Isolation and regional mapping of NotI and EagI clones from human chromosome 21

NotI and EagI boundary libraries were constructed for human chromosome 21. One hundred forty-seven clones were isolated from the somatic cell hybrid 72532X-6 and localized using a hybrid mapping panel. After identification of those clones, which were isolated more than once, as well as those probes derived from a previously unrecognized integrated non-chromosome-21 fragment, 58 individual boundary clones (plus 2 additional NotI-EcoRI clones isolated from a flow-sorted library) were localized to 11 separate regions. The distribution of these probes is highly nonrandom, with 50% of the clones located in the distal band 21q22.3. Two probes, Not50 and Eag101, map to regions in the very proximal long arm which may contain the gene responsible for familial Alzheimer's disease (AD1), and Not50 would appear to be more proximal than D21S16 (E9). Twenty-eight probes map to the region between superoxide dismutase (SOD1) and the ETS2 oncogene, which appears to contain genes responsible for many of the phenotypic features of Down syndrome. Twenty clones contain (GT)n repeats, as determined by hybridization to a CA polymer, and should provide additional highly polymorphic probes. Closure of gaps in the physical linkage map of chromosome 21 should be facilitated by the isolation of these probes, as they identify many of the unmethylated CpG-rich islands that have hindered pulsed-field gel analysis. They will also be useful in identifying a set of genes in proximity to NotI and EagI restriction sites, as well as conserved DNA sequences for comparative mapping studies.     

Adenylate kinase isoenzymes in Aspergillus nidulans

Multiple HindIII-restriction fragments of Salmonella typhimurium and Salmonella typhi chromosomal DNA exhibited homology with the heat-labile enterotoxin (LT1) gene of Escherichia coli as determined by Southern blot analysis. A 9.4 kb HindIII restriction fragment identified in S. typhimurium and S. typhi chromosomal DNA reacted with both eltA and eltB gene probes. However, the homology of the 9.4 kb DNA fragment from these Salmonella species was greater with eltB than eltA. In addition, a synthetic oligonucleotide probe, made to a portion of the putative GM1-ganglioside binding region of cholera toxin (CT) and LT1, hybridized with the 9.4 kb DNA fragment of S. typhimurium but not with the 9.4 kb fragment found in S. typhi isolates. The hybridization of multiple restriction fragments of Salmonella DNA with eltA and eltB gene sequences further suggests duplication of the stx operon on the chromosome of these bacteria.     

Construction of a NotI linking library and isolation of new markers close to the Huntington''s disease gene.

Linking clones contain sequences flanking recognition sites for enzymes cutting rarely in mammalian DNA. They can be used to obtain and correlate both physical and genetic mapping information over subregions of mammalian chromosomes. We have constructed and used a NotI linking clone library representing unmethylated NotI sites from HHW693 DNA, a hamster hybrid cell line containing 4p15-4pter and a fragment of 5p as its only human chromosome contribution. Human clones were identified by hybridisation with a cloned human repeat sequence, and localised further to subregions of human chromosome 4p15-4pter using a panel of additional hybrids. Clones from the region distal to the DNA probes (D4S10, D4S43, D4S95) linked to the Huntington's disease mutation, were further analysed. Four markers close to the HD gene: D4S111, D4S113, D4S114 and clone 417 are described here. In addition to serving as markers in physical and genetic mapping experiments, these linking clones provide probes next to cleavable NotI sites, and can therefore be used to screen NotI based chromosome jumping libraries. They also provide indications for potential gene sequences, identifiable as evolutionarily conserved sequences.     

A highly polymorphic locus in human DNA revealed by probes from cosmid 1-5 maps to chromosome 2q35----37.

The highly polymorphic locus D2S3 is revealed by three single-copy probes from cosmid C1-5. These probes, 1-30, 1-32, and 2-96, collectively reveal seven restriction fragment length polymorphisms. Fifty-three of 56 unrelated individuals (93%) were heterozygous at one or more of the seven loci, making the compound locus a very useful marker for gene mapping. Chromosomal assignment of D2S3 was obtained using a panel of human X hamster and human X mouse somatic cell hybrids. Molecular hybridization of EcoRI-digested DNA from these cell lines with the DNA inserts from subclones 1-30, 1-32, and 2-96 showed that all three probes mapped to the long arm of chromosome 2. Additionally, in situ hybridization of [3H]-labeled probe 2-96 to metaphase chromosome preparations allowed more precise assignment of the locus to the region 2q35----37.     

