Biology subjects

Pimpale, L.

Publications and source records attributed to Pimpale, L..

5 recordsLinked to original sources

bioRxiv2026

Dissecting human fetal cardiac repair using cardioids

Human cardiac injury responses are governed by dynamic interacting processes that are difficult to resolve. Unlike adults, fetal mammalian hearts regenerate through coordinated remodeling and proliferation supported by a pro-regenerative immune environment, extracellular matrix (ECM), and immature cardiomyocytes, including trabecular subtypes. Here, we establish a modular human cardioid injury platform to dissect these interactions. We show that anti-inflammatory macrophages selectively migrate to the injury, clear debris, and promote ECM remodeling, whereas inflammatory macrophages suppress cardiomyocyte proliferation. Synergistic FGF2-NRG1 signaling induces trabecular identity and morphology in a hyaluronan-dependent manner, conferring enhanced injury repair, characterized by cytoskeletal remodeling and cardiomyocyte proliferation mediated by YAP and WNT signaling. Exogenous YAP, but not WNT, is sufficient to promote repair in non-trabecular cardioids. These findings uncover coordinated immune-ECM-cardiomyocyte interactions governing human fetal regenerative competence and mechanistically resolve remodeling and proliferative components of cardiac repair. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC="FIGDIR/small/735236v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@1e647a2org.highwire.dtl.DTLVardef@16911f8org.highwire.dtl.DTLVardef@11ad14eorg.highwire.dtl.DTLVardef@1a35d94_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2022

Multi-chamber cardioids unravel human heart development and cardiac defects

The number one cause of human fetal death are defects in heart development. Because the human embryonic heart is inaccessible, and the impacts of mutations, drugs, and environmental factors on the specialized functions of different heart compartments are not captured by in vitro models, determining the underlying causes is difficult. Here, we established a human cardioid platform that recapitulates the development of all major embryonic heart compartments, including right and left ventricles, atria, outflow tract, and atrioventricular canal. By leveraging both 2D and 3D differentiation, we efficiently generated progenitor subsets with distinct first, anterior, and posterior second heart field identities. This advance enabled the reproducible generation of cardioids with compartment-specific in vivo-like gene expression profiles, morphologies, and functions. We used this platform to unravel the ontogeny of signal and contraction propagation between interacting heart chambers and dissect how genetic and environmental factors cause region-specific defects in the developing human heart. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/499699v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@c9c629org.highwire.dtl.DTLVardef@f0d521org.highwire.dtl.DTLVardef@1389411org.highwire.dtl.DTLVardef@181098a_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTS- Mesoderm induction and patterning signals specify aSHF, pSHF, and FHF progenitors - Cardiac progenitors sort, co-develop and functionally connect in multi-chamber cardioids - Multi-chamber cardioids coordinate contraction propagation and share a lumen - Multi-chamber platform dissects genetic (ISL1, TBX5, FOXF1) and teratogenic defects

developmental biology↗

bioRxiv2019

Cell lineage-dependent chiral actomyosin flows drive cellular rearrangements in early development

Proper positioning of cells is important for many aspects of embryonic development, tissue homeostasis, and regeneration. A simple mechanism by which cell positions can be specified is via orienting the cell division axis. This axis is specified at the onset of cytokinesis, but can be reoriented as cytokinesis proceeds. Rotatory actomyosin flows have been implied in specifying and reorienting the cell division axis in certain cases, but how general such reorientation events are, and how they are controlled, remains unclear. In this study, we set out to address these questions by investigating early Caenorhabditis elegans development. In particular, we determined which of the early embryonic cell divisions exhibit chiral counter-rotating actomyosin flows, and which do not. We follow the first nine divisions of the early embryo, and discover that chiral counter-rotating flows arise systematically in the early AB lineage, but not in early P/EMS lineage cell divisions. Combining our experiments with thin film active chiral fluid theory we identify specific properties of the actomyosin cortex in the symmetric AB lineage divisions that favor chiral counter-rotating actomyosin flows of the two halves of the dividing cell. Finally, we show that these counter-rotations are the driving force of both the AB lineage spindle skew and cell reorientation events. In conclusion, we here have shed light on the physical basis of lineage-specific actomyosin-based processes that drive chiral morphogenesis during development.

cell biology↗

bioRxiv2019

Regionalized tissue fluidization by an actomyosin cable is required for epithelial gap closure during insect gastrulation

Many animal embryos pull and close an epithelial sheet around the spherical or ellipsoidal egg surface during a gastrulation process known as epiboly. The ovoidal geometry dictates that the epithelial sheet first expands and subsequently compacts. Moreover, the epithelial sheet spreading over the sphere is mechanically stressed and this stress needs to be released. Here we show that during extraembryonic tissue (serosa) epiboly in the red flour beetle Tribolium castaneum, the non-proliferative serosa becomes regionalized into two distinct territories: a dorsal region under higher tension away from the leading edge with larger non-rearranging cells, and a more fluid ventral region under lower tension surrounding the leading edge with smaller cells undergoing cell intercalation. Our results suggest that fluidization of the leading edge is caused by a heterogeneous actomyosin cable that drives sequential eviction and intercalation of individual cells away from the serosa margin. Since this developmental solution utilized during epiboly resembles the mechanism of wound healing in other systems, we propose actomyosin cable-driven local tissue fluidization as a conserved morphogenetic module for closure of epithelial gaps.

developmental biology↗

bioRxiv2018

SOD1 activity thresholds and TOR signalling modulate VAP(P58S) aggregation via ROS-induced proteasomal degradation in a Drosophila model of Amyotrophic Lateral Sclerosis

Familial Amyotrophic Lateral Sclerosis (F-ALS) is an incurable, late onset motor neuron disease, linked strongly to various causative genetic loci. ALS8 codes for a missense mutation, P56S, in VAMP-associated Protein B (VAPB) that causes the protein to misfold and form cellular aggregates. Uncovering genes and mechanisms that affect aggregation dynamics would greatly help increase our understanding of the disease and lead to potential therapeutics.\n\nHere, we develop a quantitative high-throughput, Drosophila S2R+ cell-based kinetic assay coupled with fluorescent microscopy to score for genes involved in the modulation of aggregates of fly ortholog, VAP(P58S), tagged with GFP. As proof of principle, we conducted a targeted RNAi screen against 900 genes, consisting of VAP genetic interactors, other ALS loci, as also genes involved in proteostasis. The screen identified 150 hits that modify aggregation, including the ALS loci SOD1, TDP43 and also genes belonging to the TOR pathway.\n\nTo validate these modifiers, we developed a system to measure the extent of VAP(P58S) aggregation in the Drosophila third instar larval brain using the UAS-GAL4 system, followed by quantitative imaging of cellular inclusions. We find that reduction of SOD1 activity or decreased TOR signalling reduces aggregation. Interestingly, we find that increase in cellular reactive oxygen species (ROS) levels, assessed by measuring oxidation of cellular lipids and proteins, in response to SOD1 knockdown or by inhibition of TOR signalling appears to be the trigger for clearing of aggregates. The mechanism of aggregate clearance is, primarily, the proteasomal machinery, and not autophagy. Increase in VAP, but not VAP(P58S) levels, appears to elevate ROS, which may in turn regulate VAP transcription in a feedback loop.\n\nWe have thus uncovered an interesting interplay between SOD1, ROS and TOR signalling that regulates the dynamics of VAP aggregation. Mechanistic processes underlying such cellular regulatory networks will lead us to a better understanding of initiation and progression of ALS.

neuroscience↗