Biology subjects

Lyons, D. C.

Publications and source records attributed to Lyons, D. C..

5 recordsLinked to original sources

bioRxiv2025

A subset of conserved phagocytic genes are likely used for the intracellular theft of cnidarian stinging organelles in nudibranch gastropods

BackgroundPhagocytosis is a universal physiological process in eukaryotes with many important biological functions. In nudibranch gastropods, a novel form of phagocytosis called nematocyst sequestration is specialized for the uptake of venomous stinging organelles stolen from their cnidarian prey. This process is highly selective. Here we use the emerging model nudibranch species Berghia stephanieae and Hermissenda opalescens to identify genes enriched within the body regions where nematocyst sequestration occurs, and investigate how the expression profile of phagocytosis, immune, and digestive genes differs between nematocyst sequestering regions relative to those where other phagocytic functions occur. ResultsWe identified 166 genes with significantly higher expression in sequestering regions in B. stephanieae, including genes associated with development, membrane transport, and metabolism. Of these, 41 overlap with transcripts upregulated in H. opalescens sequestering tissues. Using Hybridization Chain Reaction in situs, we show that at least two of these genes were localized to sequestering cells in B. stephanieae, including a putative C-type lectin receptor and a collagen. Genes annotated with phagocytosis, digestion, or immunity GO terms were often expressed in both sequestering and non-sequestering tissues, suggesting that they may also play a role in sequestration processes. ConclusionOur results suggest that phagocytosis genes likely play a role in the sequestration phenotype, and that a small subset of genes (e.g., collagen) may play unique functions yet to be uncovered. However, we also show that genes categorized in GO terms related to endocytosis, immunity, and digestion show a clear decrease in overall expression in sequestering tissues. This study lays the foundation for further inquiry into mechanisms of organelle sequestration in nudibranchs and other organisms.

evolutionary biology↗

bioRxiv2024

Advances in culturing of the sea star Patiria miniata

The use of the sea star Patiria miniata as a model system has produced groundbreaking advances in a disparate set of biomedical research fields, including embryology, immunology, regeneration, cell biology and evolution of development. Nonetheless, the life cycle of P. miniata has not yet been closed in the laboratory, precluding the generation of stable transgenic and mutant lines, which would greatly expand the toolset for experimentation with this model system. Rearing P. miniata in the laboratory has been challenging due to limited knowledge about metamorphosis cues, feeding habits of juveniles and their relatively long generation time. Here we report protocols to rear P. miniata embryos through sexual maturity in a laboratory setting. We provide detailed staging of early embryonic development at different temperatures, and show that larvae can be raised to competence in as little as 15 days. We find that retinoic acid induces metamorphosis effectively and present methods to rear juveniles on commercially available foods. We show that in a flow-through system, juveniles double in size every 2 months and reach sexual maturity in approximately 2 years. We report the first example of P. miniata raised through sexual maturity in a laboratory setting, paving the way for the generation of stable mutant sea star lines.

developmental biology↗

bioRxiv2023

Spatial-temporal expression analysis of lineage-restricted shell matrix proteins reveals shell field regionalization and distinct cell populations in the slipper snail Crepidula atrasolea

Molluscs are one of the most morphologically diverse clades of metazoans, exhibiting an immense diversification of calcium carbonate structures, such as the shell. Biomineralization of the calcified shell is dependent on shell matrix proteins (SMPs). While SMP diversity is hypothesized to drive molluscan shell diversity, we are just starting to unravel SMP evolutionary history and biology. Here we leveraged two complementary model mollusc systems, Crepidula fornicata and Crepidula atrasolea, to determine the lineage-specificity of 185 Crepidula SMPs. We found that 95% of the adult C. fornicata shell proteome belongs to conserved metazoan and molluscan orthogroups, with molluscan-restricted orthogroups containing half of all SMPs in the shell proteome. The low number of C. fornicata-restricted SMPs contradicts the generally-held notion that an animals biomineralization toolkit is dominated by mostly novel genes. Next, we selected a subset of lineage-restricted SMPs for spatial-temporal analysis using in situ hybridization chain reaction (HCR) during larval stages in C. atrasolea. We found that 12 out of 18 SMPs analyzed are expressed in the shell field. Notably, these genes are present in 5 expression patterns, which define at least three distinct cell populations within the shell field. These results represent the most comprehensive analysis of gastropod SMP evolutionary age and shell field expression patterns to date. Collectively, these data lay the foundation for future work to interrogate the molecular mechanisms and cell fate decisions underlying molluscan mantle specification and diversification.

