Biology subjects

Boileau, R. M.

Publications and source records attributed to Boileau, R. M..

6 recordsLinked to original sources

bioRxiv2026

KMT2C and KMT2D amplify GRHL2-driven enhancer activation

The activation of cis-regulatory enhancers is essential for cell fate specification by driving cell type-specific gene expression. Differentiation models are widely used to study enhancer biology but the asynchronous and interdependent nature of gene regulatory changes during cell state transitions can complicate mechanistic studies. To overcome these limitations, here we develop a tamoxifen-gated system for acute enhancer activation in embryonic stem cells (ESCs) based on GRHL2, a pioneer transcription factor which naturally becomes expressed as naive ESCs differentiate into the formative ESC state. Using this system, we investigate the functional relationship between GRHL2 and the histone mono-methyltransferases KMT2C and KMT2D (KMT2C/D). GRHL2 readily binds its target sites independent of KMT2C/D. However, in the absence of KMT2C/D, there are dramatic reductions in H3K4me1/2, P300 recruitment, and H3K27ac deposition at these sites as well as diminished transcriptional activation. Still, strikingly, a basal level of active enhancer mark acquisition and transcriptional activation occurs. Consistent with these findings, during the naive to formative ESC differentiation, GRHL2 enhancer remodeling and target expression is also strongly but incompletely dependent on KMT2C/D. Together, these results define a functional co-activator relationship in which KMT2C/D act as important amplifiers of GRHL2-driven enhancer activation in ESCs and establish a rapid inducible system for dissecting the kinetics and enzymatic dependencies of pioneer transcription factor mediated enhancer remodeling.

molecular biology↗

bioRxiv2026

An autonomous system for multi-objective continuous evolution at scale

Natural evolution is high-dimensional; organisms adapt to many pressures at once, across substrates, environments, and genetic backgrounds. Yet most directed evolution methods flatten this landscape to a single selection axis, hiding tradeoffs, and limiting what can be learned. Phage-assisted continuous evolution (PACE) is uniquely suited for multivariate selection because horizontal gene transfer couples genotype to propagation and allows the same phage lineage to traverse different selection environments. In practice, implementing this at scale has been prohibitive because each selection demands its own host culture, and every culture must be held for days to weeks within a narrow, infectable density window using continuously responsive bioreactors. In this work, TurboPRANCE is presented as an open-source, queueable robotic platform that integrates [~]200 independently controlled turbidostats with 96 parallel PACE lagoons under closed-loop control. Each turbidostat operates as a fully separate unit that can be equilibrated and initiated on its own schedule, enabling asynchronous starts and sustained operation without intervention. Automated media formulation, programmable dosing, on-deck sterilization, and adaptive scheduling coordinate growth control with the changing needs of the robotic workflow, dynamically adjusting dilution and transfer timing around formulation, sampling, and handling steps to keep each culture at consistent infectable densities despite unpredictable method demands. Cultures can be multiplexed and titrated into lagoons at defined ratios, swapped in and out on a schedule, or kept fully separate across experiments, creating a combinatorial space of selection pressures and programs that is effectively unbounded. Additionally, to enable high-throughput evolutionary tracking that scales with TurboPRANCE, Nanopore long-read sequencing was combined with DeepVariant, a deep learning-based variant caller, enabling population-level tracking of evolving variants. The result is a system that generates high-resolution time-resolvable evolutionary trajectories and large parallel datasets spanning diverse selection regimes, yielding dense, multivariate training data to map and engineer complex fitness landscapes at scale. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/709196v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@b0f8daorg.highwire.dtl.DTLVardef@a1d57eorg.highwire.dtl.DTLVardef@c771aeorg.highwire.dtl.DTLVardef@1f8729a_HPS_FORMAT_FIGEXP M_FIG Turbidostat, Phage, and Robotics-Assisted Near Continuous Evolution (TurboPRANCE) In phage-assisted continuous evolution (PACE), biomolecular activity is coupled to pIII expression, linking function to phage propagation. By altering the host strain, distinct selection pressures can be imposed on the same evolving phage population. In TurboPRANCE, [~]200 selection programs can vary over time, including periodic "drift" (mutagenesis), alternation between pressures, or rotational reassignment of host sources, enabling a combinatorial space of selection pressures. C_FIG

bioengineering↗

bioRxiv2024

Synergy between cis-regulatory elements can render cohesin dispensable for distal enhancer function

Enhancers are critical genetic elements controlling transcription from promoters, but the mechanisms by which they convey regulatory information across large genomic distances remain elusive. Here, we engineered pluripotent stem cells in which cohesin loop extrusion can be inducibly disrupted without causing confounding cell cycle defects. While evident, transcriptional dysregulation was cell-type specific, and not all loci with distal enhancers depend equally on cohesin extrusion. Using comparative genome editing, we demonstrate that enhancer-promoter communication across as little as 20 kilobases can rely on cohesin. However, promoter-proximal regulatory elements can support long-range, cohesin-independent enhancer action - either upon disabling extrusion or across strong CTCF insulators. Finally, transcriptional dynamics and the emergence of new embryonic cell types in response to differentiation cues remained largely robust to disrupting cohesin extrusion. Beyond establishing novel experimental strategies to study cohesin functions in enhancer biology, our work provides mechanistic insight accounting for both cell type- and genomic context-specificity.

