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Mapping of cosmid clones in Huntington's disease region of chromosome 4.

Huntington's disease (HD) is tightly linked to genetic markers in 4p16.3. We have used a regional somatic cell hybrid mapping panel to isolate and map 25 cosmids to the proximal portion of 4p16.3 and 17 cosmids to the distal portion. The latter were positioned by long-range restriction mapping relative to previously mapped markers. One cosmid, L6 (D4S166), spans the critical breakpoint in the mapping panel that distinguishes proximal and distal 4p16.3. Four of the cosmids mapped distal to D4S90, the previous terminal marker on 4p, and stretched to within 75 kb of the telomere. Several of the cosmids that mapped between L6 and D4S90 were clustered near a number of previously isolated clones in a region with many NotI sites. Cosmid E4 (D4S168) was localized immediately proximal to the one remaining gap in the long-range restriction map of distal 4p16.3. Although pulsed field gel mapping with E4 failed to link the two segments of the map, the intervening gap was excluded as a potential site for the HD gene by genetic analysis.

Chromosome Mapping↗

Comparative map alignment of BTA27 and HSA4 and 8 to identify conserved segments of genome containing fat deposition QTL.

Quantitative trait loci (QTL) associated with fat deposition have been identified on bovine Chromosome 27 (BTA27) in two different cattle populations. To generate more informative markers for verification and refinement of these QTL-containing intervals, we initiated construction of a BTA27 comparative map. Fourteen genes were selected for mapping based on previously identified regions of conservation between the cattle and human genomes. Markers were developed from the bovine orthologs of genes found on human Chromosomes 1 (HSA1), 4, 8, and 14. Twelve genes were mapped on the bovine linkage map by using markers associated with single nucleotide polymorphisms or microsatellites. Seven of these genes were also anchored to the physical map by assignment of fluorescence in situ hybridization probes. The remaining two genes not associated with an identifiable polymorphism were assigned only to the physical map. In all, seven genes were mapped to BTA27. Map information generated from the other seven genes not syntenic with BTA27 refined the breakpoint locations of conserved segments between species and revealed three areas of disagreement with the previous comparative map. Consequently, portions of HSA1 and 14 are not conserved on BTA27, and a previously undefined conserved segment corresponding to HSA8p22 was identified near the pericentromeric region of BTA8. These results show that BTA27 contains two conserved segments corresponding to HSA8p, which are separated by a segment corresponding to HSA4q. Comparative map alignment strongly suggests the conserved segment orthologous to HSA8p21-q11 contains QTL for fat deposition in cattle.

Adipose Tissue↗

A complete BAC-based physical map of the Arabidopsis thaliana genome.

Arabidopsis thaliana is a small flowering plant that serves as the major model system in plant molecular genetics. The efforts of many scientists have produced genetic maps that provide extensive coverage of the genome (http://genome-www. stanford.edu/Arabidopsis/maps.html). Recently, detailed YAC, BAC, P1 and cosmid-based physical maps (that is, representations of genomic regions as sets of overlapping clones of corresponding libraries) have been established that extend over wide genomic areas ranging from several hundreds of kilobases to entire chromosomes. These maps provide an entry to gain deeper insight into the A. thaliana genome structure. A. thaliana has been chosen as the subject of the first large-scale project intended to determine the full genome sequence of a plant. This sequencing project, together with the increasing interest in map-based gene cloning, has highlighted the requirement for a complete and accurate physical map of this plant species. To supply the scientific community with a high-quality resource, we present here a complete physical map of A. thaliana using essentially the IGF BAC library. The map consists of 27 contigs that cover the entire genome, except for the presumptive centromeric regions, nucleolar organization regions (NOR) and telomeric areas. This is the first reported map of a complex organism based entirely on BAC clones and it represents the most homogeneous and complete physical map established to date for any plant genome. Furthermore, the analysis performed here serves as a model for an efficient physical mapping procedure using BAC clones that can be applied to other complex genomes.

Arabidopsis↗

A detailed physical map of the horse Y chromosome.

