NotI clones in the analysis of the human genome

NotI linking clones contain sequences flanking NotI recognition sites and were previously shown to be tightly associated with CpG islands and genes. To directly assess the value of NotI clones in genome research, high density grids with 50 000 NotI linking clones originating from six representative NotI linking libraries were constructed. Altogether, these libraries contained nearly 100 times the total number of NotI sites in the human genome. A total of 3437 sequences flanking NotI sites were generated. Analysis of 3265 unique sequences demonstrated that 51% of the clones displayed significant protein similarity to SWISSPROT and TREMBL database proteins based on MSPcrunch filtering with stringent parameters. Of the 3265 sequences, 1868 (57.2%) were new sequences, not present in the EMBL and EST databases (similarity ≤ 90%). Among these new sequences, 795 (24.3%) showed similarity to known proteins and 712 (21.8%) displayed an identity of >75% at the nucleotide level to sequences from EMBL or EST databases. The remaining 361 (11.1%) sequences were completely new, i.e. <75% identical. The work also showed tight, specific association of NotI sites with the first exon and suggest that the so-called 3′ ESTs can actually be generated from 5′-ends of genes that contain NotI sites in their first exon.     

Efficient identification and regional positioning of YAC and cosmid clones to human Chromosome 21 by radiation fusion hybrids

The use of integrated mapping strategies involving bacterial, yeast, and rodent cells as hosts simplifies the construction of maps, which combine long-range order, high resolution, and easy access to the cloned DNA. Radiation-fusion hybrids offer a specially powerful long-range mapping system for human chromosomes. We describe here techniques for establishing a radiation-fusion hybrid map of Chromsome (Chr) 21 q and its integration with local information on YAC and cosmid positions.     

Physical assignments of 68 porcine cosmid and lambda clones containing polymorphic microsatellites

Two lambda phage and 66 cosmids containing informative porcine microsatellites were assigned to 17 of 18 porcine autosomes and the X Chromosome (Chr) by fluorescence in situ hybridization (FISH). These assignments provide additional physically anchored markers to integrate the porcine physical and genetic maps. Received: 2 October 1995 / Accepted: 12 December 1995     

Expression of human histocompatibility antigens on the surface of murine cells transformed by cosmid clones containing HLA genes

Thymidine kinase-negative C3H mouse L fibroblasts (LMTK⁻) transformed with cosmid clones containing both herpes virus-derived thymidine kinase (TK) and HLA class I genes were first selected in HAT (hypoxanthine, aminopterin, thymidine) medium and subsequently analyzed for the expression of human transplantation antigens. TK⁺-transformed cells expressing HLA class I molecules were characterized by surface radioimmunoassay, cytofluorimetric analysis and immunoperoxidase PAP technique at the light and electron microscopic levels, using a set of monoclonal antibodies. Comparisons were made with human B (Raji) and T (1 301) lymphoblastoid cell lines which respectively express high and low levels of HLA molecules on their surface. The expression of HLA class I in association with murine β2-microglobulin on the surface of transformed cells did not reduce the level of expression of H-2 molecules.     

Localization of the NotI clones from human chromosome 3 on quail microchromosomes

For the purpose of comparative mapping of quail (Coturnix c. japonica) and human (Homo sapiens) genomes, DNA fragments from human chromosome 3 (HSA3p14-21 and HSA3q13-23) were localized on quail mitotic chromosomes. Using the method of double-color fluorescence DNA-DNA in situ hybridization, these fragments were mapped to two different microchromosomes. Earlier, similar studies were performed using chicken mitotic chromosomes. There it was demonstrated that the clones of interest were distributed among three microchromosomes (GGA12, GGA14, and GGA15). Thus, interspecific difference in the location of human chromosome 3 DNA fragments in the genomes of closely related avian species was discovered. A new confirmation of the hypothesis on the preferable localization of the gene-rich human chromosome regions on avian microchromosomes was obtained. At the same time, a suggestion on the localization of some orthologous genes in the genome of the organism under study was made: ARF4, SCN5A, PHF7, ABHD6, ZDHHC3, MAPKAPK3, ADSYNA (homolog of chicken chromosome 12), DRD2, PP2C-ETA, RAB7, CCKAR, and PKD1 (homolog of chicken chromosome 15). However, localization of the corresponding quail genes needs to be confirmed, as far as the sequences used were only the orthologs of the corresponding chicken genes.     

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.     

Use of short oligonucleotides to screen cosmid libraries for clones containing G/C-rich sequences

We have developed a method to identify clones containing recognition sequences for enzymes that cut mammalian genomes infrequently by direct screening of genomic libraries. The degenerate oligonucleotide NNGCGGCCGCNN, in which the internal 8 bases correspond to the recognition sequence of Not I, was used to screen a cosmid library, and it led to a greater than 10-fold enrichment in the number of clones containing Not I sites. This technique permits the efficient identification of sufficient clones from a chromosome-specific library to allow the construction of a complete pulsed-field map of that chromosome and to assist in finding genes in genomic DNA.     

