Showing papers on "Human genome published in 1989"

Detection of polymorphisms of human DNA by gel electrophoresis as single-strand conformation polymorphisms

Abstract: We developed mobility shift analysis of single-stranded DNAs on neutral polyacrylamide gel electrophoresis to detect DNA polymorphisms. This method follows digestion of genomic DNA with restriction endonucleases, denaturation in alkaline solution, and electrophoresis on a neutral polyacrylamide gel. After transfer to a nylon membrane, the mobility shift due to a nucleotide substitution of a single-stranded DNA fragment could be detected by hybridization with a nick-translated DNA fragment or more clearly with RNA copies synthesized on each strand of the DNA fragment as probes. As the mobility shift caused by nucleotide substitutions might be due to a conformational change of single-stranded DNAs, we designate the features of single-stranded DNAs as single-strand conformation polymorphisms (SSCPs). Like restriction fragment length polymorphisms (RFLPs), SSCPs were found to be allelic variants of true Mendelian traits, and therefore they should be useful genetic markers. Moreover, SSCP analysis has the advantage over RFLP analysis that it can detect DNA polymorphisms and point mutations at a variety of positions in DNA fragments. Since DNA polymorphisms have been estimated to occur every few hundred nucleotides in the human genome, SSCPs may provide many genetic markers.

Alu polymerase chain reaction: a method for rapid isolation of human-specific sequences from complex DNA sources.

Abstract: Current efforts to map the human genome are focused on individual chromosomes or smaller regions and frequently rely on the use of somatic cell hybrids. We report the application of the polymerase chain reaction to direct amplification of human DNA from hybrid cells containing regions of the human genome in rodent cell backgrounds using primers directed to the human Alu repeat element. We demonstrate Alu-directed amplification of a fragment of the human HPRT gene from both hybrid cell and cloned DNA and identify through sequence analysis the Alu repeats involved in this amplification. We also demonstrate the application of this technique to identify the chromosomal locations of large fragments of the human X chromosome cloned in a yeast artificial chromosome and the general applicability of the method to the preparation of DNA probes from cloned human sequences. The technique allows rapid gene mapping and provides a simple method for the isolation and analysis of specific chromosomal regions.

The isochore organization of the human genome

Abstract: The investigations reviewed here indicate that the eukaryotic genome is an integrated structural, functional, and evolutionary system. This view arose from a comparative study of vertebrate genomes, centered on the analysis of their compositional patterms, namely of the compositional distributions of large DNA fragments, coding sequences, and introns

Cloning defined regions of the human genome by microdissection of banded chromosomes and enzymatic amplification

Abstract: THE molecular analysis of many genetic diseases requires the isolation of probes for defined human chromosome regions. Existing techniques such as the screening of chromosome-specific libraries1, subtractive DNA cloning2 and chromosome jumping3 are either tedious or not generally applicable. Microdissection and microcloning has successfully been applied to various chromosome regions in Drosophila and mouse4–9, but conventional microtechniques are too coarse and inefficient for analysis of the human genome10–12. Because microdissection has previously been used on unhanded chromosomes only, cell lines in which the chromosome of interest could be identified without banding had to be used. At least one hundred chromosomes were needed for dissection and λ vectors used to achieve maximum cloning efficiency. Recombinant phage clones are, however, more difficult to characterize than plasmid clones. Here we describe the dissection of the Langer-Giedion syndrome region on chromosome 8 from GTG-banded metaphase chromosomes (G-banding with trypsin-Giemsa) and the universal enzymatic amplification of the dissected DNA. Eighty per cent of clones from this library (total yield 20,000) identify single-copy DNA sequences. Fifty per cent of clones detect deletions in two patients with Langer–Giedion syndrome. Although the other clones have not yet been mapped, this result demonstrates that thousands of region-specific probes can be isolated within ten days.

Cytosine methylation and the fate of CpG dinucleotides in vertebrate genomes.

