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A physical and genetic map of the Stigmatella aurantiaca DW4/3.1 chromosome.

A physical map of the myxobacterium Stigmatella aurantiaca DW4/3.1 chromosome was constructed by pulsed-field gel (PFG) long-range mapping. One-and two-dimensional pulsed-field gel analyses were used together with reciprocal double-restriction, cross-hybridization and hybridization fingerprint analysis. These PFG results were confirmed by Smith-Birnstiel analysis, by Southern hybridization using linking clones and clones of a lambda genomic library for the determination of adjacent restriction fragments and by transposon insertion mapping using defined genomic sequences for hybridization. It was thus possible to construct a circular restriction map of the single 9.35 Mbp chromosome of S. aurantiaca based on the endonucleases Asel and Spel. Genetic loci as well as the replication origin were located on the physical map by Southern hybridization using heterologous (derived from Myxococcus xanthus, Escherichia coli and Streptomyces lividans) and homologous probes that are mainly involved in development and cell motility.

Bacteriophage lambda↗

Genetic mapping of quantitative trait loci affecting susceptibility in chicken to develop pulmonary hypertension syndrome.

Pulmonary hypertension syndrome (PHS), also referred to as ascites syndrome, is a growth-related disorder of chickens frequently observed in fast-growing broilers with insufficient pulmonary vascular capacity at low temperature and/or at high altitude. A cross between two genetically different broiler dam lines that originated from the White Plymouth Rock breed was used to produce a three-generation population. This population was used for the detection and localization of quantitative trait loci (QTL) affecting PHS-related traits. Ten full-sib families consisting of 456 G2 birds were typed with 420 microsatellite markers covering 24 autosomal chromosomes. Phenotypic observations were collected on 4202 G3 birds and a full-sib across family regression interval mapping approach was used to identify QTL. There was statistical evidence for QTL on chicken chromosome 2 (GGA2), GGA4 and GGA6. Suggestive QTL were found on chromosomes 5, 8, 10, 27 and 28. The most significant QTL were located on GGA2 for right and total ventricular weight as percentage of body weight (%RV and %TV respectively). A related trait, the ratio of right ventricular weight as percentage to total ventricular weight (RATIO), reached the suggestive threshold on this chromosome. All three QTL effects identified on GGA2 had their maximum test statistic in the region flanked by markers MCW0185 and MCW0245 (335-421 cM).

Animals↗

Physical and genetic mapping of novel microsatellite polymorphisms on human chromosome 19.

We describe here the identification of 11 novel microsatellite polymorphisms on human chromosome 19. These dinucleotide repeat polymorphisms were detected in chromosome 19-specific cosmids that were physically mapped by fluorescence in situ hybridization. For each repeat, flanking oligonucleotide primers were synthesized and the polymerase chain reaction assay was performed on a panel of 100 unrelated individuals to determine the heterozygosity and allele frequencies. To characterize these markers further, genetic and radiation hybrid maps were constructed. These microsatellite polymorphisms will be valuable in further linkage analysis of inherited diseases on chromosome 19p.

Chromosomes, Human, Pair 19↗

Genetic mapping of a pulmonary adenoma resistance (Par1) in mouse.

Lung cancer, a major cause of death in the Western world, has a poor prognosis. So far, therapeutic strategies have had only a limited effect. Lung cancer risk is strongly associated with cigarette smoking and lung cancer pedigrees are rare. However, a possible polygenic nature of inherited predisposition to this cancer has been envisaged. Mouse inbred strains with inherited predisposition and resistance to lung cancer provide an important tool for the dissection of the genetics of this complex disease. The A/J strain carries the pulmonary adenoma susceptibility 1 (Pas1) locus and develops many lung tumours. We have mapped the M. spretus-derived locus that strongly resists the lung tumorigenesis in Pas1/+ mice. This locus, pulmonary adenoma resistance 1 (Par1) maps to mouse chromosome 11, near the Rara locus, with a lod score of 5.3. In Pas1/+ mice Par1 accounts for 23% of the phenotypic variance and 10 fold reduction in total tumour volume. These results provide evidence for a major resistance locus affecting the expression of an inherited predisposition to lung cancer.