Molecular analysis of rearrangements in human ribosomal RNA gene clones

Human placental DNA, enriched for ribosomal sequences, was cloned in the phage vector lambda Charon 16A. Recombinants containing 28S rDNA sequences were isolated, and all were found to have deletions in the insert and/or vector DNA. Electron microscopic analysis was used to map the deletions and provide evidence that unstable forms of the recombinants can revert to the original vector or undergo further rearrangements. Specific deletions are manifested as previously unreported plaque phenotypes.     

Evaluation of a cosmid contig physical map of human chromosome 16.

A cosmid contig physical map of human chromosome 16 has been developed by repetitive sequence finger-printing of approximately 4000 cosmid clones obtained from a chromosome 16-specific cosmid library. The arrangement of clones in contigs is determined by (1) estimating cosmid length and determining the likelihoods for all possible pairwise clone overlaps, using the fingerprint data, and (2) using an optimization technique to fit contig maps to these estimates. Two important questions concerning this contig map are how much of chromosome 16 is covered and how accurate are the assembled contigs. Both questions can be addressed by hybridization of single-copy sequence probes to gridded arrays of the cosmids. All of the fingerprinted clones have been arrayed on nylon membranes so that any region of interest can be identified by hybridization. The hybridization experiments indicate that approximately 84% of the euchromatic arms of chromosome 16 are covered by contigs and singleton cosmids. Both grid hybridization (26 contigs) and pulsed-field gel electrophoresis experiments (11 contigs) confirmed the assembled contigs, indicating that false positive overlaps occur infrequently in the present map. Furthermore, regional localization of 93 contigs and singleton cosmids to a somatic cell hybrid mapping panel indicates that there is no bias in the coverage of the euchromatic arms.     

Construction and regional localization of clones from a NotI linking library from human chromosome 17q

A NotI linking library was constructed from a somatic cell hybrid containing chromosome 17q as its only human material. A total of 112 human clones were assigned to nine regions of 17q using a somatic cell hybrid mapping panel. The library includes clones that detect the acute promyelocytic leukemia and von Recklinghausen neurofibromatosis translocation breakpoints at 17q11.2-12 and 17q11.2, respectively, on pulsed-field gel electrophoresis. The mapped clones represent over 50% of the estimated number of NotI sites on 17q, and therefore constitute an important resource for long-distance mapping.     

Generation of bovine multisite haplotypes using random cosmid clones.

One hundred ten random cosmids were used to probe Southern blots of DNA from nine unrelated cattle digested with 12 restriction enzymes. Although only one-third of the expected fragments were explored, 85% of the cosmids revealed at least one polymorphism. The mean heterozygosity of the generated haplotypes was estimated at 51.9%. A surprisingly high proportion of polymorphisms (approximately 25%) was attributed to insertion-deletion events, compensating for the lower level of nucleotide diversity observed in cattle (pi approximately 0.0007) compared to that in human. The mutation rate at cytosines in the CpG dinucleotide was estimated approximately 10 times higher than that at other nucleotides. When used in linkage studies, the generated markers should cover approximately 50% of the bovine genome.     

The generation of ordered sets of cosmid DNA clones from human chromosome region 11p.

We describe progress in a continuing project aimed at the generation of an overlapping cosmid DNA clone map of the short arm of human chromosome 11. The automated procedures used to prepare DNA samples and the computerized data collection and recording systems are described. We also demonstrate the use of the clones as reagents for the rapid isolation of genomic DNAs containing smaller probed regions. We have isolated approximately 4700 human cosmid DNA clones from mouse/human hybrid cell lines that contain predominantly human chromosomal region 11p. Of the DNA in the cell lines, 60% is derived from this chromosomal region, and the remaining 40% is derived from regions of chromosomes 3, 19, and 20. A total of 4159 clones have been fingerprinted to identify potential overlaps, and we have developed 535 sets ("contigs"). Using random modeling, it is estimated that 65% of 11p must be contained in the analyzed cosmids. The database of clones has been used to identify single or overlapping clones from noncosmid DNA probes. Examples are presented. It is proposed that cosmid reference filters be distributed to requesting laboratories.     

HLA cosmid clones show complete, widely spaced human class I genes with occasional clusters

To understand the organization of the human leukocyte antigen (HLA) gene region and its relationship to the transplantation antigens expressed at the cell surface we have isolated clones containing HLA class I genes from a cosmid library (Grosveld et al., Gene 13, 227, 1981) constructed with the DNA from an individual of defined haplotype. Most of the cosmids contain a single HLA gene in 30–40 kb of human DNA, indicating that human class I genes are rather widely spaced; two contain two genes and one contains three. Most of these genes appear to be complete; the double or multiple genes are found in the same orientation. Differences in restriction maps are evident but some common features are observed in particular in the 5' half of these genes.