Biology subjects

Seiradake, E.

Publications and source records attributed to Seiradake, E..

9 recordsLinked to original sources

bioRxiv2026

The atypical RHO-GTPase RND3/RHOE interacts with FLRT3 to regulate cortical migration and folding

Cortical gyrification, characterized by the formation of sulcal fissures and gyral peaks, is a distinctive feature of large mammalian brains and is associated with the emergence of higher cognitive functions. This contrasts with small mammals, like mice, which generally display smooth (lissencephalic) cortices. Gyrification results from the integration of several complex processes such as neuron progenitor amplification and migration. However, the underlying molecular mechanisms remain poorly understood. Here, we show that genetic ablation of Rnd3, encoding the atypical RHO-GTPase RND3/RHOE, induces spontaneous cortical sulci in a subset of mouse embryos without increasing neural progenitor amplification. Instead, RND3 regulates cortical neuron migration, as RND3 overexpression delays neuronal migration, whereas its loss accelerates this process. Similar phenotypes reported in the double Flrt1/3 mutants, suggested a functional interaction between the transmembrane FLRTs and RND3 during cortex development. We demonstrate that Rnd3 and Flrt3 are co-expressed in migrating cortical neurons and interact through a {beta}-strand-mediated binding mechanism, involving a conserved motif in RND3. Disruption of this motif abolishes FLRT3 binding, impairs RND3-mediated regulation of neuronal migration and promotes sulcus formation, indicating that FLRT3-RND3 suppresses cortical folding by regulating neuronal migration in mice. Consistently, Rnd3 expression is reduced in the outer subventricular zone of the prospective sulcal regions in the gyrencephalic ferret brain, supporting the notion that RND3 downregulation contributes to sulci development. Together, these findings identify FLRT3-RND3 signalling as a conserved negative regulator of cortical neuron migration and cortical folding.

neuroscience↗

bioRxiv2026

LRRTM4 controls cell migration via Glypican interactions

Leucine-rich-repeat-transmembrane neuronal proteins (LRRTMs) play a major role in neuronal connectivity and synapse formation, but their function during early development remains largely unexplored and roles in cell migration have not been described. Here, we identify LRRTM4 as a major coordinator of cell migration within the developing cortex and in cancer cells. Using structural predictions and site-directed mutagenesis to abolish the LRRTM4-glypican interaction, we show that LRRTMs interact with the core domain of glypicans, which, in the midgestational murine cortex, are presented by radial glia cells. We demonstrate that glypican-bound LRRTM4 mediates contact-repulsion in migrating neurons and cancer cells in vitro. Our results demonstrate that LRRTMs are used by migrating cells responding to glypicans, and that this signaling system is active in migrating cancer cells and during development.

developmental biology↗

bioRxiv2026

The schizophrenia associated protein DISC1 is a multivalent tetrameric hub of conserved ancient fold

DISC1 is a pleiotropic protein with essential roles in neuronal proliferation and migration, intracellular signalling and cargo transport. It associates with a diverse array of partner molecules in these contexts. Mutations at the DISC1 locus are strongly associated with a spectrum of mental illnesses such as schizophrenia and depression. Despite its clinical relevance, the molecular architecture and function of DISC1 have remained largely elusive. We present a cryo-EM structure of the entire conserved core region of DISC1. The structure reveals an intricate homotetrameric assembly that harbours conserved bacteria-derived UVR domains. Four of these domains, one from each monomer, mediate extensive contacts forming two asymmetric dimer units. The dimers in turn interface with each other at two distinct coiled coil domains to achieve a two-fold symmetric tetramer. Mutational analysis shows that this tetrameric architecture enables DISC1 to simultaneously bind multiple copies of NDE1 client protein. Importantly, tetramerization and partner binding are structurally independent functions of DISC1. Altogether, our study provides a compelling molecular model of an ancient bacteria protein fold participating in the assembly of a multivalent mammalian scaffold hub that can coordinate multiple partner molecules.

