Biology subjects

Bischof, J.

Publications and source records attributed to Bischof, J..

8 recordsLinked to original sources

bioRxiv2026

Clinical grade cryopreservation unlocks transplant ready human pancreatic and stem cell derived islets for diabetes therapy

Pancreatic islet transplantation can restore endogenous insulin production and offers a potential cure for diabetes, but its clinical impact has been limited by the inability to preserve large numbers of functional islets for timely use. Cryopreservation could provide an on-demand supply, yet conventional methods cause ice formation, cell injury, and loss of insulin secretion. We developed CryoMesh, a vitrification platform that combines a low-toxicity cryoprotectant with a thermally conductive, biocompatible mesh to enable ultra-rapid cooling and rewarming for ice-free cryopreservation. This approach supports long-term, clinical-scale preservation of both human pancreatic and stem cell-derived islets while maintaining viability, architecture, mitochondrial integrity, and glucose-responsive insulin secretion. Human islets preserved for up to one year restored normoglycemia in diabetic mice, with complete recovery of function and no increase in immunogenicity or loss of potency. The combination of high viability, recovery, and functional preservation at clinical scale has not been achieved previously. By decoupling islet isolation and manufacture from transplantation, CryoMesh enables extended quality, potency, and safety testing, cost-effective batch production, and global banking and distribution. These capabilities remove a major barrier to curative cell therapy for diabetes and establish a generalizable strategy for preserving complex multicellular therapeutics. One Sentence SummaryA clinical scale vitrification platform enables long-term banking of human pancreatic and stem cell-derived islets for transplantation.

cell biology↗

bioRxiv2023

A machine vision guided robot for fully automated embryonic microinjection

Microinjection is a widely used technique for transgenesis, mutagenesis, cell labeling, cryopreservation, and in vitro fertilization in multiple single and multicellular organisms. Microinjection requires specialized skills acquired for each target organism and involves rate limiting and labor-intensive preparatory steps. Here we constructed a machine vision (MV) guided generalized robot that fully automates the process of microinjection in fruit fly (Drosophila melanogaster) and zebrafish (Danio rerio) embryos. The robot uses machine learning (ML) models trained to detect individual embryos in images of agar plates, and models trained to identify specific anatomical locations within each embryo in 3D space using dual view microscopes. The robot uses this information to serially perform microinjection in each detected embryo without any human intervention. We constructed and used three such robots to automatically microinject tens of thousands of Drosophila and zebrafish embryos. We systematically optimized robotic microinjection for each species and validated the use of the robot by performing routine transgenesis with proficiency comparable to highly skilled human practitioners while achieving up to 4x increases in microinjection throughput in Drosophila. The automated microinjection robot was utilized to microinject pools of over 20,000 uniquely barcoded plasmids into 1,713 embryos in two days to rapidly generate more than 400 unique transgenic Drosophila lines. This high throughput microinjection experiment enabled a novel measurement of the number of independent germline integration events per successfully injected embryo. Finally, we showed that robotic microinjection of cryoprotective agents in zebrafish embryos significantly improves vitrification rates and survival of cryopreserved embryos post-thaw as compared to manual microinjection, opening the tantalizing possibility of large-scale cryobanking of aquatic species at an industrial scale. We anticipate that this versatile automated microinjection system can be applied to carry out microinjection for genome-wide manipulation and cryopreservation at scale in a wide range of other organisms.

genetics↗

bioRxiv2023

The first proof of concept demonstration of nanowarming in coral tissue

Climate change is causing ocean acidification and warming, resulting in mass bleaching and death of corals globally. Cryopreservation and biobanking to secure the genetics of threatened populations is currently limited to coral sperm and larvae, which are only available during brief annual spawning events and are impacted by ocean warming, so there is an urgent need for methods to enable biobanking activities year-round. Here, we used vitrification and nanowarming to successfully recover adult coral tissues in a novel sample type, the single-polyp microfragment (SPMF). Fluorescence and confocal microscopy showed clearly defined tissues and green fluorescent protein fluorescence around the polyp mouth post-warming in 43.3% of SPMFs at 24 hours post-warming, and 30.0% at one month. These advances provide a basis for continued research and development of a field-ready protocol for cryopreservation of adult coral tissues, to permit biobanking of threatened coral species throughout the year and support reef restoration efforts.

ecology↗

bioRxiv2021

Formation and Spontaneous Long-Term Repatterning of Headless Planarian Flatworms

Regeneration requires the production of large numbers of new cells, and thus cell division regulators, particularly ERK signaling, are critical in regulating this process. In the highly regenerative planarian flatworm, questions remain as to whether ERK signaling controls overall regeneration or plays a head-specific role. Here we show that ERK inhibition in the 3 days following amputation delays regeneration, but that all tissues except the head can overcome this inhibition, resulting in headless regenerates. This prevention of head regeneration happens to a different degree along the anterior-posterior axis, with very anterior wounds regenerating heads even under ERK inhibition. Remarkably, 4 to 18 weeks after injury, the headless animals induced by ERK inhibition remodel to regain single-headed morphology, in the absence of further injury, in a process driven by Wnt/{beta}-catenin signaling. Interestingly, headless animals are likely to exhibit unstable axial polarity, and cutting or fissioning prior to remodeling can result in body-wide reversal of anterior-posterior polarity. Our data reveal new aspects of how ERK signaling regulates regeneration in planaria and show anatomical remodeling on very long timescales.

