Biology subjects

Spanjaard, B.

Publications and source records attributed to Spanjaard, B..

9 recordsLinked to original sources

bioRxiv2026

Quantitative and sensitive neuroblastoma minimal residual disease detection using extrachromosomal DNA (ecDNA) breakpoints

Sensitive detection of minimal residual disease (MRD) remains a major unmet need in high-risk neuroblastoma. MYCN amplification, a hallmark of high-risk disease, typically occurs on extrachromosomal DNA (ecDNA), but the potential of ecDNA-associated genomic rearrangements for individualized MRD monitoring has not been fully exploited. Here, we applied neuroblastoma-specific hybrid capture-based panel sequencing to identify patient-unique breakpoints within MYCN amplicons, and used Circle-seq and Nanopore sequencing to resolve the extrachromosomal amplicon structure in representative samples. Analysis of 8 neuroblastoma cell lines and 22 primary tumors identified 69 tumor-specific breakpoints. Those selected for assay development were validated by breakpoint-specific PCR and Sanger sequencing. Breakpoints detected in primary tumors remained detectable at relapse, supporting their stability as MRD markers. Breakpoint-specific real-time quantitative PCR and droplet digital PCR detected these junctions in bone marrow aspirates with high specificity and reached sensitivities down to a tumor DNA fraction of 10^-6. We applied this approach to 53 serial bone marrow aspirates from 14 patients with high-risk neuroblastoma to monitor MRD dynamics, resolving treatment response and molecular persistence. In six samples, breakpoint-positive DNA was detected in bone marrow that was negative by conventional cytology and immunocytology, highlighting the added value of molecular monitoring. Together, these findings establish ecDNA breakpoint-based detection as a strategy for MRD assessment in neuroblastoma, that is, in principle, applicable to any ecDNA-amplified oncogene.

cancer biology↗

bioRxiv2025

Lineage origin and microenvironment shape neuroblastoma transcriptional state and plasticity

Neuroblastoma, a neural-crest-derived malignancy of the peripheral nervous system, is a devastating pediatric disease characterized by high intra- and intertumoral heterogeneity. While several tumor expression programs correlate with patient outcome, the developmental and contextual determinants of their emergence remain incompletely understood. Here, we systematically dissected neuroblastoma transcriptional heterogeneity and measured how tumor expression programs are associated with lineage history and developmental context. To achieve this, we combined single-cell transcriptomics with high-throughput lineage tracing and tumor cell transplantation in zebrafish models of MYCN-driven neuroblastoma. We identified developmental cell-state-associated programs that align with sympathoadrenal development, as well as general cellular-process programs. Clonal analysis showed that developmental programs are preferentially clone-associated, whereas cellular-process programs are more context-responsive. Transplantation into an embryonic environment reshaped the activation of several initially clone-associated programs, consistent with developmentally determined state reconfiguration and/or selection of state-competent cells. Together, our results show that lineage history and developmental context jointly shape tumor-state architecture in vivo.

cancer biology↗

bioRxiv2025

Oncogene Silencing via ecDNA Micronucleation

Extrachromosomal DNA (ecDNA) contributes to cancer genome instability by enabling high-copy oncogene amplification, intratumoural heterogeneity and rapid genetic change. Micronuclei (MN) are frequently observed in chromosomally unstable cancers, yet their origins and relevance in ecDNA-driven tumours remain incompletely understood. Here, we investigate the relationship between ecDNA segregation errors and MN formation. We find that ecDNA frequently localizes to MN and represents a prominent source of MN content in ecDNA-positive cancer cells. Mitotic clustering of oncogene-bearing ecDNAs is associated with asymmetric inheritance and mis-segregation into MN. Transfer of oncogenes from ecDNA into MN is accompanied by reduced transcriptional output. Single-MN sequencing shows that individual MN are enriched for ecDNA to a degree that exceeds expectations from stochastic mis-segregation and that in MN oncogenes originating from multiple distinct ecDNAs coalesce. Using live-cell imaging, we observe that cells inheriting ecDNA-positive MN show limited proliferative capacity and an increased likelihood of cell death. In neuroblastoma patients with MYCN-amplified ecDNA, higher frequencies of ecDNA-positive MN at diagnosis are associated with improved event-free and overall survival. Together, these findings link ecDNA mis-segregation to MN formation and reduced cellular fitness, suggesting that ecDNA-positive MN may reflect a state of impaired oncogenic ecDNA function with potential relevance for clinical outcome.

cancer biology↗

bioRxiv2023

Mapping lineage-traced cells across time points with moslin

Simultaneous profiling of single-cell gene expression and lineage history holds enormous potential for studying cellular decision-making beyond simpler pseudotime-based approaches. However, it is currently unclear how lineage and gene expression information across experimental time points can be combined in destructive experiments, which is particularly challenging for in-vivo systems. Here we present moslin, a Fused Gromov-Wasserstein-based model to couple matching cellular profiles across time points. In contrast to existing methods, moslin leverages both intra-individual lineage relations and inter-individual gene expression similarity. We demonstrate on simulated and real data that moslin outperforms state-of-the-art approaches that use either one or both data modalities, even when the lineage information is noisy. On C. elegans embryonic development, we show how moslin, combined with trajectory inference methods, predicts fate probabilities and putative decision driver genes. Finally, we use moslin to delineate lineage relationships among transiently activated fibroblast states during zebrafish heart regeneration. We anticipate moslin to play a crucial role in deciphering complex state change trajectories from lineage-traced single-cell data.

bioinformatics↗

bioRxiv2021

A single-cell atlas of de novo β-cell regeneration reveals the contribution of hybrid β/δ cells to diabetes recovery in zebrafish

