Pulsed-field Gel Electrophoresis Mapping Research Articles

Assessment of Whole-Genome Mapping in a Well-Defined Outbreak of Salmonella enterica Serotype Saintpaul

We investigated the use of whole-genome mapping and pulsed-field gel electrophoresis (PFGE) with isolates from an outbreak of Salmonella enterica serotype Saintpaul. PFGE and whole-genome mapping were concordant with 22 of 23 isolates. Whole-genome mapping is a viable alternative tool for the epidemiological analysis of Salmonella food-borne disease investigations.

Evidence for a fast, intrachromosomal conversion mechanism from mapping of nucleotide variants within a homogeneous alpha-satellite DNA array.

Assuming that patterns of sequence variants within highly homogeneous centromeric tandem repeat arrays can tell us which molecular turnover mechanisms are presently at work, we analyzed the alpha-satellite tandem repeat array DXZ1 of one human X chromosome. Here we present accurate snapshots from this dark matter of the genome. We demonstrate stable and representative cloning of the array in a P1 artificial chromosome (PAC) library, use samples of higher-order repeats subcloned from five unmapped PACs (120-160 kb) to identify common variants, and show that such variants are presently in a fixed transition state. To characterize patterns of variant spread throughout homogeneous array segments, we use a novel partial restriction and pulsed-field gel electrophoresis mapping approach. We find an older large-scale (35-50 kb) duplication event supporting the evolutionarily important unequal crossing-over hypothesis, but generally find independent variant occurrence and a paucity of potential de novo mutations within segments of highest homogeneity (99.1%-99.3%). Within such segments, a highly nonrandom variant clustering within adjacent higher-order repeats was found in the absence of haplotypic repeats. Such variant clusters are hardly explained by interchromosomal, fixation-driving mechanisms and likely reflect a fast, localized, intrachromosomal sequence conversion mechanism.

Long-range map of a 3.5-Mb region in Xp11.23-22 with a sequence-ready map from a 1.1-Mb gene-rich interval.

Most of the yeast artificial chromosomes (YACs) isolated from the Xp11.23-22 region have shown instability and chimerism and are not a reliable resource for determining physical distances. We therefore constructed a long-range pulsed-field gel electrophoresis map that encompasses approximately 3.5 Mb of genomic DNA between the loci TIMP and DXS146 including a CpG-rich region around the WASP and TFE-3 gene loci. A combined YAC-cosmid contig was constructed along the genomic map and was used for fine-mapping of 15 polymorphic microsatellites and 30 expressed sequence tags (ESTs) or sequence transcribed sites (STSs), revealing the following order: tel-(SYN-TIMP)-(DXS426-ELK1)-ZNF(CA) n-L1-DXS1367-ZNF81-ZNF21-DXS6616- (HB3-OATL1pseudogenes-DXS6950)-DXS6949-DXS694 1-DXS7464E(MG61)-GW1E(EBP)- DXS7927E(MG81)-RBM- DXS722-DXS7467E(MG21)-DXS1011E-WASP-DXS6940++ +-DXS7466E(MG44)-GF1- DXS226-DXS1126-DXS1240-HB1- DXS7469E-(DXS6665-DXS1470)-TFE3-DXS7468E-+ ++SYP-DXS1208-HB2E-DXS573-DXS1331- DXS6666-DXS1039-DXS 1426-DXS1416-DXS7647-DXS8222-DXS6850-DXS255++ +-CIC-5-DXS146-cen. A sequence-ready map was constructed for an 1100-kb gene-rich interval flanked by the markers HB3 and DXS1039, from which six novel ESTs/STSs were isolated, thus increasing the number of markers used in this interval to thirty. This precise ordering is a prerequisite for the construction of a transcription map of this region that contains numerous disease loci, including those for several forms of retinal degeneration and mental retardation. In addition, the map provides the base to delineate the corresponding syntenic region in the mouse, where the mutants scurfy and tattered are localized.

