Biology subjects

Kretzschmar, J.

Publications and source records attributed to Kretzschmar, J..

5 recordsLinked to original sources

bioRxiv2026

Choreographed morphogenetic events underlie early foregut development in the mouse embryo

Between embryonic days 7.5 and 8.5, the mouse embryo undergoes a dramatic rearrangement of its entire anterior, a process known as ventral folding: the near-simultaneous morphogenesis of the cardiac crescent, cranial headfolds, and anterior foregut that together establish the antero-ventral body plan. While cardiac morphogenesis has been studied in detail, the cellular and mechanical basis of foregut involution remains largely undefined. Using combined light-sheet and spinning-disk live imaging spanning the full window of foregut formation, we show that involution proceeds through a stereotyped morphological programme that does not require actomyosin contractility for its initiation. Additionally, involution is preceded by a spatiotemporally restricted wave of apoptosis in embryonic visceral endoderm (emVE) cells, which extrude bidirectionally. A lineage- and stage-resolved bulk RNA-sequencing of emVE, definitive endoderm, and epiblast populations identifies a differential-adhesion and cell-cycle signature underlying this behaviour. Revisiting a visceral-endoderm-specific Bmp2 knock-out mutant, we find that BMP2 controls involution indirectly, by directing notochord positioning and thereby the geometry of the surrounding heart and headfold mechanics. Together, these findings reframe ventral folding as a single coordinated geometric process rather than a set of independent organ forming events.

developmental biology↗

bioRxiv2022

Deterministic and probabilistic fate decisions co-exist in a single retinal lineage

Correct nervous system development depends on the timely differentiation of progenitor cells into neurons. While the output of progenitor differentiation is well investigated at the population and clonal level, the possibilities and constraints for fate decisions of specific progenitors over development are less explored. Particularly little is known about their variability and competence plasticity. To fill this gap, we here use long-term live imaging to follow the outcome of progenitor divisions in the zebrafish retina. We find that neurogenic Atoh7 expressing progenitors produce different neuronal types over development with time-dependent probabilities. Interestingly, deterministic and probabilistic fate decisions co-exist in the same lineage. While interference with the deterministic fate affects lineage progression, interference with fate probabilities of the stochastic lineage branch results in a broader range of fate possibilities than seen in controls. When tissue development is challenged, Atoh7 expressing progenitors can produce any neuronal type, arguing against the concept of fixed competence windows. Stochastic modelling of fate probabilities in challenged conditions revealed a simple gene regulatory network able to recapitulate the observed competence changes during development. Based on our results, we postulate that fate plasticity could be involved in robust retinal development, a concept possibly applicable to other tissues.

developmental biology↗

bioRxiv2021

Bidirectional neuronal migration coordinates retinal morphogenesis bypreventing spatial competition

While the design of industrial products is often optimized for the sequential assembly of single components, organismal development is hallmarked by the concomitant occurrence of tissue growth and organization. Often this means that proliferating and differentiating cells occur at the same time in a shared tissue environment that continuously changes. How cells adapt to architectural changes in order to prevent spatial interference remains unclear. To understand how cell movements important for growth and organization are orchestrated, we here study the emergence of photoreceptor neurons that occur during the peak of retinal growth using zebrafish, human tissue and human organoids. Quantitative imaging reveals that successful retinal morphogenesis depends on active bidirectional photoreceptor translocation. This leads to a transient transfer of the entire cell population away from the apical proliferative zone. This migration pattern is driven by distinct cytoskeletal machineries, depending on direction: microtubules are required for basal translocation, while actomyosin drives apical movement. Blocking photoreceptor translocation leads to apical overcrowding that hampers progenitor movements. Thus, photoreceptor migration is crucial to prevent competition for space and thereby allows concurrent tissue growth and lamination. This shows that neuronal migration, in addition to its canonical role in cell positioning, is involved in coordinating morphogenesis.

developmental biology↗

bioRxiv2020

Diet and heat - one neuronal subset two responses

The Insulin signal cascade is one of the best studied metabolic circuits, and shows a remarkable high molecular and functional conservation across the animal kingdom. Insulin-producing cells respond directly to nutritional cues in circulation and receive modulatory input from connected neuronal networks. Neuronal control is rapid and integrates a wide range of variables including dietary change or environmental temperature. However, despite various detailed studies that demonstrated the potential of neuronal regulation the physiological relevance of this circuit remains elusive. In Drosophila, Insulin-like peptide 7 (dIlp7)-producing neurons are wired with Insulin-producing cells. We found a dual role for this neuronal subset: a.) activated dilp7-producing neurons are required to facilitate development at high temperatures, and if confronted with calorie-rich food that represses neuronal activity b.) their product, dIlp7, regulates Insulin signalling levels. Our work shows that Insulin-producing cells not simply integrate signals from circulating nutritional cues and neuronal inputs, but switch to neuronal control in response to dietary composition.

physiology↗

bioRxiv2019

Systematic analyses of factors required for adhesion of Salmonella enterica serovar Typhimurium to corn salad (Valerianella locusta)

Salmonella enterica is a foodborne pathogen leading to gastroenteritis and is commonly acquired by consumption of contaminated food of animal origin. However, numbers of outbreaks linked to the consumption of fresh or minimally processed food of non-animal origin are increasing. New infection routes of S. enterica by vegetables, fruits, nuts and herbs have to be considered. This leads to special interest in S. enterica interactions with leafy products, e.g. salads, that are consumed unprocessed. The attachment of S. enterica to salad is a crucial step in contamination, but little is known about the bacterial factors required and mechanisms of adhesion. S. enterica possesses a complex set of adhesive structures whose functions are only partly understood. Potentially, S. enterica may deploy multiple adhesive strategies for adhering to various salad species, and other vegetables. Here, we systematically analyzed the contribution of the complete adhesiome, of LPS, and of flagella-mediated motility of S. enterica serovar Typhimurium (STM) in adhesion to corn salad. We deployed a reductionist, synthetic approach to identify factors involved in the surface binding of STM to leaves of corn salad with particular regard to the expression of all known adhesive structures using the Tet-on system. This work reveals the contribution of Saf fimbriae, type 1 secretion system-secreted BapA, an intact LPS, and flagella-mediated motility of STM in adhesion to corn salad leaves. Importance Human gastrointestinal pathogens are often transmitted by animal products, but recent outbreaks show increasing importance of vegetables as source of infection by pathogenic E. coli or Salmonella enterica. The mechanisms of binding of S. enterica to vegetables such as salad are only poorly understood. We established an experimental model system to systematically investigate the role of adhesive structures of S. enterica serovar Typhimurium in binding to corn salad leaves. The contributions of all members of the complex adhesiome, flagella, and O-antigen were evaluated. We identified that Saf fimbriae, type 1 secretion system-secreted BapA, an intact LPS, and flagella-mediated motility contribute to adhesion of Salmonella to corn salad leaves. These results will enable future investigations on factors contributing to contamination of vegetables under agricultural conditions.

microbiology↗