ComHapDet: a spatial community detection algorithm for haplotype assembly

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ComHapDet: a spatial community detection algorithm for haplotype assembly Abishek Sankararaman1* , Haris Vikalo1 and François Baccelli1,2 From The Sixth International Workshop on Computational Network Biology: Modeling, Analysis, and Control (CNB-MAC 2019) Niagara Falls, NY, USA. 07 September 2019

Abstract Background: Haplotypes, the ordered lists of single nucleotide variations that distinguish chromosomal sequences from their homologous pairs, may reveal an individual’s susceptibility to hereditary and complex diseases and affect how our bodies respond to therapeutic drugs. Reconstructing haplotypes of an individual from short sequencing reads is an NP-hard problem that becomes even more challenging in the case of polyploids. While increasing lengths of sequencing reads and insert sizes helps improve accuracy of reconstruction, it also exacerbates computational complexity of the haplotype assembly task. This has motivated the pursuit of algorithmic frameworks capable of accurate yet efficient assembly of haplotypes from high-throughput sequencing data. Results: We propose a novel graphical representation of sequencing reads and pose the haplotype assembly problem as an instance of community detection on a spatial random graph. To this end, we construct a graph where each read is a node with an unknown community label associating the read with the haplotype it samples. Haplotype reconstruction can then be thought of as a two-step procedure: first, one recovers the community labels on the nodes (i.e., the reads), and then uses the estimated labels to assemble the haplotypes. Based on this observation, we propose ComHapDet – a novel assembly algorithm for diploid and ployploid haplotypes which allows both bialleleic and multi-allelic variants. Conclusions: Performance of the proposed algorithm is benchmarked on simulated as well as experimental data obtained by sequencing Chromosome 5 of tetraploid biallelic Solanum-Tuberosum (Potato). The results demonstrate the efficacy of the proposed method and that it compares favorably with the existing techniques. Keywords: Haplotype assembly, Spatial random graph, Graph clustering

Background Technological advancements in DNA sequencing have enabled unprecedented studies of genetic blueprints and variations between individual genomes. An individual genome of a eukaryotic organism is organized in K-tuples of homologous chromosomes; diploids (K = 2), including *Correspondence: [email protected] Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX, USA Full list of author information is available at the end of the article 1

humans, have genomes organized in pairs of homologous chromosomes where the chromosomes in a pair differ from each other at a small fraction of positions. The ordered lists of such variants – the so-called single nucleotide polymorphisms (SNPs) – are referred to as haplotypes. Many plants are polyploid, i.e., have genomes organized in K-tuples, K > 2, of homologous chromosomes; for instanc