Similar Datasets
Project description:Current organoid protocols are widely used to mechanistically study cortical development, evolution and brain pathologies. While these systems generate all major cortical cell types in histologically distinct compartments, they lack cortical area topography, which is initiated by gradients of signaling molecules released by signaling organizers that establish transcriptionally distinct domains along the rostro-caudal axis of the developing cortex. Here, we engineer human cortical assembloids that combine an organizer-like structure expressing FGF8 with an elongated organoid design to enable the controlled modulation of FGF8 signaling along the longitudinal organoid axis. We demonstrate that individual polarized cortical assembloids (polCA) mount a position-dependent transcriptional program that matches the in vivo rostro-caudal gene expression patterns. Importantly, positional identity is lost in polCA carrying a mutation in the FGFR3 gene associated with temporal lobe malformations and intellectual disability in humans. Similar to in vivo, this program is accompanied by transcriptional divergence of radial glia cells and excitatory neurons and their segregation along the longitudinal axis of individual organoids. Thus, this method reproduces in vivo cortical topography in individual organoids and enables the analysis of area-related phenotypes underlying human disorders.
2024-05-03 | GSE231319 | GEO
Project description:Current organoid protocols are widely used to mechanistically study cortical development, evolution and brain pathologies. While these systems generate all major cortical cell types in histologically distinct compartments, they lack cortical area topography, which is initiated by gradients of signaling molecules released by signaling organizers that establish transcriptionally distinct domains along the rostro-caudal axis of the developing cortex. Here, we engineer human cortical assembloids that combine an organizer-like structure expressing FGF8 with an elongated organoid design to enable the controlled modulation of FGF8 signaling along the longitudinal organoid axis. We demonstrate that individual polarized cortical assembloids (polCA) mount a position-dependent transcriptional program that matches the in vivo rostro-caudal gene expression patterns. Importantly, positional identity is lost in polCA carrying a mutation in the FGFR3 gene associated with temporal lobe malformations and intellectual disability in humans. Similar to in vivo, this program is accompanied by transcriptional divergence of radial glia cells and excitatory neurons and their segregation along the longitudinal axis of individual organoids. Thus, this method reproduces in vivo cortical topography in individual organoids and enables the analysis of area-related phenotypes underlying human disorders.
2024-05-03 | GSE231318 | GEO
Project description:Specification of a rostro-caudal axis in cortical assembloids through a polarized source of FGF8
| PRJNA963209 | ENA
Project description:Specification of a rostro-caudal axis in cortical assembloids through a polarized source of FGF8 (scRNA-Seq)
| PRJNA963211 | ENA
Project description:Specification of a rostro-caudal axis in cortical assembloids through a polarized source of FGF8 (bulk RNA-Seq)
| PRJNA963210 | ENA
Project description:During vertebrate axis extension, adjacent tissue layers undergo profound morphological changes: within the neuroepithelium, neural tube closure and neural crest formation are occurring, while within the paraxial mesoderm somites are segmenting from the presomitic mesoderm (PSM). Little is known about the signals between these tissues that regulate their coordinated morphogenesis. Here, we analyze the posterior axis truncation of mouse Fgf3 null homozygotes and demonstrate that the earliest role of PSM-derived FGF3 is to regulate BMP signals in the adjacent neuroepithelium. FGF3 loss causes elevated BMP signals leading to increased neuroepithelium proliferation, delay in neural tube closure and premature neural crest specification. We demonstrate that elevated BMP4 depletes PSM progenitors in vitro, phenocopying the Fgf3 mutant, suggesting that excessive BMP signals cause the Fgf3 axis defect. To test this in vivo we increased BMP signaling in Fgf3 mutants by removing one copy of Noggin, which encodes a BMP antagonist. In such mutants, all parameters of the Fgf3 phenotype were exacerbated: neural tube closure delay, premature neural crest specification, and premature axis termination. Conversely, genetically decreasing BMP signaling in Fgf3 mutants, via loss of BMP receptor activity, alleviates morphological defects. Aberrant apoptosis is observed in the Fgf3 mutant tailbud. However, we demonstrate that cell death does not cause the Fgf3 phenotype: blocking apoptosis via deletion of pro-apoptotic genes surprisingly increases all Fgf3 defects including causing spina bifida. We demonstrate that this counterintuitive consequence of blocking apoptosis is caused by the increased survival of BMP-producing cells in the neuroepithelium. Thus, we show that FGF3 in the caudal vertebrate embryo regulates BMP signaling in the neuroepithelium, which in turn regulates neural tube closure, neural crest specification and axis termination. Uncovering this FGF3-BMP signaling axis is a major advance toward understanding how these tissue layers interact during axis extension with important implications in human disease.
