Dataset Information

Fine scale structural variants distinguish the genomes of Drosophila melanogaster and D. pseudoobscura.

ABSTRACT:

Background

A primary objective of comparative genomics is to identify genomic elements of functional significance that contribute to phenotypic diversity. Complex changes in genome structure (insertions, duplications, rearrangements, translocations) may be widespread, and have important effects on organismal diversity. Any survey of genomic variation is incomplete without an assessment of structural changes.

Results

We re-examine the genome sequences of the diverged species Drosophila melanogaster and D. pseudoobscura to identify fine-scale structural features that distinguish the genomes. We detect 95 large insertion/deletion events that occur within the introns of orthologous gene pairs, the majority of which represent insertion of transposable elements. We also identify 143 microinversions below 5 kb in size. These microinversions reside within introns or just upstream or downstream of genes, and invert conserved DNA sequence. The sequence conservation within microinversions suggests they may be enriched for functional genetic elements, and their position with respect to known genes implicates them in the regulation of gene expression. Although we found a distinct pattern of GC content across microinversions, this was indistinguishable from the pattern observed across blocks of conserved non-coding sequence.

Conclusion

Drosophila has long been known as a genus harboring a variety of large inversions that disrupt chromosome colinearity. Here we demonstrate that microinversions, many of which are below 1 kb in length, located in/near genes may also be an important source of genetic variation in Drosophila. Further examination of other Drosophila genome sequences will likely identify an array of novel microinversion events.

SUBMITTER: Macdonald SJ

PROVIDER: S-EPMC1779558 | biostudies-literature | 2006

REPOSITORIES: biostudies-literature

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Publications

Fine scale structural variants distinguish the genomes of Drosophila melanogaster and D. pseudoobscura.

Macdonald Stuart J SJ Long Anthony D AD

Genome biology 20060101 7

<h4>Background</h4>A primary objective of comparative genomics is to identify genomic elements of functional significance that contribute to phenotypic diversity. Complex changes in genome structure (insertions, duplications, rearrangements, translocations) may be widespread, and have important effects on organismal diversity. Any survey of genomic variation is incomplete without an assessment of structural changes.<h4>Results</h4>We re-examine the genome sequences of the diverged species Drosop ...[more]

PMID: 16872532

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Project description:Genetic variation amongst individual humans occurs on many different scales, ranging from gross alterations in the human karyotype to single-nucleotide changes. In this manuscript we explore variation on an intermediate scale-particularly insertions, deletions, and inversions affecting from a few thousand to a few million base pairs. We employed a clone-based method to interrogate this intermediate structural variation in eight individuals of diverse geographic ancestry. Our analysis provides a comprehensive overview of the normal pattern of structural variation present in these genomes, refining the location of 1695 structural variants. We find that 50% were seen in more than one individual and that nearly half lay outside regions of the genome previously described as structurally variant. We discover 525 new insertion sequences that are not present in the human reference genome and show that many of these are variable in copy number among individuals. Sequencing of a subset of structural variants reveals considerable locus complexity and provides insights into the different mutational processes that have shaped the human genome. These data provide the first high-resolution sequence-map of human structural variation-an important standard for genotyping platforms and a prelude to future individual genome sequencing projects. Keywords: comparative genomic hybridization The DNA samples are a panel of 8 Hapmap samples, described by E. Eichler et al. (2007, Nature 447, 161-165). This set of 7 female, and one male samples are from from the Coriell Cell Repository, and is comprised of samples from four populations: four Yoruban, two CEPH, one Chinese, and one Japanese. The reference sample, NA15510, is female and also from the Corriel Cell Repository. This sample has been extensively characterized, (for example in Tuzan et al. 2005, Nature Genetics 10, p1038) and has been recommended for use in CNV detection programs to allow meaningful comparison of data between studies (discussed in Scherer, et al. 2007, Nature Genetics Supplement 39: S7-S15). Each of these samples was hybridized in pairs with the reversed labeling polarities. Additionally, 3 self-self control hybridizations were carried out for the reference sample, NA15510, one on each hybridization date.

Project description:Estimating fine-scale recombination maps of Drosophila from population genomic data is a challenging problem, in particular because of the high background recombination rate. In this paper, a new computational method is developed to address this challenge. Through an extensive simulation study, it is demonstrated that the method allows more accurate inference, and exhibits greater robustness to the effects of natural selection and noise, compared to a well-used previous method developed for studying fine-scale recombination rate variation in the human genome. As an application, a genome-wide analysis of genetic variation data is performed for two Drosophila melanogaster populations, one from North America (Raleigh, USA) and the other from Africa (Gikongoro, Rwanda). It is shown that fine-scale recombination rate variation is widespread throughout the D. melanogaster genome, across all chromosomes and in both populations. At the fine-scale, a conservative, systematic search for evidence of recombination hotspots suggests the existence of a handful of putative hotspots each with at least a tenfold increase in intensity over the background rate. A wavelet analysis is carried out to compare the estimated recombination maps in the two populations and to quantify the extent to which recombination rates are conserved. In general, similarity is observed at very broad scales, but substantial differences are seen at fine scales. The average recombination rate of the X chromosome appears to be higher than that of the autosomes in both populations, and this pattern is much more pronounced in the African population than the North American population. The correlation between various genomic features-including recombination rates, diversity, divergence, GC content, gene content, and sequence quality-is examined using the wavelet analysis, and it is shown that the most notable difference between D. melanogaster and humans is in the correlation between recombination and diversity.

Dataset Information

Fine scale structural variants distinguish the genomes of Drosophila melanogaster and D. pseudoobscura.

Background

Results

Conclusion

Publications

Fine scale structural variants distinguish the genomes of Drosophila melanogaster and D. pseudoobscura.

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