Closing Gaps in the Human Genome with Fosmid Resources Generated from Multiple Individuals

The published finished human genome contained 340 gaps including 250 gaps in the euchromatic region. The reasons for these gaps were not fully understood, although subsequent analysis revealed that presence of segmentally duplicated sequences were a good predictor for the presence of gaps. However, not all segmentally duplicated regions contained gaps. We made a systemic effort to close euchromatic gaps and understand the nature of gap closing sequences. Our studies clearly demonstrate that the gap closing sequences analyzed were over 2.3-fold more enriched in segmental duplications and that about 40% of the gap closing sequences were structurally variant. The structural variant nature of gap closing sequences was verified by aCGH analysis, and by paired-end-sequence and fingerprint analysis of gap spanning clones from recently available human genome fosmid libraries from eight individuals. Identification and characterization of gap closing sequences provides an effective approach for closing the remaining euchromatic gaps in the human genome. 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.