dab2 is required for the scavenging function of lymphatic endothelial cells in the zebrafish meninges.

To date it is only partially understood how the brain is cleared of waste products resulting from its high metabolic activity, although this process has important implications for the development and progression of neurodegenerative diseases. Lymphatic vessels play a central role in maintaining fluid and tissue homeostasis, and the recent description of meningeal lymphatic vessels within the dura mater of mice, human and zebrafish has raised considerable interest in unraveling the function of these vessels. In zebrafish, brain lymphatic endothelial cells (BLECs) constitute an additional meningeal lymphatic endothelial cell population.

Epigenetic regulation by polycomb repressive complex 1 promotes cerebral cavernous malformations.

Cerebral cavernous malformations (CCMs) are anomalies of the cerebral vasculature. Loss of the CCM proteins CCM1/KRIT1, CCM2, or CCM3/PDCD10 trigger a MAPK-Krüppel-like factor 2 (KLF2) signaling cascade, which induces a pathophysiological pattern of gene expression. The downstream target genes that are activated by KLF2 are mostly unknown.

Neural plate progenitors give rise to both anterior and posterior pituitary cells.

The pituitary is the master neuroendocrine gland, which regulates body homeostasis. It consists of the anterior pituitary/adenohypophysis harboring hormones producing cells and the posterior pituitary/neurohypophysis, which relays the passage of hormones from the brain to the periphery. It is accepted that the adenohypophysis originates from the oral ectoderm (Rathke's pouch), whereas the neural ectoderm contributes to the neurohypophysis.

Deciphering the heterogeneity of the Lyve1 perivascular macrophages in the mouse brain.

Perivascular macrophages (pvMs) are associated with cerebral vasculature and mediate brain drainage and immune regulation. Here, using reporter mouse models, whole brain and section immunofluorescence, flow cytometry, and single cell RNA sequencing, besides the Lyve1F4/80CD206CX3CR1 pvMs, we identify a CX3CR1 pvM population that shares phagocytic functions and location. Furthermore, the brain parenchyma vasculature mostly hosts Lyve1MHCII pvMs with low to intermediate CD45 expression.

A robust and tunable system for targeted cell ablation in developing embryos.

Cell ablation is a key method in the research fields of developmental biology, tissue regeneration, and tissue homeostasis. Eliminating specific cell populations allows for characterizing interactions that control cell differentiation, death, behavior, and spatial organization of cells. Current methodologies for inducing cell death suffer from relatively slow kinetics, making them unsuitable for analyzing rapid events and following primary and immediate consequences of the ablation.

Cells with Many Talents: Lymphatic Endothelial Cells in the Brain Meninges.

The lymphatic system serves key functions in maintaining fluid homeostasis, the uptake of dietary fats in the small intestine, and the trafficking of immune cells. Almost all vascularized peripheral tissues and organs contain lymphatic vessels. The brain parenchyma, however, is considered immune privileged and devoid of lymphatic structures.

Phosphatidylinositol-3 kinase signaling controls survival and stemness of hematopoietic stem and progenitor cells.

Hematopoietic stem and progenitor cells (HSPCs) are multipotent cells giving rise to all blood lineages during life. HSPCs emerge from the ventral wall of the dorsal aorta (VDA) during a specific timespan in embryonic development through endothelial hematopoietic transition (EHT). We investigated the ontogeny of HSPCs in mutant zebrafish embryos lacking functional pten, an important tumor suppressor with a central role in cell signaling.

The adaptor protein Grb2b is an essential modulator for lympho-venous sprout formation in the zebrafish trunk.

Vegfc/Vegfr3 signaling is critical for lymphangiogenesis, the sprouting of lymphatic vessels. In zebrafish, cells sprouting from the posterior cardinal vein can either form lymphatic precursor cells or contribute to intersegmental vein formation. Both, the Vegfc-dependent differential induction of Prox1a in sprouting cells as well as a Notch-mediated pre-pattern within intersegmental vessels have been associated with the regulation of secondary sprout behavior.

Tetracyclines improve experimental lymphatic filariasis pathology by disrupting interleukin-4 receptor-mediated lymphangiogenesis.

Lymphatic filariasis is the major global cause of nonhereditary lymphedema. We demonstrate that the filarial nematode Brugia malayi induced lymphatic remodeling and impaired lymphatic drainage following parasitism of limb lymphatics in a mouse model. Lymphatic insufficiency was associated with elevated circulating lymphangiogenic mediators, including vascular endothelial growth factor C.

Specific fibroblast subpopulations and neuronal structures provide local sources of Vegfc-processing components during zebrafish lymphangiogenesis.

Proteolytical processing of the growth factor VEGFC through the concerted activity of CCBE1 and ADAMTS3 is required for lymphatic development to occur. How these factors act together in time and space, and which cell types produce these factors is not understood. Here we assess the function of Adamts3 and the related protease Adamts14 during zebrafish lymphangiogenesis and show both proteins to be able to process Vegfc.

Multispecies RNA tomography reveals regulators of hematopoietic stem cell birth in the embryonic aorta.