We herein report a detailed physical map of the horse Y chromosome. The euchromatic region of the chromosome comprises approximately 15 megabases (Mb) of the total 45- to 50-Mb size and lies in the distal one-third of the long arm, where the pseudoautosomal region (PAR) is located terminally. The rest of the chromosome is predominantly heterochromatic. Because of the unusual organization of the chromosome (common to all mammalian Y chromosomes), a number of approaches were used to crossvalidate the results. Analysis of the 5,000-rad horse x hamster radiation hybrid panel produced a map spanning 88 centirays with 8 genes and 15 sequence-tagged site (STS) markers. The map was verified by several fluorescence in situ hybridization approaches. Isolation of bacterial artificial chromosome (BAC) clones for the radiation hybrid-mapped markers, end sequencing of the BACs, STS development, and bidirectional chromosome walking yielded 109 markers (100 STS and 9 genes) contained in 73 BACs. STS content mapping grouped the BACs into seven physically ordered contigs (of which one is predominantly ampliconic) that were verified by metaphase-, interphase-, and fiber-fluorescence in situ hybridization and also BAC fingerprinting. The map spans almost the entire euchromatic region of the chromosome, of which 20-25% (approximately 4 Mb) is covered by isolated BACs. The map is presently the most informative among Y chromosome maps in domesticated species, third only to the human and mouse maps. The foundation laid through the map will be critical in obtaining complete sequence of the euchromatic region of the horse Y chromosome, with an aim to identify Y specific factors governing male infertility and phenotypic sex variation.

Animals↗

A high-resolution whole-genome cattle-human comparative map reveals details of mammalian chromosome evolution.

Approximately 3,000 cattle bacterial artificial chromosome (BAC)-end sequences were added to the Illinois-Texas 5,000-rad RH (RH, radiation hybrid) map. The BAC-end sequences selected for mapping are approximately 1 Mbp apart on the human chromosomes as determined by blastn analysis. The map has 3,484 ordered markers, of which 3,204 are anchored in the human genome. Two hundred-and-one homologous synteny blocks (HSBs) were identified, of which 27 are previously undiscovered, 79 are extended, 26 were formed by previously unrecognized breakpoints in 18 previously defined HSBs, and 23 are the result of fusions. The comparative coverage relative to the human genome is approximately 91%, or 97% of the theoretical maximum. The positions of 64% of all cattle centromeres and telomeres were reassigned relative to their positions on the previous map, thus facilitating a more detailed comparative analysis of centromere and telomere evolution. As an example of the utility of the high-resolution map, 22 cattle BAC fingerprint contigs were directly anchored to cattle chromosome 19 [Bos taurus, (BTA) 19]. The order of markers on the cattle RH and fingerprint maps of BTA19 and the sequence-based map of human chromosome 17 [Homo sapiens, (HSA) 17] were found to be highly consistent, with only two minor ordering discrepancies between the RH map and fingerprint contigs. The high-resolution Illinois-Texas 5,000-rad RH and comparative maps will facilitate identification of candidate genes for economically important traits, the phylogenomic analysis of mammalian chromosomes, proofing of the BAC fingerprint map and, ultimately, aid the assembly of cattle whole-genome sequence.

Animals↗

Genetic linkage mapping of zebrafish genes and ESTs.

Genetic screens in zebrafish (Danio rerio) have isolated mutations in hundreds of genes essential for vertebrate development, physiology, and behavior. We have constructed a genetic linkage map that will facilitate the identification of candidate genes for these mutations and allow comparisons among the genomes of zebrafish and other vertebrates. On this map, we have localized 771 zebrafish genes and expressed sequence tags (ESTs) by scoring single-stranded conformational polymorphisms (SSCPs) in a meiotic mapping panel. Of these sequences, 642 represent previously unmapped genes and ESTs. The mapping panel was comprised of 42 homozygous diploid individuals produced by heat shock treatment of haploid embryos at the one-cell stage (HS diploids). This "doubled haploid" strategy combines the advantages of mapping in haploid and standard diploid systems, because heat shock diploid individuals have only one allele at each locus and can survive to adulthood, enabling a relatively large quantity of genomic DNA to be prepared from each individual in the mapping panel. To integrate this map with others, we also scored 593 previously mapped simple-sequence length polymorphisms (SSLPs) in the mapping panel. This map will accelerate the molecular analysis of zebrafish mutations and facilitate comparative analysis of vertebrate genomes.