neuroscience↗

bioRxiv2025

Ancestral neuronal receptors are bacterial accessory toxins

Symbiosis and horizontal gene transfer events were crucial in the emergence of eukaryotic and multicellular life. A striking example is the acquisition of Teneurins, putative surface-exposed toxins in bacteria that function as cell adhesion receptors in metazoan neuronal development. Here, we demonstrate the evolutionary relationships between metazoan and bacterial Teneurins. We show that bacterial Teneurins are accessory proteins, that harbour diverse encapsulated toxins. They predominate in species with complex social behaviours, suggesting roles in both cell-to-cell competition and cooperation. Metazoan Teneurins are therefore repurposed bacterial toxins central to cell-to-cell communication in nervous systems. Their acquisition was a foundational event in the evolution of metazoans.

biochemistry↗

bioRxiv2025

Teneurin-4 switches between self-recognition and canonical Latrophilin binding to direct neuronal migration

Cortical migration is a complex process in which neurons migrate along radial glial cells (RGC) to form functional layers. Teneurins (Ten1-4) play a role by interacting with Latrophilins (Lphn/ADGRL1-3). Teneurins are also known as cell adhesion molecules, but how homophilic and heterophilic Teneurin interactions are integrated is unknown. Here, single-particle-cryo-EM data of Ten2 shows that canonical Latrophilin-binding is sterically incompatible with Ten2-dimerisation, making these interactions exclusive. We engineered surface mutations that specifically disrupt Ten2-Ten2 or Ten2-Latrophilin interactions. These are transferrable to Ten4, suggesting conserved binding mechanisms. Proteomics, in-vivo-gene-editing and super-resolution-microscopy show that Ten4 is expressed along RGC fibres and that migrating neurons switch from low-to-high Ten4-expression. Ten4 expression is highest in the cortical plate where Ten4-Ten4 interactions reduce RGC-attachment. In the intermediate zone, Ten4-Latrophilin interactions are required to promote neuron-RGC association. The results show how Ten4 orchestrates cortical migration by exclusive structural mechanisms, underpinning the integration of distinct migration programmes. Note: the adhesion GPCR ADGRL is largely referred to as Latrophilin, which is in line with previous papers in the Teneurin field. We would be happy to implement a different naming scheme if recommended.

neuroscience↗

bioRxiv2025

Teneurin-3 and latrophilin-2 are required for somatotopic map formation and somatosensory topognosis

Somatotopy is a recurring organisational feature of the somatosensory system where adjacent neurons and their connections represent adjacent regions of the body. The molecular mechanisms governing the formation of such "body maps" remain largely unknown. Here we demonstrate that the cell surface proteins teneurin-3 and latrophilin-2 are expressed in opposing gradients aligning with the somatotopic map in the dorsal horn of the mouse spinal cord. Genetic manipulation of these proteins in spinal dorsal horn or sensory neurons distorts the somatotopy of neuronal connections and impairs accurate localisation of a noxious stimulus on the surface of the body. Our work provides the foundation for a molecular model of somatotopic map formation and insights into the role of somatotopic maps in the ability to accurately locate somatosensory stimuli or topognosis.

neuroscience↗

bioRxiv2025

EphA2 and Ephrin-A1 Use the Same Interface for Both in cis and in trans Interactions That Regulate Distinct Cell Signaling and Function

