Biology subjects

Gross, K.

Publications and source records attributed to Gross, K..

6 recordsLinked to original sources

bioRxiv2022

Organ-Founder Stem Cells Mediate Post-Embryonic Neuromast Formation In Medaka

Mammals display a species-specific number, size and location of organs exclusively built during embryogenesis. In fish and amphibians, however, organs must adapt to life-long growth either by expanding in size and/or increasing in number. Here we use neuromasts, small sensory organs that increase in number as fish grow in size, to explore organogenesis during post-embryonic stages. Using iterative imaging, we reveal that post-embryonic organogenesis in the medaka caudal-neuromast-cluster (CNC) is mediated by organ-founder stem cells that delaminate from a functional neuromast. Organ-founder stem cells undergo epithelial-to-mesenchymal (EMT) transition as shown by molecular markers and cellular rearrangements. Chemokine signaling controls the dynamics of organ-founder stem cell delamination, which occurs at a stereotypic position that endures experimental and genetic perturbations. 2-photon laser ablation experiments reveal that organ-founder stem cells are rapidly reconstituted and suggest that these do not constitute a pre-defined population but are rather specified in situ. Our findings contribute to better understanding physiological stem-cell mediated organogenesis, a growth strategy present in life-long growing vertebrates. We speculate that a similar strategy could operate in vertebrates with determined-size as a template for pathological conditions like metastasis, where cells detach from their original organ and expand remotely.

developmental biology↗

bioRxiv2021

Resonance in physiologically structured population models

Ecologists have long sought to understand how the dynamics of natural populations are affected by the environmental variation those populations experience. A transfer function is a useful tool for this purpose, as it uses linearization theory to show how the frequency spectrum of the fluctuations in a populations abundance relates to the frequency spectrum of environmental variation. Here, we show how to derive and to compute the transfer function for a continuous-time model of a population that is structured by a continuous individual-level state variable such as size. To illustrate, we derive, compute, and analyze the transfer function for a size-structured population model of stony corals with open recruitment, parameterized for a common Indo-Pacific coral species complex. This analysis identifies a sharp multi-decade resonance driven by space competition between existing coral colonies and incoming recruits. The resonant frequency is most strongly determined by the rate at which colonies grow, and the potential for resonant oscillations is greatest when colony growth is only weakly density-dependent. While these resonant oscillations are unlikely to be a predominant dynamical feature of degraded reefs, they suggest dynamical possibilities for marine invertebrates in more pristine waters. The size-structured model that we analyze is a leading example of a broader class of physiologically structured population models, and the methods we present should apply to a wide variety of models in this class.

ecology↗

bioRxiv2020

Tissue interactions govern pattern formation in the posterior lateral line of medaka

Vertebrate organs are arranged in a stereotypic, species-specific position along the animal body plan. Substantial morphological variation exists between related species, especially so in the vastly diversified teleost clade. It is still unclear how tissues, organs and systems can accommodate such diverse scaffolds. Here, we use the sequential formation of neuromasts in the posterior lateral line (pLL) system of medaka fish to address tissue-interactions defining a pattern. We show that the pLL pattern is established independently of its neuronal wiring, and demonstrate that the neuromast precursors that constitute the pLL behave as autonomous units during pattern construction. We uncover the necessity of epithelial integrity for correct pLL patterning by disrupting keratin 15 (krt15) and creating epithelial lesions that lead to novel neuromast positioning. By using krt15/wt chimeras, we determined that the new pLL pattern depends exclusively on the mutant epithelium, which instructs wt neuromast to locate ectopically. Inducing epithelial lesions by 2-photon laser ablation during pLL morphogenesis phenocopies krt15 genetic mutants and reveals that epithelial integrity defines the final position of the embryonic pLL neuromasts. Our results show that a fine-balance between primordium intrinsic properties and instructive interactions with the surrounding tissues is necessary to achieve proper organ morphogenesis and patterning. We speculate that this logic likely facilitates the accommodation of sensory modules to changing and diverse body plans.

developmental biology↗

bioRxiv2020

Stony coral populations are more sensitive tochanges in vital rates in disturbed environments