Animals↗

Automated construction of high-density comparative maps between rat, human, and mouse.

Animal models have been used primarily as surrogates for humans, having similar disease-based phenotypes. Genomic organization also tends to be conserved between species, leading to the generation of comparative genome maps. The emergence of radiation hybrid (RH) maps, coupled with the large numbers of available Expressed Sequence Tags (ESTs), has revolutionized the way comparative maps can be built. We used publicly available rat, mouse, and human data to identify genes and ESTs with interspecies sequence identity (homology), identified their UniGene relationships, and incorporated their RH map positions to build integrated comparative maps with >2100 homologous UniGenes mapped in more than one species (approximately 6% of all mammalian genes). The generation of these maps is iterative and labor intensive; therefore, we developed a series of computer tools (not described here) based on our algorithm that identifies anchors between species and produces printable and on-line clickable comparative maps that link to a wide variety of useful tools and databases. The maps were constructed using sequence-based comparisons, thus creating "hooks" for further sequence-based annotation of human, mouse, and rat sequences. Currently, this map enables investigators to link the physiology of the rat with the genetics of the mouse and the clinical significance of the human.

Algorithms↗

An integrated 4249 marker FISH/RH map of the canine genome.

BACKGROUND: The 156 breeds of dog recognized by the American Kennel Club offer a unique opportunity to map genes important in genetic variation. Each breed features a defining constellation of morphological and behavioral traits, often generated by deliberate crossing of closely related individuals, leading to a high rate of genetic disease in many breeds. Understanding the genetic basis of both phenotypic variation and disease susceptibility in the dog provides new ways in which to dissect the genetics of human health and biology. RESULTS: To facilitate both genetic mapping and cloning efforts, we have constructed an integrated canine genome map that is both dense and accurate. The resulting resource encompasses 4249 markers, and was constructed using the RHDF5000-2 whole genome radiation hybrid panel. The radiation hybrid (RH) map features a density of one marker every 900 Kb and contains 1760 bacterial artificial chromosome clones (BACs) localized to 1423 unique positions, 851 of which have also been mapped by fluorescence in situ hybridization (FISH). The two data sets show excellent concordance. Excluding the Y chromosome, the map features an RH/FISH mapped BAC every 3.5 Mb and an RH mapped BAC-end, on average, every 2 Mb. For 2233 markers, the orthologous human genes have been established, allowing the identification of 79 conserved segments (CS) between the dog and human genomes, dramatically extending the length of most previously described CS. CONCLUSIONS: These results provide a necessary resource for the canine genome mapping community to undertake positional cloning experiments and provide new insights into the comparative canine-human genome maps.

Animals↗

Refinement of the background genetic map of Xq26-q27 and gene localisation for Börjeson-Forssman-Lehmann Syndrome.