evolutionary biology↗

bioRxiv2022

Live imaging of echinoderm embryos to illuminate evo-devo

Echinoderm embryos have been model systems for cell and developmental biology for over 150 years, in good part because of their optical clarity. Discoveries that shaped our understanding of fertilization, cell division and cell differentiation were only possible because of the transparency of sea urchin eggs and embryos, which allowed direct observations of intracellular structures. More recently, live imaging of sea urchin embryos, coupled with fluorescence microscopy, has proven pivotal to uncovering mechanisms of epithelial to mesenchymal transition, cell migration and gastrulation. However, live imaging has mainly been performed on sea urchin embryos, while echinoderms include numerous experimentally tractable species that present interesting variation in key aspects of morphogenesis, including differences in embryo compaction and mechanisms of blastula formation. The study of such variation would allow us not only to understand how tissues are formed in echinoderms, but also to identify which changes in cell shape, cell-matrix and cell-cell contact formation are more likely to result in evolution of new embryonic shapes. Here we argue that adapting live imaging techniques to more echinoderm species will be fundamental to exploit such an evolutionary approach to the study of morphogenesis, as it will allow measuring differences in dynamic cellular behaviors - such as changes in cell shape and cell adhesion - between species. We briefly review existing methods for live imaging of echinoderm embryos and describe in detail how we adapted those methods to allow long-term live imaging of several species, namely the sea urchin Lytechinus pictus and the sea stars Patiria miniata and Patiriella regularis. We outline procedures to successfully label, mount and image early embryos for 10-16 hours, from cleavage stages to early blastula. We show that data obtained with these methods allows 3D segmentation and tracking of individual cells over time, the first step to analyze how cell shape and cell contact differ among species. The methods presented here can be easily adopted by most cell and developmental biology laboratories and adapted to successfully image early embryos of additional species, therefore broadening our understanding of the evolution of morphogenesis.

developmental biology↗

bioRxiv2022

Precocious sperm exchange in the simultaneously hermaphroditic nudibranch, Berghia stephanieae

Sexual systems vary greatly across molluscs. This diversity includes simultaneous hermaphroditism, with both sexes functional at the same time. Most nudibranch molluscs are thought to be simultaneous hermaphrodites, but detailed studies of reproductive development and timing remain rare as most species cannot be cultured in the lab. The aeolid nudibranch, Berghia stephanieae, is one such species that can be cultured through multiple generations on the benchtop. We studied B. stephanieae reproductive timing to establish when animals first exchange sperm and how long sperm can be stored. We isolated age- and size-matched individuals at sequential timepoints to learn how early individuals exchange sperm. Individuals isolated at 13 weeks post laying (wpl) can produce fertilized eggs. This is 6 weeks before animals first lay egg masses, indicating that sperm exchange occurs well before individuals are capable of laying eggs. Our results indicate that male gonads become functional for animals between 6 mm (~9 wpl) and 9 mm (~15 wpl) in length. That is much smaller (and sooner) than the size (and age) of individuals at first laying (12-19 mm; ~19 wpl), indicating that male and female functions do not develop simultaneously. We also tracked the number of fertilized eggs in each egg mass, which remained steady for the first 10-15 egg masses, followed by a decline to near-to-no fertilization. This large, novel dataset provides insights into precise timing of the onset of functionality of the male and female reproductive systems in B. stephanieae. These data contribute to a broader understanding of reproductive development and the potential for understanding evolution of diverse sexual systems in molluscs.

zoology↗