The 14 members of Eph receptor tyrosine kinases (RTK) bind to membrane-tethered ligand called ephrins and mediate cell contact signaling where the receptors and ligands engage in trans on adjacent cells. Previous studies reveal that some Eph and ephrin pairs are coexpressed on the same cells, including EphA3-ephrin-A3 and EphA4/ephrin-A5, can also interact with each other in cis. However, significant discrepancies persist as to the molecular basis and functional significance of the cis interactions, owning to the difficulties to directly interrogate the interactions. Here, we utilize time-resolved live cell fluorescence spectroscopy to demonstrate direct in cis interactions between EphA2 and ephrin-A1. Structure-guided mutagenesis mapped interactions to two salt bridges between the ligand- and receptor-binding domains of EphA2 and ephrin-A1. Interestingly, the same interface is shared with in trans interaction. Consequently, EphA2-ephrin-A1 interaction in cis competes with their interaction in trans, which leads to attenuation of EphA2 canonical signaling and inhibition of cell rounding when ligand is presented in trans. EphA2 and ephrin-A1 are widely coexpressed in many epithelial tissues, and dysregulation of their expression is known to contribute to tumor initiation and progression. The detailed molecular characterization of the mutually exclusive cis and trans interactions uncovers a new mechanism underpinning their unique roles in oncogenesis. Significance StatementEphA2 exerts dual functions in tumorigenesis, depending on the binding status of its membrane-tethered ephrin-A ligands. Ligands presented in trans on adjacent cells activate EphA2 canonical signaling associated with tumor suppression, whereas loss of ligand expression promotes oncogenic noncanonical signaling of EphA2 via serine 897 phosphorylation. Combining time-resolved spectroscopy in live cells, structure-guided mutagenesis, we show strong in cis interactions between EphA2 and ephrin-A1, which shares the same interface as interaction in trans. Moreover, the cis interaction interferes with ligand binding in trans, attenuates EphA2 canonical signaling. Our results uncover a new mechanism of EphA2 regulation by its co-expressed ligand ephrin-A1 with important implications in its known roles in oncogenesis as well as other disease processes including development of cataract.

biophysics↗

bioRxiv2022

GPC3-Unc5D complex structure and role in cell migration

Neural migration is a critical step during brain development that requires the interactions of cell-surface guidance receptors. Cancer cells often hijack these mechanisms to disseminate. Here we reveal crystal structures of Uncoordinated-5 receptor D (Unc5D) in complex with morphogen receptor glypican-3 (GPC3), forming an octameric glycoprotein complex. In the complex, four Unc5D molecules pack into an antiparallel bundle, flanked by four GPC3 molecules. Central glycan-glycan interactions are formed by N-linked glycans emanating from GPC3 (N241 in human) and C-mannosylated tryptophans of the Unc5D thrombospondin-like domains. MD simulations, mass-spectrometry and structure-based mutants validate the crystallographic data. Anti-GPC3 nanobodies enhance or weaken Unc5-GPC3 binding. Using these tools in vivo, we show that Unc5/GPC3 guide migrating pyramidal neurons in the mouse cortex, and cancer cells in an embryonic xenograft neuroblastoma model. The results demonstrate a conserved structural mechanism of cell-guidance, with the potential for wide- ranging biomedical implications in development and cancer biology.

neuroscience↗

bioRxiv2020

The guidance and adhesion protein FLRT2 dimerizes in cis via dual Small-X3-Small transmembrane motifs

Fibronectin Leucine-rich Repeat Transmembrane (FLRT 1-3) proteins are a family of broadly expressed single-spanning transmembrane receptors that play key roles in development. Their extracellular domains mediate homotypic cell-cell adhesion and heterotypic protein interactions with other receptors to regulate cell adhesion and guidance. These in trans FLRT interactions determine the formation of signaling complexes of varying complexity and function. Whether FLRTs also interact at the surface of the same cell, in cis, remains unknown. Here, molecular dynamics simulations reveal two dimerization motifs in the FLRT2 transmembrane helix. Single particle tracking experiments show that these Small-X3-Small motifs synergize with a third dimerization motif encoded in the extracellular domain to permit the cis association and co-diffusion patterns of FLRT2 receptors on cells. These results may point to a competitive switching mechanism between in cis and in trans interactions which suggests that homotypic FLRT interaction mirrors the functionalities of classic adhesion molecules. FieldsStructural Biology and Biophysics / Computational Biology

biophysics↗