Reef-building corals, like many long-lived organisms, experience environmental change as a combination of separate but concurrent processes, some of which are gradual yet long-lasting, while others are more acute but short-lived. For corals, some chronic environmental stressors, such as rising temperature and ocean acidification, are thought to induce gradual changes in colonies vital rates. Meanwhile, other environmental changes, such as the intensification of tropical cyclones, change the disturbance regime that corals experience. Here, we use a physiologically structured population model to explore how chronic environmental stressors that impact the vital rates of individual coral colonies interact with the intensity and magnitude of disturbance to affect coral population dynamics and cover. We find that when disturbances are relatively benign, intraspecific density dependence driven by space competition partially buffers coral populations against gradual changes in vital rates. However, the impact of chronic stressors is amplified in more highly disturbed environments, because disturbance weakens the buffering effect of space competition. We also show that coral cover is more sensitive to changes in colony growth and mortality than to external recruitment, at least in non-self-seeding populations, and that space competition and size structure mediate the extent and pace of coral-population recovery following a large-scale mortality event. Understanding the complex interplay among chronic environmental stressors, mass-mortality events, and population size structure sharpens our ability to project coral dynamics in an increasingly disturbed future.

ecology↗

bioRxiv2019

The desmosomal cadherin Desmogon is necessary for the structural integrity of the Medaka notochord

The notochord is an embryonic tissue that acts as a precursor to the spine. It is composed of outer sheath cells and inner vacuolated cells. Together they ensure the ability of the notochord to act as a hydrostatic skeleton until ossification begins. To date, there is still a paucity in our understanding of how the notochord cell types are specified and the molecular players controlling both their formation and maintenance remain poorly understood. Here we report that desmogon, a desmosomal cadherin, is essential for proper vacuolated cell shape and therefore correct notochord morphology. We trace desmogon+ precursors and uncover an early developmental heterogeneity that dictates the balance of vacuolated and sheath cell formation. We demonstrate that the growth of vacuolated cells occurs asynchronously and reveal the presence of distinct injury sensing mechanisms in the notochord. Additionally, using a small-scale F0 CRISPR screen we implicate uncharacterized genes in notochordal integrity.

developmental biology↗

bioRxiv2019

A new comprehensive Eye-Tracking Test Battery concurrently evaluating the Pupil Labs Glasses and the EyeLink 1000

Eye-tracking experiments rely heavily on good data quality of eye-trackers. Unfortunately, it is often that only the spatial accuracy and precision values are available from the manufacturers. These two values alone are not sufficient enough to serve as a benchmark for an eye-tracker: Eye-tracking quality deteriorates during an experimental session due to head movements, changing illumination or calibration decay. Additionally, different experimental paradigms require the analysis of different types of eye movements, for instance smooth pursuit movements, blinks or microsaccades, which themselves cannot readily be evaluated by using spatial accuracy or precision alone. To obtain a more comprehensive description of properties, we developed an extensive eye-tracking test battery. In 10 different tasks, we evaluated eye-tracking related measures such as: the decay of accuracy, fixation durations, pupil dilation, smooth pursuit movement, microsaccade detection, blink detection, or the influence of head motion. For some measures, true theoretical values exist. For others, a relative comparison to a gold standard eye-tracker is needed. Therefore, we collected our gaze data simultaneously from a gold standard remote EyeLink 1000 eye-tracker and compared it with the mobile Pupil Labs glasses. As expected, the average spatial accuracy of 0.57{degrees} for the EyeLink 1000 eye-tracker was better than the 0.82{degrees} for the Pupil Labs glasses (N=15). Furthermore, we detected less fixations and shorter saccade durations for the Pupil Labs glasses. Similarly, we found fewer microsaccades using the Pupil Labs glasses. The accuracy over time decayed only slightly for the EyeLink 1000, but strongly for the Pupil Labs glasses. Finally we observed that the measured pupil diameters differed between eye-trackers on the individual subject level but not the group level. To conclude, our eye-tracking test battery offers 10 tasks that allow us to benchmark the many parameters of interest in stereotypical eye-tracking situations, or addresses a common source of confounds in measurement errors (e.g. yaw and roll head movements). All recorded eye-tracking data (including Pupil Labs eye video files), the stimulus code for the test battery and the modular analysis pipeline are available (https://github.com/behinger/etcomp). BVE, KG, II and PK conceived the experiment. II and BVE created the experiment and recorded the gaze data. BVE and KG performed the analysis. BVE, KG and PK reviewed the manuscript critically.

neuroscience↗