A detailed map of genetic markers was constructed around the gene for the X-linked mental retardation syndrome of Börjeson-Forssman-Lehmann (BFLS). A multipoint linkage map of framework markers across Xq26-27, based on CEPH families, was integrated with the physical map, based on a YAC contig, to confirm marker order. The remaining genetic markers, which could not be ordered by linkage, were added to create the comprehensive genetic back-ground map, in the order determined by physical mapping, to determine genetic distances between adjacent markers. This background genetic map is applicable to the refinement of the regional localisation for any disease gene mapping to this region. The BFLS gene was localised using this background map in an extended version of the family described by Turner et al. [1989]. The regional localisation for BFLS extends between recombination events at DXS425 and DXS105, an interval of 24.6 cM on the background genetic map. The phenotypic findings commonly seen in the feet of affected males and obligate carrier females may represent a useful clinical indicator of carrier status in potential female carriers in the family. Recombination between DXS425 and DXS105 in a female with such characteristic feet suggests that the distal limit of the regional localisation for the BFLS gene might reasonably be reduced to DXS294 for the purpose of selecting candidate genes, reducing the interval for the BFLS gene to 15.5 cM. Positional candidate genes from the interval between DXS425 and DXS105 include the SOX3 gene, mapped between DXS51(52A) and DXS98(4D-8). SOX3 may have a role in regulating the development of the nervous system. The HMG-box region of this single exon gene was examined by PCR for a deletion and then sequenced. No deviation from normal was observed, excluding mutations in the conserved HMG-box region as the cause of BFLS in this family.

Chromosome Mapping↗

Bias in multipoint linkage analysis arising from map misspecification.

Multipoint linkage analysis methods are often used in human genetic studies. Although multipoint methods increase power for a linkage analysis and will become essential if use of diallelic markers becomes widespread, the methods in use assume an accurate meiotic marker map. Unfortunately, uncertainties in estimates of between-marker meiotic distances are large. Also, sex-averaged maps are generally used, but recombination rates differ in males and females. Both these types of map misspecification can lead to lod score bias, but such bias has not previously been systematically quantified. We examine multipoint lod score bias arising from these map misspecifications, in both the presence and absence of actual linkage. We define bias as the expected difference between the lod score computed under the misspecified map and that computed under the true map. With actual linkage, any map misspecification causes negative bias in lod scores, resulting in loss of power to detect linkage. In most cases, bias is modest, only reaching clearly detectable levels when both types of misspecification are substantial. In the absence of linkage, map misspecification can cause positive or negative bias: falsely assuming a 1:1 female:male ratio always causes positive bias; using too large a distance gives a positive bias; using too small a distance gives a negative bias. This bias can inflate the false-positive rate, especially when the sample size is modest. We conclude that although current sex-averaged maps are suitable for a first-pass multipoint screen, the potential for bias from map misspecification should be evaluated in following up results from such an analysis.

Bias↗

STS map of genes and anonymous DNA fragments on human chromosome 18 using a panel of somatic cell hybrids.

Somatic cell hybrids containing different deleted regions of chromosome 18 derived from patients with balanced translocations or terminal deletions were used to create a deletion mapping panel. Twenty-four sequence-tagged sites (STSs) for 17 genes and 7 anonymous polymorphic DNA fragments were identified. These STSs were used to map the 24 loci to 18 defined regions of chromosome 18. Both ERV1, previously mapped to 18q22-q23, and YES1, previously mapped to 18q21.3, were found to map to 18q11.21-pter. Several genes previously mapped to 18q21 were found to be in the order cen-SSAV1-DCC-FECH-GRP-BCL2-PLANH2-tel. The precise mapping of genes to chromosome 18 should help in determining whether these genes may be involved in the etiology of specific chromosomal syndromes associated with chromosome 18. The mapping of the polymorphic loci will assist in the integration of the physical map with the recombination map of chromosome 18.

Base Sequence↗

CEPH consortium Map of chromosome 9.

This paper describes the Centre d'Etude du Polymorphisme Humain (CEPH) consortium linkage map of chromosome 9. A total of 124 markers were typed in the CEPH family DNAs by 14 contributing laboratories; of these, 42 loci are ordered on the map with likelihood support of at least 1000:1. The uniquely placed markers include 31 that can be typed by PCR. A further 28 markers that can be typed by PCR are approximately positioned on the map. Multilocus linkage analysis with CRI-MAP has produced male, female, and sex-averaged maps extending for 176, 237, and 209 cM, respectively, while sex-averaged maps produced with MAPMAKER and the multiple two-point program MAP extended for 170 and 129 cM, respectively. The male map contains only two intervals greater than 10 cM, and the mean genetic distance between the 42 uniquely placed loci is 4.3 cM. However, no markers were available to anchor the map at either telomere or the centromere. The results confirm the high level of interference suggested by chiasma maps of chromosome 9. Detailed meiotic breakpoints for three of the families are shown. These can be used to provide rapid placement of any new marker without the need for statistical analysis.