molecular biology↗

bioRxiv2024

The miR-290 and miR-302 clusters are essential for reprogramming of fibroblasts to induced pluripotent stem cells

The miR-290 and miR-302 clusters of microRNAs are highly expressed in naive and primed pluripotent stem cells, respectively. Ectopic expression of the embryonic stem cell-specific cell cycle regulating (ESCC) family of microRNAs arising from these two clusters dramatically enhances the reprogramming of both mouse and human somatic cells to induced pluripotency. Here, we used genetic knockouts to dissect the requirement for the miR-290 and miR-302 clusters during the reprogramming of mouse fibroblasts into induced pluripotent stem cells (iPSCs) with retrovirally introduced Oct4, Sox2, and Klf4. Knockout of either cluster alone did not negatively impact the efficiency of reprogramming. Resulting cells appeared identical to their embryonic stem cell microRNA cluster knockout counterparts. In contrast, the combined loss of both clusters blocked the formation of iPSCs. While rare double knockout clones could be isolated, they showed a dramatically reduced proliferation rate, a persistent inability to fully silence the exogenously introduced pluripotency factors, and a transcriptome distinct from individual miR-290 or miR-302 mutant ESC and iPSCs. Taken together, our data show that miR-290 and miR-302 are essential yet interchangeable in reprogramming to the induced pluripotent state. Impact StatementThe process by which somatic cell reprogramming yields induced pluripotent stem cells (iPSCs) is incompletely understood. MicroRNAs from the miR-290 and miR-302 clusters have been shown to greatly increase reprogramming efficiency, but their requirement in the process has not been studied. Here, we examine this requirement by genetically removing the miRNA clusters in somatic cells. We discover that somatic cells lacking either, but not both, of these miRNA clusters can form iPSC cells. This work thus provides new important insight into mechanisms underlying reprogramming to pluripotency.

developmental biology↗

bioRxiv2023

MLL3/MLL4 enzymatic activity shapes DNA replication timing

Mammalian genomes are replicated in a precise order during S phase, which is cell-type-specific1-3 and correlates with local transcriptional activity2,4-8, chromatin modifications9 and chromatin architecture1,10,11,12. However, the causal relationships between these features and the key regulators of DNA replication timing (RT) are largely unknown. Here, machine learning was applied to quantify chromatin features, including epigenetic marks, histone variants and chromatin architectural factors, best predicting local RT under steady-state and RT changes during early embryonic stem (ES) cell differentiation. About one-third of genome exhibited RT changes during the differentiation. Combined, chromatin features predicted steady-state RT and RT changes with high accuracy. Of these features, histone H3 lysine 4 monomethylation (H3K4me1) catalyzed by MLL3/4 (also known as KMT2C/D) emerged as a top predictor. Loss of Mll3/4 (but not Mll3 alone) or their enzymatic activity resulted in erasure of genome-wide RT dynamics during ES cell differentiation. Sites that normally gain H3K4me1 in a MLL3/4-dependent fashion during the transition failed to transition towards earlier RT, often with transcriptional activation unaffected. Further analysis revealed a requirement for MLL3/4 in promoting DNA replication initiation zones through MCM2 recruitment, providing a direct link for its role in regulating RT. Our results uncover MLL3/4-dependent H3K4me1 as a functional regulator of RT and highlight a causal relationship between the epigenome and RT that is largely uncoupled from transcription. These findings uncover a previously unknown role for MLL3/4-dependent chromatin functions which is likely relevant to the numerous diseases associated with MLL3/4 mutations.

genomics↗

bioRxiv2022

Loss of MLL3/4 decouples enhancer H3K4 monomethylation, H3K27 acetylation, and gene activation during ESC differentiation

Enhancers are essential in defining cell fates through the control of cell type specific gene expression. Enhancer activation is a multi-step process involving chromatin remodelers and histone modifiers including the monomethylation of H3K4 (H3K4me1) by MLL3 (KMT2C) and MLL4 (KMT2D). MLL3/4 are thought to be critical for enhancer activation and cognate gene expression including through the recruitment of acetyltransferases for H3K27. Here we test this model by evaluating the impact of MLL3/4 loss on chromatin and transcription during early embryonic stem cell differentiation. We find that MLL3/4 activity is required at most if not all sites that gain or lose H3K4me1 but is largely dispensable at sites that remain stably methylated during this transition. This requirement extends to H3K27 acetylation (H3K27ac) at most transitional sites. However, many sites gain H3K27ac independent of MLL3/4 or H3K4me1 including enhancers regulating key factors in early differentiation. Furthermore, despite the failure to gain active histone marks at thousands of enhancers, transcriptional activation of nearby genes is largely unaffected, thus uncoupling the regulation of these chromatin events from transcriptional changes during this transition. These data challenge current models of enhancer activation and imply distinct mechanisms between stable and dynamically changing enhancers. Collectively, our study highlights gaps in knowledge about the steps and epistatic relationships of enzymes necessary for enhancer activation and cognate gene transcription.

genomics↗