Adenoma↗

Retrograde trans-synaptic transfer of green fluorescent protein allows the genetic mapping of neuronal circuits in transgenic mice.

The function of the nervous system is a consequence of the intricate synaptic connectivity of its neurons. Our understanding of these highly complex networks has profited enormously from methods used over the past two decades that are based on the mechanical injection of tracer molecules into brain regions. We have developed a genetic system for the mapping of synaptic connections during development of the mammalian central nervous system and in the mature brain. It is based on the transsynaptic transfer of green fluorescent protein (GFP) in the brains of mice using a fusion protein with a nontoxic fragment of tetanus toxin (TTC) expressed in defined neurons. These transgenic mice allowed us to visualize neurons, at single-cell resolution, that are in synaptic contact by the detection of GFP in interconnected circuits. Targeted genetic expression with a specific promoter permitted us to transfer GFP to defined subsets of neurons and brain regions. GFP-TTC is coexpressed with a lacZ reporter gene to discriminate neurons that produce the tracer from cells that have acquired it transneuronally. The marker shows selective transfer in the retrograde direction. We have used electron microscopic detection of GFP to define the ultrastructural features of the system. Our work opens up a range of possibilities for brain slice and in vivo studies taking advantage of the fluorescence of GFP. We point the way toward the use of powerful multiphoton technology and set the stage for the transsynaptic transfer of other proteins in the brains of mice.

Animals↗

Revised genetic map of the distal end of the F transfer operon: implications for DNA helicase I, nicking at oriT, and conjugal DNA transport.

The DNA transfer stage of conjugation requires the products of the F sex factor genes traMYDIZ and the cis-acting site oriT. Previous interpretation of genetic and protein analyses suggested that traD, traI, and traZ mapped as contiguous genes at the distal end of the transfer operon and saturated this portion of the F transfer region (which ends with an IS3 element). Using antibodies prepared against the purified TraD and TraI proteins, we analyzed the products encoded by a collection of chimeric plasmids constructed with various segments of traDIZ DNA. We found the traI gene to be located 1 kilobase to the right of the position suggested on previous maps. This creates an unsaturated space between traD and traI where unidentified tra genes may be located and leaves insufficient space between traI and IS3 for coding the 94-kilodalton protein previously thought to be the product of traZ. We found that the 94-kilodalton protein arose from a translational restart and corresponds to the carboxy terminus of traI; we named it TraI*. The precise physical location of the traZ gene and the identity of its product are unknown. The oriT nicking activity known as TraZ may stem from unassigned regions between traD and traI and between traI and IS3, but a more interesting possibility is that it is actually a function of traI. On our revised map, the position of a previously detected RNA polymerase-binding site corresponds to a site at the amino terminus of traI rather than a location 1 kilobase into the coding region of the gene. Furthermore, the physical and genetic comparison of the F traD and traI genes with those of the closely related F-like conjugative plasmids R1 and R100 is greatly simplified. The translational organization we found for traI, together with its identity as the structural gene for DNA helicase I, suggests a possible functional link to several other genes from which translational restart polypeptides are expressed. These include the primases of the conjugative plasmids ColI and R16, the primase-helicase of bacteriophage T7, and the cisA product (nickase) of phage phi X174.

Bacterial Proteins↗

DNA variants with telomere probe enable genetic mapping of ends of mouse chromosomes.

