Biology subjects

Roche, F.

Publications and source records attributed to Roche, F..

8 recordsLinked to original sources

bioRxiv2026

Temporal tuning of actin nucleation by the repurposed DNA repair complex RAD51/fignl1 encodes distinct axon guidance decisions

Axon guidance is essential for neural circuit assembly and function. While much of the repertoire of guidance cues and receptors is known, its limited diversity cannot fully explain the remarkable complexity of the brain connectome. How temporally ordered, context-dependent intrinsic programs shape the diversity of axonal responses to guidance signals remains poorly understood. We reveal how non-canonical Wnt5a signalling repurposes the DNA repair complex RAD51/fignl1 as a downstream integrator to control retinal ganglion cell axon decision-making at the midline. We demonstrate that differential RAD51/fignl1 expression and interaction dynamics between ipsilateral and contralateral axons tunes the magnitude and temporal dynamics of F-actin nucleation, thereby encoding their trajectory choice. Our findings establish temporal control of cytoskeletal dynamics as a key determinant of axon decision-making and thereby a fundamental layer of circuit wiring. They provide a potential mechanistic framework linking mutations in the DNA repair gene RAD51 to neurodevelopmental disorders with midline guidance defects.

neuroscience↗

bioRxiv2026

MIGRATION OF SCHWANN CELL PRECURSORS (SCPs) IS REGULATED BY INTERACTIONS OF N-CADHERIN-MEDIATED ADHESION AND EPHRIN-A2-INDUCED SCP CONTRACTILITY

Schwann cell precursors (SCPs) migrate with peripheral sensory axons from DRGs to target regions. SCP migration involves adhesions to substrata to stabilize advancing cell margins, and contractile forces that pull a SCP forward and break rear adhesions. Ncadherin on axons provides adhesion for SCPs, and ephrin-A2 signaling from axons stimulates SCP contractions to complete SCP translocation. Modulation of these adhesive and contractile forces regulates SCP migratioin during development of peripheral nerves.

developmental biology↗

bioRxiv2024

Point contact-restricted cAMP signaling controls ephrin-A5-induced axon repulsion

Signal transduction downstream of axon guidance molecules is essential to steer developing axons. Second messengers including cAMP are key molecules shared by a multitude of signaling pathways and are required for a wide range of cellular processes including axon pathfinding. Yet, how these signaling molecules achieve specificity for each of their downstream pathways remains elusive. Subcellular compartmentation emerged as a flexible strategy to reach such a specificity. Here, we show that point contact-restricted cAMP signals control ephrin-A5-evoked axon repulsion in vitro by modulating Focal Adhesion Kinase phosphorylation and the assembly and disassembly rate of point contacts. Consistently, preventing point contact-specific cAMP signals, in developing retinal ganglion cells in vivo alters the refinement of their terminal axonal arbor in the brain. Altogether, our study identifies point contacts as a compartment containing a local cAMP signal required for ephrin-A5-dependent axon guidance and highlights the crucial role of such subcellularly restricted second messenger signals in the wiring of neuronal circuits.

developmental biology↗

bioRxiv2023

CXCL12 targets the primary cilium cAMP/cGMP ratio to regulate cell polarity during migration

Directed cell migration requires sustained cell polarisation. In migrating cortical interneurons, nuclear movements are directed towards the centrosome that organises the primary cilium signalling hub. Primary cilium-elicited signalling, and how it affects migration, remain however ill characterised. Here, we show that altering cAMP/cGMP levels in the primary cilium by buffering cAMP, cGMP or by locally increasing cAMP, influences the polarity and directionality of migrating interneurons, whereas buffering cAMP or cGMP in the apposed centrosome compartment alters their motility. Remarkably, we identify CXCL12 as a trigger that alters the ciliary cAMP/cGMP ratio to promote sustained polarity and directed migration. We thereby uncover cAMP/cGMP levels in the primary cilium as a major target of extrinsic cues and as the steering wheel of neuronal migration.

developmental biology↗

bioRxiv2023

Subcellular second messenger networks drive distinct repellent-induced axon behaviors

AO_SCPLOWBSTRACTC_SCPLOWSecond messengers, including cAMP, cGMP and Ca2+ are often placed in an integrating position to combine the extracellular cues that orient growing axons in the developing brain. This view suggests that axon repellents share the same set of cellular messenger signals and that axon attractants evoke opposite cAMP, cGMP and Ca2+ changes. Investigating the confinement of these second messengers in cellular nanodomains, we instead demonstrate that two repellent cues, ephrin-A5 and Slit1, induce spatially segregated signals. These guidance molecules activate subcellular-specific second messenger crosstalks, each signaling network controlling distinct axonal morphology changes in vitro and pathfinding decisions in vivo.

developmental biology↗

bioRxiv2022

Enhanced flavour profiles through radicicol induced genomic variation in S. pastorianus lager yeast