Abstract: The dinucleotide CpG is a “hotspot” for mutation in the human genome as a result of (1) the modification of the 5′ cytosine by cellular DNA methyltransferases and (2) the consequent high frequency of spontaneous deamination of 5-methyl cytosine (5mC) to thymidine. DNA methylation thus contributes significantly, albeit indirectly, to the incidence of human genetic disease. We have attempted to estimate for the first time the in vivo rate of deamination of 5mC from the measured rate of 5mC deamination in vitro and the known error frequency of the cellular G/T mismatch-repair system. The accuracy and utility of this estimate (m d ) was then assessed by comparison with clinical data, and an improved estimate of m d (1.66x10-16 s-1) was derived. Comparison of the CpG mutation rates exibited by globin gene and pseudogene sequences from human, chimpanzee and macaque provided further estimates of m d , all of which were consistent with the first. Use of this value in a mathematical model then permitted the estimation of the length of time required to produce the level of “CpG suppression” currently found in the “bulk DNA” of vertebrate genomes. This time span, approximately 450 million years, corresponds closely to the estimated time since the emergence and adaptive radiation of the vertebrates and thus coincides with the probable advent of heavily methylated genomes. An accurate estimate of the 5mC deamination rate is important not only for clinical medicine but also for studies of gene evolution. Our data suggest both that patterns of vertebrate gene methylation may be comparatively stable over relatively long periods of evolutionary time, and that the rate of CpG deamination can, under certain limited conditions, serve as a “molecular clock”.

Isolation of single-copy human genes from a library of yeast artificial chromosome clones.

Abstract: A recently developed cloning system based on the propagation of large DNA molecules as linear, artificial chromosomes in the yeast Saccharomyces cerevisiae provides a potential method of cloning the entire human genome in segments of several hundred kilobase pairs. Most application of this system will require the ability to recover specific sequences from libraries of yeast artificial chromosome clones and to propagate these sequences in yeast without alterations. Two single-copy genes have now been cloned from a library of yeast artificial chromosome clones that was prepared from total human DNA. Multiple, independent isolates were obtained of the genes encoding factor IX and plasminogen activator inhibitor type 2. The clones, which ranged in size from 60 to 650 kilobases, were stable on prolonged propagation in yeast and appear to contain faithful replicas of human DNA.

The human genome contains hundreds of genes coding for finger proteins of the Krüppel type.

Abstract: Our aim was to identify new human proteins with potential DNA binding activity, related to the Kruppel protein which regulates Drosophila segmentation. We screened a human placenta cDNA library and a human genomic DNA library with a synthetic oligonucleotide probe corresponding to the H/C link region that connects finger loops in the multifingered Kruppel protein. We found more than 100 different mRNAs encoding Kruppel multifingered proteins in the human placenta. In the whole human genome, the number of genes encoding such proteins reaches about 300. Sequence analysis of 14 cloned cDNAs indicated that they code for at least nine undescribed human finger proteins. The sequences of the 106 finger repeats present in these nine proteins are highly homologous. Most of the variability lies in a limited number of positions located in their postulated alpha-helical structure, and therefore could be implicated in their DNA-binding specificity.

Human population genetic studies of five hypervariable DNA loci.

Abstract: Population genetic studies were performed using DNA probes that recognize five hypervariable loci (D2S44, D14S1, D14S13, D17S79, and DXYS14) in the human genome. DNA from approximately 900 unrelated individuals, subdivided into three ethnic groups (American blacks, Caucasians, and Hispanics) were digested with PstI and were successively hybridized to each DNA probe. The number of distinct DNA fragments identified for each of these regions varies from 30 to more than 80. An allele frequency distribution was determined for each locus and each ethnic group. The results show significant differences, between ethnic groups, in the pattern of distribution as well as in the relative frequency of the most common alleles of D2S44, D14S1, and D14S13 but only small differences in others (i.e., D17S79 and DXYS14). The results presented show that the analysis of these loci can have useful applications in population genetics as well as in identity tests.

Detection of DNA sequence polymorphisms by enzymatic amplification and direct genomic sequencing.

