The Hindbrain Choroid Plexus is a complex, cerebrospinal fluid-secreting tissue that projects into the 4th vertebrate brain ventricle. Despite its irreplaceability in the development and homeostasis of the entire central nervous system, the research of Hindbrain Choroid Plexus and other Choroid Plexuses has been neglected by neuroscientists for decades. One of the obstacles is the lack of tools that describe the complex shape of the Hindbrain Choroid Plexus in the context of brain ventricles. Here we introduce an effective tool, termed ChOP-CT, for the noninvasive, X-ray micro-computed tomography-based, three-dimensional visualization and subsequent quantitative spatial morphological analysis of developing mouse Hindbrain Choroid Plexus. ChOP-CT can reliably quantify Hindbrain Choroid Plexus volume, surface area, length, outgrowth angle, the proportion of the ventricular space occupied, asymmetries and general shape alterations in mouse embryos from embryonic day 13.5 onwards. We provide evidence that ChOP-CT is suitable for the unbiased evaluation and detection of the Hindbrain Choroid Plexus alterations within various mutant embryos. We believe, that thanks to its versatility, quantitative nature and the possibility of automation, ChOP-CT will facilitate the analysis of the Hindbrain Choroid Plexus in the mouse models. This will ultimately accelerate the screening of the candidate genes and mechanisms involved in the onset of various Hindbrain Choroid Plexus-related diseases.

• Keywords
• 3D visualization, Hindbrain choroid plexus, Morphometrics, X-ray micro-computed tomography,
• MeSH
• Brain MeSH
• Cerebral Ventricles * MeSH
• Mice MeSH
• Choroid Plexus * diagnostic imaging   MeSH
• X-Ray Microtomography MeSH
• Rhombencephalon diagnostic imaging   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

The choroid plexus (ChP) is an extensively vascularized tissue that protrudes into the brain ventricular system of all vertebrates. This highly specialized structure, consisting of the polarized epithelial sheet and underlying stroma, serves a spectrum of functions within the central nervous system (CNS), most notably the production of cerebrospinal fluid (CSF). The epithelial cells of the ChP have the competence to tightly modulate the biomolecule composition of CSF, which acts as a milieu functionally connecting ChP with other brain structures. This review aims to eloquently summarize the current knowledge about the development of ChP. We describe the mechanisms that control its early specification from roof plate followed by the formation of proliferative regions-cortical hem and rhombic lips-feeding later development of ChP. Next, we summarized the current knowledge on the maturation of ChP and mechanisms that control its morphological and cellular diversity. Furthermore, we attempted to review the currently available battery of molecular markers and mouse strains available for the research of ChP, and identified some technological shortcomings that must be overcome to accelerate the ChP research field. Overall, the central principle of this review is to highlight ChP as an intriguing and surprisingly poorly known structure that is vital for the development and function of the whole CNS. We believe that our summary will increase the interest in further studies of ChP that aim to describe the molecular and cellular principles guiding the development and function of this tissue.

• Keywords
• Cerebrospinal fluid (CSF), ChP epithelial cells, Choroid plexus (ChP), Cortical hem, Morphogenesis, Rhombic lips,
• MeSH
• Central Nervous System * MeSH
• Epithelial Cells MeSH
• Brain MeSH
• Mice MeSH
• Choroid Plexus * physiology   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

RNF43 is an E3 ubiquitin ligase and known negative regulator of WNT/β-catenin signaling. We demonstrate that RNF43 is also a regulator of noncanonical WNT5A-induced signaling in human cells. Analysis of the RNF43 interactome using BioID and immunoprecipitation showed that RNF43 can interact with the core receptor complex components dedicated to the noncanonical Wnt pathway such as ROR1, ROR2, VANGL1, and VANGL2. RNF43 triggers VANGL2 ubiquitination and proteasomal degradation and clathrin-dependent internalization of ROR1 receptor and inhibits ROR2 activation. These activities of RNF43 are physiologically relevant and block pro-metastatic WNT5A signaling in melanoma. RNF43 inhibits responses to WNT5A, which results in the suppression of invasive properties of melanoma cells. Furthermore, RNF43 prevented WNT5A-assisted development of resistance to BRAF V600E and MEK inhibitors. Next, RNF43 acted as melanoma suppressor and improved response to targeted therapies in vivo. In line with these findings, RNF43 expression decreases during melanoma progression and RNF43-low patients have a worse prognosis. We conclude that RNF43 is a newly discovered negative regulator of WNT5A-mediated biological responses that desensitizes cells to WNT5A.