Tandem Repeats 3′ of the IGHA Genes in the Human Immunoglobulin Heavy Chain Gene Cluster

The human IGH constant region spans 350 kb and includes nine genes and two pseudogenes. All of the constant region gene cluster has been cloned except for sequences between the IGHD and IGHG3 genes, between the IGHA1 and IGHG2 genes, and the 3′ region downstream of the IGHA2 gene. The regions 3′ of the IGHA genes, which are not cloned, are of interest since transcriptional control elements were found downstream of the IGHA genes in the rat and the mouse IGH loci. In addition, by pulsed-field gel electrophoresis mapping, CpG islands were identified approximately 30 kb downstream of each IGHA gene, within the uncloned portion of the human IGH. These findings indicate that the regions 3′ of the IGHA genes are candidate regions for additional transcriptional elements of the human IGH genes. In an effort to characterize these regions, we screened five different libraries and determined the regions 3′ of the IGHA genes to be unclonable by standard cloning methods. Therefore, we applied the Inverse-PCR technique to amplify the sequences flanking the IGHA genes. We obtained 1418 bp of new sequence 3′ of the IGHA1 gene. The new sequence included tandem repeats of 20 bp, which we propose is the cause of the unclonability of this region.

A 9.75-Mb Map across the Centromere of Human Chromosome 10

We present a yeast artificial chromosome (YAC) and pulsed-field gel electrophoresis (PFGE) map across the centromere of human chromosome 10 that links expressed sequences in 10p11 to expressed sequences in 10q11.2. This map is the first of its kind to link genes across a human centromere. It consists of a 2.5-Mb YAC contig extending from 10p11 to our previously published 5.35-Mb PFGE map of the centromeric satellite arrays, and a 2.65-Mb YAC contig extending from these satellite arrays to 10q11.2. This map covers approximately 6.5–7% of the total DNA of chromosome 10. Two Généthon genetic markers,D10S578andD10S604,are included. These markers are only 1 cM apart but are separated by a physical distance of more than 9.2 Mb, including the centromere. This gives a ratio of genetic to physical distance of 0.11 cM/Mb, 9–11 times lower than average estimates for the human genome and chromosome 10. Markers linked to the centromere include the duplicated zinc finger genesZNF11A, ZNF33A,andZNF37A(which map to 10p11) andZNF11B, ZNF33B,andZNF37B(which map to 10q11.2). Restriction mapping confirms that the genes on each arm lie in opposite orientation with respect to the centromere, consistent with the hypothesis that a pericentric inversion has occurred in this region during primate evolution.

A 5.4-Mb Continuous Pulsed-Field Gel Electrophoresis Map of Human 9q34.1 between ABL and D9S114, Including the Tuberous Sclerosis (TSC1) Region

We constructed a long-range restriction map of the tuberous sclerosis (TSC1) region of human chromosome 9q34, extending from ABL (T39-2-2) to D9S114. The physical map includes five genes and seven anonymous markers. The maximum distance between ABL and D9S114 is 5.4 Mb. The TSC1 critical region, between D9S149 and D9S114, has a maximum distance of 2.7 Mb. The ratio of genetic and physical distance in the region is 1 cM:600 kb. We also used Southern blot analysis and a radiation hybrid cell line, E6B, to exclude 3 genes—PBX3A, RXR α, and TAN1—from the AK1 to D9S114 interval. This excludes them as disease genes for tuberous sclerosis.

Physical maps of human α(1,3)fucosyltransferase genes FUT3–FUT6 on chromosomes 19p13.3 and 11q21

Sialyl Lewis x and related fucosylated glycans are differentially expressed in human cells and form ligands for selectin adhesion receptors. α(1,3)Fucosyltransferases (FUTs) that complete their biosynthesis also show tissue specificity. We have established physical maps of the FUT3–6 loci to study regulation of this gene family. FUT4 has previously been localized to chromosome 11q21; FUT3, FUT6, and now FUT5 are localized to chromosome 19p13.3. Conventional and pulsed-field gel electrophoresis mapping of total genomic DNA and large genomic clones were used to generate a fine map of both loci, defining the order, orientation, and distances between FUTs. A P1 clone with all three 19p FUT genes in tandem orientation was isolated and used to study regions flanking FUT3, −5, and −6. Our studies provide preliminary information to study regulation of human FUT genes.

Left-handed Z-DNA and in vivo supercoil density in the Escherichia coli chromosome.

