Biology subjects

Gogou, C.

Publications and source records attributed to Gogou, C..

4 recordsLinked to original sources

bioRxiv2025

A teneurin-3 microphthalmia mutation disrupts trans adhesion for specific alternative splicing isoforms

Microphthalmia (MCOP) is a developmental eye disorder in which one or both eyes are abnormally small. This condition is often accompanied by cognitive impairments. Teneurin-3, a cell adhesion molecule with important functions in axon pathfinding and synaptic organization, has been repeatedly implicated with MCOP, suggesting its potential role in the etiology of this complex developmental disorder. It was previously shown that two small alternatively spliced exons - inserts A and B - instigate large structural reorganizations of the teneurin-3 covalent homodimer. Here, we map the MCOP mutation R2579W to an intramolecular interface specific to splice insert A-containing isoforms. We demonstrate that the MCOP mutation leads to a loss of transcellular adhesion, predominantly affecting these isoforms. Using small-angle X-ray scattering we establish that, despite these functional disruptions, the structural compactness of all mutant isoforms is preserved. Molecular dynamics simulations predict a global stabilization of the A1 mutant molecule compared to its wildtype counterpart, due to changes in local compact dimer interactions around the mutated residue. We experimentally validate these findings with biophysical assays. With cryo-EM analysis, we confirm the overall compactness with reduced conformational flexibility and reveal that the mutant tryptophan binds to a hydrophobic pocket in the structure. With these data, we provide a model for how increased stability in cis disrupts trans oligomerization needed for cellular adhesion. Altogether, we demonstrate that the MCOP-associated mutation in teneurin-3 causally disrupts cellular adhesion in an isoform-specific manner, thereby likely directly contributing to the development of the disease in MCOP patients.

molecular biology↗

bioRxiv2023

Alternative splicing controls teneurin-3 compact dimer formation for neuronalrecognition

Neuronal network formation is facilitated by recognition between synaptic cell adhesion molecules (CAMs) at the cell surface. Alternative splicing of CAMs provides additional specificity in forming neuronal connections. For the teneurin family of CAMs, alternative splicing of the EGF-repeats and NHL domain controls protein-protein interactions at the synapse. Here we present a 3.2 [A] cryo-EM structure of the compact dimeric ectodomain of teneurin-3 harbouring both splice inserts. This dimer is stabilised by an EGF8-ABD contact between subunits. Cryo-EM reconstructions of all four splice variants, together with SAXS and negative stain EM, reveal compacted dimers for each, with variant-specific dimeric arrangements. This results in specific trans-cellular interactions, as tested in cell clustering and stripe assays. The compact conformations provide a structural basis for teneurin homo- and heterophilic interactions. Altogether, our findings demonstrate how alternative splicing results in rearrangements of the dimeric subunits, influencing neuronal recognition and circuit wiring.

biochemistry↗

bioRxiv2022

MukBEF-dependent chromosomal organization in widened Escherichia coli

The bacterial chromosome is spatially organized through protein-mediated compaction, supercoiling, and cell-boundary confinement. Structural Maintenance of Chromosomes (SMC) complexes are a major class of chromosome-organizing proteins present throughout all domains of life. Here, we study the role of the Escherichia coli SMC complex MukBEF in chromosome architecture and segregation. Using quantitative live-cell imaging of shape-manipulated cells, we show that MukBEF is crucial to preserve the toroidal topology of the E. coli chromosome and that it is non-uniformly distributed along the chromosome: it prefers locations towards the origin and away from the terminus of replication, and it is unevenly distributed over the origin of replication along the two chromosome arms. Using an ATP hydrolysis-deficient MukB mutant, we find that MukBEF translocation along the chromosome is ATP-dependent, in contrast to its loading onto DNA. MukBEF and MatP are furthermore found to be essential for sister chromosome decatenation. We propose a model that explains how MukBEF, MatP, and their interacting partners organize the chromosome and contribute to sister segregation and recombination. The combination of bacterial cell-shape modification and quantitative fluorescence microscopy paves way to investigating chromosome-organization factors in vivo.

microbiology↗

bioRxiv2019

Direct observation of independently moving replisomes in Escherichia coli

The replication and transfer of genomic material from a cell to its progeny are vital processes in all living systems. Here we visualize the process of chromosome replication in E. coli cells with an increased width. Monitoring the replication of single chromosomes yields clear examples of replication bubbles that reveal that the two replisomes move independently from the origin to the terminus of replication along each of the two arms of the circular chromosome, providing direct support for the so-called train-track model, and against a factory model for replisomes. The origin of replication duplicates near midcell, initially splitting to random directions and subsequently towards the poles. The probability of successful segregation of chromosomes significantly decreases with increasing cell width, indicating that chromosome confinement by the cell boundary is an important driver of DNA segregation. Our findings resolve long standing questions in bacterial chromosome organization.

cell biology↗