Biomedical subjects

Yael Danin-Poleg

Publications and source records attributed to Yael Danin-Poleg.

3 recordsLinked to original sources

PubMed2005

Array-based binary analysis for bacterial typing.

An allele-specific oligonucleotide microarray was developed for rapid typing of pathogens based on analysis of genomic variations. Using a panel of Escherichia coli strains as a model system, selected loci were sequenced to uncover differences, such as single- or multiple-nucleotide polymorphisms as well as insertion/deletions (indels). While typical genomic profiling experiments employ specific sequences targeted to genomic DNA unique to a single strain or virulent gene, the present array is designed to type bacteria based on a patterned signature response across multiple loci. In the signature concept, all strains are interrogated by hybridizing their amplified DNA to an array containing multiple probe sequences. Allele-specific oligonucleotide probe sequences targeting each of these variable regions were synthesized and included in a custom fiber-optic array. For each locus, a set of specific probe sequences is selected, such that hybridization gives a binary signal/no signal response to each of the probes. Using this strategy for multiple loci, many pathogens or microorganisms could be classified using a limited number of probes. Because of the advantages of the fiber-optic array platform over other array formats, including sensitivity and speed, the platform described in this paper is capable of supporting a high-throughput diagnostic strategy.

Bacterial Typing Techniques↗

PubMed2005

Amplified intergenic locus polymorphism as a basis for bacterial typing of Listeria spp. and Escherichia coli.

DNA-based methods are increasingly important for bacterial typing. The high number of polymorphic sites present among closely related bacterial genomes is the basis for the presented method. The method identifies multilocus genomic polymorphisms in intergenic regions termed AILP (amplified intergenic locus polymorphism). For each locus, a pair of unique PCR primers was designed to amplify an intergenic sequence from one open reading frame (ORF) to the adjacent ORF. Presence, absence, and size variation of the amplification products were identified and used as genetic markers for rapidly differentiating among strains. Polymorphism was evaluated using 18 AILP sites among 28 strains of Listeria monocytogenes and 6 strains of Listeria spp. and 30 AILP markers among 27 strains of Escherichia coli. Up to four alleles per locus were identified among Listeria strains, and up to six were identified among E. coli strains. In both species, more than half of the AILP sites revealed intraspecies polymorphism. The AILP data were applied to phylogenetic analysis among Listeria and E. coli strains. A clear distinction between L. monocytogenes and Listeria spp. was demonstrated. In addition, the method separated L. monocytogenes into the three known lineages and discriminated the most common virulent serotypic group, 4b. In E. coli, AILP analysis separated the known groups as well as the virulent O157:H7 isolates. These findings for both Listeria and E. coli are in agreement with other phylogenetic studies using molecular markers. The AILP method was found to be rapid, simple, reproducible, and a low-cost method for initial bacterial typing that could serve as a basis for epidemiological investigation.

Bacterial Typing Techniques↗

PubMed2004

Mono-nucleotide repeats (MNRs): a neglected polymorphism for generating high density genetic maps in silico.

Short, tandemly repeated DNA motifs, termed SSRs (simple sequence repeats) are widely distributed throughout eukaryotic genomes and exhibit a high degree of polymorphism. The availability of size-based methods for genotyping SSRs has made them the markers of choice for genetic linkage studies in all higher eukaryotes. These genotyping methods are not efficiently applicable to mononucleotide repeats (MNRs). Consequently, MNRs, although highly frequent in the genome, have generally been ignored as genetic markers. In contrast to single nucleotide polymorphisms (SNPs), SSRs can be identified in silico once the genomic sequence or segment of interest is available, without requiring any additional information. This makes possible ad-hoc saturation of a target chromosomal region with informative markers. In this context, MNRs appear to have much to offer by increasing the degree of marker saturation that can be obtained. By using the human genome sequence as a model, computational analysis demonstrates that MNRs in the size of 9-15 bp are highly abundant, with an average appearance every 2.9 kb, exceeding di- and tri-nucleotide SSRs frequencies by two- and five-fold, respectively. In order to enable practical, high throughput MNR genotyping, a rapid method was developed, based on sizing of fluorescent-labeled primer extension products. Genotyping of 16 arbitrarily chosen non-coding MNR sites along human chromosome 22 revealed that almost two-thirds (63%) of them were polymorphic, having 2-5 alleles per locus, with 20% of the polymorphic MNRs having more than two alleles. Thus, MNRs have potential for in silico saturation of sequenced eukaryote genomes with informative genetic markers.

Chromosome Mapping↗