Publications (9)36.48 Total impact
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Article: Towards accurate detection and genotyping of expressed variants from whole transcriptome sequencing data.
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ABSTRACT: Massively parallel transcriptome sequencing (RNA-Seq) is becoming the method of choice for studying functional effects of genetic variability and establishing causal relationships between genetic variants and disease. However, RNA-Seq poses new technical and computational challenges compared to genome sequencing. In particular, mapping transcriptome reads onto the genome is more challenging than mapping genomic reads due to splicing. Furthermore, detection and genotyping of single nucleotide variants (SNVs) requires statistical models that are robust to variability in read coverage due to unequal transcript expression levels. In this paper we present a strategy to more reliably map transcriptome reads by taking advantage of the availability of both the genome reference sequence and transcript databases such as CCDS. We also present a novel Bayesian model for SNV discovery and genotyping based on quality scores. Experimental results on RNA-Seq data generated from blood cell tissue of three Hapmap individuals show that our methods yield increased accuracy compared to several widely used methods. The open source code implementing our methods, released under the GNU General Public License, is available at http://dna.engr.uconn.edu/software/NGSTools/.BMC Genomics 01/2012; 13 Suppl 2:S6. · 4.07 Impact Factor -
Article: Fosmid-based whole genome haplotyping of a HapMap trio child: evaluation of Single Individual Haplotyping techniques.
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ABSTRACT: Determining the underlying haplotypes of individual human genomes is an essential, but currently difficult, step toward a complete understanding of genome function. Fosmid pool-based next-generation sequencing allows genome-wide generation of 40-kb haploid DNA segments, which can be phased into contiguous molecular haplotypes computationally by Single Individual Haplotyping (SIH). Many SIH algorithms have been proposed, but the accuracy of such methods has been difficult to assess due to the lack of real benchmark data. To address this problem, we generated whole genome fosmid sequence data from a HapMap trio child, NA12878, for which reliable haplotypes have already been produced. We assembled haplotypes using eight algorithms for SIH and carried out direct comparisons of their accuracy, completeness and efficiency. Our comparisons indicate that fosmid-based haplotyping can deliver highly accurate results even at low coverage and that our SIH algorithm, ReFHap, is able to efficiently produce high-quality haplotypes. We expanded the haplotypes for NA12878 by combining the current haplotypes with our fosmid-based haplotypes, producing near-to-complete new gold-standard haplotypes containing almost 98% of heterozygous SNPs. This improvement includes notable fractions of disease-related and GWA SNPs. Integrated with other molecular biological data sets, this phase information will advance the emerging field of diploid genomics.Nucleic Acids Research 11/2011; 40(5):2041-53. · 8.03 Impact Factor -
Article: A comprehensively molecular haplotype-resolved genome of a European individual.
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ABSTRACT: Independent determination of both haplotype sequences of an individual genome is essential to relate genetic variation to genome function, phenotype, and disease. To address the importance of phase, we have generated the most complete haplotype-resolved genome to date, "Max Planck One" (MP1), by fosmid pool-based next generation sequencing. Virtually all SNPs (>99%) and 80,000 indels were phased into haploid sequences of up to 6.3 Mb (N50 ~1 Mb). The completeness of phasing allowed determination of the concrete molecular haplotype pairs for the vast majority of genes (81%) including potential regulatory sequences, of which >90% were found to be constituted by two different molecular forms. A subset of 159 genes with potentially severe mutations in either cis or trans configurations exemplified in particular the role of phase for gene function, disease, and clinical interpretation of personal genomes (e.g., BRCA1). Extended genomic regions harboring manifold combinations of physically and/or functionally related genes and regulatory elements were resolved into their underlying "haploid landscapes," which may define the functional genome. Moreover, the majority of genes and functional sequences were found to contain individual or rare SNPs, which cannot be phased from population data alone, emphasizing the importance of molecular phasing for characterizing a genome in its molecular individuality. Our work provides the foundation to understand that the distinction of molecular haplotypes is essential to resolve the (inherently individual) biology of genes, genomes, and disease, establishing a reference point for "phase-sensitive" personal genomics. MP1's annotated haploid genomes are available as a public resource.Genome Research 08/2011; 21(10):1672-85. · 13.61 Impact Factor -
Conference Proceeding: Workshop: Bioinformatics pipeline for fosmid based molecular haplotype sequencing.
IEEE 1st International Conference on Computational Advances in Bio and Medical Sciences, ICCABS 2011, Orlando, FL, USA, February 3-5, 2011; 01/2011 -
Conference Proceeding: Towards accurate detection and genotyping of expressed variants from whole transcriptome sequencing data.