A system for studying Z-DNA formation in the Escherichia coli chromosome was developed. Prior investigations in recombinant plasmids showed that alternating (Pur-Pyr) sequences can adopt a left-handed Z-DNA conformation both in vitro and in vivo. We constructed mobile, transposon-based cassettes carrying cloned (Pur-Pyr) sequences containing an EcoRI site in the center. These cassettes were subsequently inserted into different locations in the E. coli chromosome in a random fashion. A number of stable insertions were characterized by Southern analysis and pulsed-field gel electrophoresis mapping. A cloned temperature-sensitive MEcoRI methylase was expressed in trans as the probe to study Z-DNA formation in vivo. In this system, the control EcoRI sites were quickly methylated when cells were placed at the permissive temperature. Strong inhibition of the methylation was observed, however, only for the EcoRI sites embedded in a 56-bp run of (C-G). In contrast, the shorter sequence of 32 bp did not show this behavior. Prior in vitro determinations revealed that the longer tract required less energy to stabilize the Z-helix than the shorter block. We conclude that the observed inhibition of methylation is due to Z-DNA formation in the E. coli chromosome. In vitro, these sequences undergo the B- to Z-DNA transition at a supercoil density of -0.026 for the 56-bp insert and -0.032 for the 32-bp block. Since only the longer (C-G) tract but not the shorter run adopted the left-handed conformation in the chromosome, we propose that these densities establish the boundaries in the different chromosomal loci investigated; these boundaries are in good agreement with the extremes found in plasmids.

A Pulsed-Field Gel Electrophoresis (PFGE) Map of Twelve Loci on Chromosome 11q11-q13

We report a pulsed-field gel electrophoresis map of 12 loci on proximal human chromosome 11q. Linkage studies have shown that this region of chromosome 11 contains the genes for familial atopic disease (APY) and multiple endocrine neoplasia type I (MEN1)(4). A physical map containing polymorphic loci will aid in the isolation of these disease genes. The map reported here has two noncontiguous groups of loci accounting for 8 of the 12 loci evaluated, One group spans a maximum distance of 1600 kb and includes D11S146, BCL1, PRAD1, INT2, and HSTF1. The other group includes FTH1, C1NH, and COX8 . TCN1, PGA, and PYGM did not yield any comigrating fragments and could not be physically linked on this PFGE map. These data enhance previously published physical maps of proximal 11q by refining the localization of and distances between markers in the BCL1 region. Additionally, new information about the locations and physical relationships between FTH1, C1NH, and COX8 is presented.

New chromosome 21 DNA markers isolated by pulsed field gel electrophoresis from an ETS2-containing Down syndrome chromosomal region.

To generate new chromosome 21 markers in a region that is critical for the pathogenesis of Down syndrome (D21S55-MX1), we used pulsed field gel electrophoresis (PFGE) to isolate a 600-kb NruI DNA fragment from the WA17 hybrid cell line, which has retained chromosome 21 as the only human material. This fragment, which contains the oncogene ETS2, was used to construct a partial genomic library. Among the 14 unique sequences that were isolated, 3 were polymorphic markers and contained sequences that are conserved in mammals. Five of these markers mapped on the ETS2-containing NruI fragment and allowed us to define an 800-kb high-resolution PFGE map.

Distinct breakpoints in band 11q23 of the t(4;11) and t(11;14) associated with leukocyte malignancy.

Several non-random translocation breakpoints associated with leukemia or lymphoma have been shown to occur in chromosome band 11q23 between the genes CD3G and PBGD, a distance of approximately 750 kb. A combination of yeast artificial chromosome (YAC) cloning, in situ hybridization, and pulsed field gel electrophoresis (PFGE) experiments has further refined the interval containing one of these breakpoints, t(4;11)(q21;q23), to within 200 kb of CD3G. We have extended the PFGE analysis to show that the t(4;11) breakpoint lies in a region of approximately 100 kb, situated 100 kb distal to CD3G. Furthermore, we show that a second 11q23 breakpoint, t(11;14)(q23;q32), which was also previously mapped between CD3G and PBGD, is distinct from that of the t(4;11) chromosome. The 11q23 sequences that are involved at the t(11;14) breakpoint are not present in a YAC containing the t(4;11) breakpoint. The t(11;14) breakpoint has been localized on the PFGE map of the CD3G-PBGD interval and is at least 110 kb distal to the t(4;11) breakpoint, thus demonstrating heterogeneity among 11q23 breakpoints.

A PacI/SwaI map of the Pseudomonas aeruginosa PAO chromosome.

