Biology subjects

Weissensteiner, H.

Publications and source records attributed to Weissensteiner, H..

3 recordsLinked to original sources

bioRxiv2024

Nanopore sequencing with unique molecular identifiers enables accurate mutation analysis and haplotyping in the complex Lipoprotein(a) KIV-2 VNTR

BackgroundRepetitive genome regions, such as variable number of tandem repeats (VNTR) or short tandem repeats (STR), are major constituents of the uncharted dark genome and evade conventional sequencing approaches. The protein-coding LPA kringle IV type-2 (KIV-2) VNTR (5.6 kb per unit, 1-40 units per allele) is a medically highly relevant example with a particularly intricate structure, multiple haplotypes, intragenic homologies and an intra-VNTR STR. It is the primary regulator of plasma lipoprotein(a) [Lp(a)] concentrations, an important cardiovascular risk factor. However, despite Lp(a) variance is mostly genetically determined, Lp(a) concentrations vary widely between individuals and ancestries. This VNTR region hides multiple causal variants and functional haplotypes. MethodsWe evaluated the performance of amplicon-based nanopore sequencing with unique molecular identifiers (UMI-ONT-Seq) for SNP detection, haplotype mapping, VNTR unit consensus sequence generation and copy number estimation via coverage-corrected haplotypes quantification in the KIV-2 VNTR. We used 15 human samples and low-level mixtures (0.5% to 5%) of KIV-2 plasmids as a validation set. We then applied UMI-ONT-Seq to extract KIV-2 VNTR haplotypes in 48 multi-ancestry 1000-Genome samples and analyzed at scale a poorly characterized STR within the KIV-2 VNTR. ResultsUMI-ONT-Seq detected KIV-2 SNPs down to 1% variant level with high sensitivity, specificity and precision (0.977{+/-}0.018; 1.000{+/-}0.0005; 0.993{+/-}0.02) and accurately retrieved the full-length haplotype of each VNTR unit. Human variant levels were highly correlated with next-generation sequencing (R2=0.983) without bias across the whole variant level range. Six reads per UMI produced sequences of each KIV-2 unit with Q40-quality. The KIV-2 repeat number determined by coverage-corrected unique haplotype counting was in close agreement with droplet digital PCR (ddPCR), with 70% of the samples falling even within the narrow confidence interval of ddPCR. We then analyzed 62,679 intra-KIV-2 STR sequences and identified ancestry-specific STR patterns. Finally, we characterized the KIV-2 haplotype patterns across multiple ancestries. ConclusionsUMI-ONT-Seq accurately retrieves the SNP haplotype and precisely quantifies the VNTR copy number of each repeat unit of the complex KIV-2 VNTR region across multiple ancestries. This study utilizes the KIV-2 VNTR, presenting a novel and potent tool for comprehensive characterization of medically relevant complex genome regions at scale.

genomics↗

bioRxiv2020

Haplocheck: Phylogeny-based Contamination Detection in Mitochondrial and Whole-Genome Sequencing Studies

Within-species contamination is a major issue in sequencing studies, especially for mitochondrial studies. Contamination can be detected by analysing the nuclear genome or by inspecting the heteroplasmic sites in the mitochondrial genome. Existing methods using the nuclear genome are computationally expensive, and no suitable tool for detecting contamination in large-scale mitochondrial datasets is available. Here we present haplocheck, a tool that requires only the mitochondrial genome to detect contamination in both mitochondrial and whole-genome sequencing studies. Haplocheck is able to distinguish between contaminated and real heteroplasmic sites using the mitochondrial phylogeny. By applying haplocheck to the 1000 Genomes Project data, we show (1) high concordance in contamination estimates between mitochondrial and nuclear DNA and (2) quantify the impact of mitochondrial copy numbers on the mitochondrial based contamination results. Haplocheck complements leading nuclear DNA based contamination tools, and can therefore be used as a proxy tool in nuclear genome studies. Haplocheck is available both as a command-line tool at https://github.com/genepi/haplocheck and as a cloud web-service producing interactive reports that facilitates the navigation through the phylogeny of contaminated samples.

bioinformatics↗

bioRxiv2019

Extraordinary claims require extraordinary evidence in the case of asserted mtDNA biparental inheritance

A breakthrough article published in PNAS by Luo et al. (2018) challenges a central dogma in biology which states that the mitochondrial DNA (mtDNA) is inherited exclusively from the mother. By sequencing the mitogenomes of several members of three independent families, the authors inferred an unprecedented pattern of biparental inheritance that requires the participation of an autosomal nuclear factor in the molecular process. However, a comprehensive analysis of their data reveals a number of issues that must be carefully addressed before challenging the current paradigm. Unfortunately, the methods section lacks any description of sample management, validation of their results in independent laboratories was deficient, and the reported findings have been observed at a frequency at complete variance with established evidence. Moreover, the remarkably high (and unusually homogeneous) levels of heteroplasmy reported can be readily detected using classical techniques for DNA sequencing. By reassessing the raw sequencing data with an alternative computational pipeline, we report strong correlation to the NextGENe results provided by the authors on a per sample base. However, the sequencing replicates from the same donors show aberrations in the variants detected that need further investigation to exclude contributions from other sources or methodological artifacts. Finally, applying the principle of reductio ad absurdum, we demonstrate that the nuclear factor invoked by the authors would need to be extraordinarily complex and precise in order to preclude linear accumulation of mtDNA lineages across generations. We discuss alternate scenarios that explain findings of the same nature as reported by Luo et al., in the context of in-vitro fertilization and therapeutic mtDNA replacement ooplasmic transplantation.

genetics↗