Open-Access STRhub Platform Bridges Electrophoresis and Sequencing in Forensic Genetics

Forensic geneticists navigating the technological evolution of human identification now have access to STRhub, a dedicated, open-access, multilingual web platform designed to bridge the conceptual divide between conventional capillary electrophoresis and emerging next-generation sequencing methodologies. Short tandem repeats have long served as the fundamental molecular benchmarks for human identification, kinship verification, and anthropological population genetics across global forensic laboratories. While the underlying analytical principles governing short tandem repeat interpretation remain firmly established, the software platforms, genomic reference repositories, and computational workflows required to inspect repeat variation have traditionally remained scattered across independent, non-communicating tools. Electropherogram simulators, sequence viewers, population allele frequency databases, and genomic structural repositories have historically been accessed through discrete web interfaces, creating substantial operational friction and complicating the educational progression of analysts transitioning between distinct laboratory technologies. STRhub directly addresses this historical fragmentation by integrating essential, openly accessible short tandem repeat resources into a coherent visual ecosystem hosted at strhub.app. Rather than attempting to replace validated casework software or primary research databases, the platform functions as an interactive educational bridge that contextualizes established resources, helping investigators and students explore complex genetic profiles across both length-based and sequence-resolved paradigms simultaneously.

The analytical transition from capillary electrophoresis to high-throughput next-generation sequencing marks a transformative era for forensic genetics, yet it introduces profound interpretive challenges regarding how molecular variation is defined and reported. Capillary electrophoresis separates amplified short tandem repeat fragments purely by length, generating electropherograms where peaks correspond to overall fragment sizes without revealing the underlying nucleotide sequence. Consequently, alleles of identical base-pair length that harbor distinct internal sequence arrangements, known as isoalleles, remain entirely unresolved on routine electrophoretic traces. Next-generation sequencing successfully exposes these hidden structural variations, illuminating internal motif interruptions, sequence substitutions, and flanking-region polymorphisms that substantially elevate statistical discrimination power in challenging evidence samples. However, this deeper structural resolution introduces considerable interpretive complexity, particularly when reporting findings in strict accordance with the nomenclature guidelines established by the International Society for Forensic Genetics. Transitioning from simple length-based numerical designations to detailed sequence strings demands rigorous training, especially when navigating complex multi-motif loci where varying analytical pipelines may designate repeat boundaries or strand orientations differently. By anchoring sequence representations directly to contemporary International Society for Forensic Genetics standards through specialized automated nomenclature tools, STRhub allows practitioners to directly explore how structural nuances alter formal allele designations.

Constructed upon a modern computational framework utilizing Next.js, React, and TypeScript alongside responsive interfaces styled with Shadcn and TailwindCSS, STRhub prioritizes intuitive usability, structural responsiveness, and educational clarity. A central engineering breakthrough of the system is its simultaneous trilingual architecture, providing equivalent, native interfaces in English, Spanish, and Portuguese. Forensic tools and specialized bioinformatics databases have overwhelmingly been developed exclusively in English, erecting persistent educational and linguistic barriers that hinder adoption among laboratory scientists and academic students across non-Anglophone regions, particularly in Latin America. By incorporating comprehensive trilingual support directly into its core design rather than offering it as an afterthought, STRhub dismantles language-related obstacles and fosters more equitable global participation in sequence-based forensic genetics training. The open-source code, maintained transparently on GitHub, reflects a modular structure designed to accommodate continuous community contributions, technical notes, and iterative platform improvements.

Central to STRhub’s educational utility is its integrated mixture exploration module, which couples conceptual capillary electrophoresis simulation with synchronized, sequence-resolved next-generation sequencing outputs for the identical contributor scenario within a unified viewing pane. Within this module, simulated DNA mixtures are constructed using real single-source genomic profiles derived from the 1000 Genomes Project, providing realistic genetic foundations for exploratory testing. Users retain complete interactive control over contributor identities, contributor proportions, degradation gradients, baseline instrument noise, locus-specific stutter coefficients, and analytical and stochastic detection thresholds. The simulation engine explicitly decouples physical signal generation from interpretive threshold filtering, modeling peak heights through defined biophysical variables such as heterozygote imbalance, stochastic variability, and locus-specific stutter behavior derived from empirical literature rather than laboratory-specific casework calibrations. When an analyst adjusts parameters, the upper panel dynamically renders the resulting electropherogram trace, demonstrating how minor contributor peaks may drop below stochastic thresholds, merge into baseline noise, or become obscured beneath stutter artifacts generated by dominant major contributors under diverse simulated degradation scenarios.

