Biology subjects

Eggeler, F.

Publications and source records attributed to Eggeler, F..

3 recordsLinked to original sources

bioRxiv2025

Lrrns define a visual circuit underlying brightness and contrast perception

Brightness and contrast are fundamental features of vision, crucial for object detection, environmental navigation, and feeding. Here, we identify a brightness-and contrast-processing circuit in the zebrafish visual system and uncover the role of Leucine-rich repeat neuronal (Lrrn) cell adhesion molecules (CAMs) in regulating its assembly. Deep-projecting retinal ganglion cells (RGCs) serve as the first synaptic relay to the brain requiring Lrrn2 and Lrrn3a for precise axonal targeting and connectivity within the optic tectum. Genetic targeting of these CAMs leads to circuit disorganization and impairments in contrast sensitivity, leading to deficits in visually guided behaviors. Additionally, ultrastructural circuit reconstruction and functional imaging analysis revealed their critical role in luminance processing. These studies define a fundamental visual processing pathway and establish Lrrn CAMs as essential molecular drivers of its assembly.

neuroscience↗

bioRxiv2025

Immune surveillance and pruning of neuronal stem cells in the medaka retina

Stem cell populations in tissues require precise regulation of their number and quality to maintain proper organ growth. Amongst various regulatory mechanisms, immune cells are emerging to directly regulate stem cell populations. The medaka retinal stem cell (RSC) niche, a model for lifelong neurogenic growth, provides a system to study immune-stem cell interactions. We investigate how microglia, resident macrophages of the central nervous system, regulate the RSC niche. We identify that bona fide RSCs express the chemokine Ccl25b while its cognate receptor, Ccr9a, is expressed in microglia. These microglia form a surveillance ring adjacent to the RSC niche and actively phagocytose RSCs. Interference with microglia by deletion of spi1b reveals that microglia absence leads to increased numbers of ccl25b-positive RSCs and results in morphological defects of the retina. Targeted mutation of ccl25b specifically affects microglia mobility under injury conditions, however, we did not observe any morphological defects indicating that Ccl25b-Ccr9a signaling is not essential for stem cell maintenance. Overall, our data show that under homeostatic conditions the individual RSCs, essential for proper eye development, are actively phagocytosed by immune surveillance.

developmental biology↗

bioRxiv2023

Meteorins regulate the formation of the left-right organizer and the establishment of vertebrate body asymmetry

While the exterior of vertebrate bodies appears bilaterally symmetrical, internal organ positioning and morphology frequently exhibit left-right (L-R) asymmetries. In several vertebrates, including human, mouse, frog and zebrafish, left-right symmetry-breaking during embryonic development is initiated by a ciliated organ called the Node or left-right organizer. Within the Node, a leftward flow of extraembryonic fluid named the Nodal flow mediates the asymmetric expressions of Nodal factors. Although downstream Nodal pathway components leading to the establishment of the embryonic left-right axis are well known, less is known about the development and formation of the embryonic Node itself. Here we reveal a novel role for the Meteorin protein family in the establishment of the left-right axis and in the formation of the Kupffers vesicle, the Node equivalent structure in zebrafish. We show that the genetic inactivation of each or all three members of the zebrafish Meteorin family (metrn, metrn-like a and metrn-like b) leads to defects in properties of the Kupffers vesicle, caused by impaired assembly and migration of the Kupffers vesicle forming dorsal forerunner cells. In addition, we demonstrate that Meteorins genetically interact with integrins ItgaV and Itg{beta}1b regulating the dorsal forerunner cell clustering and that meteorins loss-of-function results in disturbed Nodal factor expression and consequently in randomized or symmetric heart looping and jogging. These results identify a new role for the Meteorin protein family in the left-right asymmetry patterning during embryonic vertebrate development.

developmental biology↗