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Biology subjects

Petersen, M. B.

Publications and source records attributed to Petersen, M. B..

2 recordsLinked to original sources

Setting the SCENE for Interpretable Cell-Gene Embeddings in Single-Cell RNA-seq

Single-cell RNA sequencing measures cellular states at high resolution, but sparse high-dimensional count data remain difficult to model interpretably. We introduce the Single-Cell Euclidean Network Embedding (SCENE), a probabilistic latent-distance model that jointly embeds cells and genes from Unique Molecular Identifier (UMI) counts. SCENE treats the count matrix as a weighted bipartite cell-gene graph, where Euclidean distances represent transcriptional affinity, and combines this geometry with a zero-inflated count likelihood that separates gene detection from expression magnitude. Across real and simulated scRNA-seq datasets, SCENE recovers biologically structured cell and gene embeddings with state-of-the-art performance. Surprisingly, major biological structure is preserved in native two- and three-dimensional latent spaces, enabling directly interpretable visualization. Perturbation analyses show that SCENE organizes glucocorticoid-response genes and T-cell receptor regulatory programs coherently in gene space, capturing biology beyond cell-type separation. SCENE provides a transparent representation learning framework in which low-dimensional Euclidean geometry supports accurate modeling and biological interpretation.

bioinformatics↗

PAF15-PCNA assembly exhaustion governs lagging strand replication and replisome integrity

Genome replication in eukaryotic cells is surveyed by the S-phase checkpoint, which orchestrates sequential replication origin activation to avoid exhaustion of hitherto poorly defined rate-limiting replisome components. Here, we find that excessive activation of replication origins depletes chromatin-bound PCNA and lagging strand components, thereby limiting additional PCNA loading at new origins when checkpoint control is disrupted. PAF15 (PCNA-associated factor 15) emerges as a dosage-sensitive regulator of PCNA, delineating the dynamic range of global genome duplication and defining distinct roles for PCNA on the leading and lagging strands. Through its high-affinity PIP motif and interaction within the DNA encircling channel of PCNA, PAF15 stabilizes PCNA exclusively on the lagging strand, optimizing and rate-limiting lagging strand processing. On the other hand, misregulation of PAF15--whether by overexpression or mislocalization to the leading strand--impairs replication fork progression and leads to cell death. These defects are mitigated by TIMELESS and CLASPIN, which restrain PAF15-PCNA interactions beyond the lagging strand. E2F4-mediated repression orchestrates PAF15 expression in normal and cancer cells, maintaining its optimal dosage for lagging strand-specific interactions with PCNA. Thus, the S-phase checkpoint functions in concert to restrict origin activation when lagging strand PAF15-PCNA assembly is exhausted, linking a previously concealed strand-specific rate limitation to overall replication dynamics.

biochemistry↗