Regeneration-competent species possess the ability to reverse the progression of severe diseases by restoring the function of the damaged tissue. However, the cellular dynamics underlying this capability remain unexplored. Here, we use single-cell transcriptomics to map de novo {beta}-cell regeneration during induction and recovery from diabetes in zebrafish. We show that the zebrafish has evolved two distinct types of somatostatin-producing {delta}-cells, which we term {delta}1- and {delta}2-cells. Moreover, we characterize a small population of glucose-responsive islet cells, which share the hormones and fate-determinants of both {beta}- and {delta}1-cells. The transcriptomic analysis of {beta}-cell regeneration reveals that {beta}/{delta} hybrid cells constitute a prominent source of insulin-expression during diabetes recovery. Using in vivo calcium imaging and cell tracking, we further show that the hybrid cells form de novo and acquire glucose-responsiveness in the course of regeneration. The overexpression of dkk3, a gene enriched in hybrid cells, increases their formation in the absence of {beta}-cell injury. Finally, interspecies comparison shows that plastic {delta}1-cells are partially related to PP-cells in the human pancreas. Our work provides an atlas of {beta}-cell regeneration and indicates that the rapid formation of glucose-responsive hybrid cells contributes to the resolution of diabetes in zebrafish

developmental biology↗

bioRxiv2021

Cellular drivers of injury response and regeneration in the adult zebrafish heart

Myocardial infarction is a leading cause of death worldwide, as the adult human heart does not have the ability to regenerate efficiently after insults. In contrast, the adult zebrafish heart has a high capacity for regeneration, and understanding the mechanisms of regenerative processes in fish allows identification of novel therapeutic strategies. While several pro-regenerative factors have been described, the cell types orchestrating heart regeneration remain largely elusive. To overcome this conceptual limitation, we dissected cell type diversity in the regenerating zebrafish heart based on single cell transcriptomics and spatiotemporal analysis. We discovered a dramatic induction of several pro-regenerative cell types with fibroblast characteristics. To understand the cascade of events leading to heart regeneration, we determined the origin of these cell types by high-throughput lineage tracing. We found that pro-regenerative fibroblasts are derived from two separate sources, the epicardium and the endocardium. Mechanistically, we identified Wnt signaling as a key regulator of the endocardial regenerative response. In summary, our results uncover specialized fibroblast cell types as major drivers of heart regeneration, thereby opening up new possibilities to interfere with the regenerative capacity of the vertebrate heart.

systems biology↗

bioRxiv2020

Spatio-temporal mRNA dynamics in the early zebrafish embryo

Early stages of embryogenesis depend heavily on subcellular localization and transport of maternally deposited mRNA. However, systematic analysis of these processes is currently hindered by a lack of spatio-temporal information in single-cell RNA sequencing. Here, we combined spatially-resolved transcriptomics and single-cell RNA labeling to study the spatio-temporal dynamics of the transcriptome during the first few hours of zebrafish development. We measured spatial localization of mRNA molecules with sub-single-cell resolution at the one-cell stage, which allowed us to identify a class of mRNAs that are specifically localized at an extraembryonic position, the vegetal pole. Furthermore, we established a method for high-throughput single-cell RNA labeling in early zebrafish embryos, which enabled us to follow the fate of individual maternal transcripts until gastrulation. This approach revealed that many localized transcripts are specifically transported to the primordial germ cells. Finally, we acquired spatial transcriptomes of two xenopus species, and we compared evolutionary conservation of localized genes as well as enriched sequence motifs. In summary, we established sub-single-cell spatial transcriptomics and single-cell RNA labeling to reveal principles of mRNA localization in early vertebrate development.

systems biology↗

bioRxiv2018

Spatial transcriptomics of C. elegans males and hermaphrodites identifies novel fertility genes

To advance our understanding of the genetic programs that drive cell and tissue specialization, it is necessary to obtain a comprehensive overview of gene expression patterns. Here, we have used RNA tomography to generate the first high-resolution, anteroposterior gene expression maps of C. elegans males and hermaphrodites. To explore these maps, we have developed computational methods for discovering region and tissue-specific genes. Moreover, by combining pattern-based analysis with differential gene expression analysis, we have found extensive sex-specific gene expression differences in the germline and sperm. We have also identified genes that are specifically expressed in the male reproductive tract, including a group of uncharacterized genes that encode small secreted proteins that are required for male fertility. We conclude that spatial gene expression maps provide a powerful resource for identifying novel tissue-specific gene functions in C. elegans. Importantly, we found that expression maps from different animals can be precisely aligned, which opens up new possibilities for transcriptome-wide comparisons of gene expression patterns.

genomics↗

bioRxiv2017

Massively parallel single cell lineage tracing using CRISPR/Cas9 induced genetic scars

A key goal of developmental biology is to understand how a single cell transforms into a full-grown organism consisting of many different cell types. Single-cell RNA-sequencing (scRNA-seq) has become a widely-used method due to its ability to identify all cell types in a tissue or organ in a systematic manner 1-3. However, a major challenge is to organize the resulting taxonomy of cell types into lineage trees revealing the developmental origin of cells. Here, we present a strategy for simultaneous lineage tracing and transcriptome profiling in thousands of single cells. By combining scRNA-seq with computational analysis of lineage barcodes generated by genome editing of transgenic reporter genes, we reconstruct developmental lineage trees in zebrafish larvae and adult fish. In future analyses, LINNAEUS (LINeage tracing by Nuclease-Activated Editing of Ubiquitous Sequences) can be used as a systematic approach for identifying the lineage origin of novel cell types, or of known cell types under different conditions.

systems biology↗