The yeasts, Saccharomyces pastorianus, are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus and have acquired traits from the combined parental genomes such as ability to ferment a range of sugars at low temperatures and to produce aromatic flavour compounds, allowing for the production of lager beers with crisp, clean flavours. The polyploid strains are sterile and have reached an evolutionary bottleneck for genetic variation. Here we describe an accelerated evolution approach to obtain lager yeasts with enhanced flavour profiles. As the relative expression of orthologous alleles is a significant contributor to the transcriptome during fermentation, we aimed to induce genetic variation by altering the S. cerevisiae to S. eubayanus chromosome ratio. Aneuploidy was induced through the temporary inhibition of the cells stress response and strains with increased production of aromatic amino acids via the Shikimate pathway were selected by resistance to amino acid analogues. Genomic changes such as gross chromosomal rearrangements, chromosome loss and chromosome gain were detected in the characterised mutants, as were Single Nucleotide Polymorphisms in ARO4, encoding for DAHP synthase, the catalytic enzyme in the first step of the Shikimate pathway. Transcriptome analysis confirmed the upregulation of genes encoding enzymes in the Ehrlich pathway and the concomitant increase in the production of higher alcohols and esters such as 2-phenylethanol, 2-phenylethyl acetate, tryptophol, and tyrosol. We propose that the plasticity of polyploid S. pastorianus genomes is an advantageous trait supporting opportunities for genetic diversity in otherwise sterile strains. Significance StatementLager beer is the product of fermentations conducted with Saccharomyces pastorianus, which are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus. A quintessential property of lager beers is the distinctive flavours produced during fermentation. Hybrids are sterile and have reached an evolutionary bottleneck. Finding ways to introduce genetic variation as a means of enhancing the flavour profiles is a challenge. Here, we describe an approach to introduce genetic variation by inducing aneuploidy through the temporary inhibition of the cells stress response. Strains with an enhanced flavour production were selected by resistance to amino acid analogues. We identified genomic changes and transcriptome analysis confirmed the upregulation of genes in the Ehrlich pathway which is responsible for the production of flavour compounds.

microbiology↗

bioRxiv2021

Aneuploidy influences the gene expression profiles in Saccharomyces pastorianus group I and II strains during fermentation.

The lager yeasts, Saccharomyces pastorianus, are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus and are divided into two broad groups, Group I and II. The two groups evolved from at least one common hybridisation event but have subsequently diverged with Group I strains losing many S. cerevisiae chromosomes while the Group II strains retain both sub-genomes. The complex genomes, containing orthologous alleles from the parental chromosomes, pose interesting questions regarding gene regulation and its impact on the fermentation properties of the strains. Superimposed on the presence of orthologous alleles are complexities of gene dosage due to the aneuploid nature of the genomes. We examined the contribution of the S. cerevisiae and S. eubayanus alleles to the gene expression patterns of Group I and II strains during fermentation. We show that the relative expression of S. cerevisiae and S. eubayanus orthologues is positively correlated with gene copy number. Despite the reduced S. cerevisiae content in the Group I strain, S. cerevisiae orthologues contribute to biochemical pathways upregulated during fermentation which may explain the retention of specific chromosomes in the strain. Conversely, S. eubayanus genes are significantly overrepresented in the upregulated gene pool in the Group II strain. Comparison of the transcription profiles of Group I and II strains during fermentation identified both common and unique gene expression patterns, with gene copy number being a dominant contributory factor. Thus, the aneuploid genomes create complex patterns of gene expression during fermentation with gene dosage playing a crucial role both within and between strains.

genetics↗

bioRxiv2021

Next generation SARM1 knockout and epitope tagged CRISPR-Cas9-generated isogenic mice reveal that SARM1 does not participate in regulating nuclear transcription, despite confirmation of protein expression in macrophages

SARM1 is an ancient and highly conserved TIR-domain containing protein, with a diverse range of proposed roles in both innate immunity and neuronal death and degeneration. Murine SARM1 has been reported to regulate the transcription of specific chemokines in both neurons and macrophages, however the extent and mechanism by which SARM1 contributes to transcription regulation remains to be fully understood. Here, using RNA sequencing we identify differential gene expression in bone marrow-derived macrophages (BMDM) from C57BL/6 congenic 129 ES cell-derived Sarm1-/- mice compared to wild type (WT). However, we show that passenger genes which are derived from the 129 donor strain of mice flank the Sarm1 locus, confounding interpretation of results, since many of the identified differentially regulated genes come from the region containing passenger genes. To re-examine the transcriptional role of SARM1 in the absence of such passenger genes, we generated three different Sarm1-/- mice using CRISPR/Cas9 technology. Vincristine treatment of ex vivo cultured post-natal neurons from these mice confirmed SARM1s previously identified key function as an executor of axon degeneration. However, using these mice, we show that the absence of SARM1 has no impact on transcription of genes previously shown to be altered in macrophages or in the brainstem. To gain further insight into SARM1 function, we generated and characterized a mouse expressing epitope-tagged SARM1, as it has been difficult to date to confirm which cells and tissues express SARM1 protein. In these mice we see high SARM1 protein expression in the brain and brainstem, and lower but detectable levels in macrophages. Overall, the generation of these next generation SARM1 knockout and epitope-tagged mice has clarified that SARM1 is expressed in mouse macrophages but has no general role in transcriptional regulation in these cells, and has provided important new animal models to further explore SARM1 function.

immunology↗