Dde I-digested DNA fragments from 11 inbred mouse strains were separated by electrophoresis, blotted and probed with a labeled oligomer, TELO, containing five repeats of the consensus mammalian telomere sequence, TTAGGG. Each strain produced a unique set of hybridizing fragments. Segregation analysis of TELO-hybridizing fragments from the BXD RI strains indicated that each fragment segregated as expected for a single gene. One fragment from strain DBA/2J was genetically linked to locus Xmv-9, previously mapped near the distal end of the map of chromosome (Chr) 4 and three fragments to Cck, near the distal end of Chr 9, suggesting that these fragments are telomeric and represent the ends of the chromosome maps. Confirmation of these map positions was obtained from a backcross. Fragments associated with the short arm of the Y Chr were found in DNA from strains C57BL/6J and DBA/2J. TELO-hybridizing fragments from DBA/2J were digested by the exonuclease Bal 31, under conditions in which fragments hybridizing to a cDNA probe for the metallothionein locus, located at the middle of mouse Chr 8, remained intact. Thus both biochemical and genetic tests indicate that several TELO-hybridizing fragments from Dde I-digested DNA are at the ends of chromosomes and probably derive from mouse telomeres. Using this approach should allow the mapping of genes relative to the ends of other mouse chromosomes.

Animals↗

Physical and genetic map of Streptococcus thermophilus A054.

The three restriction endonucleases SfiI, BssHII, and SmaI were found to generate fragments with suitable size distributions for mapping the genome of Streptococcus thermophilus A054. A total of 5, 8, and 24 fragments were produced with SfiI, BssHII, and SmaI, respectively. An average genome size of 1,824 kb was determined by summing the total fragment sizes obtained by digestions with these three enzymes. Partial and multiple digestions of genomic DNA in conjunction with Southern hybridization were used to map SfiI, BssHII, and SmaI fragments. All restriction fragments were arranged in a unique circular chromosome. Southern hybridization analysis with specific probes allowed 23 genetic markers to be located on the restriction map. Among them, six rrn loci were precisely located. The area of the chromosome containing the ribosomal operons was further detailed by mapping some of the ApaI and SgrAI sites. Comparison of macrorestriction patterns from three clones derived from strain A054 revealed two variable regions in the chromosome. One was associated with the tandem rrnD and rrnE loci, and the other was mapped in the region of the lactose operon.

Blotting, Southern↗

Genetic mapping of eleven spo genes essential for ascospore formation in the fission yeast Schizosaccharomyces pombe.

Sporulation-deficient mutants of the fission yeast Schizosaccharomyces pombe were isolated from a homothallic strain mutagenized with ethyl methanesulfonate. Complementation tests defined two new genetic loci (spo19 and spo20) essential for ascospore formation, in addition to the 18 known spo loci (Bresch et al. 1968). A novel mapping procedure using random spore analysis prior to tetrad analysis allowed us to map 11 spo genes. Four genes (spo3, spo15, spo19 and spo20) were mapped on chromosome I, 6 genes (spo2, spo4, spo5, spo6, spo14 and spo18) on chromosome III and 1 gene (spo13) on chromosome III. Although there was no noticeable clustering of spo genes on the chromosomes, three pairs of linked genes (spo15-spo20, spo3-spo19 and spo2-spo18) were found.

Chromosome Mapping↗

Construction of comparative genetic maps of two 4Bs.4Bl-5Rl translocations in bread wheat (Triticum aestivum L.).

The physical length of the rye segment of a 4BS.4BL-5RL translocation derived from the Cornell Wheat Selection 82a1-2-4-7 in a Triticum aestivum 'Chinese Spring' background was measured using genomic in situ hybridization (GISH) and found to be 16% of the long arm. The size of this translocation was similar to previously published GISH measurements of another 4BS.4BL-5RL translocation in a Triticum aestivum 'Viking' wheat background. Molecular maps of both 4BS.4BL-5RL translocations for 2 different wheat backgrounds were developed using RFLP analysis. The locations of the translocation breakpoints of the 2 4BS.4BL-5RL translocations were similar even though they arose in different populations. This suggests a unique property of the region at or near the translocation breakpoint that could be associated with their similarity and spontaneous formation. These segments of rye chromosome 5 also contain a gene for copper efficiency that improves the wheat's ability to cope with low-copper soils. Genetic markers in these maps can also be used to screen for copper efficiency in bread wheat lines derived from the Cornell Wheat Selection 82a1 2-4-7.

