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Glennis A Logsdon

Publications and source records attributed to Glennis A Logsdon.

2 recordsLinked to original sources

A complete diploid human genome benchmark for personalized genomics.

Human genome resequencing typically involves mapping reads to a reference genome to call variants; however, this approach suffers from both technical and reference biases, leaving many duplicated and structurally polymorphic regions of the genome unmapped. Consequently, existing variant benchmarks, generated by the same methods, fail to assess these complex regions. To address this limitation, we present a telomere-to-telomere genome benchmark that achieves near-perfect accuracy (i.e. no detectable errors) across 99.4% of the complete, diploid HG002 genome. This benchmark adds 701.4 Mb of autosomal sequence and both sex chromosomes (216.8 Mb), totaling 15.3% of the genome that was absent from prior benchmarks. We also provide a diploid annotation of genes, transposable elements, segmental duplications, and satellite repeats, including 39,144 protein-coding genes across both haplotypes. To facilitate application of the benchmark, we developed tools for measuring the accuracy of sequencing reads, phased variant call sets, and genome assemblies against a diploid reference. Genome-wide analyses show that state-of-the-art de novo assembly methods resolve 2-7% more sequence and outperform variant calling accuracy by an order of magnitude, yielding just one error per 100 kb across 99.9% of the benchmark regions. Adoption of genome-based benchmarking is expected to accelerate the development of cost-effective methods for complete genome sequencing, expanding the reach of genomic medicine to the entire genome and enabling a new era of personalized genomics.

Journal Article

Complete chromosome 21 centromere sequencing of families with Down syndrome reveals centromere size asymmetry.

Down syndrome, the most common form of human intellectual disability, is caused by nondisjunction and chromosome 21 trisomy (T21). Small centromeres have been hypothesized to contribute to its aetiology and studies on mammals suggest that larger centromeres are more efficiently transmitted, yet complete sequencing of chromosome 21 (chr21) centromeres has been particularly challenging. Using long-read sequencing, we sequenced and assembled the centromeres from eight families that include a child with free T21 (1 trio, 6 child-mother duos, and 1 singleton) all resulting from maternal meiosis I errors. Two of these families carry the smallest chr21 centromeres (143 and 181 kbp) observed in female individuals to date, exhibiting a ~10.7- and ~19.4-fold centromeric α-satellite higher-order repeat array size difference between the maternally inherited homologs, respectively. In both cases, the longer centromere harbors a poorly defined centromere dip region, marked by DNA hypomethylation, in the proband but not in the mother. A comparison of all proband chr21 centromeres (n=24) to those of controls (n=261) shows that small centromeres are not enriched in families with T21 (p-value=0.73); contrarily, chr21 extreme centromere size asymmetry (>10-fold) is unique of T21 (p-value=0.003), suggesting that this feature may represent a genetic risk factor for a subset of families with free T21. Additionally, phylogenetic reconstruction reveals that human chr21 has been particularly prone to such variation with some of the biggest size differences occurring over the last ~17 thousand years of human evolution.

Down syndrome