Characterization of radiation/fusion hybrids containing parts of human chromosome 10 and their use in mapping chromosome 10-specific probes.

We have characterized a panel of somatic cell hybrid cell lines which contain different portions of human chromosome 10. Genomic DNA from the somatic cell hybrids was tested for hybridization with each of an ordered set of probes used previously to construct a genetic map of chromosome 10, as well as several additional probes, previously localized by in situ hybridization. Hybridization of an unmapped probe to the cell line DNAs can be used to determine its most likely position on the chromosome relative to the mapped set of probes. Genomic DNA from two of the cell lines has been used to construct region-specific cosmid and bacteriophage libraries, and clones derived from these libraries were localized by hybridization to the panel of hybrid cell lines. Several of these probes reveal restriction fragment length polymorphisms which have been genetically mapped. Three of the probes map near the locus for multiple endocrine neoplasia type 2A, and one of these probes, BG-JC353 (D10S167), maps between RBP3 and TB14.34 (D10S34). Another probe, CRI-J282 (D10S104), is close to the FNRB locus. The panel of hybrid cell lines is thus useful for rapidly localizing unmapped probes and as a source of DNA for the construction of recombinant libraries derived from specific regions of the chromosome.     

Localization of the human thyroxine-binding globulin gene to the long arm of the X chromosome (Xq21-22).

Thyroxine-binding globulin (TBG) is the major thyroid-hormone transport protein in the plasma of most vertebrate species. A recombinant phage (lambda cTBG8) containing a cDNA insert of human TBG recently has been described. With the cDNA insert from lambda cTBG8 used as a radiolabeled probe, DNA from a series of somatic-cell hybrids containing deletions of the X chromosome was analyzed by means of blot hybridization. The results indicated that the TBG gene is located in the midportion of the long arm of the X chromosome between bands Xq11 and Xq23. The gene then was mapped to band region Xq21-22 by means of in situ hybridization to metaphase chromosomes. Sequences on the X chromosome that are homologous to the cDNA probe are contained within a single EcoRI restriction fragment of 12.5 kb in human DNA. On the basis of the intensity of the hybridization signal on Southern blots, it was determined that the human TBG cDNA probe used in the present study shares significant homology with hamster and mouse sequences. A single EcoRI restriction fragment was recognized in both hamster (8.0-kb) and mouse (5.1-kb) DNA.     

Molecular definition of a region of chromosome 21 that causes features of the Down syndrome phenotype

Down syndrome (DS) is a major cause of mental retardation and heart disease. Although it is usually caused by the presence of an extra chromosome 21, a subset of the diagnostic features may be caused by the presence of only band 21q22. We now present evidence that significantly narrows the chromosomal region responsible for several of the phenotypic features of DS. We report a molecular and cytogenetic analysis of a three-generation family containing four individuals with clinical DS as manifested by the characteristic facial appearance, endocardial cushion defect, mental retardation, and probably dermatoglyphic changes. Autoradiograms of quantitative Southern blots of DNAs from two affected sisters, their carrier father, and a normal control were analyzed after hybridization with two to six unique DNA sequences regionally mapped on chromosome 21. These include cDNA probes for the genes for CuZn-superoxide dismutase (SOD1) mapping in 21q22.1 and for the amyloid precursor protein (APP) mapping in 21q11.2-21.05, in addition to six probes for single-copy sequences: D21S46 in 21q11.2-21.05, D21S47 and SF57 in 21q22.1-22.3, and D21S39, D21S42, and D21S43 in 21q22.3. All sequences located in 21q22.3 were present in three copies in the affected individuals, whereas those located proximal to this region were present in only two copies. In the carrier father, all DNA sequences were present in only two copies. Cytogenetic analysis of affected individuals employing R and G banding of prometaphase preparations combined with in situ hybridization revealed a translocation of the region from very distal 21q22.1 to 21qter to chromosome 4q. Except for a possible phenotypic contribution from the deletion of chromosome band 4q35, these data provide a molecular definition of the minimal region of chromosome 21 which, when duplicated, generates the facial features, heart defect, a component of the mental retardation, and probably several of the dermatoglyphic changes of DS. This region may include parts of bands 21q22.2 and 21q22.3, but it must exclude the genes S0D1 and APP and most of band 21q22.1, specifically the region defined by S0D1, SF57 and D21S47.     

Physical map of the Methanobacterium thermoautotrophicum Marburg chromosome.