Abstract: The discovery of RFLPs and their utilization as genetic markers has revolutionized research in human molecular genetics However, only a fraction of the DNA sequence polymorphisms in the human genome affect the length of a restriction fragment and hence result in an RFLP Polymorphisms that are not detected as RFLPs are typically passed over in the screening process though they represent a potentially important source of informative genetic markers We have used a rapid method for the detection of naturally occurring DNA sequence variations that is based on enzymatic amplification and direct sequencing of genomic DNA This approach can detect essentially all useful sequence variations within the region screened We demonstrate the feasibility of the technique by applying it to the human retinoblastoma susceptibility locus We screened 3,712 bp of genomic DNA from each of nine individuals and found four DNA sequence polymorphisms At least one of these DNA sequence polymorphisms was informative in each of three families with hereditary retinoblastoma that were not informative with any of the known RFLPs at this locus We believe that direct sequencing is a reasonable alternative to other methods of screening for DNA sequence polymorphisms and that it represents a step forward for obtaining informative markers at well-characterized loci that have been minimally informative in the past

Evolution of chromosome bands: molecular ecology of noncoding DNA.

Abstract: Giemsa dark bands, G-bands, are a derived chromatin character that evolved along the chromosomes of early chordates. They are facultative heterochromatin reflecting acquisition of a late replication mechanism to repress tissue-specific genes. Subsequently, R-bands, the primitive chromatin state, became directionally GC rich as evidenced by Q-banding of mammalian and avian chromosomes. Contrary to predictions from the neutral mutation theory, noncoding DNA is positionally constrained along the banding pattern with short interspersed repeats in R-bands and long interspersed repeats in G-bands. Chromosomes seem dynamically stable: the banding pattern and gene arrangement along several human and murine autosomes has remained constant for 100 million years, whereas much of the noncoding DNA, especially retroposons, has changed. Several coding sequence attributes and probably mutation rates are determined more by where a gene lives than by what it does. R-band exons in homeotherms but not G-band exons have directionally acquired GC-rich wobble bases and the corresponding codon usage: CpG islands in mammals are specific to R-band exons, exons not facultatively heterochromatinized, and are independent of the tissue expression pattern of the gene. The dynamic organization of noncoding DNA suggests a feedback loop that could influence codon usage and stabilize the chromosome’s chromatin pattern: DNA sequences determine affinities of → proteins that together form → a chromatin that modulates → rate constants for DNA modification that determine → DNA sequences. Theories of hierarchical selection and molecular ecology show how selection can act on Darwinian units of noncoding DNA at the genome level thus creating positionally constrained DNA and contributing minimal genetic load at the individual level.

Human beta satellite DNA: genomic organization and sequence definition of a class of highly repetitive tandem DNA

Abstract: We describe a class of human repetitive DNA, called beta satellite, that, at a most fundamental level, exists as tandem arrays of diverged approximately equal to 68-base-pair monomer repeat units. The monomer units are organized as distinct subsets, each characterized by a multimeric higher-order repeat unit that is tandemly reiterated and represents a recent unit of amplification. We have cloned, characterized, and determined the sequence of two beta satellite higher-order repeat units: one located on chromosome 9, the other on the acrocentric chromosomes (13, 14, 15, 21, and 22) and perhaps other sites in the genome. Analysis by pulsed-field gel electrophoresis reveals that these tandem arrays are localized in large domains (50-300 kilobase pairs) that are marked by restriction fragment length polymorphisms. In total, beta satellite sequences comprise several million base pairs of DNA in the human genome. Analysis of this DNA family should permit insights into the nature of chromosome-specific and nonspecific modes of satellite DNA evolution and provide useful tools for probing the molecular organization and concerted evolution of the acrocentric chromosomes.

Detection of sequences homologous to human retroviral DNA in multiple sclerosis by gene amplification.

Abstract: Twenty-one patients with multiple sclerosis, chronic progressive type, were examined for DNA sequences homologous to a human retrovirus. Genomic DNA from peripheral blood mononuclear cells was analyzed for the presence of homologous sequences to the human T-cell leukemia/lymphoma virus type I (HTLV-I) long terminal repeat, 3' gag, pol, and env domains by the enzymatic in vitro gene amplification technique, polymerase chain reaction. Positive identification of homologous pol sequences was made in the amplified DNA from six of these patients (29%). Three of these six patients (14%) also tested positive for the env region, but not for the other regions tested. In contrast, none of the samples from 35 normal individuals studied was positive when amplified and tested with the same primers and probes. Comparison of patterns obtained from controls and from patients with adult T-cell leukemia or tropical spastic paraparesis suggests that the DNA sequences identified are exogenous to the human genome and may correspond to a human retroviral species. The data support the detection of a human retroviral agent in some patients with multiple sclerosis.

