Biology subjects

Pabba, M. K.

Publications and source records attributed to Pabba, M. K..

4 recordsLinked to original sources

bioRxiv2026

RepliCNN: High-resolution inference of the DNA replication program from strand-specific 3' DNA end sequencing

During S phase, the genome is replicated in a tightly regulated spatiotemporal order described as DNA replication timing (RT). Discontinuous lagging-strand synthesis produces Okazaki fragments whose strand-specific distribution reflects replication dynamics. Here, we present RepliCNN, a deep learning framework based on one-dimensional convolutional neural networks to predict RT from Okazaki fragment distributions obtained from strand-specific 3' DNA end sequencing methods such as GLOE-Seq, TrAEL-seq, or OK-Seq. RepliCNN also automatically annotates replication origins, termination zones, replication fork directionality, and origin efficiency genome-wide from a single dataset. Benchmarking on public and in-house human and yeast datasets using leave-one-chromosome-out cross-validation demonstrates high predictive accuracy in both wild-type and perturbation experiments, enabling comprehensive analyses of replication dynamics from strand-specific DNA 3' end sequencing data. HighlightsO_LIRepliCNN enables integrated analysis of replication timing, fork directionality and replication features from strand-specific 3' DNA end sequencing data. C_LIO_LIHigh-resolution replication dynamics can be inferred from a single experiment, bypassing complex multi-fraction labelling approaches. C_LIO_LIThe framework generalizes across experimental protocols, datasets, and species. C_LIO_LIThis enables cost-effective comparative analysis of replication programs across biological conditions. C_LI

bioinformatics↗

bioRxiv2025

Chromatin organization controls nuclear stiffness

Cellular differentiation is driven by epigenetic modifiers and readers, including the methyl CpG binding protein 2 (MeCP2), whose level and mutations cause the neurological disorder Rett syndrome. During differentiation, most of the genome gets densely packed into heterochromatin, whose function has been simplistically viewed as gene silencing. However, gene expression changes reported in mutations leading to Rett syndrome have failed to be a predictor of disease severity. Here, we show that MeCP2 increases nuclear stiffness in a concentration dependent manner and dependent on its ability to cluster heterochromatin during differentiation. MeCP2-dependent stiffness increase could not be explained by changes in the expression of mechanobiology-related genes, but we found it is disrupted by Rett syndrome mutations and correlated with disease severity. Our results highlight the impact of chromatin organization in the mechanical properties of the cell as an alternative or complementary mechanism to changes in cytoskeleton components. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/643219v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cb077dorg.highwire.dtl.DTLVardef@158c0c6org.highwire.dtl.DTLVardef@1d830e3org.highwire.dtl.DTLVardef@719456_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Super-resolution compatible DNA labeling technique reveals chromatin mobility and organization changes during differentiation

Chromatin dynamics play a crucial role in cellular differentiation, yet tools for studying global chromatin mobility in living cells remain limited. Here, we developed a novel probe for the metabolic labeling of chromatin and tracking its mobility during neural differentiation. The labeling system utilizes a newly developed silicon rhodamine-conjugated deoxycytidine triphosphate (dCSiRTP). We show that this dCTP is efficiently delivered into living human induced pluripotent stem cells (iPSCs) and neural stem cells (NSCs) via a synthetic transporter (SNTT1). Using correlative confocal microscopy and stimulated emission depletion (STED) super-resolution microscopy, we quantified the sizes of labeled chromatin domains. Time lapse super-resolution microscopy combined with single particle tracking revealed that chromatin mobility decreases during the transition from iPSCs (pluripotent state) to NSCs and neurons (differentiated state). This reduction in mobility correlates with the differentiation state, suggesting a role for chromatin dynamics in cellular plasticity. Concomitant mechanistic insights obtained from MNase digestion assays, chromatin compaction and histone modification analyses revealed a decrease in chromatin accessibility during neuronal differentiation, indicating that chromatin adopts a more constrained and compacted structure. These findings provide new insights into chromatin regulation during neurogenesis.

cell biology↗

bioRxiv2023

Replisome loading reduces chromatin motion independent of DNA synthesis

Chromatin has been shown to undergo diffusional motion, which is affected during gene transcription by RNA polymerase activity. However, the relationship between chromatin mobility and other genomic processes remains unclear. Hence, we set out to label the DNA directly in a sequence unbiased manner and followed labeled chromatin dynamics in interphase human cells expressing GFP-tagged PCNA, a cell cycle marker and core component of the DNA replication machinery. We detected decreased chromatin mobility during the S-phase compared to G1 and G2 phases in tumor as well as normal diploid cells using automated particle tracking. To gain insight into the dynamical organization of the genome during DNA replication, we determined labeled chromatin domain sizes and analyzed their motion in replicating cells. By correlating chromatin mobility proximal to the active sites of DNA synthesis, we showed that chromatin motion was locally constrained at the sites of DNA replication. Furthermore, inhibiting DNA synthesis led to increased loading of DNA polymerases. This was accompanied by accumulation of the single-stranded DNA binding protein on the chromatin and activation of DNA helicases further restricting local chromatin motion. We, therefore, propose that it is the loading of replisomes but not their catalytic activity that reduces the dynamics of replicating chromatin segments in the S-phase as well as their accessibility and probability of interactions with other genomic regions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/531331v2_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@ed9743org.highwire.dtl.DTLVardef@65c9d4org.highwire.dtl.DTLVardef@a583a7org.highwire.dtl.DTLVardef@6681b1_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- Direct and sequence unbiased labeling of DNA genome-wide - DNA labeled chromatin is more mobile in G1/G2 relative to the S-phase - Restriction of chromatin motion occurs proximal to sites of DNA replication - Loading of replisomes, even in the absence of processive DNA synthesis, restricts chromatin motion

cell biology↗