Alleles↗

Integrated mapping analysis of the Werner syndrome region of chromosome 8.

The Werner syndrome locus (WRN) is located at 8p11-p12. To facilitate eventual cloning of the WRN gene, a 10,000-rad radiation-reduced hybrid (RH) cell panel was generated to map genetic markers, sequence-tagged sites (STSs), and genes in this region. A hamster cell line carrying an intact human chromosome 8 was fused with another hamster cell line. Two sets of hybrid cell panels from 2 separate fusions were generated; each panel consisted of 50 independent clones; 33 and 34 cell lines from the 2 fusions retained human chromsome material as determined by inter-Alu PCR. The combined panel was genotyped for 52 markers spanning the entire chromosome, including 10 genes, 29 anonymous polymorphic loci, and 13 STSs. Seventeen of these markers have not been previously described. Markers near the centromere were retained at a higher frequency than more distal markers. Fluorescence in situ hybridization was also used to localize and order a subset of the markers. A RH map of the WRN region was constructed using a maximum likelihood method, giving the following most likely order: D8S131-D8S339 (GSR)-D8S124-D8S278-D8S259-(D8S71)-D8S283- D8S87-D8S105-D8S135 (FGFR1)-D8S135PB-D8S255-ANK1. A genetic map of 15 short tandem repeat polymorphic loci in the WRN region was also constructed. The marker orders from the genetic and RH maps were consistent. In addition, an integrated map of 24 loci in the WRN region was generated using information from both genetic and RH mapping methods. A 1000:1 framework map for 6 loci (LPL-D8S136-D8S137-D8S87-FGFR1-ANK1) was determined by genetic mapping, and the resulting locus order was fixed during analysis of the RH genotype data. The resulting integrated map contained more markers than could confidently be ordered by either genetic or RH mapping alone.

Base Sequence↗

Physical mapping of genetic markers on the short arm of chromosome 5.

The deletion of the short arm of chromosome 5 is associated with the cri-du-chat syndrome. In addition, loss of this portion of a chromosome is a common cytogenetic marker in a number of malignancies. However, to date, no genes associated with these disorders have been identified. Physical maps are the first step in isolating causative genes, and genes involved in autosomal recessive disorders are now routinely mapped through the identification of linked markers. Extensive genetic maps based upon polymorphic short tandem repeats (STRs) have provided researchers with a large number of markers to which such disorders can be genetically mapped. However, the physical locations of many of these STRs have not been determined. Toward the goal of integrating the human genetic maps with the physical maps, a 5p somatic cell hybrid deletion mapping panel that was derived from patients with 5p deletions or translocations was used to physically map 47 STRs that have been used to construct genetic maps of 5p. These data will be useful in the localization of disease genes that map to 5p and may be involved in the etiology of the cri-du-chat syndrome.

Animals↗

A transcript map of a 10-Mb region of chromosome 19: a source of genes for human disorders, including candidates for genes involved in asthma, heart defects, and eye development.

Several projects have produced maps of the physical position of genes within the human genome, either on a genome-wide scale or of a more detailed subsection of a chromosome. However, these maps largely rely on the mapping of expressed sequences (cDNAs and ESTs) back onto physical maps by their localization onto specific fragments of DNA within the radiation hybrid panels. In this report we present a gene map of a section of chromosome 19 that has been derived by combining the use of a method of gene identification (exon trapping) that does not rely on expression patterns, with data available in the genome databases to produce a fine-detailed transcript map. This map also provides several potential candidates for disorders that map to this region of the genome. Details of the maps and more detailed descriptions of cosmid contigs, exon sequences, and expression patterns for the 96 exons that form the basis of this transcript map are available on a series of Web pages that are referenced in this report. These Web pages can be accessed from http://www.nottingham.ac.uk/ pdzmgh/tm/livemap19q. html.

