Biology subjects

Zuch, D. T.

Publications and source records attributed to Zuch, D. T..

5 recordsLinked to original sources

bioRxiv2022

Polychrome labeling reveals skeletal triradiate and elongation dynamics and abnormalities in patterning cue-perturbed embryos

The larval skeleton of the sea urchin Lytechinus variegatus is an ideal model system for studying skeletal patterning; however, our understanding of the etiology of skeletal patterning in sea urchin larvae is limited due to the lack of approaches to live-image skeleton formation. Calcium-binding fluorochromes have been used to study the temporal dynamics of bone growth and healing. To date, only calcein green has been used in sea urchin larvae to fluorescently label the larval skeleton. Here, we optimize labeling protocols for four other calcium-binding fluorochromes-alizarin red, xylenol orange, tetracycline, and calcein blue- and demonstrate that these fluorochromes can be used individually or in nested pulse-chase experiments to understand the temporal dynamics of skeletogenesis and patterning. Using this pulse-chase approach we reveal that the initiation of skeletogenesis begins around 15 hours post fertilization, which is earlier than previously thought. We also explore the timing of triradiate formation in embryos treated with a range of patterning perturbagens, and demonstrate that triradiates form late and asynchronously in embryos ventralized via treatment with either nickel at early gastrula stage or with chlorate from fertilization. Finally, we measure the extent of fluorochrome incorporation in triple-labeled embryos to determine the elongation rate of numerous skeletal elements throughout early skeletal patterning and compare this to the rate of skeletal growth in axitinib-treated embryos. We find that skeletal elements elongate much more slowly in axitinib-treated embryos, and that axitinib treatment is sufficient to induce abnormal orientation of the triradiates. HighlightsO_LICalcium-binding fluorochromes selectively label the sea urchin larval skeleton C_LIO_LIPulsed, nested polychrome labeling offers temporal insight into skeletal patterning C_LIO_LITriradiate formation is delayed and asynchronous in ventralized embryos C_LIO_LIVEGFR inhibition slows skeletal elongation and perturbs triradiate orientation C_LI

developmental biology↗

bioRxiv2022

Cell cycle dynamics and window of MUTE action during the terminal division of stomata and ramification of its loss-of-function on the cell cycle of an uncommitted precursor

Plants develop in the absence of cell migration. As such, cell division and differentiation need to be coordinated for functional tissue formation. Cellular valves on the plant epidermis, stomata, are generated through a stereotypical sequence of cell division and differentiation events. In Arabidopsis, three master-regulatory transcription factors, SPEECHLESS (SPCH), MUTE, and FAMA sequentially drive initiation, proliferation, and differentiation of stomata. Among them, MUTE switches the cell cycle mode from proliferative asymmetric division to terminal symmetric division and orchestrates the execution of the single symmetric division event. However, it remains unclear to what extent MUTE regulates the expression of cell cycle genes through the symmetric division and whether MUTE accumulation itself is gated by the cell cycle. Here, we show that MUTE directly upregulates the expression of cell cycle components throughout the terminal cell cycle phases of a stomatal precursor, not only the core cell cycle engines but also checkpoint regulators. Time-lapse live imaging using the multi-color cell cycle indicator PlaCCI revealed that MUTE accumulates up to the early G2 phase, whereas its successor and direct target, FAMA, accumulates at late G2 through terminal mitosis. In the absence of MUTE, meristemoids fail to differentiate, and their G1 phase elongates as they reiterate asymmetric divisions. Combined, our work provides the framework of cell cycle and master regulatory transcription factors to coordinate a single symmetric cell division, and suggests a mechanism for the eventual cell cycle arrest of an uncommitted stem-cell-like precursor at the G1 phase.

plant biology↗

bioRxiv2022

ICAT: A Novel Algorithm to Robustly Identify Cell States Following Perturbations in Single Cell Transcriptomes

MotivationThe detection of distinct cellular identities is central to the analysis of single-cell RNA sequencing experiments. However, in perturbation experiments, current methods typically fail to correctly match cell states between conditions or erroneously remove population substructure. Here we present the novel, unsupervised algorithm ICAT that employs self-supervised feature weighting and control-guided clustering to accurately resolve cell states across heterogeneous conditions. ResultsUsing simulated and real datasets, we show ICAT is superior in identifying and resolving cell states compared to current integration workflows. While requiring no a priori knowledge of extant cell states or discriminatory marker genes, ICAT is robust to low signal strength, high perturbation severity, and disparate cell type proportions. We empirically validate ICAT in a developmental model and find that only ICAT identifies a perturbation-unique cellular response. Taken together, our results demonstrate that ICAT offers a significant improvement in defining cellular responses to perturbation in single-cell RNA sequencing data. Availability and implementationhttps://github.com/BradhamLab/icat Supplemental Methods, Tables and Figures are available online.

bioinformatics↗

bioRxiv2021

V-type H+ ATPase Activity is Required for Embryonic Dorsal-Ventral Symmetry Breaking

The mechanism for embryonic dorsal-ventral (DV) symmetry breaking is idiosyncratic to the species, then converges on polarized expression of BMP signaling ligands. Here, we show that V-ATPase (VHA) activity is an early requirement for DV symmetry breaking in sea urchin embryos. In these basal deuterostomes, DV specification is mediated by ventral Nodal expression that leads to the establishment of a BMP signaling gradient. Nodal expression occurs downstream from p38 MAPK, which is transiently asymmetrically active. We show that VHA activity is required for DV symmetry breaking upstream from both p38 MAPK and Nodal. We rescue VHA-mediated ventralization by enforcing Nodal signaling asymmetry. We identify a VHA-dependent DV voltage gradient and also find that VHA activity is required for hypoxia inducible factor (HIF) activation. However, neither hyperpolarization nor HIF activation account for the dorsalizing effects of VHA, implicating a third unknown pathway that connects VHA activity to p38 MAPK symmetry breaking. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/464707v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@d905dforg.highwire.dtl.DTLVardef@108452org.highwire.dtl.DTLVardef@5f27a0org.highwire.dtl.DTLVardef@122b510_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental 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↗