The defined location of a stem cell within a niche regulates its fate, behavior, and molecular identity via a complex extrinsic regulation that is far from being fully elucidated. To explore the molecular characteristics and key components of the aortic microenvironment, where the first hematopoietic stem cells are generated during development, we performed genome-wide RNA tomography sequencing on zebrafish, chicken, mouse, and human embryos. The resulting anterior-posterior and dorsal-ventral transcriptional maps provided a powerful resource for exploring genes and regulatory pathways active in the aortic microenvironment.

Zebrafish: Housing and husbandry recommendations.

This article provides recommendations for the care of laboratory zebrafish () as part of the further implementation of Annex A to the European Convention on the protection of vertebrate animals used for experimental and other scientific purposes, EU Commission Recommendation 2007/526/EC and the fulfilment of Article 33 of EU Directive 2010/63, both concerning the housing and care of experimental animals. The recommendations provide guidance on best practices and ranges of husbandry parameters within which zebrafish welfare, as well as reproducibility of experimental procedures, are assured. Husbandry procedures found today in zebrafish facilities are numerous.

Cerebrovascular endothelial cells form transient Notch-dependent cystic structures in zebrafish.

We identify a novel endothelial membrane behaviour in transgenic zebrafish. Cerebral blood vessels extrude large transient spherical structures that persist for an average of 23 min before regressing into the parent vessel. We term these structures "kugeln", after the German for sphere.

Zebrafish and medaka as models for biomedical research of bone diseases.

The identification of disease-causing mutations has in recent years progressed immensely due to whole genome sequencing approaches using patient material. The task accordingly is shifting from gene identification to functional analysis of putative disease-causing genes, preferably in an in vivo setting which also allows testing of drug candidates or biotherapeutics in whole animal disease models. In this review, we highlight the advances made in the field of bone diseases using small laboratory fish, focusing on zebrafish and medaka.

Neural Crest Methodologies in Zebrafish and Medaka.

Neural crest cells are highly multipotent and strongly migratory cells and generate adult neural crest stem cells with varied roles in cellular homeostasis and regeneration. The optical transparency and ready accessibility of fish embryos make them particularly well-suited to high-resolution analysis of neural crest development. However, the dispersive nature of these cells adds to the challenge of their study, requiring that they be identified using marker expression.

Zebrafish facial lymphatics develop through sequential addition of venous and non-venous progenitors.

Lymphatic vessels are known to be derived from veins; however, recent lineage-tracing experiments propose that specific lymphatic networks may originate from both venous and non-venous sources. Despite this, direct evidence of a non-venous lymphatic progenitor is missing. Here, we show that the zebrafish facial lymphatic network is derived from three distinct progenitor populations that add sequentially to the developing facial lymphatic through a relay-like mechanism.

Notochord Injury Assays that Stimulate Transcriptional Responses in Zebrafish Larvae.

Zebrafish have become an increasingly important model organism in the field of wound healing and regenerative medicine, due to their high regenerative capacity coupled with high-resolution imaging in living animals. In a recent study, we described multiple physical and chemical methods to induce notochord injury that led to highly specific transcriptional responses in notochord cellular subpopulations. The notochord is a critical embryonic structure that functions to shape and pattern the vertebrae and spinal column.

From fish embryos to human patients: lymphangiogenesis in development and disease.

The lymphatic vasculature plays vital roles in immune surveillance, fluid homeostasis and fat absorption in the body. Lined by endothelial cells, the lymphatic system is functionally distinct from the blood vasculature, and fulfills different physiological functions. In recent years, insight from zebrafish, mice and human patients have improved our understanding of lymphatics, and the interplay between zebrafish genetics, studies in mice and GWAS analysis in human patients have identified genes that, when mutated, will lead to lymphedema formation.

A blood capillary plexus-derived population of progenitor cells contributes to genesis of the dermal lymphatic vasculature during embryonic development.

Despite the essential role of the lymphatic vasculature in tissue homeostasis and disease, knowledge of the organ-specific origins of lymphatic endothelial progenitor cells remains limited. The assumption that most murine embryonic lymphatic endothelial cells (LECs) are venous derived has recently been challenged. Here, we show that the embryonic dermal blood capillary plexus constitutes an additional, local source of LECs that contributes to the formation of the dermal lymphatic vascular network.

Spine Patterning Is Guided by Segmentation of the Notochord Sheath.

The spine is a segmented axial structure made of alternating vertebral bodies (centra) and intervertebral discs (IVDs) assembled around the notochord. Here, we show that, prior to centra formation, the outer epithelial cell layer of the zebrafish notochord, the sheath, segments into alternating domains corresponding to the prospective centra and IVD areas. This process occurs sequentially in an anteroposterior direction via the activation of Notch signaling in alternating segments of the sheath, which transition from cartilaginous to mineralizing domains.

defines a wound-specific sheath cell subpopulation associated with notochord repair.

Regenerative therapy for degenerative spine disorders requires the identification of cells that can slow down and possibly reverse degenerative processes. Here, we identify an unanticipated wound-specific notochord sheath cell subpopulation that expresses Wilms Tumor (WT) 1b following injury in zebrafish. We show that localized damage leads to Wt1b expression in sheath cells, and that cells migrate into the wound to form a stopper-like structure, likely to maintain structural integrity.