The PacI/SwaI macrorestriction map of the 5.9 Mb Pseudomonas aeruginosa PAO (DSM 1707) genome was constructed by fragment size comparisons of complete single and double digests and hybridization with probes of known genomic localization. P. aeruginosa PAO contains five recognition sites for PacI and six sites for SwaI. An integrated DpnI/PacI/SpeI/SwaI map was obtained by fragment pattern and Southern blot hybridization analyses of all combinations of double digestions and by two-dimensional pulsed-field gel electrophoresis mapping protocols.

A YAC contig in Xp21 containing the adrenal hypoplasia congenita and glycerol kinase deficiency genes.

The gene loci for adrenal hypoplasia congenita (AHC) and glycerol kinase deficiency (GK) map in Xp21 distal to Duchenne muscular dystrophy (DMD), and proximal to DXS28 (C7), by analysis of patient deletions. We have constructed a yeast artificial chromosome (YAC) contig encompassing a 1.2 Mb region extending distally from DMD, and containing DXS708 (JC-1), the distal junction clone of a patient with GK and DMD. A pulsed-field gel electrophoresis map of the YAC contig identified 3 potential CpG islands. Whole YAC hybridization identified cosmids both for construction of cosmid contigs, and isolation of single copy probes. Thirteen new single copy probes and DXS28 and DXS708 were hybridized on a panel of patients; the deletion mapping indicates that the YAC contig contains both GK and at least part of AHC, and together with the physical map defines a GK critical region of 50-250 kb. In one AHC patient with a cytogenetically detectable deletion we used the new probes to characterize a complex double deletion. Non-overlapping deletions observed in other unrelated AHC patients indicate that the AHC gene is large, extending over at least 200-500 kb. This mapping provides the basis for the identification of the AHC and GK genes.

Detailed physical map of human chromosomal region 11q12-13 shows high meiotic recombination rate around the MEN1 locus.

We have constructed a physical map of the region q12-13 on chromosome 11 by combining data generated from a panel of radiation-reduced somatic cell hybrids and pulsed-field gel electrophoresis (PFGE). Twenty different genetic markers have been sublocalized and ordered within this region and a total of 8.0 megabases has been mapped in detail using rare-cutting restriction endonucleases and PFGE. In two instances, the long-range restriction PFGE map spans the total distance between pairs of loci that have been previously mapped by genetic linkage in reference families. Comparison of this physical map with the available linkage map indicates a great variation in the recombination frequency over the region. The recombination rate is higher than expected, particularly for markers flanking the MEN1 region. Thus, for the closest pair of linked markers on the centromeric side, one centimorgan corresponds to approximately 300 kilobases, and for markers on the telomeric side, one centimorgan corresponds to approximately 350-600 kilobases.

A pulsed-field gel electrophoresis map locates the polymorphic probes for ERBA2 and ErbAβ within 120 kb of each other, confirming that THRB (formerly ERBA2) maps to chromosome 3

A pulsed-field gel electrophoresis map locates the polymorphic probes for ERBA2 and ErbAβ within 120 kb of each other, confirming that THRB (formerly ERBA2) maps to chromosome 3

Two families of low-copy-number repeats are interspersed on Xp22.3: Implications for the high frequency of deletions in this region

The locations of two families of low-copy-number repeats (CRI-S232 and G1.3) in the physical and genetic maps of the distal short arm of the human X chromosome (Xp22.3) have been determined. Single-copy fragments flanking several repeat elements from each family have been cloned and assigned to specific intervals on a deletion map of Xp22.3. Physical distances between these loci and previously isolated Xp22.3 markers have been determined by pulsed-field gel electrophoresis (PFGE). The positions of some of these markers on the genetic map of the region have been established by segregation analysis in CEPH families. Four members of the CRI-S232 family have been localized within 3 Mb on Xp22.3, interspersed with two members of the G1.3 family. Both deletion and PFGE mapping data suggest that a CpG island localized in a specific position on the map might be associated with the Kallmann syndrome gene. Unlike the previously reported data on hyperpolymorphic minisatellite sequences, no increase in the recombination rate was detected around the CRI-S232 repeats. The presence of several repeat elements in a region with a very high frequency of deletions, such as Xp22.3, is highly suggestive of the occurrence of unequal crossovers between the various elements, leading to deletion events.