Two bovine genes for mitochondrial ADP/ATP translocase expressed differences in various tissues.

Abstract: Two different bovine cDNAs have been characterized that encode closely related homologues of the mitochondrial membrane carrier protein ADP/ATP translocase. One of them codes for the protein that has been characterized previously from bovine heart mitochondria, and the other codes for a protein that differs from it in 33 amino acids out of 297. Including the base substitutions required to bring about these changes in amino acid sequence, the coding regions of the cDNAs differ at 184 positions. In addition, they are extensively diverged in their 3' noncoding sequences, which differ greatly in both length and sequence, and these segments of the cDNAs have been used as hybridization probes to demonstrate that the expression of the two genes giving rise to the two proteins is very different in various bovine tissues. Expression of one gene predominates in heart muscle and that of the other in intestine. Hybridization experiments with digests of genomic DNA have shown the presence of numerous sequences related to the two cDNAs in both the bovine and human genomes. Some of these probably arise from pseudogenes, but three expressed genes have been detected in the human genome. The study of the regulation of the expression of these genes may help to illuminate the basis of tissue-specific human mitochondrial diseases which arise because of defects in mitochondrial enzymes only in the affected tissue and not in other tissues of the same individual.

Rapid screening of a human genomic library in yeast artificial chromosomes for single-copy sequences.

Abstract: A yeast artificial chromosome (YAC) library in Saccharomyces cerevisiae consisting of 30,000 clones with an average insert size of 0.1 megabase pair of human DNA has been generated from primary fibroblast DNA. A YAC vector was modified to enable the recovery of both ends of a human DNA insert in plasmids in Escherichia coli and to confer G418 resistance to mammalian cells. A rapid method for yeast colony hybridization was used that exploits the ability of yeast spheroplasts to regenerate in a thin layer of calcium alginate. This method permits direct replica plating and processing of colonies from the primary transformation plate to nitrocellulose filters. Yeast colony hybridization conditions have been established to identify, within a YAC library of human genomic DNA, artificial chromosomes with homology to human DNA probes of unique single-copy sequence. An artificial chromosome with a 0.1-megabase-pair insert from the human Xq28 region has been identified by hybridization to a DNA probe that detects a unique sequence near the 3' end of the factor VIII gene.

Use of variable simple sequence motifs as genetic markers: application to study of myotonic dystrophy.

Abstract: Among the many classes of repetitive elements present in the human genome, the ubiquitous "simple sequence motifs" (SSMs) composed of [A]n, [TG]n, [AG]n or codon-tandem repeats form a major source of genetic variation. Here we report a detailed molecular-genetic study of a "variable simple sequence motif" (VSSM) in the apolipoprotein C2 (apoC2) gene, which maps to the 19q13.2 region in the vicinity of the myotonic dystrophy (DM) locus. By combining in vitro DNA-amplification using the polymerase chain reaction and high-resolution gel electrophoresis, we could demonstrate a high degree of allelic variation with at least ten alleles, which differ in the number of repeated [TG] or [AG] dinucleotide units. Similar results were found for the somatostatin I gene locus. To evaluate the usefulness of SSM-length polymorphisms as genetic markers, the apoC2-VSSM was employed for linkage analysis in DM families. Our results establish that the orientation of the apolipoprotein gene cluster on 19q is cenapoE-apoC2-ter and indicate that the many thousands of structurally similar VSSMs in the human genome represent a rich source of highly informative genetic and diagnostic markers.

Use of yeast artificial chromosome clones for mapping and walking within human chromosome segment 18q21.3.