| S-EPMC4856314 | biostudies-literature
Project description:The organismal body axes that are formed during embryogenesis are intimately linked to intrinsic asymmetries established at the cellular scale in oocytes.1 However, the mechanisms that generate cellular asymmetries within the oocyte and then transduce that polarity to organismal scale body axes are poorly understood outside of select model organisms. Here, we report an axis-defining event in meiotic oocytes of the sea star Patiria miniata. Dishevelled (Dvl) is a cytoplasmic Wnt pathway effector required for axis development in diverse species,2-4 but the mechanisms governing its function and distribution remain poorly defined. Using time-lapse imaging, we find that Dvl localizes uniformly to puncta throughout the cell cortex in Prophase I-arrested oocytes but becomes enriched at the vegetal pole following meiotic resumption through a dissolution-reassembly mechanism. This process is driven by an initial disassembly phase of Dvl puncta, followed by selective reformation of Dvl assemblies at the vegetal pole. Rather than being driven by Wnt signaling, this localization behavior is coupled to meiotic cell cycle progression and influenced by Lamp1+ endosome association and Frizzled receptors pre-localized within the oocyte cortex. Our results reveal a cell cycle-linked mechanism by which maternal cellular polarity is transduced to the embryo through spatially regulated Dvl dynamics.
| S-EPMC8692449 | biostudies-literature
Project description:Three-dimensional (3D), submillimeter-scale constructs of neural cells, known as cortical spheroids, are of rapidly growing importance in biological research because these systems reproduce complex features of the brain in vitro. Despite their great potential for studies of neurodevelopment and neurological disease modeling, 3D living objects cannot be studied easily using conventional approaches to neuromodulation, sensing, and manipulation. Here, we introduce classes of microfabricated 3D frameworks as compliant, multifunctional neural interfaces to spheroids and to assembloids. Electrical, optical, chemical, and thermal interfaces to cortical spheroids demonstrate some of the capabilities. Complex architectures and high-resolution features highlight the design versatility. Detailed studies of the spreading of coordinated bursting events across the surface of an isolated cortical spheroid and of the cascade of processes associated with formation and regrowth of bridging tissues across a pair of such spheroids represent two of the many opportunities in basic neuroscience research enabled by these platforms.
| S-EPMC7968849 | biostudies-literature
Project description:The establishment of the fronto-temporal axis in the developing human cortex is achieved by temporary signaling activity coming from secondary organizers. However, studying this process remains challenging due to the limited access to fetal material and inaccuracy of animal models in mimicking human-specific aspects. Although human brain organoids provide a potential solution to study this, their lack of axial organization does not supply the appropriate positional information needed to recapitulate detailed patterning processes in situ. Here, we develop a method that combines a cell line expressing the morphogen FGF8 fused to organoids engineered with PDMS moulds representing the exact length of the developing brain, resulting in the formation of polarized cortical organoids, or PolarOids. Thanks to a dose-sensitive reporter for anterior cortical differentiation, we carefully titrate and time the fusion dynamics to elicit a gradient in the patterned tissue while preserving neural activity as assessed through electrophysiology. We show that our localized FGF8 source is sufficient to trigger a distance-dependent transcriptional signature that matches fronto-temporal cortical fates in vivo. Lastly, we use these PolarOids to model a disease-relevant FGFR3 mutation and describe the transcriptional loss of axial gradient formation underlying a dramatic cortical phenotype observed in patients. As such, Polaroids provide a powerful tool to model hitherto neglected human diseases caused by defects in antero-posterior patterning in the brain
2024-05-03 | GSE175592 | GEO
Project description:Vertebrate axis specification is an evolutionarily conserved developmental process that relies on asymmetric activation of Wnt signaling and subsequent organizer formation on the future dorsal side of the embryo. Although roles of Wnt signaling during organizer formation have been studied extensively, it is unclear how the Wnt pathway is asymmetrically activated. In Xenopus and zebrafish, the Wnt pathway is triggered by dorsal determinants, which are translocated from the vegetal pole to the future dorsal side of the embryo shortly after fertilization. The transport of dorsal determinants requires a unique microtubule network formed in the vegetal cortex shortly after fertilization. However, molecular mechanisms governing the formation of vegetal cortical microtubule arrays are not fully understood. Here we report that Dead-End 1 (Dnd1), an RNA-binding protein required for primordial germ cell development during later stages of embryogenesis, is essential for Xenopus axis specification. We show that knockdown of maternal Dnd1 specifically interferes with the formation of vegetal cortical microtubules. This, in turn, impairs translocation of dorsal determinants, the initiation of Wnt signaling, organizer formation, and ultimately results in ventralized embryos. Furthermore, we found that Dnd1 binds to a uridine-rich sequence in the 3'-UTR of trim36, a vegetally localized maternal RNA essential for vegetal cortical microtubule assembly. Dnd1 anchors trim36 to the vegetal cortex in the egg, promoting high concentrations of Trim36 protein there. Our work thus demonstrates a novel and surprising function for Dnd1 during early development and provides an important link between Dnd1, mRNA localization, the microtubule cytoskeleton and axis specification.
| S-EPMC3653556 | biostudies-literature