Biology subjects

Piacentino, M. L.

Publications and source records attributed to Piacentino, M. L..

7 recordsLinked to original sources

bioRxiv2026

Evolution of new cerebellar nuclei by excitatory progenitor diversification in the early rhombic lip

The cerebellar nuclei, the output regions of the cerebellum, have evolved via repeated duplication of a conserved cell type set to produce different numbers of nuclei across species. Here, we investigate the mechanism underlying this process using developmental single-cell and spatial transcriptomics time courses in mouse and chicken. We show that new nuclei formation is governed by excitatory neurons born from nucleus-specific progenitors in the early and late rhombic lip (RL), with inhibitory neurons incorporating into established nuclear territories. Evolutionarily newer canonical cerebellar nuclei with increasingly higher-order functions are produced by diversification of the early RL, where nuclear identity and spatial organization are established in part by co-option of border formation programs in conserved progenitor cell types. In contrast, the late RL generates the higher-order subnuclei of the medial nucleus and forms a non-canonical olivocerebellar circuit. Together, our findings suggest that new brain regions can evolve through developmental diversification of excitatory progenitors and spatial segregation of conserved sister cell types with generic inhibitory neurons filling in after.

neuroscience↗

bioRxiv2026

Lipid-mediated reinforcement of FGF/MAPK signaling enables robust otic placode specification

The formation of cranial placodes requires groups of ectodermal cells to interpret inductive signals in a robust and organized manner, yet how signaling responses are coordinated across a developing field remains incompletely understood. During otic placode specification, fibroblast growth factor (FGF) signaling must overcome intrinsic noise and rising inhibitory feedback to drive collective transcriptional responses, suggesting the existence of reinforcing regulatory events beyond ligand-receptor interactions and gene regulatory networks alone. Here we identify the secreted lipid-binding protein Apolipoprotein D (APOD) as an essential mediator of otic placode specification that links lipid-dependent regulation to FGF/MAPK signaling during early development. We find that APOD is strongly expressed in the forming otic placode, where it is necessary for otic specification and morphogenesis. Loss of APOD attenuates ERK1/2 activation, indicating impaired cellular responsiveness to FGF/MAPK signaling. Notably, FGF signaling induces APOD expression, establishing a positive feedback loop that reinforces signaling at the tissue level. These findings reveal lipid-mediated regulation of cell signaling as a critical mechanism enabling robust interpretation of developmental signals during sensory placode formation. More broadly, our work highlights lipid management as a key organizational principle by which embryonic tissues achieve coordinated responses to morphogenetic cues. HighlightsO_LIThe lipocalin Apolipoprotein D (APOD) is expressed transiently during early otic development C_LIO_LIAPOD is required for specification and morphogenesis of the otic placode C_LIO_LIAPOD functions upstream MAPK activation during otic specification C_LIO_LIFGF induces APOD expression to build a positive feedback loop C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=183 HEIGHT=200 SRC="FIGDIR/small/698011v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@12001ceorg.highwire.dtl.DTLVardef@56b35aorg.highwire.dtl.DTLVardef@1902eaorg.highwire.dtl.DTLVardef@e8817_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2023

Sphingolipid metabolism is spatially regulated in the developing embryo by SOXE genes

During epithelial-to-mesenchymal transition (EMT), significant rearrangements occur in plasma membrane protein and lipid content that are important for membrane function and acquisition of cell motility. To gain insight into how neural crest cells regulate their lipid content at the transcriptional level during EMT, here we identify critical enhancer sequences that regulate the expression of SMPD3, a gene responsible for sphingomyelin hydrolysis to produce ceramide, which is necessary for neural crest EMT. We uncovered three enhancer regions within the first intron of the SMPD3 locus that drive reporter expression in distinct spatial and temporal domains, together collectively recapitulating the expression domains of endogenous SMPD3 within the ectodermal lineages. We further dissected one enhancer that is specifically active in the migrating neural crest. By mutating putative transcriptional input sites or knocking down upstream regulators, we find that the SoxE-family transcription factors Sox9 and Sox10 regulate the expression of SMPD3 in migrating neural crest cells. Together these results shed light on how core components of developmental gene regulatory networks interact with metabolic effector genes to control changes in membrane lipid content. HighlightsO_LISMPD3 is expressed in the neural tube, neural crest, and notochord during early development C_LIO_LISMPD3 expression is regulated by at least three intronic enhancers C_LIO_LISox10 and its binding sites are required for expression by a migratory neural crest-specific SMPD3 enhancer C_LIO_LISox10 is a positive regulator of endogenous SMPD3 expression during neural crest migration C_LI

developmental biology↗

bioRxiv2023

Extracellular vesicle-localized miR-203 mediates neural crest-placode communication required for trigeminal ganglia formation