Chromosome Mapping↗

Genetic mapping of two murine loci that influence the development of IL-4-producing Thy-1dull gamma delta thymocytes.

IL-4-producing gamma delta cells belong to a novel subset of gamma delta lymphocytes that expresses a very restricted repertoire of TCRs. To gain a deeper insight into the development and in vivo functions of these cells, we have analyzed the genetic control of their representation in the thymus. Using an intercross between C57BL/6 and DBA/2 mice we found two loci on chromosomes 13 and 17-named LadT1 and LadT2, respectively-with marked influence in their development. The LadT2 locus does not appear to be the MHC locus. The region identified on mouse chromosome 13 contains the structural genes for TCR gamma as well as the IL-9 gene, which has been suggested as a candidate gene influencing the complex pathogenesis of asthma.

Animals↗

A high-density genetic map of hexaploid wheat (Triticum aestivum L.) from the cross Chinese Spring x SQ1 and its use to compare QTLs for grain yield across a range of environments.

A population of 96 doubled haploid lines (DHLs) was prepared from F1 plants of the hexaploid wheat cross Chinese Spring x SQ1 (a high abscisic acid-expressing breeding line) and was mapped with 567 RFLP, AFLP, SSR, morphological and biochemical markers covering all 21 chromosomes, with a total map length of 3,522 cM. Although the map lengths for each genome were very similar, the D genome had only half the markers of the other two genomes. The map was used to identify quantitative trait loci (QTLs) for yield and yield components from a combination of 24 site x treatment x year combinations, including nutrient stress, drought stress and salt stress treatments. Although yield QTLs were widely distributed around the genome, 17 clusters of yield QTLs from five or more trials were identified: two on group 1 chromosomes, one each on group 2 and group 3, five on group 4, four on group 5, one on group 6 and three on group 7. The strongest yield QTL effects were on chromosomes 7AL and 7BL, due mainly to variation in grain numbers per ear. Three of the yield QTL clusters were largely site-specific, while four clusters were largely associated with one or other of the stress treatments. Three of the yield QTL clusters were coincident with the dwarfing gene Rht-B1 on 4BS and with the vernalisation genes Vrn-A1 on 5AL and Vrn-D1 on 5DL. Yields of each DHL were calculated for trial mean yields of 6 g plant(-1) and 2 g plant(-1) (equivalent to about 8 t ha(-1) and 2.5 t ha(-1), respectively), representing optimum and moderately stressed conditions. Analyses of these yield estimates using interval mapping confirmed the group-7 effects on yield and, at 2 g plant(-1), identified two additional major yield QTLs on chromosomes 1D and 5A. Many of the yield QTL clusters corresponded with QTLs already reported in wheat and, on the basis of comparative genetics, also in rice. The implications of these results for improving wheat yield stability are discussed.

Biomass↗

Identification and genetic mapping of differentially expressed genes in mice differing at the If1 interferon regulatory locus.

A subtractive cDNA library was used to identify differentially expressed genes in mouse strains that differ at If1, a locus that regulates response to interferon induction by Newcastle Disease Virus infection. Among the isolated clones, sequence analysis identified the ribosomal proteins L37a and S8 as well as cDNAs for thymosine beta4, the QM transcriptional factor, and a novel genetic sequence. Analysis of two multilocus mouse crosses showed that the thymosine beta4 gene, Ptmb4, is present as a single-copy gene that maps to distal Chr X. The L37a, S8, and QM clones are all members of large multilocus families. These five clones were used to determine the map locations for 37 loci, of which 31 had not previously been described. The novel genetic sequence, D3Ppr1, mapped to distal Chr 3 near the position of the If1 locus, suggesting it may be a candidate for this regulatory gene.

Animals↗

Molecular genetic maps in wild emmer wheat, Triticum dicoccoides: genome-wide coverage, massive negative interference, and putative quasi-linkage.

