Biology subjects

Srour, M.

Publications and source records attributed to Srour, M..

3 recordsLinked to original sources

bioRxiv2025

The microtubule-binding protein EML3 is required for mammalian embryonic growth and cerebral cortical development; Eml3 null mice are a model of cobblestone brain malformation

The cerebral cortex is a multi-layered structure generated through the migration of neural precursors from their birthplace in the ventricular zone to their destination within the cortical plate. Neuronal migration defects are responsible for many human pathologies collectively called neuronal migration disorders, which include subcortical band heterotopia and cobblestone brain (COB) malformation. One example of a protein involved in a neuronal migration disorder is the echinoderm microtubule-associated protein-like 1 (EML1) protein, one of six members of the mammalian EML family. Absence of EML1 protein results in subcortical band heterotopia in mice and humans. Here, we report that absence of the paralogous protein EML3 leads to delayed embryonic development and small size, and a COB-like phenotype with neuronal ectopias in the dorsal telencephalon. We found that EML3 is expressed in the neuroepithelium and meningeal mesenchyme when those tissues participate in pial basement membrane (PBM) formation. Transmission electron microscopy demonstrated that the extracellular matrix of the PBM is structurally abnormal in Eml3 null mice when the first radially migrating neurons arrive. The reduced structural integrity of the PBM leads to focal over-migration of neurons into the subarachnoid space. These findings strengthen the link between the EML protein family and cortical neuronal migration defects by identifying Eml3 as the first EML family member whose absence leads to over-migration of neuroblasts. Moreover, we report the first COB-like phenotype with PBM structural defects when a single microtubule-associated protein is deleted.

developmental biology↗

bioRxiv2024

The functional and pathogenic consequences of fibrinogen on human oligodendroglia

Fibrinogen is a blood-derived protein involved in coagulation, and can make its way into the central nervous system (CNS) following breakdown of the blood-brain barrier. This molecule has been implicated in multiple sclerosis (MS), a disease marked by inflammation and demyelination in the CNS, as well as other neurological disorders. However, the effect of this molecule has not been studied on human myelinating cells. This study examines how fibrinogen influences human oligodendrocyte (OL) lineage cells at various stages of development. Using induced pluripotent stem cell-derived (iPSC) OL precursors and human primary OLs, we examined the effects of fibrinogen on cell differentiation, viability and myelination-related function. Here we show that fibrinogen induces an aberrant differentiation of early lineage OLs, by inhibiting their maturation and inducing an astrocytic phenotype, as seen in previous studies. On mature OLs, fibrinogen was found to promote myelination capacity as shown by ensheathment assays as well as on the RNA level. These effects were associated with the activation of BMP signalling, both in early and mature OLs. Transcriptomic analysis of human MS brain tissue shows similar pro-myelination changes in a subset of OLs, suggesting in vivo relevance. These findings indicate that fibrinogen has a lineage-dependent effect, where it may be inhibitory earlier in the lineage while promoting OL function in later stages. Understanding this dual role will provide insight into remyelination failure in MS and highlights the importance of timing and target in future therapeutic strategies. Significance StatementIn multiple sclerosis (MS), the blood protein fibrinogen leaks into the brain and has been shown to interfere with myelin repair. This study demonstrates that fibrinogen has opposite effects on human oligodendrocyte-lineage cells depending on their stage of maturation. While it blocks the differentiation of early-stage cells, it enhances the functional capacity of mature oligodendrocytes. These findings help explain why remyelination may fail in MS and suggest that fibrinogen could both hinder and support repair, depending on the cell context. This dual role has important implications for developing stage-specific therapies for MS.

neuroscience↗

bioRxiv2022

A human DCC variant causing mirror movement disorder reveals an essential role for the Wave regulatory complex in Netrin/DCC signaling

The axon guidance cue, Netrin-1, signals through its receptor DCC to attract commissural axons to the midline. Pathogenic variants in DCC frequently lead to congenital mirror movements (CMM), but how these variants impact DCC function is largely unknown. Screening of DCC in individuals with CMM recently revealed a novel variant located in a conserved motif in the cytoplasmic tail of DCC that is predicted to bind to a central actin nucleation promoting factor, the WAVE regulatory complex (WRC). Here, we use biochemical and axon guidance assays to show that this CMM-associated DCC variant is pathogenic by disrupting the interaction between DCC and the WRC. This DCC-WRC interaction is evolutionarily conserved and is required for Netrin-1 mediated commissural axon outgrowth and guidance. Together, we identify the WRC as a pivotal component of Netrin-1/DCC signaling and further provide a molecular mechanism explaining how genetic variants in DCC may lead to CMM.

neuroscience↗