A physical map of the Methanobacterium thermoautotrophicum Marburg chromosome was constructed by using pulsed-field gel electrophoresis of restriction fragments generated by NotI, PmeI, and NheI. The order of the fragments was deduced from Southern blot hybridization of NotI fragment probes to various restriction digests and from partial digests. The derived map is circular, and the genome size was estimated to be 1,623 kb. Several cloned genes were hybridized to restriction fragments to locate their positions on the map. Genes coding for proteins involved in the methanogenic pathway were located on the same segment of the circular chromosome. In addition, the genomes of a variety of thermophilic Methanobacterium strains were treated with restriction enzymes and analyzed by pulsed-field gel electrophoresis. The sums of the fragment sizes varied from 1,600 to 1,728 kb among the strains, and widely different macrorestriction patterns were observed.     

Regional localization of chromosome 3-specific DNA fragments by using a hybrid cell deletion mapping panel.

A series of human chromosome 3-specific DNA fragments isolated and characterized from a lamda phage genomic library were regionally localized on human chromosome 3. This was accomplished using filter hybridization blot analysis of a human chromosome 3 hybrid cell deletion mapping panel. Twenty-three new anonymous DNA fragments were assigned to one of four physical regions of chromosome 3. Seventeen DNA fragments were mapped to the long arm of chromosome 3, including one DNA fragment that demonstrated a restriction fragment length polymorphism (RFLP). Five DNA fragments were assigned to 3p14.2----pter, including one highly polymorphic fragment sublocalized at 3p25----pter by in situ hybridization. This DNA fragment is the second reported distal 3p polymorphic probe. One DNA fragment was localized to 3p14----p14.2. In addition, three fragments previously assigned to chromosome 3 were confirmed. Polymorphic DNA probes DNF15S2 (formerly D1S1) and D3S2 were mapped to 3p14.2----pter. The previous 3p25 in situ localization of the c-raf-1 oncogene was supported by deletion panel mapping. The physical localization of these twenty-three new DNA fragments has more than doubled the number of cloned DNA fragments assigned to chromosome 3. These and future regional assignments of DNA fragment probes will facilitate construction of both a physical and genetic linkage map of chromosome 3. They may also be useful in characterizing the chromosomal and molecular aberrations involved in small-cell lung cancer (SCLC), renal cell carcinoma, other malignancies, and the 3p14.2 common fragile site.     

Physical Map of the Saccharomyces Cerevisiae Genome at 110-Kilobase Resolution

A physical map of the Saccharomyces cerevisiae genome is presented. It was derived by mapping the sites for two restriction endonucleases, SfiI and NotI, each of which recognizes an 8-bp sequence. DNA-DNA hybridization probes for genetically mapped genes and probes that span particular SfiI and NotI sites were used to construct a map that contains 131 physical landmarks--32 chromosome ends, 61 SfiI sites and 38 NotI sites. These landmarks are distributed throughout the non-rDNA component of the yeast genome, which comprises 12.5 Mbp of DNA. The physical map suggests that those genes that can be detected and mapped by standard genetic methods are distributed rather uniformly over the full physical extent of the yeast genome. The map has immediate applications to the mapping of genes for which single-copy DNA-DNA hybridization probes are available.     

Detection of submicroscopic deletions and a DNA polymorphism at the retinoblastoma locus

Summary DNA samples from 60 unrelated patients with retinoblastoma were screened by Southern blot hybridization using two probes that are closely linked to the retinoblastoma locus within human chromosome band 13q14. Seven of 44 patients with bilateral or multifocal unilateral retinoblastoma and one patient with unifocal unilateral retinoblastoma were found to have a heterozygous deletion for the anonymous DNA sequence H3-8. Three of the eight deletions did not include the esterase D locus and were undetectable by conventional cytogenetic analysis. The findings are compatible with the deletions being the cause of retinoblastoma in these cases and provide a basis for DNA diagnosis in nearly 20% of patients with bilateral and multifocal unilateral retinoblastoma. The H3-8 probe also detects a restriction fragment length polymorphism that is a useful genetic marker in some families.     

Shotgun polymerase chain reaction: construction of clone libraries specific to a NotI fragment of flow-sorted human chromosome 22.

We have developed the "shotgun polymerase chain reaction," a method for obtaining a large number of DNA markers specific to a giant DNA fragment, which facilitates analysis of a particular chromosomal region. We applied this method to a giant NotI fragment which carries the immunoglobulin lambda constant region on chromosome 22. NotI digests of chromosome 22 flow-sorted from human B-lymphoblastoid cell line GM130B were size fractionated by pulsed-field gel electrophoresis. Preliminary Southern hybridization analysis revealed that the immunoglobulin lambda constant region was conveyed on 1.4- and 1.3-Mb NotI fragments in this cell line. The agarose gel corresponding to 1.2 to 1.5 Mb in size was excised into slices and subjected to polymerase chain reaction to identify gel slices containing NotI fragments carrying Ke-Oz+, a subtype of the immunoglobulin lambda constant region. From the NotI fragment thus identified, a large number of small DNA segments were amplified through the ligation-mediated random polymerase chain reaction method. The amplified products were cloned and analyzed for chromosomal origin and localization to particular NotI fragments. Seven of eighteen clones originated from the 1.4-Mb NotI fragment of chromosome 22 in GM130B cells, which appears to be exactly the same as detected by a probe for the immunoglobulin lambda constant region.     

Identification of polymorphisms by genomic denaturing gradient gel electrophoresis: application to the proximal region of human chromosome 21.

Genomic Denaturing Gradient Gel Electrophoresis (gDGGE) provides an alternative to the standard method of restriction fragment length polymorphism (RFLP) analysis for identifying polymorphic sequence variation in genomic DNA. For gDGGE, genomic DNA is cleaved by restriction enzymes, separated in a polyacrylamide gel containing a gradient of DNA denaturants, and then transferred by electroblotting to nylon membranes. Unlike other applications of DGGE, gDGGE is not limited by the size of the probe and does not require probe sequence information. gDGGE can be used in conjunction with any unique DNA probe. Here we use gDGGE with probes from the proximal region of the long arm of human chromosome 21 to identify polymorphic DNA sequence variation in this segment of the chromosome. Our screening panel consisted of DNA from nine individuals, which was cleaved with five restriction enzymes and submitted to electrophoresis in two denaturing gradient conditions. We detected at least one potential polymorphism for nine of eleven probes that were tested. Two polymorphisms, one at D21S4 and one at D21S90, were characterized in detail. Our study demonstrates that gDGGE is a fast and efficient method for identifying polymorphisms that are useful for genetic linkage analysis.     

Isolation of giant DNA fragments from flow-sorted human chromosomes

We have established a method using a conventional cell sorter equipped with a single argon laser to sort intact human chromosomes that can be used as a source for the production of giant DNA fragments. Various improvements were made to both the equipment and sorting method to enhance the sorting resolution and avoid destruction of chromosomal DNA. Using this improved method chromosomes 21 and 22 were sorted from the B-lymphoblastoid line GM00130B, digested with the rare cutting restriction endonuclease NotI, and analyzed by pulsed field gel electrophoresis followed by Southern hybridization using the Alu repetitive sequence as a probe. More than 25 discrete NotI giant DNA fragments ranging from 50 kb to longer than 2.5 Mb were separated and the size distribution pattern was unique for each chromosome, indicating successful sorting of intact chromosomes. The cumulative size of these Alu-positive NotI DNA fragments were 22.7 Mb and 25.5 Mb for chromosomes 21 and 22, respectively. These values are 47% and 49% of the estimated size of chromosomes 21 (48 Mb) and 22 (52 Mb).     

The number of ribosomal RNA genes in Thermus thermophilus HB8.

We have examined the number of rRNA genes in Thermus thermophilus HB8 by hybridization of Bam HI -, Hind III - and Pst I - digests of DNA to 3'- (3 2p) 23S, 16S and 5S rRNAs according to the Southern procedure. The restriction gels gave two radioactive bands with 23S and 5S rRNA. Furthermore, band positions were indistinguishable from one another when 23S and 5S rRNAs were used as probes to Bam HI and Hind III digests, indicating that each band contains sequences corresponding to the 3'-end of 23S and 5S rRNAs. The Pst I digest also gave two radioactive bands with 23S and 5S rRNAs as probes, where one band position was identical, but the other different. The 16S rRNA did hybridize with two fragments, using a Bam HI, as well as a Bam HI - Hind III double digest. The Hind III digest gave one band using 16S rRNA as a probe. It is concluded that the Thermus thermophilus HB8 chromosome carries at least two sets of genes for 23S, 16S and 5S rRNAs.     

Huntington disease-linked restriction fragment length polymorphism localized within band p16.1 of chromosome 4 by in situ hybridization.

A 5.5-kilobase (kb) single sequence DNA fragment (G8) reveals the DNA polymorphic locus D4S10 on Southern blot analysis. This locus is closely linked to Huntington disease and has been mapped to chromosome 4 short arm using human-mouse somatic cell hybrids, and specifically to chromosome 4 band p16 using DNA from individuals with deletions of chromosome 4 short arm who exhibit Wolf-Hirschhorn syndrome. With in situ hybridization techniques, we have confirmed the location of D4S10 on chromosome 4 and further localized it within band p16 utilizing five patients, four with overlapping chromosome 4 short-arm aberrations. The DNA segment G8 was hybridized to the mataphase chromosomes of the five patients. Two of them have different interstitial deletions of one of the chromosome 4 short arms (TA and BA), two have different chromosome 4 short-arm terminal deletions (RG and DQ), and one has a normal male karyotype. By noting the presence or absence of hybridization to the partially deleted chromosomes with known precise breakpoints, we were able to more accurately localize probe G8 to the distal half of band p16.1 of chromosome 4.     

Aerobactin genes in clinical isolates of Escherichia coli.

The location of the aerobactin gene complex on either the chromosome or plasmid was determined in eight aerobactin-positive clinical isolates of Escherichia coli by Southern hybridization analysis, using as probes the cloned aerobactin genes from the ColV-K30 plasmid. The aerobactin genes were in two cases detected on large plasmids, whereas in the other strains the aerobactin genes are most likely located on the chromosome. Restriction mapping revealed only slight variations in the structural genes and an at least 3.4-kilobase-long upstream region conserved in all three plasmid-coded systems. A 7.7-kilobase HindIII fragment upstream and adjacent to the 16.3-kilobase HindIII fragment carrying the complete aerobactin system was cloned from the ColV-K30 plasmid. Fine-structure restriction mapping identified the left insertion sequence in the upstream region as IS1, in inverted orientation to the IS1 element downstream from the aerobactin operon. The upstream and downstream sequences of IS1 appear to have perfect homology, as indicated by S1 nuclease resistance of a 760-base-pair DNA duplex formed by both IS1 elements.     

Cloned DNA probes regionally mapped to human chromosome 21 and their use in determining the origin of nondisjunction.

A number of unique sequence recombinant DNA clones were isolated from a recombinant DNA library constructed from DNA enriched for chromosome 21 by flow sorting. Of these, five were mapped to chromosome 21 using a somatic cell hybrid. Regional mapping of these probes and of a probe previously assigned to chromosome 21, was carried out with the aid of chromosome 21 rearrangements using both chromosome sorting and a somatic cell hybrid. Three probes were shown to be located on either side of the breakpoint 21q21.2. Two of the probes were shown to identify restriction fragment length polymorphisms (RFLPs) with high rare-allele frequencies (0.46 and 0.43). A Bgl II RFLP revealed the parental origin of non-disjunction in three of ten families with Down's syndrome.     

Mapping of seven polymorphic loci on human chromosome 13 by in situ hybridization

Summary Human chromosome 13 loci homologous to seven recombinant DNA probes were mapped using in situ hybridization of ³H-radiolabeled probes to metaphase chromosomes. Each of these seven probes reveals at least one restriction fragment length polymorphism, and thus each probe is potentially valuable in a genetic linkage map of this autosome. The data presented in this paper map the seven loci to specific regions of chromosome 13. This mapping should allow a future comparison of genetic distance with physical distance on this chromosome, and may permit better utilization of these probes in the clinical diagnosis of human chromosomal rearrangements involving chromosome 13.     

Definition of the limits of the Wilms tumor locus on human chromosome 11p13

In a previous report, we described a contiguous restriction map of chromosome band 11p13 that localized the Wilms tumor locus to a small group of NotI fragments. In an effort to identify and isolate the 11p13-associated sporadic Wilms tumor locus, we developed a panel of NotI fragment-specific DNA probes. These probes were selected from genomic libraries constructed using the Chinese hamster ovary-human somatic cell hybrid carrying only human 11p. The libraries were prepared from NotI-digested DNA after size selection by pulsed-field gel electrophoresis. The selected NotI fragments had been previously targeted on the basis of deletion mapping as having a high probability of containing the Wilms tumor locus. We used these newly identified 11p13-specific probes to improve the resolution of the restriction map spanning the Wilms tumor locus. The locus has been defined by a homozygous deletion in a sporadic Wilms tumor. Using these probes, the region of homozygous deletion in this tumor and presumably all or part of the Wilms tumor gene have been confined to two small SfiI fragments spanning less than 350 kb.