The main objectives of the study reported here were to construct a molecular map of wild emmer wheat, Triticum dicoccoides, to characterize the marker-related anatomy of the genome, and to evaluate segregation and recombination patterns upon crossing T. dicoccoides with its domesticated descendant Triticum durum (cultivar Langdon). The total map length exceeded 3000 cM and possibly covered the entire tetraploid genome (AABB). Clusters of molecular markers were observed on most of the 14 chromosomes. AFLP (amplified fragment length polymorphism) markers manifested a random distribution among homologous groups, but not among genomes and chromosomes. Genetic differentiation between T. dicoccoides and T. durum was attributed mainly to the B genome as revealed by AFLP markers. The segregation-distorted markers were mainly clustered on 4A, 5A, and 5B chromosomes. Homeoalleles, differentially conferring the vigor of gametes, might be responsible for the distortion on 5A and 5B chromosomes. Quasilinkage, deviation from free recombination between markers of nonhomologous chromosomes, was discovered. Massive negative interference was observed in most of the chromosomes (an excess of double crossovers in adjacent intervals relative to the expected rates on the assumption of no interference). The general pattern of distribution of islands of negative interference included near-centromeric location, spanning the centromere, and median/subterminal location. [An appendix describing the molecular marker loci is available as an online supplement at http://www.genome.org.]

Binomial Distribution↗

22-Mb integrated physical and genetic map based on YAC/STS content spanning the interval DXS1125-DXS95 in human Xq12-q21.31.

A YAC/STS map has been assembled spanning 22 Mb across Xq12-q21.31, between markers DXS1125 and DXS95. In addition to the landmark loci for the X-inactivation center XIST and the ATRX, ATP7A, phosphoglycerate kinase, POU3F4, and choroideremia genes, the candidate disease gene regions for torsion dystonia 3 and two X-linked mental retardation syndromes are included. Also, the human voltage-dependent anion channel gene (HVDAC1) has been placed near DXS986. The current map incorporates 211 YACs from five different libraries, formatted with 185 STSs that comprise 26 genetic linkage markers, 60 newly-developed YAC-end STSs, and eight ESTs. The multiple clone coverage and average resolution of one STS per 120 kb provide resources for disease gene searches and are facilitating complete sequencing of the region.

Base Sequence↗

A genetic map of mouse chromosome 1 near the Lsh-Ity-Bcg disease resistance locus.

Isozyme and restriction fragment length polymorphism (RFLP) analyses of backcross progeny, recombinant inbred strains, and congenic strains of mice positioned eight genetic markers with respect to the Lsh-Ity-Bcg disease resistance locus. Allelic isoforms of Idh-1 and Pep-3 and RFLPs detected by Southern hybridization for Myl-1, Cryg, Vil, Achrg, bcl-2, and Ren-1,2, between BALB/cAnPt and DBA/2NPt mice, were utilized to examine the cosegregation of these markers with the Lsh-Ity-Bcg resistance phenotype in 103 backcross progeny. An additional 47 backcross progeny from a cross between C57BL/10ScSn and B10.L-Lshr/s mice were examined for the cosegregation of Myl-1 and Vil RFLPs with Lsh phenotypic differences. Similarly, BXD recombinant inbred strains were typed for RFLPs upon hybridization with Vil and Achrg. Recombination frequencies generated in the different test systems were statistically similar, and villin (Vil) was identified as the molecular marker closest (1.7 +/- 0.8 cM) to the Lsh-Ity-Bcg locus. Two other DNA sequences, nebulin (Neb) and an anonymous DNA fragment (D2S3), which map to a region of human chromosome 2q that is homologous to proximal mouse chromosome 1, were not closely linked to the Lsh-Ity-Bcg locus. This multipoint linkage analysis of chromosome 1 surrounding the Lsh-Ity-Bcg locus provides a basis for the eventual isolation of the disease gene.

Animals↗