developmental biology↗

bioRxiv2020

S-adenosylhomocysteine hydrolase regulates anterior patterning in Dugesia japonica

BackgroundBiological methylation requires S-adenosylmethionine (SAM) and participates in a range of processes from modulation of gene expression via histone modifications to neurotransmitter synthesis. An important factor in all methylation reactions is the concentration ratio of SAM to methylation byproduct S-adenosylhomocysteine (SAH). SAH hydrolase, also known as adenosylhomocysteinase, depletes SAH and thereby facilitates metabolite recycling and maintains the methylation permissive SAM/SAH ratio. While the importance of SAH hydrolase in sustaining methylation is obvious on the cellular level, the function of this metabolic process on the organismal scale is not clear. ResultsWe used planarian Dugesia japonica to investigate the role SAH hydrolase in physiological homeostasis on the body-wide scale. Remarkably, pharmacological inhibition of the SAH hydrolase results in regression of anterior tissues and is accompanied by extensive apoptosis throughout the planarian body. Moreover, exposure to the SAHH inhibitor AdOx leads to changes in brain morphology and spatial shift in the expression of Wnt-modulator Notum. Strikingly, planarians are able to overcome these destructive patterning defects through regeneration of the anterior tissues and adaptation to the used inhibitor. Transcriptome analysis indicates that resistance to the SAHH inhibitor is at least partly mediated by changes in folate cycle and lipid metabolism. ConclusionsSAH hydrolase plays a critical role in planarian homeostasis and anterior patterning potentially through modulation of Wnt signaling. Moreover, planarian adaptation to the SAHH inhibitor via metabolic reprogramming suggests potential targets for addressing methylation-related human conditions.

physiology↗

bioRxiv2019

Nervous System and Tissue Polarity Dynamically Adapt to New Morphologies in Planaria

The coordination of tissue-level polarity with organism-level polarity is crucial in development, disease, and regeneration. Exploiting the flexibility of the body plan in regenerating planarians, we used mirror duplication of the primary axis to show how established tissue-level polarity adapts to new organism-level polarity. Tracking of cilia-driven flow to characterize planar cell polarity of the epithelium revealed a remarkable reorientation of tissue polarity in double-headed planarians. This reorientation is driven by signals produced by the intact brain and is not hampered by radiation-induced removal of stem cells. The nervous system itself adapts its polarity to match the new organismal anatomy in these animals as revealed by distinct regenerative outcomes driven by polarized nerve transport. Thus, signals from the central nervous system can dynamically control and re-orient tissue-level polarity to match the organism-level anatomical configuration, illustrating a novel role of the nervous system in the regulation of patterning.

physiology↗

bioRxiv2018

Generation of a versatile BiFC ORFeome library for analyzing protein-protein interactions in live Drosophila

Transcription factors achieve specificity by establishing intricate interaction networks that will change depending on the cell context. Capturing these interactions in live condition is however a challenging issue that requires sensitive and non-invasive methods. We present a set of fly lines, called \"multicolor BiFC library\", which covers most of the Drosophila transcription factors for performing Bimolecular Fluorescence Complementation (BiFC). The multicolor BiFC library can be used to probe binary or tripartite interactions and is compatible for large-scale interaction screens. The library can also be coupled with established Drosophila genetic resources to analyze interactions in the developmentally relevant expression domain of each protein partner. We provide proof of principle experiments of these various applications, using Hox proteins in the live Drosophila embryo as a case study. Overall this novel collection of ready-to-use fly lines constitutes an unprecedented genetic toolbox for the identification and analysis of protein-protein interactions in vivo.

genomics↗

bioRxiv2017

Drosophila beta-Tubulin 97EF is upregulated at low temperature and stabilizes microtubules

Summary statementEctotherms thrive within an often remarkable temperature range. At low temperature, betaTub97EF, a beta-tubulin paralog stabilizing microtubules, is upregulated in a tissue-specific manner in the fly Drosophila melanogaster.\n\nAbstractCells in ectotherms function normally within an often wide temperature range. As temperature dependence is not uniform across all the distinct biological processes, acclimation presumably requires complex regulation. The molecular mechanisms coping with the disruptive effects of temperature variation are still poorly understood. Interestingly, one of five different beta-tubulin paralogs, betaTub97EF, was among the genes up-regulated at low temperature in cultured Drosophila cells. As microtubules are known to be cold-sensitive, we analyzed whether betaTub97EF protects microtubules at low temperatures. During development at the optimal temperature (25{degrees}C), betaTub97EF was expressed in a tissue-specific pattern primarily in the gut. There, as well as in hemocytes, expression was increased at low temperature (14{degrees}C). While betaTub97EF mutants were viable and fertile at 25{degrees}C, their sensitivity within the well-tolerated range was slightly enhanced during embryogenesis specifically at low temperatures. Changing beta-tubulin isoform ratios in hemocytes demonstrated that beta-Tubulin 97EF has a pronounced microtubule stabilizing effect. Moreover, betaTub97EF is required for normal microtubule stability in the gut. These results suggest that betaTub97EF up-regulation at low temperature contributes to acclimation by stabilizing microtubules.

developmental biology↗