While interactions between neural crest and placode cells are critical for the proper formation of the trigeminal ganglion, the mechanisms underlying this process remain largely uncharacterized. Here, we show that the microRNA-(miR)203, whose epigenetic repression is required for neural crest migration, is reactivated in coalescing and condensing trigeminal ganglion cells. Overexpression of miR-203 induces ectopic coalescence of neural crest cells and increases ganglion size. Reciprocally, loss of miR-203 function in placode, but not neural crest, cells perturbs trigeminal ganglion condensation. Demonstrating intercellular communication, overexpression of miR-203 in the neural crest in vitro or in vivo represses a miR-responsive sensor in placode cells. Moreover, neural crest-secreted extracellular vesicles (EVs), visualized using pHluorin-CD63 vector, become incorporated into the cytoplasm of placode cells. Finally, RT-PCR analysis shows that small EVs isolated from condensing trigeminal ganglia are selectively loaded with miR-203. Together, our findings reveal a critical role in vivo for neural crest-placode communication mediated by sEVs and their selective microRNA cargo for proper trigeminal ganglion formation. SIGNIFICANCE STRATEMENTCellular communication during early development plays a critical role. In this study, we demonstrate a unique role for a microRNA in cell-cell communication between the neural crest (NC) and placode cells (PC) during trigeminal ganglia (TG) formation. By utilizing loss and gain of function experiments in vivo, we demonstrate a requirement for miR-203 during cellular condensation to form the TG. We revealed that NC produces extracellular vesicles, selectively carrying miR-203, which is then taken up by the PC and regulates a sensor vector exclusively expressed in the placode. Taken together, our findings reveal a critical role in TG condensation for miR-203, produced by post-migratory NC and taken up by PC via extracellular vesicles.

developmental biology↗

bioRxiv2020

Temporal changes in plasma membrane lipid content induce endocytosis to regulate developmental epithelial-to-mesenchymal transition

Epithelial-to-mesenchymal transition (EMT) is a dramatic change in cellular physiology during development and metastasis which involves coordination between cell signaling, adhesion, and membrane protrusions. These processes all involve dynamic changes in the plasma membrane, yet how membrane lipid content regulates membrane function during developmental EMT remains incompletely understood. By screening for differential expression of lipid-modifying genes over the course of EMT in avian neural crest, we have identified the ceramide-producing enzyme neutral sphingomyelinase 2 (nSMase2) as a critical regulator of a developmental EMT. nSMase2 expression begins at the onset of EMT, and in vivo knockdown experiments demonstrate that nSMase2 is necessary for neural crest migration. Further, we find that nSMase2 promotes Wnt and BMP signaling, and is required to activate the mesenchymal gene expression program. Mechanistically, we show that nSMase2 is sufficient to induce endocytosis, and that inhibition of endocytosis mimics nSMase2 knockdown. Our results support a model in which nSMase2 is expressed at the onset of neural crest EMT to produce ceramide and induce membrane curvature, thus increasing endocytosis of Wnt and BMP signaling complexes and activating pro-migratory gene expression. These results highlight the critical role of plasma membrane lipid metabolism in regulating transcriptional changes during developmental EMT programs.

developmental biology↗

bioRxiv2020

P-bodies are sites of rapid RNA decay during the neural crest epithelial-mesenchymal transition

The epithelial--mesenchymal transition (EMT) drives cellular movements during development to create specialized tissues and structures in metazoans, using mechanisms often coopted during metastasis. Neural crest cells are a multipotent stem cell population that undergo a developmentally regulated EMT and are prone to metastasis in the adult, providing an excellent model to study cell state changes and mechanisms underlying EMT. A hallmark of neural crest EMT during avian development is temporally restricted expression followed by rapid down-regulation of the Wnt antagonist Draxin. Using live RNA imaging, here we demonstrate that rapid clearance of Draxin transcripts is mediated post-transcriptionally via localization to processing bodies (P-bodies), small cytoplasmic granules which are established sites of RNA processing. Contrasting with recent work in immortalized cell lines suggesting that P-bodies are sites of storage rather than degradation, we show that targeted decay of Draxin occurs within P-bodies during neural crest migration. Furthermore, P-body disruption via DDX6 knockdown inhibits not only endogenous Draxin down-regulation but also neural crest EMT in vivo. Together, our data highlight a novel and important role for P-bodies in an intact organismal context--controlling a developmental EMT program via post-transcriptional target degradation.

cell biology↗

bioRxiv2019

The Developmental Transcriptome for Lytechinus variegatus Exhibits Temporally Punctuated Gene Expression Changes

Embryonic development is arguably the most complex process an organism undergoes during its lifetime, and understanding this complexity is best approached with a systems-level perspective. The sea urchin has become a highly valuable model organism for understanding developmental specification, morphogenesis, and evolution. As a non-chordate deuterostome, the sea urchin occupies an important evolutionary niche between protostomes and vertebrates. Lytechinus variegatus (Lv) is an Atlantic species that has been well studied, and which has provided important insights into signal transduction, patterning, and morphogenetic changes during embryonic and larval development. The Pacific species, Strongylocentrotus purpuratus (Sp), is another well-studied sea urchin, particularly for gene regulatory networks (GRNs) and cis-regulatory analyses. A well-annotated genome and transcriptome for Sp are available, but similar resources have not been developed for Lv. Here, we provide an analysis of the Lv transcriptome at 11 timepoints during embryonic and larval development. The data indicate that the gene regulatory networks that underlie specification are well-conserved among sea urchin species. We show that the major transitions in variation of embryonic transcription divide the developmental time series into four distinct, temporally sequential phases. Our work shows that sea urchin development occurs via sequential intervals of relatively stable gene expression states that are punctuated by abrupt transitions.

developmental biology↗