Asthma↗

Conservation of gene order between horse and human X chromosomes as evidenced through radiation hybrid mapping.

A radiation hybrid (RH) map of the equine X chromosome (ECAX) was obtained using the recently produced 5000(rad) horse x hamster hybrid panel. The map comprises 34 markers (16 genes and 18 microsatellites) and spans a total of 676 cR(5000), covering almost the entire length of ECAX. Cytogenetic alignment of the RH map was improved by fluorescent in situ hybridization mapping of six of the markers. The map integrates and refines the currently available genetic linkage, syntenic, and cytogenetic maps, and adds new loci. Comparison of the physical location of the 16 genes mapped in this study with the human genome reveals similarity in the order of the genes along the entire length of the two X chromosomes. This degree of gene order conservation across evolutionarily distantly related species has up to now been reported only between human and cat. The ECAX RH map provides a framework for the generation of a high-density map for this chromosome. The map will serve as an important tool for positional cloning of X-linked diseases/conditions in the horse.

Animals↗

Comparison of orientation maps obtained with different number of stimulus orientations.

The structure of orientation maps computed from a different number of stimulus orientations was studied in visual cortical area 18 of the cat. Single condition maps (SCMs) were obtained to 16 stimulus orientations, of which angle maps were generated using 4, 8, and 16 SCMs corresponding to multiples of 45, 22.5, and 11.25 degrees, respectively. The overall orientation distribution of the three types of maps was compared on a pixel-by-pixel basis. Twenty percent of the pixels of the 4-orientations maps differed by more than +/-17 degrees from those produced by 16 orientations. Maps of 8 orientations differed by 6.4 and 5.8% from those of 4 and 16 orientations, respectively. Structural differences between the maps were mainly found at locations displaying high rate of change in orientation preference, i.e., orientation centers and adjoining short, fracture-like zones. These changes included lateral shifts up to 155 microm (average: 38.7 microm) in the position of orientation centers and appearance/disappearance of orientation centers when compared between different conditions. In general, these changes were three times more frequent between maps of 4/8 and 4/16 orientations than 8/16 orientations. It is concluded that orientation maps should be calculated from activity maps representing 8 or more stimulus orientations.

Animals↗

Genetic mapping studies of 40 loci and 23 cosmids in chromosome 11p13-11q13, and exclusion of mu-calpain as the multiple endocrine neoplasia type 1 gene.

Forty loci (16 polymorphic and 24 non-polymorphic) together with 23 cosmids isolated from a chromosome 11-specific library were used to construct a detailed genetic map of 11p13-11q13. The map was constructed by using a panel of 13 somatic cell hybrids that sub-divided this region into 19 intervals, a meiotic mapping panel of 33 multiple endocrine neoplasia type 1 (MEN1) families (134 affected and 269 unaffected members) and a mitotic mapping panel that was used to identify loss of heterozygosity in 38 MEN1-associated tumours. The results defined the most likely order of the 16 loci as being: 11pter-D11S871-(D11S288, D11S149)-11cen-CNTF-PGA-ROM1-D11S480-PYGM- SEA-D11S913-D11S970-D11S97- D11S146-INT2-D11S971-D11S533-11qter. The meiotic mapping studies indicated that the most likely location of the MEN1 gene was in the interval flanked by PYGM and D11S97, and the results of mitotic mapping suggested a possible location of the MEN1 gene telomeric to SEA. Mapping studies of the gene encoding mu-calpain (CAPN1) located CAPN1 to 11q13 and in the vicinity of the MEN1 locus. However, mutational analysis studies did not detect any germ-line CAPN1 DNA sequence abnormalities in 47 unrelated MEN1 patients and the results therefore exclude CAPN1 as the MEN1 gene. The detailed genetic map that has been constructed of the 11p13-11q13 region should facilitate the construction of a physical map and the identification of candidate genes for disease loci mapped to this region.

Animals↗