Abstract: Well-characterized large genomic clones obtained from yeast artificial chromosome (YAC) libraries provide the framework to localize genes and approach genetic disease. We developed universally applicable approaches to establish authenticity, localize and orient internal genes, map restriction sites, and rescue the distal ends of large human genomic DNA inserts. We selected human chromosome segment 18q21.3 as a model system. Molecular cloning of this segment was initiated by characterizing three plasminogen activator inhibitor type 2 (PAI-2) clones [290, 180, and 60 kilobases (kb)] isolated from a YAC library. Comparison of YAC and bacteriophage lambda genomic DNA clones confirmed the fidelity of the PAI-2 locus. Detailed rare cutting restriction maps were generated by ramped contour-clamped homogeneous electric field electrophoresis. The PAI-2 locus was located and oriented within the YACs, which span a distance 70 kb 5' to 220 kb 3' of PAI-2. Moreover, both left and right ends of the YAC genomic DNA inserts were rescued by amplifying circularized cloning sites with an inverted form of the polymerase chain reaction. These unique terminal genomic DNA fragments were used to rescreen the YAC library and isolate overlapping clones that extend the map. These approaches will enable neighboring loci to be definitively linked and establish the feasibility of using YAC technology to clone and map chromosomal segments.

Two-dimensional DNA fingerprinting of human individuals

Abstract: The limiting factor in the presently available techniques for the detection of DNA sequence variation in the human genome is the low resolution of Southern blot analysis. To increase the analytical power of this technique, we applied size fractionation of genomic DNA restriction fragments in conjunction with their sequence-dependent separation in denaturing gradient gels; the two-dimensional separation patterns obtained were subsequently transferred to nylon membranes. Hybridization analysis using minisatellite core sequences as probes resulted in two-dimensional genomic DNA fingerprints with a resolution of up to 625 separated spots per probe per human individual; by conventional Southern blot analysis, only 20-30 bands can be resolved. Using the two-dimensional DNA fingerprinting technique, we demonstrate in a small human pedigree the simultaneous transmission of 37 polymorphic fragments (out of 365 spots) for probe 33.15 and 105 polymorphic fragments (out of 625 spots) for probe 33.6. In addition, a mutation was detected in this pedigree by probe 33.6. We anticipate that this method will be of great use in studies aimed at (i) measuring human mutation frequencies, (ii) associating genetic variation with disease, (iii) analyzing genomic instability in relation to cancer and aging, and (iv) linkage analysis and mapping of disease genes.

Polymers of random short oligonucleotides detect polymorphic loci in the human genome

Abstract: Polymers of random 14 mer oligonucleotides are shown to detect discrete loci in the human genome. Eighteen different synthetic tandem repeats of random 14 base-pair units (STRs) have been generated and all of them turn out to detect polymorphic loci on southern blots of human DNA samples, presumably corresponding to a variable number of tandem repeats (VNTR). This finding suggests that minisatellites are a major component of the human genome and are strongly associated with the generation of genetic variability. In addition, it should open new strategies to make new polymorphic probes available.

Stable maintenance of a 35-base-pair yeast mitochondrial genome

Abstract: Small deletion variants ([rho-] mutants) derived from the wild-type ([ rho+]) Saccharomyces cerevisiae mitochondrial genome were isolated and characterized. The mutant mitochondrial DNAs (mtDNAs) examined retained as little as 35 base pairs of one section of intergenic DNA, were composed entirely of A.T base pairs, and were stably maintained. These simple mtDNAs existed in tandemly repeated arrays at an amplified level that made up approximately 15% of the total cellular DNA and, as judged by fluorescence microscopy, had a nearly normal mitochondrial arrangement throughout the cell cytoplasm. The simple nature of these [rho-] genomes indicates that the sequences required to maintain mtDNA must be extremely simple.

Isolation and characterization of a human telomere

Abstract: A method is described that allows cloning of human telomeres in S. cerevisiae by joining human telomeric restriction fragments to yeast artificial chromosome halves. The resulting chimeric yeast-human chromosomes propagate as true linear chromosomes, demonstrating that the human telomere structure is capable of functioning in yeast and suggesting that telomere functions are evolutionarily conserved between yeast and human. One cloned human telomere, yHT1, contains 4 kb of human genomic DNA sequence next to the tandemly repeating TTAGGG hexanucleotide. Genomic hybridizations using both cloned DNA and TTAGGG repeats have revealed a common structural organization of human telomeres. This 4 kb of genomic DNA sequence is present in most, but not all, human telomeres, suggesting that the region is not involved in crucial chromosome-specific functions. However, the extent of common features among the human telomeres and possible similarities in organization with yeast telomeres suggest that this region may play a role in general chromosome behavior such as telomere-telomere interactions. Unlike the simple telomeric TTAGGG repeats, our cloned human genomic DNA sequence does not cross-hybridize with rodent DNA. Thus, this clone allows the identifications of the terminal restriction fragments of specific human chromosomes in human-rodent hybrid cells.