Large haplotype‐specific differences in inter‐genic distances in human MHC shown by pulsed field electrophoresis mapping of healthy and Type 1 diabetic subjects

Type 1 diabetes is associated with extended haplotypes defined by combinations of specific alleles of genes in the MHC. We have used pulsed field gel electrophoresis mapping to examine the gross structure of the Class II region of the MHC and its relationship to susceptibility to Type 1 diabetes. We have studied heterozygous members of a family in which susceptibility to Type 1 diabetes is associated with an A1/B8/DR3 haplotype and resistance with A2/B7/DR2, an unrelated diabetic DR3,4 patient and a healthy DR4,w10 subject and a DR2/Dw2 cell line. Digestion was performed with the enzymes Sst II, Mlu I, and Pvu I and hybridization with 21-hydroxylase, DRA, DQB, DOB and DPA probes. Within the DQ/DR region the DR4- and DR7-bearing haplotypes studied contain insertions of 140-150kb relative to the DR3 haplotypes whilst the DR2 haplotype in the family was smaller than the DR3 haplotypes by 130kb, whilst that in the cell line was smaller by up to 220kb. This cell line, previously thought to be homozygous by consanguinity, was also shown to be heterozygous in the DP region. Although no differences between diabetic and healthy subjects were observed within the family, these differences in long-range structure may be of importance to the etiology of Type 1 diabetes, as well as to the evolution of the MHC.

Conservation of the central MHC genome: PFGE mapping and RFLP analysis of complement, HSP70, and TNF genes in the goat

A degree of conservation of the genes located between class II and class I [central major histocompatibility complex (MHC) genes] is apparent among mammalian species including primates and the mouse. Few others have been analyzed. The caprine MHC is of particular interest, since it has recently been observed that susceptibility to a lentivirus-induced polyarthritis (caprine arthritis) segregates with serologically defined MHC class I antigens. This arthritis resembles, in a number of respects, rheumatoid arthritis in man. Human cDNA probes were used to examine the caprine central MHC and class I and II genes by restriction fragment length polymorphism (RFLP) and by pulsed field gel electrophoresis (PFGE) in order to define the polymorphism and linkage of central MHC genes to class I and class II genes. An outbred population of dairy goats (Saanen, British Alpine, Anglo Nubian, and Toggenberg) was examined for class I and class II RFLPs. Both regions were found to be highly polymorphic. The number of fragments hybridizing to an HLA-B7 probe after Eco RI, Bam HI, Bgl II, or Hind III digestion suggests there may be 10-13 class I genes. The degree of polymorphism was comparable to that reported in the mouse. Limited polymorphism was found in the central MHC genes. The caprine C4 and CYP21 genes were duplicated and demonstrated RFLP with Bam HI, Hind III, Eco RV, and Taq I. An infrequent Taq I C2 polymorphism was found. PFGE revealed substantial conservation of both the order and linkage of the central MHC genes when compared with mouse and man. C4, C2, CYP21, HSP70, and tumor necrosis factor (TNF) genes are all located within 800 kilobase (kb) of the class I loci. Distant from the class I region, the C4, C2, and CYP21 genes are linked on a short genomic segment (180 kb Not I and 190 kb Pvu I fragments). HSP70 cohybridizes with the complement genes on a 380 kb Mlu I fragment. Linkage of HSP70, TNF, and class I genes was found on a single Not I fragment (610 kb). TNF and class I cohybridize on Pvu I (730 kb) and Not I (610 kb) fragments. Conservation of a similar central MHC genomic structure across species argues for functional interaction between the central MHC genes. We postulate selection for these central MHC genes through their role as non antigen-specific regulators of immune response.

Close physical linkage of the murine Ren-1 and Ren-2 loci.

In addition to the Ren-1 gene common to all mice, some inbred strains carry a second copy of the renin structural gene, Ren-2. These two loci are tightly linked genetically on mouse chromosome one. We have used pulsed field gel electrophoresis (PFGE) to study the physical arrangement of the two renin genes in the inbred strain DBA/2. PFGE mapping permitted the construction of a restriction map of the Ren loci spanning roughly 120 Kb. The results indicate that the genes are transcribed in the same relative direction, that Ren-2 lies upstream relative to Ren-1, and that the respective coding sequences are separated by approximately 20 Kb.