Biology subjects

Florescu, M.

Publications and source records attributed to Florescu, M..

4 recordsLinked to original sources

bioRxiv2021

Hierarchical chromatin regulation during blood formation uncovered by single cell sortChIC

Post-translational histone modifications modulate chromatin packing to regulate gene expression. How chromatin states, at euchromatic and heterochromatic regions, underlie cell fate decisions in single cells is relatively unexplored. We develop sort assisted single-cell chromatin immunocleavage (sortChIC) and map active (H3K4me1 and H3K4me3) and repressive (H3K27me3 and H3K9me3) histone modifications in hematopoietic stem and progenitor cells (HSPCs), and mature blood cells in the mouse bone marrow. During differentiation, HSPCs acquire distinct active chromatin states that depend on the specific cell fate, mediated by cell type-specifying transcription factors. By contrast, most regions that gain or lose repressive marks during differentiation do so independent of cell fate. Joint profiling of H3K4me1 and H3K9me3 demonstrates that cell types within the myeloid lineage have distinct active chromatin but share similar myeloid-specific heterochromatin-repressed states. This suggests hierarchical chromatin regulation during hematopoiesis: heterochromatin dynamics define differentiation trajectories and lineages, while euchromatin dynamics establish cell types within lineages.

genomics↗

bioRxiv2021

Deconvolving multiplexed histone modifications in single cells

Recent advances have enabled mapping of histone modifications in single cells1-12, but current methods are constrained to profile only one histone modification per cell. Here we present an integrated experimental and computational framework, scChIX (single-cell chromatin immunocleavage and unmixing), to map multiple histone modifications in single cells. scChIX multiplexes two histone modification profiles together in single cells, then computationally deconvolves the signal using training data from respective histone modification profiles. We first validate this method using purified blood cells and show that although the two repressive marks, H3K27me3 and H3K9me3, are generally mutually exclusive, the transitions between the two regions can vary between cell types. Next we apply scChIX to a heterogenous cell population from mouse bone marrow to generate linked maps of active (H3K4me1) and repressive (H3K27me3) chromatin landscapes in single cells, where coordinates in the active modification map correspond to coordinates in the repressive map. Linked analysis reveals that immunoglobulin genes in the Igkv region are in a repressed chromatin state in pro-B cells, but become activated in B cells. Overall, scChIX unlocks systematic interrogation of the interplay between histone modifications in single cells.

genomics↗

bioRxiv2020

Biophysical interaction of levothyroxine with bovine serum albumin: a spectroscopic assay

Bovine serum albumin (BSA) acts as a carrier for many endogenous and exogenous compounds, such as thyroid hormones or corresponding drugs. Binding of the hydrophilic compound levothyroxine (LT4) to BSA can significantly alter the pharmacological properties of the compound. Therefore, studying its interaction with BSA could be a difficult issue. In this work, the binding mechanism and affinity of the interaction between LT4 and BSA were investigated, both in solution using UV-Vis, Fourier-transform infrared spectroscopy (FT-IR), fluorescence and fluorescence resonance energy transfer (FRET), as well as by Surface Plasmon Resonance (SPR) with BSA confined to a gold-coated chips, as far as we know for the first time used to study the interactions between LT4 and proteins. Quenching of BSA fluorescence by LT4 combined with UV-Vis spectroscopy shows a ground-state complex formation that may be accompanied by a nonradiative energy transfer process. FT-IR revealed the changes induced by LT4 in the secondary structure of BSA molecules, due to the partial unfolding of BSA native structure upon LT4 binding. Scatchard approach allowed the determination of the binding constant and the thermodynamic parameters, which correspond to an enthalpic process, driven mainly by hydrogen bonds and van der Waals forces. Using SPR, the adsorbed amount of biomolecules was calculated and the binding affinity of LT4 with confined-BSA was characterized using the Hill-Langmuir equation, indicating that the BSA immobilization plays an important role in LT4 binding. As preliminary results, both fluorescence quenching and SPR can be used as a stepping stone for the development of a spectroscopic biosensor for LT4 detection, with a limit of detection as low as 0.23 x 10-6 M.

biophysics↗

bioRxiv2018

Neuromesodermal Progenitors are a Conserved Source of Spinal Cord with Divergent Growth Dynamics

During gastrulation, embryonic cells become specified into distinct germ layers. In mouse, this continues throughout somitogenesis from a population of bipotent stem cells called neuromesodermal progenitors (NMps). However, the degree self-renewal is associated with NMps in the fast-developing zebrafish embryo is unclear. With a genetic clone tracing method, we labelled early embryonic progenitors and find a strong clonal similarity between spinal cord and mesoderm tissues. We then followed individual cell lineages by light-sheet imaging and reveal a common neuromesodermal lineage contribution to a subset of spinal cord tissue across the anterior-posterior body axis. An initial population subdivides at mid gastrula stages and is directly allocated to neural and mesodermal compartments during gastrulation. A second population in the tailbud undergoes delayed allocation to contribute to the neural and mesodermal compartment only at late somitogenesis. We suggest that NMps undergo vastly different rates of differentiation and growth in a species-specific manner.

developmental biology↗