Forensic nanopore sequencing of microhaplotype markers using QitanTech's QNome

A proof-of-principle study: The potential application of MiniHap biomarkers in ancestry inference based on the QNome nanopore sequencing

Haplotyped SNPs convey forensic-related information, and microhaplotypes (MHs), as the most representative of this kind of marker, have proved the potential value for human forensics. In recent years, nanopore sequencing technology has developed rapidly, with its outstanding ability to sequence long continuous DNA fragments and obtain phase information, making the detection of longer haplotype marker possible. In this proof-of-principle study, we proposed a new type of forensic marker, MiniHap, based on five or more SNPs within a molecular distance less than 800 bp, and investigated the haplotype data of 56 selected MiniHaps in five Chinese populations using the QNome nanopore sequencing. The sequencing performance, allele (haplotype) frequencies, forensic parameters, effective number of alleles (Ae), and informativeness (In) were subsequently calculated. In addition, we performed principal component analysis (PCA), phylogenetic tree, and structure analysis to investigate the population genetic relationships and ancestry components among the five investigated populations and 26 worldwide populations. MiniHap-04 exhibited remarkable forensic efficacy, with 148 haplotypes reported and the Ae was 66.9268. In addition, the power of discrimination (PD) was 0.9934, the probability of exclusion (PE) was 0.9898, and the In value was 0.7893. Of the 56 loci, 85.71% had PD values above 0.85, 66.07% had PE values above 0.54, 67.86% had Ae values over 7.0%, and 55.36% were with In values above 0.2 across all samples, indicating that most of the MiniHaps are suitable for individual identification, paternity testing, mixture deconvolution, and ancestry inference. Moreover, the results of PCA, phylogenetic tree and structure analysis demonstrated that this MiniHap panel had the competency in continental population ancestry inference, but the differentiation within intracontinental/linguistically restricted subpopulations was not ideal. Such findings suggested that the QNome device for MiniHap detection was feasible and this novel marker has the potential in ancestry inference. Yet, the establishment of a more comprehensive database with sufficient reference population data remains necessary to screen more suitable MiniHaps.

Adapting an established Ampliseq microhaplotype panel to nanopore sequencing through direct PCR

We have adapted an established Ampliseq microhaplotype panel for nanopore sequencing with the Oxford Nanopore Technologies (ONT) system, as a cost-effective and highly scalable solution for forensic genetics applications. For this purpose, we designed a protocol combining direct PCR amplification from unextracted DNA with ONT library construction and sequencing using the MinION device and workflow. The analysis of reference samples at input amounts of 5-10 ng of DNA demonstrates stable coverage patterns, allele balance, and strand bias, reaching profile completeness and concordance rates of ∼95%. Similar levels were achieved when using direct-PCR from blood, buccal and semen swabs. Dilution series results indicate sensitivity is maintained down to 250 pg of input DNA, and informative profiles are produced down to 62.5 pg. Finally, we demonstrated the forensic utility of the nanopore workflow by analyzing two third degree pedigrees that showed low likelihood ratio values after the analysis of an extended panel of 38 STRs, achieving likelihood ratios 2-3 orders of magnitude higher when testing with the MinION-based haplotype data.

CmVCall: An automated and adjustable nanopore analysis pipeline for heteroplasmy detection of the control region in human mitochondrial genome

Genetic associations between human mitochondrial DNA (mtDNA) heteroplasmy and mitochondrial diseases, aging, and cancer have been elaborated, contributing a lot to the further understanding of mtDNA polymorphic spectrum in anthropology, population, and forensic genetics. In the past decade, heteroplasmy detection using Sanger sequencing and next generation sequencing (NGS) was hampered by the former's inefficiency and the latter's inherent bias due to amplification and mapping of short reads, respectively. Nanopore sequencing stands out for its ability to yield long contiguous segments of DNA, providing a new insight into heterogeneity authentication. In addition to MinION from Oxford Nanopore Technologies, an alternative nanopore sequencer QNome (Qitan Technology) has also been applied to various biological research and the forensic applicability of this platform has been proved recently. In this study, we evaluated the performance of four commonly used variant callers in the heterogeneity authentication of the control region of human mtDNA based on simulations of different ratios generated by mixing QNome nanopore sequencing reads of two synthetic sequences. Then, an open-source and python-based nanopore analytics pipeline, CmVCall was developed and incorporated multiple programs including reads filtering, removal of nuclear mitochondrial sequences (NUMTs), alignment, optional 'Correction' mode, and heterogeneity identification. CmVCall can achieve high precision, accuracy, and recall of 100%, 99.9%, and 92.3% with a 5% heteroplasmy level in 'Correction' mode. Moreover, blood, saliva, and hair shaft samples from monozygotic (MZ) twins were used for heterogeneity evaluation and comparison with the NGS data. Results of MZ twin samples showed that CmVCall could identify more point heteroplasmy sites, revealing significant levels of inter- and intra-individual mtDNA polymorphism. In conclusion, we believe that this analysis pipeline will lay a solid foundation for the development of a comprehensive nanopore analysis pipeline targeting the whole mitochondrial genome.

Coexistence of tet(X4), mcr-1, and blaNDM-5 in ST6775 Escherichia coli Isolates of Animal Origin in China

Emergence of pathogens harboring multiple resistance genes incurs great concerns. Cooccurrence of mobile resistance genes conferring resistance to tigecycline, colistin, and carbapenems in Escherichia coli has not been investigated. This study aimed to characterize three E. coli isolates coharboring tet(X4), mcr-1, and bla_NDM-5. Isolates coharboring tet(X4), mcr-1, and bla_NDM-5 were identified and characterized by PCR, Sanger sequencing, antimicrobial susceptibility testing, conjugation assays, Illumina sequencing, nanopore sequencing, and bioinformatic analysis. Three E. coli isolates carrying tet(X4), mcr-1, and bla_NDM-5 were identified from pigeons in China. They were resistant to almost all antimicrobials except enrofloxacin. tet(X4) and bla_NDM-5 could be conjugated into E. coli C600, but mcr-1 was nontransferable in three isolates. Three isolates belonged to sequence type 6775 (ST6775), and clonal dissemination of isolates carrying tet(X4), mcr-1, and bla_NDM-5 existed in the pigeon farm. Genetic analysis revealed that mcr-1 mediated by the Tn6330 was located on the chromosome, tet(X4) was located on the IncFII plasmid, and bla_NDM-5 was located on the IncX3 plasmid. We first characterized the E. coli isolates carrying tet(X4), mcr-1, and bla_NDM-5 simultaneously. Relevant measures should be taken to decrease the prevalence of pathogens carrying tet(X4), mcr-1, and bla_NDM-5. IMPORTANCE Tigecycline and colistin are regarded as vital antimicrobials to treat multidrug-resistant (MDR) bacterial infections, such as that caused by carbapenemase-producing Enterobacteriaceae (CPE). Cooccurrence of mobile resistance genes conferring resistance to last-resort antimicrobials in E. coli remains unknown. Here, we characterized E. coli strains coharboring tet(X4), mcr-1, and bla_NDM-5 phenotypically and genetically. Resistance genes tet(X4), mcr-1, and bla_NDM-5 were located on transposons or plasmids that were mobile genetic elements related to the capture, accumulation, and dissemination of such important resistance genes. The emergence of E. coli isolates carrying tet(X4), mcr-1, and bla_NDM-5 highlights the importance of monitoring the coexistence of novel mobile resistance genes in different settings with a One Health approach. Risk of transmission of such MDR pathogens from animals to humans should be evaluated comprehensively.