Biomedical subjects

Andrew B Stergachis

Publications and source records attributed to Andrew B Stergachis.

6 recordsLinked to original sources

PubMed2026

A practical guide to studying genome function using single-molecule genomics.

Single-molecule genomics (SMG) has transformed our ability to study the mechanisms that regulate the genome by enabling profiling of the activity of regulatory factors on individual DNA molecules genome-wide. SMG is able to quantify molecular heterogeneity and the co-occurrence of regulatory events, including epigenetic modifications, transcription factor binding and chromatin organization on single DNA molecules. SMG reveals dynamics of chromatin interactions that cannot be measured by conventional genomics assays. Therefore, SMG offers a unique platform to study how regulatory events combine to control genome activity. In this Expert Recommendation article, we provide a practical guide for adopting SMG and outline best practices.

Journal Article↗

PubMed2026

Native yeast kinetochore structures identify an essential inner kinetochore interaction.

Kinetochores must accurately assemble on centromeres for faithful chromosome segregation. Although a conserved centromeric nucleosome is essential for kinetochore assembly, budding yeast centromeric DNA is a poor template for nucleosome formation in vitro, perhaps due to its intrinsic rigidity. To better understand yeast inner kinetochore assembly, we develop a one-step protocol to purify native inner kinetochore subcomplexes for structural studies. We perform cryoelectron microscopy on the purifications and generate density maps of four separate inner kinetochore complexes, two of which have not been previously visualized and may represent intermediate assemblage states. We identify an Ndc10 trimerization domain that engages centromeric DNA and a pair of CBF3 complexes and is associated with substantial bending of centromeric DNA. Ndc10 trimerization is essential for kinetochore assembly and chromosome segregation. We propose that Ndc10 trimerization facilitates centromeric DNA bending to stabilize the centromeric nucleosome and inner kinetochore.

Kinetochores↗

PubMed2026

Not Forgotten: Patient Experiences with Genetic Variant Reclassifications.

PURPOSE: Genetic variant reclassification is increasingly common in clinical genomics, yet limited data describe how patients experience re-contact and variant reclassification in routine clinical care. METHODS: We conducted semi-structured qualitative interviews with 20 adult patients who received a variant reclassification following routine clinical genetic testing. Interviews explored emotional responses, communication experiences, and perceived value of genetic testing. Data were analyzed using Template Analysis, a form of thematic analysis. RESULTS: Three overarching themes were identified. Participants identified a need for improved communication of reclassified results, particularly with respect to timing, modality, and contextualization (Theme 1). Experiences with reclassification also shaped perceptions of the value of genetic testing, with most participants viewing testing as worthwhile despite its evolving nature (Theme 2). Finally, many participants interpreted reclassification as evidence of personalized and ongoing care, reinforcing trust in genetic testing and biomedical research (Theme 3). Participants generally preferred to be informed of reclassified results regardless of reclassification type, although the direction of reclassification influenced emotional responses and preferred modes of communication. Downgrades from variants of uncertain significance to benign or likely benign were widely viewed as meaningful by participants. CONCLUSION: Variant reclassification was experienced as a signal of personalized, ongoing care. Timely, contextualized, patient-centered re-contact practices may reduce uncertainty, strengthen trust, and help patients not feel forgotten.

Journal Article↗

PubMed2025

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↗

PubMed2025

CUT&TIME captures the history of open chromatin in developing neurons.

Chromatin structure plays a central role in defining cell identity by regulating gene expression. During development, shifts in chromatin structure facilitate changes in gene expression needed to specify distinct cell types. To understand how changes in chromatin structure influence the developmental trajectory of neural progenitor cells, we developed CUT&TIME, a technique that uses a hyperactive 6-methyl adenosine (6mA) methyltransferase pulsed in living cells to map historical chromatin accessibility genome-wide in single cells. We show that CUT&TIME produces a record of the chromatin landscape during neurogenesis in the developing retina, specifically as neural progenitors produce the major projection neuron type, retinal ganglion cells (RGCs). We further show that this method is compatible with single cell profiling technologies, which allows us to visualize and capture the diversity of chromatin states that produce RGCs. Additionally, we identify changes in promoter accessibility associated with the transition from progenitor to RGC. Together, these data demonstrate that CUT&TIME captures a historical record of chromatin structure, which can be used to identify early changes in accessibility associated with cell-fate commitment.

Journal Article↗

PubMed2025

Imprecision medicine: Systematic gaps in reporting variants of uncertain significance (VUS) and their reclassifications.

PURPOSE: Variants of uncertain significance (VUS) are frequently encountered during clinical genetic testing. To explore the clinical burden of VUS, we developed the Brotman Baty Institute Clinical Variant Database, which is an electronic health record (EHR)-linked database of clinical germline genetic variant information from patients with rare genetic disorders seen at 2 tertiary academic medical centers. METHODS: We retrospectively reviewed EHRs and genetic testing reports from 5158 patients seen across diverse adult genetics practices at these institutions from 2015 to 2024. We also compared these EHR-based variant classifications with those in ClinVar. RESULTS: The number of reported VUS relative to pathogenic or likely pathogenic variants can vary by over 14-fold depending on the primary indication for genetic testing and 3-fold depending on self-reported race. Furthermore, at least 1.6% of variant classifications used in the EHR for clinical care are outdated based on ClinVar variant classifications, including 26 instances in which the testing lab updated ClinVar, but the reclassification was never communicated to the patient. CONCLUSION: Our findings reveal that the clinical burden of VUS in adult medical genetics is unequally distributed across patients. We also highlight a deficiency in existing systems for communicating variant reclassifications to ClinVar, patients, and providers.

Humans↗