The power of this dual-paradigm visualization becomes strikingly evident through side-by-side comparative evaluations at complex loci, demonstrating how sequencing overcomes the blind spots inherent to length-based separation. In a demonstration at the vWA locus combining two 1000 Genomes contributors in a seventy-to-thirty mixture ratio, contributor A carries alleles 14 and 16, whereas contributor B superficially appears homozygous for allele 17 when examined strictly by length-based capillary electrophoresis. In the upper electropherogram view, the profile exhibits typical length-resolved peaks subjected to baseline noise, stutter effects, and threshold constraints, leaving contributor B’s true allelic composition ambiguous. Directly below, the synchronized sequencing panel reveals the identical mixture at nucleotide resolution, displaying explicit allele calls, probabilistic depth of coverage metrics derived from HipSTR outputs, and detailed motif notations. This side-by-side juxtaposition provides an intuitive visual demonstration of how next-generation sequencing rescues hidden discrimination power from within apparent length-based homozygosity, rendering complex mathematical concepts immediately accessible to practitioners.

Beyond interactive mixture simulation, STRhub incorporates an extensive locus catalog that centralizes genomic coordinates, structural descriptions, representative allele libraries, and population frequency panels across autosomal, X-linked, and Y-linked short tandem repeat systems. Integrating disparate databases requires an internal representational harmonization pipeline that standardizes locus nomenclature, motif descriptors, genomic coordinates, and internal indexing fields strictly computational in nature. This curation pipeline rigorously preserves the underlying scientific content without altering, recalculating, or reinterpreting the primary frequency distributions reported by foundational source databases like STRBase, STRidER, and pop.STR. The catalog explicitly highlights complex structural organizations, such as the multi-motif architecture of D21S11, where interactive segmentation visually differentiates canonical uninterrupted repeat blocks, variant internal motifs, and non-contributing flanking segments. Interactive tooltips explain International Society for Forensic Genetics nomenclature conventions, clarifying why specific motif-like copies occurring outside core continuous repeat blocks are excluded from official numerical designations, thereby preventing widespread misinterpretations between differing commercial amplification kits and sequence interpretation pipelines.

STRhub also incorporates targeted bioinformatics modules to demystify raw data interpretation, featuring an embedded Integrative Genomics Viewer instance that provides immediate access to pre-aligned read data from 1000 Genomes Project samples without requiring local software installation, reference index configuration, or intensive command-line data processing. Analysts can directly inspect read alignments, visualize read depth, and examine alignment-level phenomena such as soft clipping across standardized forensic repeat loci. A companion FASTA generator facilitates the export of custom sequence constructs, allowing learners to study sequence formatting conventions encountered across high-throughput sequencing pipelines. During the computational validation of nomenclature mapping using STRNaming v1.2, developers independently identified and verified a systematic length offset of plus two repeat units in HipSTR-derived genotypes at locus D19S433 relative to capillary electrophoresis designations. This offset, previously documented in Brazilian population datasets, was transparently integrated into STRhub’s computational framework, providing documented corrections that illustrate the subtle bioinformatic discrepancies that can arise between automated length-calling pipelines and sequence-level alignments.

To maintain clear scientific boundaries, the developers explicitly emphasize that STRhub’s capillary electrophoresis simulator is a conceptual educational instrument designed solely for exploratory learning and qualitative training, not a casework-validated calculation engine. It must never be deployed for operational legal DNA interpretation or probabilistic genotyping calculations. Furthermore, STRhub’s sequence haplotypes currently derive from reference flanking regions rather than individual-specific raw reads, meaning sample-specific flanking polymorphisms cannot be inferred within the current implementation. Population panels reflect published open-access datasets in pop.STR, carrying whatever regional coverage gaps and ancestral sampling biases exist in published literature, though future platform updates aim to integrate a curated Latin American allele frequency panel alongside tutorials for long-read platforms like PacBio and Oxford Nanopore. By openly acknowledging these technical boundaries, STRhub firmly establishes its vital role not as an operational testing tool, but as an indispensable, equitable conceptual bridge guiding the global forensic community toward sequence-informed DNA interpretation.

Subject of Research: Forensic genetics educational platform integrating capillary electrophoresis and next-generation sequencing STR data

Article Title: STRhub: an open-access educational platform for CE and NGS STR data exploration in forensic genetics

Article References: Frontanilla, T. S., Kobachuk, L. D. G., Ayala, J., & Mendes-Junior, C. T. (2026). STRhub: an open-access educational platform for CE and NGS STR data exploration in forensic genetics. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04056-w

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04056-w

Keywords: forensic genetics, short tandem repeats, next-generation sequencing, capillary electrophoresis, STRhub, bioinformatics, DNA mixture interpretation, isoalleles, genomic education, ISFG nomenclature, open-access, educational