The human telomere

Abstract: An ultimate goal of human genetics is the generation of a complete physical and ''functional'' map of the human genome. Twenty-five percent of human DNA, however, consists of repetitive DNA sequences. These repetitive DNA sequences are thought to arise by many mechanisms, from direct sequence amplification by the unequal recombination of homologous DNA regions to the reverse flow of genetic information. A general outline of the chromosomal organization of these repetitive sequences will be discussed. Our working hypothesis is that certain classes of human repetitive DNA sequences ''encode'' the information necessary for defining long-range genomic structure. Evidence will be presented that the first goal of this research, the identification and cloning of the human telomere, has been achieved. A human repetitive DNA library was constructed from randomly sheared, reassociated, and oligo(G/center dot/C)-tailed DNA, a method that minimizes the potential loss of sequences devoid of a given restriction enzyme site. Sequences too large to clone efficiently in cosmid or /lambda/ vectors, such as centromeric repeats, or telomeric sequences with an end incompatible for cloning, should be present in this library. In order to isolate highly conserved repetitive DNA sequences, this library was screened with radiolabeled hamster Cot50 repetitive DNA. Two clones, containing tandem arrays of the sequence (TTAGGG), were isolated by this method. 30 refs., 1 fig., 2 tabs.

Newly arisen DNA repeats in primate phylogeny.

Abstract: We discovered the presence of an Alu and an Xba repetitive DNA element within introns 4 and 7, respectively, of the human alpha-fetoprotein (AFP) gene; these elements are absent from the same gene in the gorilla. The Alu element is flanked by 12-base-pair direct repeats, AGGATGTTGTGG ... (Alu) ... AGGATGTTGTGG, which presumably arose by way of duplication of the intronic target site AGGATGTTGTGG at the time of the Alu insertion. In the gorilla, only a single copy of the unoccupied target site is present, which is identical to the terminal repeat flanking the human Alu element. There are two copies of an Xba repeat in the human AFP gene, apparently the only two in the genome. Xba1 and Xba2, located within introns 8 and 7, respectively, differ from each other at 3 of 303 positions. Xba1 is referred to as the old (ancestral) repeat because it lacks direct repeats. The new (derived) Xba2 is flanked by direct repeats, TTTCTTTTT ... (Xba) ... TTTCTTCTT, and is thought to have arisen as a result of transposition of Xba1. The ancestral Xba1 and a single copy of the Xba2 target site are present at orthologous positions in the gorilla, but the new Xba2 is absent. We conclude that the Alu and Xba DNA repeats emerged in the human genome at a time postdating the human-gorilla divergence and became established as genetic novelties in the human lineage. We submit that the chronology of divergence of primate lines of evolution can be correlated with the timing of insertion of new DNA repeats into the genomes of those primates.

Non-random association between alleles detected at D4S95 and D4S98 and the Huntington's disease gene.

Abstract: Analysis of many families with linked DNA markers has provided support for the Huntington's disease (HD) gene being close to the telomere on the short arm of chromosome 4. However, analysis of recombination events in particular families has provided conflicting results about the precise location of the HD gene relative to these closely linked DNA markers. Here we report an investigation of linkage disequilibrium between six DNA markers and the HD gene in 75 separate families of varied ancestry. We show significant non-random association between alleles detected at D4S95 and D4S98 and the mutant gene. These data suggest that it may be possible to construct high and low risk haplotypes, which may be helpful in DNA analysis and genetic counselling for HD, and represent independent evidence that the gene for HD is centromeric to more distally located DNA markers such as D4S90. This information may be helpful in defining a strategy to clone the gene for HD based on its location in the human genome.