IEEE 1st International Conference on Computational Advances in Bio and Medical Sciences, ICCABS 2011, Orlando, FL, USA, February 3-5, 2011; 01/2011 -
Article: Linkage disequilibrium based genotype calling from low-coverage shotgun sequencing reads.
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ABSTRACT: Recent technology advances have enabled sequencing of individual genomes, promising to revolutionize biomedical research. However, deep sequencing remains more expensive than microarrays for performing whole-genome SNP genotyping. In this paper we introduce a new multi-locus statistical model and computationally efficient genotype calling algorithms that integrate shotgun sequencing data with linkage disequilibrium (LD) information extracted from reference population panels such as Hapmap or the 1000 genomes project. Experiments on publicly available 454, Illumina, and ABI SOLiD sequencing datasets suggest that integration of LD information results in genotype calling accuracy comparable to that of microarray platforms from sequencing data of low-coverage. A software package implementing our algorithm, released under the GNU General Public License, is available at http://dna.engr.uconn.edu/software/GeneSeq/. Integration of LD information leads to significant improvements in genotype calling accuracy compared to prior LD-oblivious methods, rendering low-coverage sequencing as a viable alternative to microarrays for conducting large-scale genome-wide association studies.BMC Bioinformatics 01/2011; 12 Suppl 1:S53. · 2.75 Impact Factor -
Conference Proceeding: ReFHap: a reliable and fast algorithm for single individual haplotyping.
Proceedings of the First ACM International Conference on Bioinformatics and Computational Biology, BCB 2010, Niagara Falls, NY, USA, August 2-4, 2010; 01/2010 -
Article: PrimerHunter: a primer design tool for PCR-based virus subtype identification.
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ABSTRACT: Rapid and reliable virus subtype identification is critical for accurate diagnosis of human infections, effective response to epidemic outbreaks and global-scale surveillance of highly pathogenic viral subtypes such as avian influenza H5N1. The polymerase chain reaction (PCR) has become the method of choice for virus subtype identification. However, designing subtype-specific PCR primer pairs is a very challenging task: on one hand, selected primer pairs must result in robust amplification in the presence of a significant degree of sequence heterogeneity within subtypes, on the other, they must discriminate between the subtype of interest and closely related subtypes. In this article, we present a new tool, called PrimerHunter, that can be used to select highly sensitive and specific primers for virus subtyping. Our tool takes as input sets of both target and nontarget sequences. Primers are selected such that they efficiently amplify any one of the target sequences, and none of the nontarget sequences. PrimerHunter ensures the desired amplification properties by using accurate estimates of melting temperature with mismatches, computed based on the nearest neighbor model via an efficient fractional programming algorithm. Validation experiments with three avian influenza HA subtypes confirm that primers selected by PrimerHunter have high sensitivity and specificity for target sequences.Nucleic Acids Research 04/2009; 37(8):2483-92. · 8.03 Impact Factor -
Article: ReFHap: a reliable and fast algorithm for single individual haplotyping
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ABSTRACT: Full human genomic sequences have been published in the latest two years for a growing number of individuals. Most of them are a mixed consensus of the two real haplotypes because it is still very expensive to separate information coming from the two copies of a chromosome. However, latest improvements and new experimental approaches promise to solve these issues and provide enough information to reconstruct the sequences for the two copies of each chromosome through bioinformatics methods such as single individual haplotyping. Full haploid sequences provide a complete understanding of the structure of the human genome, allowing accurate predictions of translation in protein coding regions and increasing power of association studies. In this paper we present a novel problem formulation for single individual haplotyping. We start by assigning a score to each pair of fragments based on their common allele calls and then we use these score to formulate the problem as the cut of fragments that maximize an objective function, similar to the well known max-cut problem. Our algorithm initially finds the best cut based on a heuristic algorithm for max-cut and then builds haplotypes consistent with that cut. We have compared both accuracy and running time of ReFHap with other heuristic methods on both simulated and real data and found that ReFHap performs significantly faster than previous methods without loss of accuracy.
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- Nucleic Acids Research (2)
- BMC Bioinformatics (1)
- BMC Genomics (1)
- Genome Research (1)
Institutions
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2009–2012
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University of Connecticut
- Department of Computer Science and Engineering
Storrs, CT, USA
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2011
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Max-Planck-Institut für molekulare Genetik
- Department of Vertebrate Genomics
Berlin, Land Berlin, Germany
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