• Keywords
• BRAF V600E, RNF43, ROR1, VANGL1, WNT5A, cancer biology, cell biology, human, melanoma, mouse,
• MeSH
• Neoplasm Invasiveness genetics   MeSH
• Melanoma * genetics   pathology   prevention & control   MeSH
• Mice, Inbred NOD MeSH
• Mice MeSH
• Wnt-5a Protein genetics   metabolism   MeSH
• Signal Transduction * MeSH
• Ubiquitin-Protein Ligases genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Wnt-5a Protein MeSH
• RNF43 protein, human MeSH Browser
• Ubiquitin-Protein Ligases MeSH
• WNT5A protein, human MeSH Browser

The choroid plexus (ChP) in each brain ventricle produces cerebrospinal fluid (CSF) and forms the blood-CSF barrier. Here, we construct a single-cell and spatial atlas of each ChP in the developing, adult, and aged mouse brain. We delineate diverse cell types, subtypes, cell states, and expression programs in epithelial and mesenchymal cells across ages and ventricles. In the developing ChP, we predict a common progenitor pool for epithelial and neuronal cells, validated by lineage tracing. Epithelial and fibroblast cells show regionalized expression by ventricle, starting at embryonic stages and persisting with age, with a dramatic transcriptional shift with maturation, and a smaller shift in each aged cell type. With aging, epithelial cells upregulate host-defense programs, and resident macrophages upregulate interleukin-1β (IL-1β) signaling genes. Our atlas reveals cellular diversity, architecture and signaling across ventricles during development, maturation, and aging of the ChP-brain barrier.

• Keywords
• aging, brain barrier, cerebrospinal fluid, choroid plexus, development, single-cell RNA sequencing, single-nucleus RNA sequencing,
• MeSH
• Single-Cell Analysis MeSH
• Cell Differentiation genetics   MeSH
• Cell Lineage genetics   MeSH
• Epithelial Cells metabolism   MeSH
• Blood-Brain Barrier metabolism   MeSH
• Brain metabolism   physiology   MeSH
• Mice, Inbred C57BL MeSH
• Mice embryology   MeSH
• Brain Diseases genetics   physiopathology   MeSH
• Choroid Plexus embryology   metabolism   physiology   MeSH
• Signal Transduction MeSH
• Aging physiology   MeSH
• Age Factors MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice embryology   MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

The choroid plexus (ChP) produces cerebrospinal fluid and forms an essential brain barrier. ChP tissues form in each brain ventricle, each one adopting a distinct shape, but remarkably little is known about the mechanisms underlying ChP development. Here, we show that epithelial WNT5A is crucial for determining fourth ventricle (4V) ChP morphogenesis and size in mouse. Systemic Wnt5a knockout, or forced Wnt5a overexpression beginning at embryonic day 10.5, profoundly reduced ChP size and development. However, Wnt5a expression was enriched in Foxj1-positive epithelial cells of 4V ChP plexus, and its conditional deletion in these cells affected the branched, villous morphology of the 4V ChP. We found that WNT5A was enriched in epithelial cells localized to the distal tips of 4V ChP villi, where WNT5A acted locally to activate non-canonical WNT signaling via ROR1 and ROR2 receptors. During 4V ChP development, MEIS1 bound to the proximal Wnt5a promoter, and gain- and loss-of-function approaches demonstrated that MEIS1 regulated Wnt5a expression. Collectively, our findings demonstrate a dual function of WNT5A in ChP development and identify MEIS transcription factors as upstream regulators of Wnt5a in the 4V ChP epithelium.

• Keywords
• Choroid plexus, Epithelium, Meis1, Meis2, Morphogenesis, WNT5a,
• MeSH
• Cell Line MeSH
• CRISPR-Cas Systems genetics   MeSH
• Fourth Ventricle embryology   MeSH
• Epithelium metabolism   MeSH
• Epithelial Cells metabolism   MeSH
• HEK293 Cells MeSH
• Humans MeSH
• Brain embryology   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Choroid Plexus embryology   MeSH
• Promoter Regions, Genetic genetics   MeSH
• Wnt-5a Protein genetics   metabolism   MeSH
• Signal Transduction physiology   MeSH
• Receptor Tyrosine Kinase-like Orphan Receptors metabolism   MeSH
• Myeloid Ecotropic Viral Integration Site 1 Protein metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Meis1 protein, mouse MeSH Browser
• Wnt-5a Protein MeSH
• Ror1 protein, mouse MeSH Browser
• Ror2 protein, mouse MeSH Browser
• Receptor Tyrosine Kinase-like Orphan Receptors MeSH
• Myeloid Ecotropic Viral Integration Site 1 Protein MeSH
• Wnt5a protein, mouse MeSH Browser

Cerebrospinal fluid (CSF) is the liquid that fills the brain ventricles. CSF represents not only a mechanical brain protection but also a rich source of signalling factors modulating diverse processes during brain development and adulthood. The choroid plexus (CP) is a major source of CSF and as such it has recently emerged as an important mediator of extracellular signalling within the brain. Growing interest in the CP revealed its capacity to release a broad variety of bioactive molecules that, via CSF, regulate processes across the whole central nervous system (CNS). Moreover, CP has been also recognized as a sensor, responding to altered composition of CSF associated with changes in the patterns of CNS activity. In this review, we summarize the recent advances in our understanding of the CP as a signalling centre that mediates long-range communication in the CNS. By providing a detailed account of the CP secretory repertoire, we describe how the CP contributes to the regulation of the extracellular environment-in the context of both the embryonal as well as the adult CNS. We highlight the role of the CP as an important regulator of CNS function that acts via CSF-mediated signalling. Further studies of CP-CSF signalling hold the potential to provide key insights into the biology of the CNS, with implications for better understanding and treatment of neuropathological conditions.

• Keywords
• cerebrospinal fluid, choroid plexus, secretion,
• MeSH
• Biological Transport physiology   MeSH
• Blood-Brain Barrier metabolism   MeSH
• Humans MeSH
• Choroid Plexus metabolism   MeSH
• Signal Transduction physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH